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La Società Geologica Italiana, i curatori scientifici (Chief, Associate and Advisory), e la Casa Editrice non sono responsabili delle ISSN 2035-8008 RENDICONTI Online della Società Geologica Italiana Volume 20 - Luglio 2012 X Congresso GEOSED “Associazione Italiana per la Geologia del sedimentario” Feltre 2-6 Luglio 2012 NOTE BREVI E RIASSUNTI A cura di: Valeria Bianchi, Giovanni Gattolin & Manuel Rigo ROMA SOCIETÀ GEOLOGICA ITALIANA 2012 www.socgeol.it X Congresso GEOSED “Associazione Italiana per la Geologia del sedimentario” Feltre 2-6 Luglio 2012 COMITATO ORGANIZZATORE Anna Breda Valeria Bianchi Giovanni Gattolin Massimiliano Ghinassi Nereo Preto Manuel Rigo Cristina Stefani Massimiliano Zattin © Società Geologica Italiana, Roma 2012 INDICE Premessa........................................................................................................................................................................................ 5 AMOROSI A. - The occurrence of glaucony in the stratigraphic record: Distribution patterns and sequence-stratigraphic significance................................................................................................................. ....................................................... 6 BAR ALE L., BERTOK C., D TR I A., DOMINI G., MARTIRE L. & PIANA F. Cretaceous-Lower Eocene hydrothermal dolomitization in the Maritime Alps (NW Italy)................................................................................................................ 7 BER NARDI E., DELA PIERR E F., GENNARI R., LOZAR F. & VIOLANTI D. - Astrochronologiacal calibration and paleoenvironmental reconstruction of the Messinian events at the Northern edge of the Mediterranean: the Govone section (Tertiary Piedmont Basin)...................................................................................................................................... 10 BER SEZIO R., FELLETTI F. & VALENTE A. - Turbidite facies changes in a base of slope basin setting (Langhe Basin, Lower Cengio Turbidite System, Oligocene, Tertiary Piedmont Basin)..................................................................................... 12 BIANCHI V.,GHINASSI M., ALDINUCCI M., BOAGA J. & DEI ANA R. - Tectonic control on fluvial aggradation: the PlioPleistocene Ambra valley-fill succession (Tuscany, Italy)............................................................................................. .... 15 BILLI P. - Sedimentology and sediment transport processes in a few ephemeral streams of the Horn of Africa......................... 17 BRANDANO M., TOMASSETTI L. & RONCA S. - Depositional processes of the carbonate-siliciclastic rhodolith rich deposits ........................................................... 20 BRANDANO M., GUARINI G., PETRUNGARO R., VELOCC I L., MELONI D., MASC ARO G. & L IPPARINI L. - Digital 3D modelling of submarine dune field by laser scanning technique (Bolognano Formation, Majella).................................................... 21 BURATTI N, BARC HI M. R., BERTINI A., CIRILLI S., GASPERINI L., MARC HEGIANO M. & PAZZAGLIA F. - Lacustrine organic facies and pollen analysis from the Trasimeno lake (Central Italy): a preliminary note.................................................... 22 CAGGIATI M., B REDA A., GIANOLLA P., RIGO M. & ROGHI G. - Depositional systems of the Eastern Southern Alps (NE Italy, W Slovenia) during the late Carnian.................................................................................................................................. 24 COZZI A. - Identifying plays and prospects in carbonates............................................................................................................ 28 D' ALPAOS A., CARNIELLO L., STEFANON L. & RINALDO A. - Modeling tidal network dynamics in response to changes in the environmental forcings....................................................................................................... ................................................ 29 ALB ERTO L. & GIORDANO D. - Jurassic extensional faulting at the Trento platform Belluno basin margin sedimentary and tectonic......................................................................................................................................................................... 32 DE MURO S., KALB C., BRAM BILLA W. & IBBA A. - Sedimentological, geomorfological and geochemical evidence of the last marine ingression in central Magellan Straits-southernmost Chile................................................................................... 33 DI CAPUA A., GROPPELLI G. & VEZZOLI G. - Stratigraphic trend evolution of the sedimentary pulses of Val d'Aveto Formation........................................................................................................................................................................ 35 FIDOLI NI F. & ANDREETTA A. - Sedimentological and pedological study of some pedogenized intervals of the PlioPleistocene Upper Valdarno Basin..................................................................................................................................... 38 GATTOLIN G., FRANCESCHI M., BREDA A. & PRETO N. - Facies and geometries of carbonate platforms of the Dolomites after the Carnian Pluvial Event (CPE)...................................................................................................................................... 41 GRILLENZONI C., CONTI S., FONTANA D. & TURCO E. - Seep-carbonates as indicators of global cooling events (Miocene, northern Apennines).......................................................................................................................................................... 42 IADANZA A., SAMPALMIER I G, FRIJIA G., CIPOLLARI P., COSENTINO D. & MOLA M. - The subsurface record of hydrocarboncharged fluids migrating through the Messinian sedimentary column (Maiella Basin, Central Italy).............................. LONGHITANO S.G. - The role of the Backshore/Foreshore length ratio in short-term beach monitoring studies.......................... 44 46 MARCHETT I L., SANTI G. & AVANZINI M. - The problem of small footprints in paleoichnology related to extramorphologies: new data from the Early Permian Erpetopus..................................................................................................................... 48 MARIN E., TER UGGI L.B., MAROCCHI NO E. & VACC ARO C. - Geochemical characterization of sediment quality in the river basin of the Rio Grande Quequén (Argentina).................................................................................. ............................... 51 MARIN E., NAC HITE D., NAJIH M., ANFUSO G., MAROCCHINO E. & VACC ARO C. - The lagoon of Nador (Morocco): geochemical and petrographic analysis of sediments and environmental conditions....................................................... 53 MARTINI I. & SANDR ELLI F. - Facies analysis and sequence stratigraphic interpretation of sandy deposits in the central part of the Siena Basin (Italy)................................................................................................... ................................................ 55 MAZZUCCHI A. & TOMASSETTI L. - Coral patch reef in a Burdigalian mixed carbonate-siliciclastic coastal system (Cala Paraguano, Corsica).......................................................................................................................................................... 57 MIETTO P. & MANFRIN S. - Mysterious Triassic ammonoids of Recoaro area: state of art........................................................ .. 59 MONEGATO G. & STEFANI C. - Upper Miocene Lower Pliocene provenance changes in the Venetian Foreland...................... 60 MOSCON G. - Provenance of the Pleistocene fluvial deposits of the Ambra valley (central Tuscany): implication for palaeodrainage evolution............................................................................................................................................................. 63 PALLADINO G. & PROSSER G. - Study and interpretation of some uncertain Triassic lithosomes at the base of the Lagonegro Basin succession: a key for a correct reconstruction of the Monte Facito Formation (Basilicata, southern Italy)........... 64 PASCUCCI V., ANDREUCCI S. & FRULIO G. - New estimation of the post Little Ice Age sea level rise.......................................... 67 PIOVAN S., STEFANI C. & MOZZI P. - Late Holocene palaeohydrography in central and southern Venetian Plain: the role of petrographical sand analysis.............................................................................................................................................. 68 RAGAZZI E., AVANZINI M., DIENI I., ROGHI G. & STEFANI C. - New amber findings in Northeastern Italy: suggestions for an integrated view on fossil resin 71 ROSSATO S., MOZZI P., MONEGATO G., CUCATO M., GAUDIOSO B. & MIOLA A. - Connections between glacial and fluvial systems in the lower Astico Valley and the piedmont plain (NE Italy)............................................................................. 76 Rend. Online Soc. Geol. It., Vol. 20 (2012), p. 5. © Società Geologica Italiana, Roma 2012 Premessa La decima riunione annuale del Gruppo di Geologia del Sedimentario GEOSED organizzata dal Dipartimento di Geoscienze a Feltre tra il 2 e il 6 luglio 2012. Il convegno è stato ospitato presso il Campus Universitario della . nelle piattaforme triassiche delle -miocenica veneta. Per i giovani è stato inoltre organizzato un corso breve sui processi ed architetture deposizionali in sistemi torbiditici. I contriburi scientifici presentati nel corso del congresso hanno affrontato una significativa molteplicità di aspetti della geologia del sedimentario, e sono stati raccolti in questo volume sotto forma di note brevi o riassunti. Il comitato organizzatore desidera ringraziare tutti i partecipanti e gli enti patrocinatori che hanno contribuito alla buona riuscita della manifestazione. Anna Breda, Valeria Bianchi, Giovanni Gattolin, Massimiliano Ghinassi, Nereo Preto, Manuel Rigo, Cristina Stefani e Massimiliano Zattin. Rend. Online Soc. Geol. It., Vol. 20 (2012), p. 6. © Società Geologica Italiana, Roma 2012 The occurrence of glaucony in the stratigraphic record: Distribution patterns and sequence-stratigraphic significance ALESSANDRO AMOROSI (*) Key words: Glaucony, Glauconite, Sequence stratigraphy, Condensed section, Maximum flooding surface. Glaucony is traditionally regarded as an indicator of low sedimentation rate and represents one of the most reliable stratigraphic markers within marine sediments. An integrated sedimentological, mineralogical and geochemical characterization of about 250 glaucony-bearing horizons from 41 sites in Western Europe provides a comprehensive framework for the definition of the sequence-stratigraphic significance of glauconitic minerals. Autochthonous glaucony follows predictable trends in abundance and maturity, with positive correlation between potassium content and proportion of green grains in the host rock. Three basic types of condensed horizons are differentiated: i) simple omission surfaces, containing < 20% (poorly-evolved) glaucony, ii) condensed sections, including 20-50% (evolved) glaucony, and iii) mega-condensed sections, with > 50% (highlyevolved) glaucony. By contrast, glauconitic grains of _________________________ (*) University of Bologna, Dipartimento di Scienze della Terra e geologico-Ambientali, Via Zam boni 67, 40127 Bologna, Italy. E-mail: [email protected] allochthonous origin do not exhibit any peculiar trend in abundance and maturity. High amounts of parautochtonous (intrasequential) glaucony are relatively common in the stratigraphic record, whereas a detrital (extrasequential) origin for the green grains accounts for anomalously low concentrations of highly-evolved glaucony. In terms of sequence stratigraphy, simple omission surfaces correspond to marine flooding surfaces at parasequence boundaries. These surfaces span intervals of time in the order of 104 years and are expected to have low correlation potential. Condensed horizons represent basin -wide stratigraphic markers that may either bracket the TST/HST boundary (i.e., the model) or comprise a significant portion of the TST (105 years). Mega-condensed sections imply huge stratigraphic condensation, spanning from systems tracts to third-order depositional sequences with episodicities of 106 years. Mega-condensed sections are likely to be correlative on a global scale. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 7-9, 2 figs. © Società Geologica Italiana, Roma 2012 Cretaceous-Lower Eocene hydrothermal dolomitization in the Maritime Alps (NW Italy) LUC A BARALE (*), CARLO BERTOK (*), ANNA D TRI (*), GABRIELE D OM INI (**), LUC A M ARTIRE (*) & FABRIZIO PIANA (°) Key words: Hydrothermal dolomitization, Jurassic limestones, Maritime Alps, Provençal-Dauphinois Domain. INTRODUCTION Hydrothermal dolomitization has recently become argument of broad interest and debate. According to the widely accepted definitions of MACHEL & LONNEE (2002) and DAVIES & SMITH (2006), a proper hydrothermal dolomitization is characterized by a fluid temperature at least 5-10 °C higher than that of the host limestone. In the Provençal-Dauphinois and Subbriançonnais Domains of the Maritime Alps, the Jurassic carbonate succession is locally characterized by a diffuse dolomitization. The stratigraphic framework, the geometric and petrographic features of the dolomitized bodies, together with preliminary data from stable isotope analysis and fluid inclusion microthermometry, allowed to define timing and modes of dolomite formation process. Dolomitization of the Jurassic limestones occurred in the Early Cretaceous-Early Eocene interval, in a very shallow burial environment, and was due to fluids significantly hotter than the host limestone. Thus, the study case represents a straightforward example of hydrothermal dolomitization, perfectly fitting with the above definition, and has important regional implications for the tectono-sedimentary evolution of this part of the passive European Tethyan margin. GEOGRAPHIC AND GEOLOGICAL SETTING The study area lies in the eastern Maritime Alps (North _________________________ (*) Dipartimento di Scienze della Terra, Università di Torino, 10125 Torino, Italy. (**) Strada M arentino 2, 10020 Andezeno (TO), Italy. (°) CNR-Istituto Geoscienze e Georisorse, 10125 Torino, Italy Lavoro eseguito con il contributo finanziario di GeoSed (Contributo Ricerca GeoSed giovani 2011, assegnato a Luca Barale). Western Italy), between the Sabbione Valley to the west and the Vermenagna Valley to the east. This sector is composed of several tectonic units, superimposed along NW-SE striking Alpine tectonic contacts, classically attributed to ProvençalDauphinois and Subbriançonnais paleogeographic domains of the Alpine Tethys European paleomargin (CARRARO et alii, 1970). The Mesozoic succession is characterized by the presence of a thick limestone succession of Middle?-Upper Jurassic age and by the marked reduction or total absence of Cretaceous deposits. The top of the Mesozoic succession is truncated by a regional unconformity corresponding to a hiatus spanning the Cretaceous-Early Eocene. Above the unconformity, the Alpine Foreland Basin succession consists of the Middle Eocene Nummulitic Limestone, followed by the hemipelagic Upper Eocene Globigerina Marl and by the Upper Eocene-Lower Oligocene turbidites (SINC LAIR, 1997). The occurrence of dolomitization affecting the Jurassic limestones in the study area was already pointed out (CAM PANINO STURANI, 1967; CARRARO et alii, 1970; M ALARODA , 1970). However, apart from the mere reporting, no description of the dolomitization features was given and no explanation was proposed regarding its genesis. DOLOMITIZATION FEATURES Host rocks Dolomitization affects the Jurassic limestones of both Provençal-Dauphinois and Subbriançonnais units. They are composed of a 200-300 m thick succession, which mainly consists of mudstones to packstones with echinoderm fragments, dubitatively attributed to the Middle -Late Jurassic (CARRARO et alii, 1970). The uppermost interval of this succession, made up of bioclastic packstones to rudstones and coral-stromatoporid boundstones, is dated to the Kimmeridgian-Tithonian (CAM PANINO STURANI, 1967). The stratigraphically highest dolomitized beds are locally represented by charophyte-rich wackestones, which could have 8 BARALE ET ALII dolomite, occurring both as replacive and as void-filling cement. 18 O values (ranging from -4 to -6 fluids. Quantitative paleotemperature data from preliminary primary fluid inclusion microthermometry on saddle dolomite, indicate fluid temperatures ranging from 170 to 220 °C. Reworked dolomite Fig. 1 Upper portion of the partially dolomitized Jurassic limestones: note the juxtaposition of cm-wide bands of rock with randomly oriented dolomitecemented veins and of subvertical tabular bodies of dolomite-cemented breccias . a Berriasian age for comparison with the adjacent successions of the Nice Arc. The basal interval of the Nummulitic Limestone, made up of conglomerate and arenite beds, locally contains abundant mm- to dm-sized clasts of dolostones. The occurrence of such clasts was already reported by CAM PREDON (1972) who, however, did not investigate their origin. Petrographic features of the dolostone clasts clearly document their provenance from the dolomitized Jurassic limestones. DISCUSSION AND CONCLUSIONS Timing of dolomitization Dolomite features Dolomite-bearing rocks show a great heterogeneity in the study area. They range from partly dolomitized limestones with only scattered dolomite crystals, to quite homogeneous medium to coarsely crystalline dolostones; the majority of dolomitized rocks, however, shows intermediate degrees of dolomitization with respect to these two end-members. Dolomitization, both partial and complete, affects discrete rock masses that are randomly distributed in the host limestone. Dolomitization frequently develops along a more or less close network of veins (100 - to 2 mm-thick), locally closely spaced and arranged along sub-vertical, cm- to dmwide, channels (Fig. 1). Mm- to cm-sized dissolution cavities, filled up with dolomite and calcite cements, can locally be observed between the veins. Tabular breccia bodies also occur within the dolomitized rocks, randomly distributed with respect to the bedding. They are clast-supported, with heterometric clasts, centimetric to decimetric in size and subrounded to angular in shape. Breccias are either polymictic or monomictic, and clasts include partially or totally dolomitized limestones, undolomitized limestones, and dolomite vein fragments. A fine matrix is rarely present; more commonly voids are filled up with mmthick rims of a coarsely crystalline whitish dolomite cement, followed by a dark sparry calcite cement (Fig. 2). Thin section observations allowed to distinguish two dolomite types. The first is a finely- to medium-crystalline, very turbid, replacive dolomite, whereas the second is a less turbid, well-zoned, coarsely- to very coarsely-crystalline saddle The age of dolomite formation can be inferred on the basis of solid stratigraphic evidence. Dolomitization can not be younger than the Early Eocene, as showed by the occurrence of clasts of the dolomitized limestones in the basal levels of the Middle Eocene Nummulitic Limestone. On the other hand, the top of the dolomitized succession has a Tithonian-Berriasian? age, and thus dolomitization can not be older. It can be therefore stated that dolomitization occurred in the Early Cretaceous-Early Eocene interval. Fig. 2 Clas t-supported breccia with fully dolomitized clasts coated by a mmthick rim of whitish dolomite cement. Remaining voids are plugged by a sparry, grey to black, calcite cem ent. Pencil tip for scale, on the left, is 1.5 cm long. CRETACEOUS-LOWER EOCENE HYDROTEHERM AL DOLOMITIZATION Dolomitization process The geometry of dolomitized bodies, cross-cutting the host limestone bedding, their close relation with vein networks, and the common occurrence of saddle dolomite (pointing to temperatures higher than about 60 °C; RADKE & M ATHIS , 1980) indicate a dolomitization process related to the circulation of hot fluids through fracture and vein networks. This hypothesis is actually confirmed by preliminary data from stable isotopes ( 18 O lower than and fluid inclusion microthermometry (homogenization temperatures around 200 °C). The reduced thickness or even absence of Cretaceous to Lower Eocene deposits in the stratigraphic succession of the study area, along with their complete lack as clasts in the transgressive Middle Eocene conglomerates, indicates that if a Cretaceous-Lower Eocene sediment package had been deposited, it was thin enough to be completely removed before the Middle Eocene transgression. A very shallow burial setting can thus be argued for the Jurassic limestones in the Early Cretaceous-Early Eocene. From the above considerations, it follows that the dolomitizing fluids were significantly warmer than the host rocks, and thus may be properly referred as hydrothermal fluids (sensu M ACHEL & LONNEE , 2002; DAVIES & SMITH, 2006). The wide occurrence, in the dolomitized rocks, of breccia bodies and vein networks, indicates that the hydrothermal system was characterized by repeated hydrofracturing events. These were probably due to the cyclic abrupt expulsion of overpressured fluids along main fluid-flow pathways, likely represented by high-angle faults and related fracture systems. Regional implications The recognized hydrothermal dolomitization indirectly documents a fault activity during the Early Cretaceous-Early Eocene interval in this sector of the Alpine Tethys European paleomargin. Evidence of tectonic activity since Early Cretaceous has been indeed recently recognized also in the adjacent External Ligurian Briançonnais Domain (BERTOK et alii, 2012) that is locally affected by an Upper Jurassic dolomitization. Such faultand fracture-controlled 9 hydrothermal dolomitization thus appears as the evidence of a major syndepositional deformation zone cutting transversally across at least three paleogeographical units (Briançonnais, Subbriançonnais, Provençal-Dauphinois domains). REFERENCES BERTOK C., M ARTIRE L., PEROTTI E., D TRI A. & P IANA F. (2012) - Kilometre-scale palaeoescarpments as evidence for Cretaceous synsedimentary tectonics in the External Briançonnais domain (Ligurian Alps, Italy). Sediment. Geol., 251-252, 58-75. CAM PANINO S TURANI F. (1967) - Sur quelques Nérinées du Malm des Alpes Maritimes (couverture sédimentaire de iées du Col de Tende). Rend. Acc. Naz. Lincei, 8, 42, 527-529. CAM PREDON R. (1972) - Les formations paléogènes des AlpesMaritimes franco-italiennes. PhD Thesis, Univ. de Nice, 539 p. CARRARO F., DAL PIAZ G.V., FRANCESCHETTI B., M ALARODA R., STURANI C. & ZANELLA E. (1970) - Note Illustrative scala 1: 50.000. Mem. Soc. Geol. Ital., IX, 557-663. D AVIES G.R. & SMITH L.B. JR. (2006) - Structurally controlled hydrothermal dolomite reservoir facies: An overview. AAPG Bull., 90, 11, sp. issue, 1641-1690. M ACHEL H.G. & LONNEE J. (2002) - Hydrothermal dolomite-a product of poor definition and imagination. Sediment. Geol., 152, 163-171. M ALARODA R. (1970) - Carta Geologica del Massiccio 1: 50.000. Mem. Soc. Geol. Ital., IX. RADKE B.M. & MATHIS R.L. (1980) - On the formation and occurrence of saddle dolomite. J. Sediment. Res., 50, 11491168. S INCLAIR H.D. (1997) - Tectonostratigraphic model for underfilled peripheral foreland basins: an Alpine perspective. GSA Bull., 109, 3, 324-346. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 10-11. © Società Geologica Italiana, Roma 2012 Astrochronological calibration and paleoenvironmental reconstruction of the Messinian events at the Northern edge of the Mediterranean: the Govone section (Tertiary Piedmont Basin) ELISA BERNARDI (*), FRANCESCO D ELA P IER RE (*), ROCCO GENNARI (**), F RANCESCA LOZAR & DONATA VIOLANTI (*) Key words: Astrochronological calibration, Biostratigraphy, Foraminifera, Mediterranean, Messinian, Paleoecology, Tertiary Piedmont Basin. The Tertiary Piedmont Basin (TPB) preserves the northernmost record of the Messinian salinity crisis (MSC); in this basin the lateral transition between marginal and deep water successions can be reconstructed in detail (DELA PIERRE et alii, 2011). As a matter of fact up to 14 cycles of primary sulphate evaporites (Primary Lower Gypsum unit = PLG; ROVERI et alii, 2008), consisting of laminated shale-gypsum couplets, were deposited in marginal settings. Conversely, in the more distal part of the basin, the lower gypsum cycles are transitional to cyclic muddy sediments, that are well exposed in the Govone section. This section comprises the entire Messinian succession and starts with the marine sediments of the Marl (the object of this study), composed of a rhythmic alternation of laminated mudstonehomogeneous marl. This unit is overlain by the PLG unit that is here composed of nine lithologic cycles consisting of laminated shale/gypsum cumulite couplets. The PLG is sharply followed by clastic gypsum facies and chaotic bodies (Resedimented Lower Gypsum= RLG; ROVERI et alii, 2008) and finally by fluvio-deltaic deposits with Lago-Mare fossil assemblages in the upper part (Cassano Spinola Conglomerates). Cyclostratigraphic and quantitative micropaleontological analyses were performed on the Marl, in order to constrain the onset of the MSC and to define the paleoenvironmental changes heralding this Mediterraneanscale palaeoceanographic event. The lithologic cyclicity of this unit is reflected by regular fluctuation of microbiological _________________________ (*) Dipartimento di Scienze della Terra Valperga Peluso, 35, 10125, Torino - Università di Torino, via (**) Dipartimento di Scienze della Terra - Università di Parma, Parco Area delle Scienze 157A - 43100, Parma assemblages, testifying to the influence of precessioncontrolled climatic changes. Several bioevents (Last Abundant Occurrence of G. miotumida, First Abundant Occurrence of T. multiloba, Neogloboquadrinids S/D coiling change, influxes of G. scitula, Last Recovery of foraminifers and calcareous nannofossils) were recognised in the section; their integration with magnetostratigraphic data has been used as the starting point for the astrochronologial calibration of the succession: each cycle was tuned to 65°N summer insolation and precession indexes of the La2004 astronomical solution ( LASKAR et alii, 2004). The results of this study allowed an accurate bed to bed correlation of the Govone section with other reference sections from both Western (Abad composite; SIERRO et alii, 2001), Southern (Falconara Gibliscemi; BLANC VALLERON et alii, 2002), and Eastern (Pissouri; KRIJGSMANN et alii, 2002) Mediterranean as well as with the Atlantic record (An el Beida section; KRIJGSMANN et alii, 2004). The phase relations between the lithologic cycles and astronomical curves since 6.60 Ma (dating for the base of the Govone section) was defined. Moreover, this study allowed to precisely constrain the main paleoenvironmental changes at the northernmost edge of the Mediterranean sea immediately before the onset of the MSC, in a time interval between 6.60 Ma and 5.96 Ma. The progressive impoverishment of the foraminiferal assemblages, that become poorly diversified and dominated by stress tolerant taxa upward, suggests a decrease of bottom water oxigenation and/or increase of water column stratification. The establishment of restricted conditions heralding the onset of MSC was dated at Govone at 6.20 Ma, approximately 200 Kyr later than in other Mediterranean sections (Cyprus e.g. K OUWENOVEN et alii, 2006; Northern Apennines e.g. K OUWENOVEN et alii, 1999; DI STEFANO et alii, 2010) in which the final increase of basin restriction occurred at around 6.4 Ma. Finally the results of this study allowed to recognize that the onset of the MSC has not sedimentological and lithological evidence and is placed within a barren succession of euxinic shale/marl couplets, six sedimentary cycles (i.e. approximately 120 kyr) below the first primary gypsum bed. These barren ASTROCHRONOLOGIC AL CALIBRATION AND PALEOENVIRONMENTAL OF THE M ESSINIAN GOVONE SECTION sediments represent the deep water counterparts of the lower PLG cycles deposited in the marginal part of the basin. REFERENCES BLANC -VALLERON M.M, PIER RE C., CAULET J.P., CARUSO A., ROUCHY J.M., CAESPUGLIO G., S PROVIERI R., PESTREA S. & D I S TEFANO E. (2002) - Sedimentary, stable isotope and micropaleontological records of paleoceanographic change in the Messinian Tripoli Formation (Sicily, Italy). Palaeogeogr., Palaeoclim., Palaeoecol., 185, 255-286. DELA PIERRE F., BERNARDI E., CAVAGNA S., CLARI P.A., GENNARI R., I RACE A., LOZAR F., LUGLI S., M ANZI V., NATALICCHIO M., ROVERI M. & V IOLANTI D. (2011) - The record of the Messinian salinity crisis in the Tertiary Piedmont Basin (NW Italy): The Alba section revisited. Palaeogeogr., Palaeoclim., Palaeoecol., 310, 238-255. DI STEFANO A., V ERDUCCI M., LIRER F., FERRARO L., IACCARINO S.M., H USING S.K. & H ILGEN F.J. (2010) Paleoenvironmental conditions preceding the Messinian Salinity Crisis in the Central Mediterranean: Integrated data from the Upper Miocene Trave section (Italy). Palaeogeogr., Palaeoclim., Palaeoecol., 297, 37-53. LASKAR J., ROBUTEL P., JOUTELL F., G ASTINEAU M., CORREIA A.C.M. & LEVRARD B. (2004) - A longterm numerical solution for the insolation quantities of the Earth. Astron. Astrophys. 428, 261 285. 11 K OUWENHOVEN T.J., SEIDENKRANTZ M.S. & VAN DER ZWAAN G.J. (1999) - Deep-water changes: the near-synchronous disappearance of a group of benthic foraminifera from the late Miocene Mediterranean. Palaeogeogr., Palaeoclim., Palaeoecol., 152, 259 281. K OUWENHOVEN T.J., SMORIGI C., N EGRI A., GIUNTA S., KRIJGSMAN W. & ROUCHY J.M. (2006) Palaeoenvironmental evolution of the eastern Mediterranean during the Messinian: constraints from integrated microfossil data of the Pissouri Basin (Cyprus). Mar. Micropalaeont. 60, 17-44. K RIJGSMAN W., BLANC -VALLERON M.M., FLEC KER R., HILGEN F.J., KOUWENHOVEN T.J., MERLE D., O RSZAG-SPERBER F. & ROUCHY J.M. (2002) - The onset of the Messinian salinity crisis in the Eastern Mediterranean (Pissouri Basin, Cyprus). EPSL, 194, 299-310. K RIJGSMAN W., G ABOARDI S., HILGEN F.J., IACCARINO S.M., DE K AENEL E. & VAN DER LAAN E. (2004) - Revised astrochronology for the Ain el Beida section (Atlantic Morocco): no glacio eustatic control for the onset of the Messinian Salinity Crisis. Stratigraphy, 1, 87 101. ROVERI M., LUGLI S., MANZI V., & SCHREIBER B.C. (2008) The Messinian Sicilian stratigraphy revisited: new insights for the Messinian Salinity Crisis. Terra Nova, 20, 483-488. S IER RO F.J., H ILGEN F.J., K RIJGSM AN W. & F LORES J.A. (2001) - The Abad composite (SE Spain): a Messinian reference section for the Mediterranean and the APTS. Palaeogeogr., Palaeoclim., Palaeoecol., 168, 141 169. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 12-14. © Società Geologica Italiana, Roma 2012 Turbidite facies changes in a base of slope basin setting (Langhe Basin, Lower Cengio Turbidite System, Oligocene, Tertiary Piedmont Basin) RICCARDO BERSEZIO (**), F ABRIZIO FELLETTI (*) & ALBERTO V ALENTE (***) Key words: Cengio turbidite system, Oligocene, slope basins, Langhe Basin, Tertiary Piedmont Basin, turbidites. FOREWORD The Langhe Basin is the major depocenter of the Tertiary Piedmont Basin, an episutural basin set upon a complex of nappes of the Liguria - Piemonte Western Alps. The basin hosts a more than 4000-m-thick Oligo-Miocene succession (GELATI & GNACCOLINI, 1998, 2003). Late Oligocene normal and strike -slip faulting, related to the opening of the Ligure Provençal Gulf (FORCELLA et alii, 1999, with references therein) resulted in the establishment of deep-water conditions in the Langhe basin. This led to deposition of an hemipelagic mudstone wedge with several lenticular bodies of sandstone and conglomerates (Rocchetta Monesiglio Fm.; Early Oligocene - Burdigalian), one of which is the Cengio Turbidite System (CTS; CAZZOLA et alii, 1981; 1985; BERSEZIO et alii, 2005; 200 9). Extension and transpression during the Oligocene delineated the complex and irregular shape of the southwestern marginal slope of the Langhe basin that included several slope and base-of-slope depressions which could accommodate a number of sparse turbidite lenses. As a consequence of the latest Oligocene - Early Burdigalian rifting and drifting of the Ligure - Provençal Gulf the basin widened and deepened, assuming an about E-W elongation during Late Burdigalian - earliest Langhian time (GELATI & GNACCOLINI, 2003). The entire TPB was lately involved by Apennine tectonics, hence it was uplifted and eroded, giving birth to the present day almost homoclinal N-wards dipping structure of its remnants. The lower part of the CTS, the Lower Cengio Turbidite _________________________ (*) Dipartim ento Scienze della Terra, Università di Milano, via Mangiagalli 34, 20133 I-Milano (**) CNR IDPA, via M angiagalli 34, 20133 I-Milano (***) Present Address: Baker Hughes S.p.A. System (LCTS; Membro delle Arenarie di Bertulla, Carta Geologica d'Italia, Foglio 228 - Cairo Montenotte), is the widest of the mentioned group of slope to base of slope clastic lenses that fill local depressions and/or minor depocenters close to, or above the western and eastern marginal slopes of the Langhe Basin. The LCTS is preserved over an area of about 16 km2 at its south-western margin in the Bormida di Millesimo valley. Its architectural features attracted our attention because some evidences of facies segregation due to basin irregularities were evident, suggesting to compare these features to those of some slope basins, as are described for instance in the Gulf of Mexic o among many others (P RATHER, 2003 with references). Hence we carried on a traditional study based on 1:10.000 and 1:5.000 geological and facies mapping for physical stratigraphy reconstruction, bed-by-bed measurement and facies analysis of 20 sedimentological logs, statistical analysis of facies changes and bed thickness distribution. BASIN SETTING OF THE LCTS The western slope of the Langhe Basin in the Cengio Millesimo area consists of a complex wedge of hemipelagic mudstones that envelopes at least 7 lens-shaped, small clastic bodies, that are mostly formed by turbiditic sandstones and only in one case by conglomerates and sandstones. They developed under control of syn-sedimentary tectonics and slope instability, during the Rupelian Chattian deepening of the former coast and shelf depositional setting of the top Molare Fm. (GELATI & G NACCOLINI, 2003). The LCTS (GELATI & GNACCOLINI, 1980; CAZZOLA et alii, 1981; 1985) is the uppermost body within this group. It is up to 35 m thick and is formed by two stacked sandstone-mudstone bodies separated by a hemipelagic m-thick interval. The LCTS has the shape of a concave-up lens, framed by hemipelagic mudstones, up to 40 m thick below its base and by an about 15 m thick interval of mudstones with thin to medium sandstone beds, above its top. The upper part of the CTS (CAZZOLA et alii, 1981; 1985; BERSEZIO et alii, 2005; 2009) lies above these mudstones, pinching out onto the western and TURBIDITE FAC IES CHANGES IN A BASE OF SLOPE BASIN SETTING northern slopes, spreading out over a progressively wider area and sealing the former morphology to which the LCTS deposition was constrained. Geological and facies mapping provided the following features: i) the LCTS is confined to the West and North by slope mudstones, onto which onlap terminations are preserved and exposed; ii) the eastern margin is not preserved in outcrops but its presence is documented by regional termination of all the sedimentary bodies to the east; iii) an intrabasinal mudstone relief, that branches from the regional western slope and shows a present day E-W strike, subdivides the LCTS depositional area into two laterally connected sectors (southern and northern). Both the sandstone bodies of the LCTS lap-out onto this relief; iv) palaeocurrent measurements document that sediments were supplied from the S and SW, hence the sector North of the mudstone relief was located downcurrent with respect to the southern one. Deflection of palaeoflows, towards SE-NW and SW-NE occurs close to the mudstone relief; v) the upper CTS seals the separation between the two LCTS sub-basins, laying directly above the top of the mudstone relief. TURBIDITE FACIES CHANGES IN THE LCTS BASE OF SLOPE SETTING The two sandstone-mudstone bodies of the LCTS are formed by different associations of 10 turbidite l.s. facies: graded to massive pebbly sandstones and sandstones; graded to massive then laminated sandstone-mudstone and mudstone-sandstone couplets; laminated pebbly sandstones, sandstones and sandstone-mudstone couplets; mudstone-sandstone couplets with Bouma sequences; complex sandstone and sandstone-mudstone beds with repetitive parallel and oblique laminated divisions; siltstone-mudstone couplets with Td-e Bouma sequence; massive to laminated mudstones; disturbed and chaotic beds with variable grain-size. All of these facies can be recognized in the lower body of the LCTS, that is formed by stacked minor genetic units with fining upwards or stationary trends separated by mudstone intervals, with a general fining and thinning upwards trend. The upper body is thinner than the lower one and is characterized by the prevalence of the graded to massive and laminated sandstone facies. This vertical evolution can be related either to progradation of the turbidite bodies or to changes of the basin configuration and of the parent flows through time. The analysis of the facies changes from the up-current sector (South) to the down-current area (North), and the statistical analysis of facies distribution provide a key also to this interpretation. We computed univariate statistics to quantify the distribution of bed thicknesses, the sand/mud ratio, the grain-size at the base of the beds, the amalgamated beds percentage, the clay chips abundance, the individual facies abundance, and the distribution of the ratios between specific internal divisions of the beds (massive or graded vs. total divisions, graded vs. massive 13 divisions, laminated vs. total divisions and laminated vs. graded plus massive divisions), comparing the two sub-units and the two sub-areas. A bivariate analysis was computed comparing two distribution has been studied also computing the exceedence bed thickness cumulative plots, for the entire LCTS, the two subunits and the two sub-areas. In synthesis the results of qualitative and statistical facies analysis show that the coarsest grained beds, the highest sand/mud ratio, the highest abundance of graded and massive sandstone divisions, the highest thicknesses of the sandstone beds are all typical of the lower unit into the up -current area, South of the intrabasinal relief. The down-current area shows an opposite statistical distribution, the lower body of LCTS being characterized by abundance of fine-grained turbidites, mudstones, laminated divisions, clay chips and of the complex beds facies. Even if sandier and generally thicker-bedded than the lower one, the upper body shows quite similar trends from S to N. In addition to these features, the percentage of bed amalgamation, the abundance of massive divisions and the sand/mud ratio have been shown to increase in correspondence of the western and northern onlaps as well as all around the intrabasinal mudstone relief, for both the lower and upper bod ies of the LCTS. The cumulative bed thickness distribution plots for both the sandstone divisions and the total thickness of beds appears of the convex upwards type (CARLSON & GROTZINGER, 2001; S INCLAIR & COWIE, 2003). This pattern is quite similar to a log normal distribution that could result from a random combination of several factors, like depositional flow patterns, grain size of clastic input, basin configuration (TALLING, 2001). In any case no aggradational patterns imputable to total ponding of parent flows are shown by the curves. The brief summary of the outstanding features of the LCTS base of slope basin permits to draw some observations: 1) the LCTS sandstone bodies were deposited within two along-current connected depressions at the, or close to, the base of the marginal slope of the Langhe Basin in the Cengio area; 2) the mudstone divide between the two sub areas acted to force facies segregation from the southern (up-current) to the northern (down-current) sectors; 3) during deposition of the lowermost body of the LCTS the effect of this basin configuration was the trapping of most of the sand in the up -current sub-basin and the by-pass, either -grained fraction that was collected by the down-current sub-basin. This p process described by several authors (WINKER, 1996; P RATHER, 2003; T ONIOLO et alii, 2006) for slope mini-basins of different regions and after flume experiments. The same process could explain also the peculiar abundance of the complex beds facies in the down-current northern sub-basin, considering that it 14 BERSEZIO ET ALII could derive from repetitive cycles of re-concentration of a parent flow that suffered a hydraulic jump, was temporarily ponded, released the coarsest fraction in the southern sub-basin then thickened and spilled over the mudstone relief towards the northern sub-basin where the repetitive laminated beds were deposited; 4) the slope physiography determined also the other facies changes that we observed: approaching the marginal slopes, deposition of amalgamated sandstone beds was promoted, together with the increase of the sand/mud ratio, that are the fingerprints of the onlaps of the LCTS. The internal mudstone divide acted also deflecting the palaeoflows, forcing expansion of the spilling over turbidites so promoting deposition of amalgamated sandstone beds along the up-current termination of LCTS within the northern sub-basin, and lastly providing the abundant clay chips that are another peculiar feature of this down-current area. REFERENCES BERSEZIO R., FELLETTI F. & M ICUCCI L. (2005) - Statistical analysis of stratal patterns and facies changes at the terminations of turbiditic sandstone bodies: the Oligocene Cengio Unit (Tertiary Piedmont Basin). Geoacta, 4, 83-104. BERSEZIO R., FELLETTI F., RIVA S.& M ICUCCI L. (2009) - Bed thickness and facies trends of turbiditic sandstone bodies: unravelling the effects of basin confinement, depositional processes and modes of sediment supply. In: B. Kneller & B. Mc Caffrey (Eds.) -Water - Special Publication. 92, 303321. CARLSON, J. & GROTZINGER, J.P. (2001). Submarine fan environment inferred from turbidite thickness distribution. Sedimentology, 48, 1331-1351. CARTA G EOLOGIC A D'I TALIA 1:50.000, Cairo Montenotte http://www.isprambiente.gov.it/, in press. CAZZOLA C., F ONNESU F., MUTTI E., RAM PONE G., SONNINO M. & VIGNA B. (1981) - Geometry and facies of small, faultcontrolled deep-sea fan systems in a transgressive depositional setting (Tertiary Piedmont Basin, Northwestern Italy). In: F. Ricci Lucchi (Ed.) IAS, 2 nd European Regional Meeting Excursion Guidebook, Bologna, 7- 53. CAZZOLA C., M UTTI E. & V IGNA B. (1985) - Cengio Turbidite System, Italy. In: A. Bouma, W.R. Normark and N.E. Barnes (Eds.) - Submarine fans and related turbidite systems. Springer Verlag, 179-183. F ORCELLA F., GELATI R., GNACCOLINI M., ROSSI P.M. & BERSEZIO R. (1999) - Il Bacino Terziario Ligure-Piemontese tra il Monregalese e la valle del T.Lemme: stato delle ricerche e prospettive future. In: Orombelli G. (Ed.) - Studi geografici e geologici in onore di Severino Belloni, Brigatti, Genova, 339-365. G ELATI R. & GNACCOLINI M. (1980) - Significato dei corpi arenacei di conoide sottomarina (Oligocene Miocene -sedimentaria del Bacino Terziario Ligure-Piemontese. Rivista Italiana di Paleontologia e Stratigrafia, 87, 167-186. G ELATI R. & G NACCOLINI M. (1998) - Synsedimentary tectonics and sedimentation inthe Tertiary Piedmont Basin, Northwestern Italy. Rivista Italiana di Paleontologia e Stratigrafia, 98, 425-452. G ELATI R & G NACCOLINI M. (2003) - Genesis and evolution of the Langhe Basin, with emphasis on the Latest Oligocene Earliest Miocene and Serravallian. Atti Ticinesi di Scienze della Terra, 44, 3 18, Pavia. P RATHER B.E. (2003) - Controls on reservoir distribution, architecture and stratigraphic trapping in slope settings. Marine and Petroleum Geology, 20, 529 545. SINCLAIR H.D. & COWIE. P.A. (2003) - Basin floor topography and the scaling of turbidites. Journal of Geology, 111, 277299. T ALLING P. (2001) - On the frequency distribution of turbidite thickness. Sedimentology, 48, 1297-1329. T ONIOLO H., LAM B M. & PARKER G. (2006) Depositional turbidity currents in diapiric minibasins on the continental slope: formulation and theory. Journal of Sedimentary Research, 76, 783-797. W INKER C. D. (1996) - High resolution seismic stratigraphy of a late Pleistocene submarine fan ponded by salt-withdrawal mini-basins on the Gulf of Mexico Continental slope. Proc. 1996 Offshore Technology Conference, paper OTC 8024 (May 6 9, 1996, Houston, Texas), 619-628. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 15-16. © Società Geologica Italiana, Roma 2012 Tectonic control on fluvial aggradation: the Plio-Pleistocene Ambra valley-fill succession (Tuscany, Italy). VALERIA BIANCHI (*), M ASSIM ILIANO GHINASSI (*), MAURO ALDINUCCI (°), JACOPO BOAGA (*), RITA DEIANA (**) Key words: non-marine valley-fill, epeirogenic movements, Northern Appennines, alluvial sedimentation. Even if most of incised-valleys documented in the stratigraphic record have been filled in response to downstream relative sea/lake-level changes, few authors highlight the importance of tectonic and climatic upstream control on valleyfill aggradation (SHANLEY & M CCABE , 1994; H OLBROOK , 2001; BLUM & TORNQVIST, 2000). In addition, the presence of sinsedimentary tectonic warping can cause a modification of fluvial patterns, along with erosion or aggradation, with consequent development of heterogeneous valley-fill architectures. The effects of sin-sedimentary tectonic warping are known in a modern setting (S CHUMM, 1986) or laboratory experiments (O UCHI, 1985), whereas study cases from fossil record are almost missing. The present study focuses on a fluvial, valley-fill succession (Ambra River valley) exposed along the Northern margin of the Chianti Mounts (Northern Apennines). The Plio-Pleistocene deposits of the Ambra River valley are located along the southern margin of the Chianti Mounts (Tuscany, Italy). This ridge separates the Siena and Upper Valdarno Basin, two depressions belonging to the external sector of the Northern Apennines (MARTINI AND S AGRI, 1993). The valley drained toward SW and was cut both on pre-neogene bedrock (northern valley reach) and Pliocene marine to transitional deposits of the Siena Basin (southern valley reach) as consequence of a Middle Pliocene regional forced regression (A LDINUCCI et alii, 2007). This valley fill is an example of a fluvial valley-fill uninfluenced by relative sea-level changes (A LDINUCCI et alii, 2007), due to the considerable elevation and several rocky shoulders between paleo-coastline and the valley. The valley fill consists of two intervals separated by an _________________________ (*) Dipartimento di Geoscienze, Università degli Studi di Padova, via G. Gradenigo, 6, 35131 Padova, Italy ([email protected]). erosive surface. The upper interval is cut in the lower one in the northern and southern part of the study area, whereas they are offset in the central part. The lower interval (40 m thick) is mainly made of gravels and has been the focus of pre vious studies, which emphasized the role of tectonic and climate in controlling accumulation of the alluvial deposits. The upper interval, which is the focus of the present study, is about 35 m thick and deposited across a sin-sedimentary normal fault dipping toward NE (i.e. upstream) which is still affected by intense CO2 emissions (BROGI et alii, 2002). The present study focuses on the upper interval and aims at unraveling the role of a tectonic warping on valley-fill aggradation. The normal fault divides the upper valley-fill interval into two segments: the downvalley and the upvalley portion. Downvalley deposits consist of cross- to plane-parallel stratified gravels with subordinate sands. These deposits are commonly organized into form set (2-4 m thick) of large scale inclined beds, which are interpreted as channel bars developed in a gravel-bed river setting. The correlative upvalley deposits have been mainly analyzed through integration of ERT (Electrical Resistivity Tomography) lines and well -core data. These deposits consist of organic-rich mud containing isolated, erosive-based sand bodies (2-4 m thick), which are interpreted as the active infill of fluvial channels. The heterogeneity of the study vallive deposits is ascribed to a sin-depositional activity of the normal fault, which is also attested by tectonic deformations in the lower valley-fill deposits. Tectonic upwarping caused a decrease in transport capability in the upstream reaches of the paleovalley, manifested by the aggradation of poorly-drained floodplain deposits. In parallel, downstream of the upwarping area, aggradation was promoted by the increase in sediment supply due to erosion of the uplifted area. The fault activity is also thought to be the cause of the local offset typifying the upper and lower valley fill deposits in the central part of the study area. REFERENCES (°)Weatherford Petroleum Consultants AS, 5147 Bergen, Norway. (**) Dipartim ento di Beni Culturali, Università degli Studi di Padova, Palazzo Liviano, Piazza Capitaniato 7, 35139 Padova. A LDINUCCI M., GHINASSI M. AND S ANDRELLI F. (2007) Climatic and tectonic signature in the fluvial infill of a late 16 BIANCHI ET ALII Pliocene valley (Siena Basin, Northern Appennines, Italy). SEPM, Journal of Sedimentary Research, 77, 398-414. BLUM, M.D., TORNQVIST, T.E. (2000) - Fluvial response to climate and sea-level change: a review and look forward. Sedimentology 47, 1 48 (Supplement). BROGI A., COSTANTINI A., LAZZAROTTO A. (2002) - Structural setting of Rapolano Trequanda ridge (Southern Tuscany, Italy). Boll. Soc. Geol. It. Vol. sp. 1, 757-767. HOLBROOK, J.M. (2001) - Origin, genetic interrelationships, and stratigraphy over the continuum of fluvial channel -form bounding surfaces: An illustration from middle Cretaceous strata, southeastern Colorado. Sedimentary Geology, 124, 202 246. M ARTINI AND SAGRI (1993) - Tectono-sedimentary characteristics of Late Miocene-Quaternary extensional basins of the Northern Appennines, Italy. Earth-Science Reviews, 34, 197-233. O UCHI S., (1985) - Response of alluvial rivers to slow active tectonic movement. Geological Society of America Bulletin, 96, 504-515. S CHUMM, S. A. (1986) - Alluvial river response to active tectonics. Active Tectonics, 80 94. S HANLEY K.W. AND M CCABE P.J. (1991) - Predicting facies architecture through sequence stratigraphy an example from the Kaiparowits Plateau, Utah. Geology, 19, 742-745. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 17-18. © Società Geologica Italiana, Roma 2012 Sedimentology and sediment transport processes in a few ephemeral streams of the Horn of Africa PAOLO BILLI (*) Key words: Bedload sheets, distributary system, ephemeral streams, hyperconcentrated flow, plane bed. Ephemeral streams are a main geomorphologic feature in many drylands of the planet. In the last decades these rivers have attracted the attention of geomorphologists and sedimentologists for the flash flood hazards connected with their impulsive nature and for providing a modern equivalent of depositional characteristics and diagnostic tools to interpret old arid river deposits as potential reservoirs in oil and gas fields exploration (N ORTH & TAYLOR, 1996). In this presentation. channel morphology, bedforms, sedimentary structures and sediment transport processes of the distributary system and the main stem of ephemeral streams in the structural basin of Kobo (northern Ethiopia) and the Samoti plain (Eritrean Danakil) are described and analysed through field observations and measurements. The distributary systems of the study ephemeral stream show peculiar characteristics differentiating them from floodouts (TOOTH , 2000) and terminal fans (PARKASH et alii, 1983; KELLY & O LSEN , 1993). The main channel is rectangular in cross-section with almost vertical banks and has an almost straight morphology recalling that of the American arroyos. Channel width expands rapidly just beyond the headwater gorge, is constant along the main stem as far as its most downstream reach (upstream of the distributary system) where widths tends to decrease in response to transmission losses. (BILLI, 2007). Bird-foot type distributary systems consist of five reach units, with different morphological, sedimentological and hydrological characteristics. They are: 1) main feeder channel; 2) primary distributary reach; 3) flow expansion reach; 4) accretionary front; 5) run out channel. In the expansion reach, partly _________________________ (*) Dipartimento Scienze della Terra, Università di Ferrara. Lavoro eseguito n transport in the ephemeral streams of the Kobo contributo finanziario di National Geographic e con il unconfined flow expands and the depositi on of coarse gravel particles takes place forming an accretionary front. This is the only site where a conspicuous accumulation of coarse material is found in the whole fluvial system making that as a distinctive feature of the study distributary systems in comparison with the terminal fans and floodouts described in the literature (PARKASH et alii, 1983; KELLY AND OLSEN, 1993). The lobate distributary systems are less common and morphologically similar to TOOTH S (2005) splays but are fed by upstream runoff and tends to become wider in a downstream direction due to flow expansion caused also by the roughnes provided by shrub vegetation. The streambed of all the sandy study rivers is flat, devoid of any bedform and punctuated by individual particles. Horizontal, planar bedding is by far the prevailing sedimentary structure in the main feeder channel as well as in the distributary reaches. The fast transit of the floods may also account for a depositional aftermath consisting only of horizontal planar laminae. A typical internal bed arrangement, consisting of four main divisions is found and a schematic model is presented (BILLI , 2008). From bottom to top it consists of: 1) the basal reversely graded or massive, fine grained division; 2) the core coarse division; 3) the horizontally laminated sandy and grainy division and 4) the receding flood flow mud and sandy mud drape. This division association model conforms very well to the vertical shear stress distribution postulated by SOHN (1997) for hyperconcentrated flows: the coarse core division coincides with the highest value of shear stress that is predicted to decrease both downward in the basal massive or reverse graded division and upward in the horizontally laminated division, near the top of the collisiona l zone. By this model it is possible to account for the characteristics and origin of horizontal laminae that are the most common sedimentary feature of ephemeral streams. The upward fining of the natural horizontal laminae and their position in the division association model indicates these bedforms are to be interpreted as thin bedload sheets rather than as generated by the migration of low amplitude bed waves as postulated by BEST & BRIDGE (1992). However, since in the upper part of the collision zone, Froude numbers higher than 18 BILLI ET ALII one were measured in the field during floods, an origin for horizontal laminae associated with plane bed to antidune transition, as reported by ALEXANDER et alii (2001), cannot be excluded. The large, individual boulders punctuating the streambed of the study rivers have their roots in the coarse core division and protrude though the overlaying massive sand and fine gravelly sand with rare flow perturbation features such as poorly developed undulated lamination in the boulder vicinity. The flow energy at bankfull discharge was found to be capable of entraining such large particles, but the lack of flow disturbance around them and the erosionless transition of the coarse core division, in which they are rooted, to the lower massive or reversely graded division and to the overlaying horizontally laminated division indicate large and small particles are subjected to conditions of almost equal mobility leading to the conclusion that, though buoyancy forces may be active on boulders, en masse bed material transport is the prevailing bedload process. The theory of GRANT (1997) that high-gradient sand to boulder bed streams achieve an equilibrium adjustment between flow, sediment transport and channel morphology at critical flow through the dissipation of the available energy by the development of bedforms and flow structures seems to apply well to the study ephemeral streams in which energy is dissipated to sustain hyperconcentrated flows and flow resistance is provided by outsize boulders transported on top of gradient of the study rivers, which is remarkably high for sandbed channels (0.014-0.044), can be accounted for. Field measurements of bed and suspended load transport in the Gereb Oda, a sandbed ephemeral stream of the Kobo basin, proved that during floods Froude number was constantly higher than one and supercritical flow conditions occurred also at shallow flow depths (BILLI, 2011). The variation of Froude number with discharge follows a counter-clockwise hysteresis curve. The suspended sediment concentration was very high (as much as 136 gl-1) leading close to hyperconcentrated flow conditions. The grain size of bedlaod is commonly finer than bed material. However, as discharge increases bedload coarsens (its median size becomes larger than that of bed material) as a larger proportion of fine bed particles is conveyed into suspension, contributing to increase the density of the water-sediment mixture. The sandy streambed of Gereb Oda is punctuated by large boulders of about 0.3-0.4 m. They were observed to be entrained and transported at discharge near to or slightly higher than banbkfull and shallow flows as deep as their size. The only bedforms observed on the stream bed of Gereb Oda are leaf-shaped, thin sand sheet. Their thickness is similar to that of bedload sheets as calculated from the bedload samples and by the KARIM AND K ENNEDY (1983) equation. The development of the leaf-shaped bedforms can be associated with the onset of bedload flux and confirms the hypothesis of BILLI (2008) about the role of sheet-like bedload transport for the wide occurrence of horizontally laminated sediment and the lack of small scale bedforms on steep, sand-bed ephemeral streams. The streambed morphology of coarse-grained, boulder bed ephemeral streams is similar to that of braided rivers in more humid environments as it consists of longitudinal and lateral bars and anabranching of shallow channels. The bars have a more or less elongated, rhomboidal shape, but they commonly have sharp margins and do not show any feature associated with depositional processes such as accretionary fronts, foresets and a fine tail. Bars and channel deposits are hardly discernible and have common features such as subtle bedding, lack of erosive surfaces, are very coarse grained, imbricated, massive with poorly defined inner divisions and, subordinately, reversely graded, and sand is present in the pockets among the large particles, on the higher bar top, as patches on the braided channel bed or, in places, as a massive 20-30 cm thick deposits in apparent pools. The overall sedimentological characteristics, in association with some morphological peculiarities such as the lack of well developed riffle and pool sequences, lead to interpret the streambed deposits of the Golina (Kobo basin) and Dandero (Eritrean Danakil) study reach as resulting from the emplacement of 1.0-1.5 m thick cobble to boulder, bedload sheets (WHITING et al., 1988) and the braided channel morphology as originated by their dissection during the receding flood flows. This depositional model well matches the meorphological and sedimentological characteristics and structure of a very coarse-grained, ephemeral streams as it accounts for : a) the lack of the accretionary front, foresets and fine deposits in the downstream side of bars as instead commonly generated by flow separation in perennial braided river bars; b) the lack of riffle and pool sequences, replaced by short and steep glides, originated from the backward reworking of the bedload sheet front, and by apparent pools marked by fine, mainly sandy material; c) bar and channel deposits sharing the same sedimentological structures consisting of horizontal, tabular, subtle stratification of clast-supported and matrix filled about 2-3D84 thick bedload sheets (BILLI, 2011). REFERENCES A LEXANDER, J., BRIDGE , J.S., CHEEL, R.J., & LEC LAIR, S.F. (2001) - Bedforms and associated sedimentary structures formed under supercritical water flows over aggrading sand beds. Sedimentology, 48, 133-152. BEST, J., BRIDGE, J. (1992) - The morphology and dynamics of low amplitude bedwaves upon upper stage plane beds and the preservation of planar laminae. Sedimentology, 39, 737-752. BILLI, P. (2007) - Morphology and sediment dynamics of ephemeral streams terminal reaches in the Kobo basin (northern Welo, Ethiopia). Geomorphology, 85, 98-113. BILLI, P. (2008) - Flash floods, sediment transport and bedforms in the ephemeral streams of Kobo basin, northern Ethiopia. CATENA, 75 (1), 5-17. SEDIMENTOLOGY AND SEDIMENT TRANSPORT PROCESSES IN A FEW EPHEMERAL STREAMS OF THE HORN OF AFRIC A BILLI, P. (2011) - Flash flood sediment transport in a steep sand-bed ephemeral stream. Int. Jour. Sediment, Res., 26(2), 193-209. GRANT, G.E. (1997) - Critical flow constraints flow hydraulic in mobile-bed streams: A new hypothesis. Water Resources Research, 33 (2), 349-358. KARIM M. F., KENNEDY J. F. (1983) - Computer-based predictors for sediment discharge and friction factor of alluvial streams. Proc. Sec. Intl. Symp. on River Sedimentation, Nanjing, China, Paper A18. 19 P ARKASH, B., AWASTHI, A.K. & G OHAIN, K. (1983) Lithofacies of the Markanda terminal fan, Kurukshetra district, Haryana, India. In: J.D. Collinson and J. Lewin, (Eds.) - Modern and Ancient Fluvial Systems. Spec. Publs. Int. Ass. Sediment., 6, 337-344. S OHN, Y.K. (1997) - On traction-carpet sedimentation. Jour. Sedim. Res., 67 (3), 502-509. T OOTH, S. (2000) - Process, form and change in dryland rivers: a review of recent research. Earth-Sci. Rev., 51, 67-107. KELLY , S.B., O LSEN, H. (1993) - Terminal fans a review with reference to Devonian examples. Sediment. Geology, 85, 339-374. T OOTH, S. (2005) - Splay formation along the lower reaches of ephemeral rivers on the Northern Plains of arid Central Australia. Jour. Sedim. Research, 75,636-649. NORTH, CP., TAYLOR , KS. (1996) - Ephemeral-fluvial deposits: Integrated outcrop and simulation studies reveal complexity. AAPG Bulletin, 80 (6), 811-830. W HITING, P.J., DIETRICH , W.E., LEOPOLD , L.B., DRAKE & T.G, S HREVE, R.L. (1988) - Bedload sheets in heterogeneous sediment . Geology, 16, 105-108. Rend. Online Soc. Geol. It., Vol. 20 (2012), p. 20. © Società Geologica Italiana, Roma 2012 Depositional processes of the carbonate-siliciclastic rhodolith rich deposits in the Saint Florant Basin (Burdigalian Formation, Corsica) M ARCO BRANDANO (*), LAURA TOM ASSETTI (*) & S ARA RONCA (*) Key words: Rhodolith, Miocene, carbonate-siliciclastic mixing. Corsica, lithofacies, Many sedimentary processes may lead to the formation of carbonate-siliciclastic sediments in shallow shelf environments. The Miocene Saint Florant Basin (Corsica), and in particular rhe Monte S. Angelo Formation, offers the possibility to analyses coarse mixed sediments produced by erosion of rocky coast, fluvial input and shallow water carbonate production. The Miocene succession of Saint Florent unconformably overlies the Nebbio tectonic unit and it consists of 4 stratigraphic units. The first unit is knowns as Fium Albino Formation, and it is up to 60 m thick. The unit crops out locally in erosional depressions cut into the underlying Nebbio nappe and consists of continental deposits pebble conglomerate and very coarse- to coarse-grained sandstone. This unit is overlaid by the Torra Formation that is 50m thick and made up of massive medium- to coarse-grain ned sandstone and pebble conglomerate with abundant skeletal remain (mollusk, echinoids and bryozoans). The up to 250m in thick, conformably overlies the Torra Formation and is overlain by the Farinole Formation. _________________________ (*) Dipartimento di Scienze della Terra, Sapienza Università di Roma. Piazzale Aldo M oro, 5 00185, Roma. E-mail: [email protected] bioclastic detritus with varying amounts of siliciclastic detritus. The skeletal assemblages of this unit is dominated by bivalves, bryozoans and foraminifera corallinacean red algae that form rhodoliths. The Farinole Formation is about 80 m thick and is dominated by pelagic components. Three main rhodolith rich facies have bee n recognized in the Monte S. Angeolo Formatiion The F1 is a rhodolith rudstone with lithoclasts organized in 2-3 m thick beds, dominated by laminar rhodoliths with elliptical shape. The F2 is a chanellized conglomerate with rhodoliths. In this lithofacies rhodoliths are ellipsoidal to subsherical in shape and show a prevalent laminar structure. The F3 is a rhodolith rudstone to floatstone with laminar, branching and columnar rhodoliths characterized ellipsoidal to subspherical shape. The nucleus of rhodoliths in all three facies is made up of lithoclasts or bryozoan colonies. The red algal assemblages is dominated by the oligophotic melobesioids and sporolithacens. Euphotic genera are only accessory. The rhodolith facies alternated with cross bedded calcarenites that were interpreted as large subacqueous dunes. The rhodolith rich deposits represent the accumulation on the distal sector of an infra-littoral prism. Rend. Online Soc. Geol. It., Vol. 20 (2012), p. 21. © Società Geologica Italiana, Roma 2012 Digital 3D modelling of submarine dune field by laser scanning technique (Bolognano Formation, Majella) M ARCO BRANDANO (*,$), G IORGIO G UARINI (**), RENZO PETRUNGARO (**), LUC A VELOCCI (**), DEM ETRIO MELONI (*), G AIA MASCARO (*) & LORENZO LIPPARINI (°) Key words: Laser scan, submarine dune, Oligocene, Majella, carbonate ramp. To study a sedimentary structures the prerequisite is the availability of 3D outcrop. Sedimentary structures reproductions may be based on drawings, supplied by photographs. However drawings and photographs present and cause different problems, for examples the accuracy of drawings as well as photographs are dependent on the direction and intensity of light. Laser sc giving an accurate and precise three dimensional representation of a considered target. Terrestrial laser scanner has been used in order to obtain a model of the trampled area taking in account that terrestrial laser scanner allows a highly detailed geometric characterization also on target situated at distances up to tens of meters. The acquisition has been performed with Riegl VZ 400 laser scanner from a distance of approximately 90 m, setting a mean point to point spacing of 0,005 m . The 3D digital modelling was performed on the sedimentary structures of the Chattian Lepidocyclina limestone of Majella (Formazione di Bolognano) along a 200 m long transect. The depositional profile of the Lepidocyclina Limestone is consistent with a high energy carbonate ramp, where most of the sediments appear to be parautochthonous in the middle ramp environment and autochthonous dominated in the outer ramp environment. the sediment as transported along the ramp by downslope currents that were able to form submarine dunes field. In this work it will be presented the result of the 3D modelling of the sedimentary structures of the sigmoidal cross-bedded grainstone that represent the record of submarine dune migration in the middle ramp environment. . _________________________ (*) Dipartimento di Scienze della Terra, La Sapienza, Università di Roma (**) Pet ra Geo Scan s .n.c., www.petrageoscan.it (°) Medoilgas Italia s pa ($) IGAG-CNR Area della Ricerca di Rom a 1 Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 22-23. © Società Geologica Italiana, Roma 2012 Lacustrine organic facies and pollen analysis from the Trasimeno lake (Central Italy): a preliminary note N ICOLETTA BURATTI (*), M ASSIM ILIANO R. BARCHI (*), ADELE BERTINI A. (°), S IMONETTA CIRILLI (*), LUC A GASPERINI (^), MARTA M ARCHEGIANO (*), & FAUSTO PAZZAGLIA (*) Key words: paleoclimate, Pleistocene, Trasimeno. palynofacies, pollen analysis, In the frame of a multidisciplinary project, aimed to reconstruct the palaeoenvironmental and paleoclimatic evolution of Trasimeno lake during the Pleistocene, one core (175 m long) was drilled along the south-eastern coast of the lake, by the Regione Umbria Geological Survey. In this first approach the aim of this study was to reconstruct vegetation changes within the catchment area, from fossil pollen assemblages, and to identify the relative contributions of the different sources of organic debris delivered to the lacustrine sediments. Sediments are the product of lake life and can be regarded as a bank of information about environmental changes occurring in both the water body and in the catchment area (de Vicente et al., 2006). The primary source of organic matter to lake sediments is mainly from the particulate detritus of plants, degraded to various degrees, and deriving from both autochthonous and allochthonous sources (Meyers & Lallier-Vergès, 1999). As the plant life in and around lakes change, the composition and amount of organic matter delivered to lake sediments changes. Optical examination of palynofacies, coupled with a preliminary pollen analysis was performed. Although a careful interpretation of the results will require a comparison with sedimentology, complete pollen record and a well-constrained sediment chronology, some reliable conclusions can be achieved. The Trasimeno lake (Umbria, Central Italy) is a mesoeutrophic, shallow (<6 m deep) lake with a large extension (~120 km2), characterized by a water balance strongly affected by the _________________________ (*)(*) Dipartimento di Scienze della Terra, Università di Perugia (°) Dipartimento di Scienze della Terra, Università di Firenze (^) Istitut o di Scienze Marine Bologna Consiglio Nazionale delle Ricerche, Geologico e Sismico della Regione Umbria e il CNR-ISMAR di Bologna. pluviometric regime (Dragoni, 2004). As is common in shallowwater ecosystems, climate change plays a fundamental role in their evolution and functioning. Today the hydrological, thermal and hydrochemical regime of Trasimeno lake are deeply influenced by climatic variations (Ludovisi & Gaino, 2010). Most of the organic production originates from t he macrophyte community, which mainly consists of submerged plants, distributed from the shore to the center of the lake and subordinately of semi-emerged plants, growing around the lake. The lake is located between two extensional basins, the Valdichiana to the west and the Valtiberina to the east. Its onset probably started in the Early Pleistocene, as evolution of a lateral branch of the Valdichiana basin. Seismic reflection data (Gasperini et alii, 2010) show below the lake floor almost 600 m of sediments overlying a deeply eroded Miocene bedrock. The geological data of the surrounding area (Barchi & Marroni, 2007; Aruta et alii, 2004) and the litology of the core suggest this evolution for the Trasimeno area: a) Early Piocene deposition of marine clays and sands in the Valdichiana basin; b) Pleistocene deposition of (fluvio?)-lacustrine clays, sandy clays in the Trasimeno basin. Quantitative analysis of organic constituents was carried out in Trasimeno sediments, within a palynologically productive interval, comprised between 15 m and 30 m. Palynofacies types were identified on the basis of visual evaluation of the relative abundances of organic constituents and then integrated by cluster analysis, in order to test group consistency. Three main palynofacies assemblages (A, B, C) and three sub -assemblages (A1, B1, C1) were recognized. Palynofacies A was dominated by poorly preserved woody remains, partially degraded in aerobic conditions (soil) before deposition, associated with relatively abundant translucent, well preserved woody remains, still maintaining tracheidal structure and cuticles. The rest of the palynofacies was composed by highly diversified pollen assemblages, gelified debris, accessory fungal remains, and framboidal pyrite. Much of the organic matter characteristic of palynofacies A was represented by fluvially or wind transported allochthonous remains. The relative abundance and good preservation of this material, which comprises numerous LACUSTRINE ORGANIC FACIES AND POLLEN ANALYSIS FROM THE TRASIM ENO LAKE centimeter-size plant remains, imply short transport distances. The organic matter would thus originate from higher plants that grew within the basin or in its immediate vicinity, as testified by the great sporomorphs diversity in palynological residues. Palynofacies B has a transitional nature between A and C. It was characterized by an analogous contribution from both allochthonous and authocthnous organic debris. As in palynofacies A, very low amount of amorphous organic matter revealed a good oxygenation of the depositional environment. Palynofacies C was almost completely composed of gelified debris, relatively abundant framboidal pyrite and amorphous organic matter. This palynofacies was dominated by an authocthnous organic fraction, produced in the lake itself. Gelified material could represent the result of submerged and semi-emerged macrophyte degradation within the water column (Siffedine et alii, 1995; Martín-Closas et alii, 2005). Low percentages of the allochthonous fraction could suggest a reduced plant cover and /or a very low land supply. The occurrence of dark brown, amorphous organic flakes and framboidal pyrite suggested reducing conditions in the depositional environment. Data obtained from the petrographic study of sedimentary organic matter will be integrated by organic geochemistry analysis (TOC, 13C, 15N, C/N), providing additional valuable information on organic matter sources and paleoproductivity. Pollen analysis revealed a vegetation landscape considerably different from the present one, for the presence of a number of taxa today extinct in Europe (e.g. Carya, Pterocarya, Tsuga), living in North America and Asia (Bertini, 2003, 2010; Magri, 2010). An interglacial cycle marked by the presence of a mixed -oak forest (mainly deciduous Quercus, Ulmus/Zelkova, Carpinus, Corylus and Fagus) followed by Juglandaceae (Carya, Pterocarya and Juglans) and then by conifers (P. diploxylontype, Cedrus, Abies, Picea, Tsuga, and Cupressaceae) has been detected in the central portion of the succession. At its base the end of a glacial is testified by the pollen of grasses and other herbs. At its top an interglacial/glacial transition as well as the start of a new glacial phase are expressed by the increase respectively of altitudinal coniferous taxa and Artemisia, Poaceae and Chenopodiaceae typical taxa of steppe phases. Such pollen record is significant to discuss the stratigraphical position of this part of the Trasimeno core (from 19 m to 21,5 m) in absence of chronological constrains. In fact the peculiar floral composition as well as the evaluation of the relative percentages of each pollen taxon (e.g. presence of Carya, Pterocarya, Tsuga and Cedrus; absence of Taxodium type, Liquidambar) permit to attempt a correlation with the Glacial/interglacial cycles within the Early/ Middle Pleistocene transition. Pollen analyses though still in progress seem to represent a valuable starting point for biostratigraphic correlations with other Italian palynological records (starting from the geographically closer ones) and for adding new information about the distributi Central Italy during the Early-Middle Pleistocene. 23 REFERENCES A RUTA G., BOR GIA A., BRUNI P., CECCHI G., CIPRIANI N., TREDICI Y. (2004) - Pliocene and Pleistocene unconformity bounded stratigraphic units (UBSU) in Val di Chiana. In Morini D. and Bruni P. (editors): The "Regione Toscana" Project of Geological Mapping, case histories and data acquisition, Regione Toscana, 133-136. BARCHI M.R. & MARRONI M. (2007) - Note illustrative del Foglio 310, Passignano sul Trasimeno. Progetto CARG (CARtografia Geologica), ISPRA. BERTINI A. (2010) - Pliocene to Pleistocene palynoflora and vegetation in Italy: State of the art. Quaternary International, 225, 5-24. BERTINI A. (2003) - Early to Middle Pleistocene changes of the Italian flora and vegetation in the light of a chronostratigraphic framework. Il Quaternario, 16, (1bis), 19-36. D E V ICENTE I., AMORES V. & CRUZ-PIZARRO L. (2006) Instability of shallow lakes: A matter of the complexity of factors involved in sediment and water interaction? Limnetica, 25, (1-2), 253-270. D RAGONI W. (2004) - Il Lago Trasimeno e le Variazioni Climatiche Difesa Idraulica, pp. 60, Perugia. G ASPERINI L., BARCHI M.R., BELLUCCI L.G., BORTOLUZZI G., LIGI M. & PAUSELLI C. (2010). Tectonostratigraphy of Lake Trasimeno (Italy) and the geological evolution of the Northern Apennines. Tectonophysics, 492, 164-174. LUDOVISI A. & GAINO E. (2010) - Meteorological and water quality changes in Lake Trasimeno (Umbria, Italy) during the last fifty years. J. Limnol., 69, (1), 174-188. M AGRI D. (2010) - Persistence of tree taxa in Europe and Quaternary climate changes. Quaternary International 219, 145-151. M ARTÍN -CLOSAS C., PERM ANYER A. & VILA M.J. (2005) Palynofacies distribution in a lacustrine basin. Geobios, 38, 197-210. M EYERS P.A. & LALLIER-VERGÈS E. (1999) - Lacustrine sedimentary organic matter records of Late Quaternary paleoclimates. Journal of Paleolimnology, 21, 345-372. S IFEDDINE A., LAGGOUN -D EFAR GE F., LALLIER-VERGES E., DISNAR J.R., W ILLIAMSON D., G ASSE F. & GIBER T E. (1995) La sédimentation organique lacustre en zone tropicale sud au cours des 36 000 dernières années (Lac Tritrivakely, Madagascar). Comptes Rendus de l'Académie des Sciences Paris, Series IIa, 321, 385-391. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 24-27, 2 figs. © Società Geologica Italiana, Roma 2012 Depositional systems of the Eastern Southern Alps (NE Italy, W Slovenia) during the late Carnian M ARCELLO CAGGIATI (*), ANNA BREDA (**), P IER O G IANOLLA (*), M ANUEL RIGO (**) & G UIDO ROGHI (°) Key words: Upper Triassic, Southern Alps, carbonate platforms, paleoenvironments, paleogeography. INTRODUCTION During the early Late Triassic, the Eastern Southern Alps (SA) were characterized by widespread flattening of the paleotopography. Mostly during the so called Carnian Pluvial Event (CPE, late Julian) a marked pulse of siliciclastics or mixed sediments filled the inherited basins and an important shift of the coastline toward N and NE occurred. As a consequence of the flattening, a general low gradient topography is documented in all the SA from latemost Julian. Typically depositional systems span from mixed carbonate-siliciclastic deposits representing ramp/lagoon environments in the late Julian-early Tuvalian (e.g. Heiligkreuz and Travenanzes Fms.) to mainly carbonate peritidal facies of the Dolomia Principale (DP) close to the Carnian/Norian boundary. The main goal of this contribution is to analyze in detail the SA palaeo-envinronmental evolution in order to better understand the start-up of the Dolomia Principale, the widest epicontinental carbonate platform of western Tethys, which lasted for over 20 million years. The paleogeographic reconstruction of the eastern sector of the SA has been possible because of the increase, in the last years, of the stratigraphic resolution: physical stratigraphy (mapping geology, lithostratigraphy, sequence stratigraphy, facies analysis) and biostratigraphy (palinomorphs, conodonts and ammonoids). Nevertheless, it is complicated by the complex structural arrangement of the area, due to the polyphasic Alpine tectonics (Fig. 1). _________________________ (*) Dipartimento di Scienze della Terra, Università di Studi di Ferrara, Via Saragat 1, 44122 Ferrara, Italy. (**) Dipartimento di Geoscienze, Università degli Studi di Padova, Via G. Gradenigo 6 , 35131 Padova, Italy. (°) Istituto di Geoscienze e Georis orse, CNR. Via G. Gradenigo 6, 35131 Padova, Italy. PALEOENVIRONMENT RECONSTRUCTION Lower Tuvalian In the Recoaro and Trento areas, as well as in the Venetian Alps, south to the Valsugana Fault System (VFS) and in the western Dolomites, an erosional gap on top of Ladinian and lower Carnian units (e.g. Cassian Dolomite) does not allow to define lower Tuvalian sedimentation patterns. The same gap is also documented by wells from successions currently under the Venetian Plain and Adriatic Sea. First evidences of lower Tuvalian lithofacies can be observed in the southern Belluno Dolomites, south of the VFS (S IORPAES & G IANOLLA , 1991; GIANOLLA et alii, 1998). Mixed terrigenouscarbonate facies from the top of Heiligkreuz Fm. (HKS), can be referred to a carbonate-lagoon depositional environment, close to a terrigenous coastline and hence characterized by frequent coarse-grained input. Significant and abrupt facies variation occurred northwards, in the Central Dolomites, marked by the presence of an oolitic shoal (ca W-E oriented) characterized by oolitic-bioclastic and hybrid calcarenites (HKS, Lagazuoi mb., NER I et alii, 2007; BREDA et alii, 2009). Locally, tidal inlets dissecting the barrier are present, infilled by high energy tidal deposits with herringbone cross-stratification (HKS, Falzarego mb., NERI et alii, 2007; BREDA et alii, 2009). Moving to the East, a similar framework is observed in eastern Cadore and western Carnia regions, where a lagoon environment is denoted by marly limestones and marls (nearby of Passo Mauria, Ampezzo and Degano valley; cf. V ENTURINI et alii, 2006) switching laterally to more carbonate terms, like well stratified dolostones (eastern Marmarole massif; cf. CASATI et alii, 1982; P ICOTTI & PROSSER , 1987), or gradually passing to a thick dolomitized body, referable to a shallow carbon ate ramp setting, and lithostratigraphically correlable to the top of HKS. The former unit is a lithomarker traceable for several kilometers CARULLI et alii, 1987; Portella dolomite in D E ZANCHE et alii, 2000), and testifies the almost complete DEPOSITIONAL SYSTEMS OF THE EASTERN SOUTHERN ALPS disappearing of the terrigenous component in the easternmost SA. Northeastwards, a rapid transition from the southern carbonate ramps and oolitic shoals to carbonate peritidal cycles representing a tidal flat environment, is locally documented both in Northeastern Dolomites (PRETO & HINNOV, 2003) and in Slovenian Julian Alps (uppermost Razor limestone in Ramovs, 1987). The top of this interval, all over in the SA, is characterized by karst surfaces, paleosols and other diagenetic features related to a long lasting emersion due to a pronounced sea level fall, well developed on inner ramp and peritidal facies (NER I et alii, 2007). Upper Tuvalian The first Carnian units from cores in the Venetian Plain and Adriatic Sea are characterized by the alternation of dolostones, anhydrites and fine red siliciclastics, referable to mud flats and/or sabkha environments. However, the paleogeographic framework of the upper Carnian in this area should be more complex: while sedimentation is recorded north of Vicenza (Villaverla well), near Udine (Cargnacco well) and in the offshore (Amanda 1 bis well), the area in between is still characterized by non deposition. A similar situation is also present in the Recoaro area, with exposed sectors facing terrigenous-evaporitic lagoons to the Fig. 1 25 south (D E ZANCHE & MIETTO , 1975). Shallow lagoon to peritidal carbonate facies with less terrigenous input have been documented also in the area west of Trento (Gola and Vela Valleys). Moving to the east, in the Western Dolomites and in the region south of the VFS, the upper Tuvalian units are not exposed, but hints can be obtained in the Passo Duran and Cibiana area, where an alluvial plain environment can be deduced by the presence of meandering-channel conglomerates and fine-grained red beds of Travenanzes Fm. (BREDA & PRETO, 2011). This fluvial system passes northwards (Cortina area) to a distal alluvial plain, where unconfined ephemeral streams splay onto the coastal mudflat. The TVZ is not cropping out in the most of the Western Dolomites, but where it is present (e.g. Sciliar massif or Mendola area), it is characterized by very thin alluvial plain successions. Alluvial facies pass northeastwards to flood basin mudstones and coastal sabkha evaporites. The two environments are irregularly distributed along a WNW-ESE belt and well correlate with upper Carnian evaporites of upper Tagliamento Valley (Passo Mauria), laterally passing to multicolored mudstones (Forni di Sotto). A transition from tidal flats to shallow lagoons is testified in northeastern Dolomites by alternations of aphanitic dolostones and multicolored mudstones. A similar shifting to shallow, coastal, low-energy environments is documented also in eastern Simplified structural scheme of the Southern Alps, with main localities and position of profiles shown in Fig. 2. Modified after Castellarin et alii (2006). 26 CAGGIATI ET ALII Carnia by the northern transition from gypsum evaporites (CARULLI et alii, 1998) to shallow water dolostones, limestones and dark shale (lower part of Monticello Fm.) that directly overlie the top of the previous massive dolomitized unit, lower Tuvalian in age. While in Dolomites and in Carnia evidences of upper Tuvalian deposition are mainly continental to marginal marine, in the S. Stefano di Cadore area marls and calciturbidites identifying a basinal setting (belonging to ammonoid subullatus and anatropites subzones) is documented (G EYER, 1900), testifying the presence of a shelf break and a carbonate margin. In the Julian Alps the shallow lagoon environment passes northwards to a margin-slope-basin system. In particular, in the Cave del Predil area, back-reef facies are interfingered with a massive serpulid/microbial bioconstructed margin referable to the Dolomia Principale (GIANOLLA et alii, 2003). Breccia bodies at the toe of slope are interfingered with marly basinal limestones of Carnizza Fm., documented in the whole Slovenian Julian Alps (Martuljek group, CELARC & K OLAR-J , 2008). DISCUSSION Despite the structural complexity affecting the Southern Alps, regional patterns of the paleoenvironmental evolution in the early l ate Triassic are recognizable and some interesting topics can be debated. Starting from the depicted paleoenvironmental reconstruction, a simplified paleogeographic scheme can be obtained. Despite few data are available about the shortening due to the alpine major fault systems, we can here consider the main direction of faulting of different thrusts. In particular, region north of the VFS should be restored several kilometers to the north-northwest, whereas Carnia and Julian Alps must be expanded in a S-N direction, with increasing shifting amount moving to the east (CASTELLARIN et alii, 2006; VENTURINI et alii., 2006). The resulting paleogeographic scheme shows a main framework structured in NW-SE oriented environmental belts, with a general transition from southwestern facies with most continental affinity, to northeastern facies related to more open carbonate environments (Fig. 2). Furthermore, other local changes can be related to sin-sedimentary tectonics, sea level oscillations and climate, and to the presence/absence of southern deltaic bodies. After the complete flattening of the topography during the latemost Julian, in the lower Tuvalian it can be noted that deeper environments were concentrated in the central b elt. These more subsiding areas were probably related with the presence of Fig. 2 SW- NE s chematic sections showing lateral paleoenvironmental changes in the lower (A) and upper (B) Tuvalian. Symbols in legend: a) exposed land; b) alluvial plain; c) flood basin; d) mud flat and evaporitic; e) mainly terrigenous lagoon/ramp; f) mainly carbonate lagoon/ramp; g) peritidal h) slope i) basin. Purple dotted lines indicate schematic sin-sedimentary faults. Vertical scale is exaggerated. DEPOSITIONAL SYSTEMS OF THE EASTERN SOUTHERN ALPS 27 underlying thick basinal successions. Differently, in the upper Tuvalian, especially in the Dolomites, the central area constituted a connection between a southern emerged belt and a northern shallow lagoon region (Fig. 2). An analogue pattern seems to be configured in Julian Alps and Carnia, even if the central area records again high subsidence patterns (thick succession of evaporites and shallow marine sediments). Due to the same northeasternwards environment transition observed in Julian Alps and Dolomites, it can be suggested that the margin-to-basin complex shad to be somewhere present also northward of the shallow lagoon facies of northern Dolomites. The S. Stefano di Cadore basinal succession could be interpreted as belonging to this northern domain, later displaced to the south by the Alpine orogeny which shortening should have been particularly strong in the Cadore area (see the convergence of thrusts of the VFS in Fig. 1). The DP margin system was a sort of energy barrier, which protected the inner platform area from the sudden marine ingression, characterizing the transgression (TST) of Car 4 of GIANOLLA et alii (1998). Basinwards, in the northeastern part of the Southern Alps, a general drowning of peritidal sediments occurred leading to the deposition of a basinal succession (LIEBERMAN, 1978; SCHLAF , 1996). CELARC B. & KOLAR-J T. (2008) The CarnianNorian basin- platform system of the Martuljek Mountain Group (Julian Alps, Slovenia): progradation of the Dachstein carbonate platform. Geologica Carpathica 59 (3), 211-224. REFERENCES LIEBERMAN H.M. (1978) Carnitza Formation. Mitt. Ges. Geol. Bergbaustud. Österr. 25, 35-60. BREDA A. & PRETO N. (2011) - Anatomy of an Upper Triassic continental to marginal-marine system: the mixed siliciclastic carbonate Travenanzes Formation (Dolomites, Northern Italy). Sedimentology, 58, 1613-1647. BREDA A., PRETO N., ROGHI G., FURIN S. et al. (2009) The Carnian Pluvial Event in the Tofane area (Cortina ). Geo.Alp, 6, 80-115. CARULLI G.B., FANTONI R., M ASETTI D., PONTON M., et al. (1998) Analisi di facies e proposta di revisione stratigrafica del Triassico Superiore del Sudalpino orientale. Atti Tic. Di Sc. Della Terra, 7 (serie sp.), 159-183. CARULLI G.B., FRIZZO P., LONGO SALVADOR G., SEM ENZA E., et al. (1987) La geologia della zona tra il T. Chiarzò e il F. Fella (Alpi Carniche). Giornale di Geologia, 49 (1), 1-32. CASATI P., JADOUL F., NICORA A., MARINELLI M., et al.(1982) Geologia della Valle dell Ansiei e dei gruppi M. Popera- Tre Cime di Lavaredo. Riv. It. Pal. Strat., 87, 371-498. CASTELLARIN A., N ICOLICH R., FANTONI R., CANTELLI L., SELLA M. & SELLI L. (2006) Structure of the lithosphere beneath the Eastern Alps (southern sector of the TRANSALP transect). Tectonophysics, 414, 259 282. D E ZANCHE V., GIANOLLA P. & ROGHI G. (2000) Carnian stratigraphy in the Raibl/Cave del Predil area (Julian Alps, Italy). Ecl. Geol. Helv., 93, 331-347. D E ZANCHE V. & MIETTO , P. (1975) Il Carnico nelle Prealpi Vicentine. Bol. Soc. Geol. It., 94, 1573-1593. G EYER G. (1900) Ueber die Verbreitung und stratigraphische Stellung der schwarzen Tropites-Kalke bei Sau Stefano in Cadore. Verhandlungen der k.k. Geologischen Reichsanstalt, 15/16, 355-370. G IANOLLA P., D E ZANCHE V. & M IETTO P. (1998) Triassic Sequence Stratigraphy in the Southern Alps (Northern Italy): definition of sequences and basin evolution. In P.C. de Gracianscky, J. Hardenbol, T. Jacquin, P.R. Vail, and D. Ulmer-Scholle (Eds) Mesozoic-Cenozoic Sequence Stratigraphy of European Basins, SEPM Sp. Pub., 60, 723751. G IANOLLA P., DE ZANCHE V. & ROGHI G. (2003) An Upper Tuvalian (Triassic) Platform-Basin System in the Julian Alps: the Start-up of the Dolomia Principale (Southern Alps, Italy). Facies, 49, 135-150. N ER I C., G IANOLLA P., FUR LANIS S., CAPUTO R., BOSELLINI A. et al. (2007) Note Illustrativscala 1:50000, Foglio 29 Cortina d Ampezzo. A.P.A.T., , 1-202. P ICOTTI V. & PROSSER G. (1987) - Studio geologico dell'area compresa tra Lozzo di Cadore e il gruppo delle Marmarole (Dolomiti, Alpi Meridionali). Giorn. Geol., 49 (1), 33-50. P RETO N. & HINNOV L.A. (2003) Unraveling the origin of carbonate platform cyclothems in the Upper Triassic Dürrenstein Formation (Dolomites, Italy). J. Of Sed. Res., 73 (5), 774-789. R A. (1987) Ausbildung der Karn-Stufe im östlichen Teil der nördlichen Julischen Alpen. Geologija, 30, 67-82. S CHLAF J. (1996) - Ein obertriadisches Intraplattformbecken aus den Südkarawanken (Kärnten, Österreich). Mitt. Ges. Geol. Berg. Österr., 39/40, 1-14. S IORPAES C. & GIANOLLA P. (1991) - Stratigrafia triassica del versante settentrionale delle cime di San Sebastiano (Dolomiti orientali). Rendiconti S.G.I., 114 (1), 155-156. V ENTURINI C. (2006) - Note illustrative della Carta Geologica d'Italia alla scala 1:50.000. Foglio 031 Ampezzo. APAT, 1232. Rend. Online Soc. Geol. It., Vol. 20 (2012), p. 28. © Società Geologica Italiana, Roma 2012 Identifying plays and prospects in carbonates ANDREA COZZI (*) Key words: Ammonoid fauna, ceratitoid, Recoaro area, German basin, Alpine basin,. ABSTRACT Carbonate rocks host ~60% of the world hydrocarbon discovered reserves and still hold 3,000 billion barrels of oil and 3,000 trillion cubic feet of gas in place. Carbonate reservoirs are affected in their rock properties by syn- and post-depositional mechanical (tectonics) and chemical (diagenesis) processes. The occurrence and distribution through the rock record of _________________________ (*) IEOC Egypt Branch, No. 1, Rd. 204 - Degla Square, Maadi, Cairo Egypt P.O. Box 52 - New Maadi 11742, email: [email protected] Hydrocarbon-bearing Carbonate reservoirs varies according to their original depositional setting (ramps, shelves, buildups) or to post-depositional tectonic settings. Eni has been producing from Carbonate rocks for more than 50 years around the globe, some of these fields stand out as Giant and Super Giant (e.g., South Pars, Khashagan, Zubair, Perla). Carbonate reservoirs and plays are highly complex and require a thorough understanding of the interaction between depositional, mechanical and c hemical controlling factors. The continuous advances in cutting-edge technology applications will have a vital role to continue exploring, finding and exploiting Hydrocarbon accumulations hosted by Carbonate rocks. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 29-31. © Società Geologica Italiana, Roma 2012 Modeling tidal network dynamics in response to changes in the environmental forcings ANDREA LPAOS (*), LUC A CARNIELLO (**), LUANA S TEFANON (**) & ANDREA RINALDO (***) Key words: Tidal landscape, Tidal networks, Drainage Density, Tidal Prism INTRODUCTION Channel networks are ubiquitous morphological features of the tidal landscape that control to a large extent water, sediment, and nutrient fluxes within tidal systems. Despite their importance in landscape evolution, tidal networks have received less attention when compared to their fluvial counterparts (e.g., HOWARD et alii, 1994) particularly in terms of the chief processes governing their initiation and evolution, and their response to changes in the external forcings (e.g., RINALDO et alii, 1995). A classical and fascinating question in geomorphology is whether the morphological features of a given landscape retain signatures of past climates or are in equilibrium with current ones (e.g., LEOPOLD , 1964). In particular, within tidal landscapes, improving our understanding of network dynamics in response to variations in Relative Mean Sea Level (RMSL) is theoretically and practically relevant for the key role exerted by tidal networks on the morphodynamic evolution of tidal systems (e.g. FAGHERAZZI & OVEREEM , 2007). Recently, several mathematical models have been developed to describe the morphogenesis and development of tidal networks (see e.g. FAGHERAZZI et alii, 2012 for a detailed review). Some of these models have also addressed tidal network response to RMSL changes (D'ALPAOS et alii, 2007; K IRWAN & M URRAY, 2007), However, the effects of cyclic variations in RMSL on the characteristics and structure of tidal networks remain poorly understood, and the possibility of detecting signatures of past _________________________ (*) Dipartimento di Geoscienze, Università di Padova. (**) Dipartimento ICEA, Università di Padova. (***)Laboratory of Ecohydrology, ECHO/IEE/ENAC, Ècole Polytechnique Fèdèrale Lausanne, Lausanne, Switzerland. conditions imprinted on the landscape justifies analyses of the type proposed herein. Here we present the results obtained from the analysis of tidal network response to changes in the landscape-forming tidal prism (i.e., the total volume of water exchanged through the inlet between low water slack and the following high water slack), triggered by RMSL variations (S TEFANON et alii, 2012), on the basis of laboratory experiments over timescales which would preclude network monitoring through field observations. The use of a controlled laboratory environment (see Fig. 1 and STEFANON et alii, 2010, for a detailed description of the experimental apparatus) allows us to isolate the effects of RMSL changes on landscape evolution, among those of the other physical and biological processes which shape the tidal landscape. The experimental results show that changes in RMSL immediately affect the tidal prism, and the tid al prism rapidly and strongly influences channel cross-sectional areas, network structure and its drainage density as a measure of network efficiency in draining the landscape. We have in fact observed that a decrease in the tidal prism leads to network retreat and contraction of channel cross sections. Conversely, an increase in the tidal prism promotes network re-incision and re-expansion of channel cross sections: Network retreat and expansion tend to occur wit hin the same planar blueprint (see Fig. 2). Our results show that the drainage density of tidal channels is linearly related to the landscape-forming prism, although this relation is speculated to hold with reasonable approximation as a statistical tendency rather than as a pointwise, instantaneous adaptation. Changes in the tidal prism rapidly influence network efficiency in draining the intertidal platform and the related transport of water, sediments, nutrients and pollutants (STEFANON et alii, 2012). These results bear significant practical implications on the predictability of the long -term eco-morphodynamics of tidal landscapes and may help refining our understanding of tidal network dynamics in response to changes in RMSL and of the extent of the imprinting of such changes in the landscape. 30 D ALPAOS ET ALII Fig. 1 Sketch of the experimental apparatus. The plan view (a) and the section A-A (b) show the lagoon basin (5.3m long and 4.0m wide) and the sea (1.6m long and 4.0m wide), connected by the lagoon inlet (0.20m wide) opened through a barrier of wooden panels. Water level measured at the sea through the ultrasonic probes are used continuously correct the motion of the weir, allowing one to generate a sinusoidal tide of fixed amplitude and period, oscillating around MWL. The laser s ys tem which measures bottom elevations has a 300 m resolution and is characterized by an accuracy of ± 1mm and a plan imetric resolution of 1cm × 1cm (from S TEFANON et alii, 2012). Fig. 2 Distribution of bottom elevations for different network configurations during the experiment of cyclic RMSL changes: (a) initial configuration; (b) 288 cycles; (c) 1752 cycles; (d) 9351 cycles; (e) 9631 cycles; (f) 11355 cycles; (g) 12459 cycles; (h) 13063 cycles ; (h) 13063 cycles. Elevations are referred to the initial mean sea level. MODELING TIDAL NETWORK DYNAMICS REFERENCES D'ALPAOS A., LANZONI S., MARANI M., & RINALDO A. (2007) Landscape evolution in tidal embayments: Modeling the interplay of erosion, sedimentation, and vegetation dynamics, Journal of Geophysical Research, 112, F01008, doi:10.1029/2006JF000537. FAGHERAZZI S. & OVEREEM I. (2007) - Models of deltaic and inner continental shelf landform evolution, Annual Review of Earth Planetary Sciences, 35, 685 715. FAGHERAZZI S., ET AL. (2012) - Numerical models of salt marsh evolution: Ecological, geomorphic, and climatic factors, Reviews of Geophysics, 50, RG1002, doi:10.1029/2011RG000359. HOWARD A., D IETRICH W. & SEIDL M. (1994) - Modeling fluvial erosion on regional to continental scales, Journal of Geophysical Research, 99(B7), 13,971 13,986. 31 K IRWAN M. & M URRAY B. (2007) - A coupled geomorphic and ecological model of tidal marsh evolution, Proceedings of the National Academy of Sciences. U.S.A., 104(15), 6118 6122. LEOPOLD L.B., WOLMAN M.G., & M ILLER J.P. (1964) - Fluvial Processes in Geomorphology, W. H. Freeman (Eds), New York. RINALDO A., DIETRICH W.E., V OGEL G., RIGON R., & RODRIGUEZ-ITURBE I. (1995) - Geomorphological signatures of varying climate; Nature, 374, 632 636. S TEFANON L., CARNIELLO L., D'ALPAOS A., & LANZONI S. (2010) - Experimental analysis of tidal network growth and development; Continental Shelf Research, 30, 950 962, doi:10.1016/j.csr.2009.08.018. S TEFANON L., CARNIELLO L., D'ALPAOS A., & RINALDO A. (2010) - Signatures of sea level changes on tidal geomorphology: Experiments on network incision and retreat, Geophysical Research Letters, 39. Rend. Online Soc. Geol. It., Vol. 20 (2012), p. 32. © Società Geologica Italiana, Roma 2012 Jurassic extensional faulting at the Trento platform - Belluno basin margin LUC IO LBERTO & D ANILO GIORDANO Key words: Ammonoid fauna, ceratitoid, Recoaro area, German basin, Alpine basin. The Jurassic paleogeography in the Venetian Prealps is composed of the Friuli Platform, the Belluno trough and the Trento plateau. The reconstrution of this paleogeographic settings is recognizable by the presence and thickness of some formations. On the Trento plateau sedimented a condensed section (Calcari Grigi Group, RAV, Maiolica p.p.) with some hiatus intervals in it. The Belluno trough instead was filled with various formations in relationship to the distance from the platform margins and to the opening stage of the basin: Soverzene Formation, Igne Formation, Lower and Upper Rosso Ammonitico, Vaiont Limestone, Fonzaso Formation, Maiolica p.p.. Various studies have described and defined the stratigraphy of the margin Trento Platform - Belluno Basin mostly of the M. Grappa, Asiago Plateau, Schiara Mountain. Less work has been done in the Vette Feltrine area (BECCARO et alii, 2002; KOLCKMANN , 1992; DAL PIAZ, 1907). _________________________ (*) [email protected] Feltre (BL); (*) The purpose of this note is to correlate data from previous works with new observations to trace better the margin evolution and its importance reflected in the deformation during the Alpine Orogenic events. The area we are focusing on belongs to the Alpi Feltrine range and in more details for the Canzoi Valley. At the head of the Canzoi Valley, deep into the Vette Feltrine range, we found some tens of meters of Vaiont Limestone that belongs to the Belluno Basin stratigraphy. Its location in the valley seems to follow the major faults alignment. Associated to this unit there are also some black shales of Toarcian age. At the entrance and in the surroundings of the valley it is possible to recognize different stratigraphic sections some with a more platform condensed sequence others with more basinal facies. From all these data we suggest that, during the Jurassic, the Canzoi Valley was a lateral engul fing area of the Belluno Basin connected also with the dolomitic realm partially raised and in erosion. Later the Alpine orogeny reactivated the same faults as lateral ramps during the compression and growth of the Alpi Feltrine. This reactivation created also some changes at the Belluno and Neva thrusts with changes in orientation and formation of secondary faults with lateral movement. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 33-34, 2 figs. © Società Geologica Italiana, Roma 2012 Sedimentological, geomorfological and geochemical evidence of the last marine ingression in central Magellan Straits-southernmost Chile SANDRO DE M URO , CLAUDIO K ALB, W ALTER BRAM BILLA & ANGELO IBBA (*) Key words: Holocene, Magellan Straits, Periantartic Areas, Quaternary Geology, Sedimentology. ABSTRACT Research along the coastal belt of the Magellan Straits was carried out in detail with mapping of morphological units. Attention was given to the study of palaeo-shorelines and different terrace orders (Fig. 1) of presumed marine and transitional origin (BRAM BATI & DE M URO , 2004; BRAM BATI et alii, 2004a; D E MURO et alii, 2000). On the basis of sedimentological , geological and geomorphological results obtained, we made a zoning of the coastal belts along the Atlantic opening of the Straits which enabled us to print three sheets on a scale of 1:200,000 (BRAM BATI et alii, 2004b; DE M URO et alii, 2004a; D I G RANDE et alii, 2004a). Detailed studies and mapping (scale 1:50,000) of the terraced sequences linked to Holo-Pleistocene glacio-eustatic variations are in course. An atlas of 12 maps topographically based on 28 sections of 1:50,000 scale maps (sheets 35, 50, 53, 67, 68, 69, 70, 84, 86, 101, 103 of the Chilean IGM), was made also using the preliminary cartography by Empresa Nacional de Petroleo (ENAP) and the Chilean IGM, aerial photos by Servicio Aerofotogrammetrico Fuerza Aerea de Chile (SAF) and TM and MSS Landsat satellite images (DE MURO et alii, 2004b, c, d, e; DE M URO & D I GRANDE , 2004b; DI GRANDE et alii, 2004b). The Atlas provides a zoning of the area distribution of the most significant deposits processes and forms relating to the coastal belt between Punta Dungeness and Cabo Froward (Fig. 2). Morphogenesis of the area was strictly controlled by the _________________________ (*) Departm ent of Chemical and Geological Sciences - OCEANS, University of Cagliari, Italy, Email: dem [email protected]; processes associated with the advance and retreat of the Magellano Glacier (CLAPPERTON , 1992) and, subordinately, by the main morphodynamic event represented by post deglaciation marine ingression. The Holocene paleogeographic evolutionary Fig. 1 - Strait of M agellan, Bahia Iutil (Tierra del Fuego). Three orders of terraces recognizable. picture of the Patagonia-Tierra del Fuego area is mainly controlled by the imposing phenomenon of glacio-isostasy, though it cannot beruled out that the morphogenesis subsequenct to deglaciation may have been affected by mild neo -tectonic movements. As previously observed, relative marine ingressions that produced terracing of the coasts and backland presumably depend on prevalently positive movements of the whole coastal system, related to the final deglaciation of the region. It is deduced that following deglaciation, a strong parallel uplift of the mean sea level was produced with initally transgressive stratigraphic effects. Isostatic rebound, that probably occurred rather late compared to post-glacial transgression, is superimposed with very complex and articulate phenomena, that are under study at present and will be the subject of future works. 34 DE M URO ET ALII (Holocene) and geomorphological map of the coastal area of Península Juan Mazía, Tierra del Fuego, Straits of Magellan, Chile (1:50,000 scale map). Map n. Proc. 2/12. 32nd International Geological Congress - Florence, Italy - August 20-28, 2004. D E M URO S., D I G RANDE A. & BRAM BATI A. (2004c) Distribution of the marine and transitional terraces (Holocene) and geomorphological map of the coastal area between Punta Paulo and Porvenir, Tierra del Fuego, Straits of Magellan, Chile (1:50,000 scale map). Map n. 3/12. Proc. 32nd International Geological Congress - Florence, Italy August 20-28, 2004. Fig. 2 Puerto Percy, Tierra del Fuego. Second-Order terrace deposits with bilvaves and gasteropods. REFERENCES BRAM BATI A. & DE M URO S. (2004) ingression in central Magellan Straits, southernmost Chile: - Proc. -28 Agosto 2004, Firenze. BRAM BATI A., D E MURO S. & D I GRANDE A. (2004a) the Marine and Transitional Terraces in the Magellan Straits - Proc. -28 Agosto 2004, Firenze. 9/12 maps, 353. BRAM BATI A., D E MURO S., DI GRANDE A. (2004b) Distribution of marine and transitional terrace (Holocene) and geomorphological map of the coastal area between Bahia San Felipe and Paso Ancho Strait of Magellan (1:200.000 scale map). Map B. Proc. 32nd International Geological Congress - Florence, Italy - August 20-28, 2004. CLAPPERTON C. M. (1992) - La ultima glociacion y deglaciacion en el Estrecho de Magallanes: implicacíones para el poblamiento de Tierra del Fuego Ans. Ins. Pat., Ser. Cs. Hs., Punta Arenas (Chile), 21, 113-128. DE M URO S., BRAM BATI A., DI G RANDE A. (2004a) Distribution of marine and transitional terrace (Holocene) and geomorphological map of the coastal area between Punta Dungeness and Bahía San Felipe, Strait of Magellan Chile (1:200.000 scale map). Map A. Proc. 32nd International Geological Congress - Florence, Italy - August 20-28, 2004. DE MURO S., DI G RANDE A. & BRAM BATI A. (2004b) - D E MURO S., D I G RANDE A., BRAM BATI A. & G. FONTOLAN (2004d) terraces (Holocene) and geomorphological map of the Punta Catalina, Tierra del Fuego, Straits of Magellan, Chile (1:50,000 scale map). Map n. 4/12. Proc. 32nd International Geological Congress - Florence, Italy - August 20-28, 2004. D E M URO S., D I G RANDE A. & BRAM BATI A. (2004e) Distribution of the marine and transitional terraces (Holocene) and geomorphological map of the coastal area of Primera Angostura, Patagonia, Tierra del Fuego, Straits of Magellan, Chile (1:50,000 scale map). Map n. 5/12. Proc. 32nd International Geological Congress - Florence, Italy August 20-28, 2004. D E MURO S. & DI G RANDE A. (2004) - Distribution of the marine and transitional terraces (Holocene) and geomorphological map between Punta Arenas And Rio Quema Angusta, Peninsula Brunswick, Patagonia, Straits of Magellan, Chile . (1:50,000 scale map) Map n. 6/12. Proc. 32nd International Geological Congress - Florence, Italy August 20-28, 2004 D E MURO S., D I G RANDE A., FONTOLAN G. & BRAM BATI A. (2000) postglacial evolutionary framework. Map n. 4/12 of the Geomorphological Atlas of the Coasts of the Strait of - Terra Antartica Reports, 4, 55-62, ISSN: 17237211 ISBN 88-900221-7-5 D I GRANDE A., D E M URO S., BRAM BATI A. (2004a) Distribution of marine and transitional terrace (Holocene) and geomorphological map of the coastal area between Punta Dungeness and Bahía San Felipe, Strait of Magellan (1:200.000 scale map). Map C. Proc. 32nd International Geological Congress - Florence, Italy - August 20-28, 2004. D I G RANDE A., S. DE M URO & BRAM BATI A. (2004b) Distribution of the marine and transitional terraces (Holocene) and geomorphological map of the coastal area between Porvenir and Puerto Yartoù, Patagonia, Straits of Magellan, Chile (1:50,000 scale map). Map n. 1/12. Proc. 32nd International Geological Congress - Florence, Italy August 20-28, 2004. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 35-37, 2 figs., 3 graphs. © Società Geologica Italiana, Roma 2012 Stratigraphic trend evolution of the sedimentary pulses of Val d'Aveto Formation ANDREA DI CAPUA (*), GIANLUCA G ROPPELLI (**) & GIOVANNI VEZZOLI (*) Key words: Alpine Chain, Apennines, petrographic counting, stratigraphic trend's evolution, Val d'Aveto Formation, Tertiary clastic sequences. main aim is to characterize the stratigraphic trend evolution of the turbidity sequences of Val d'Aveto Formation (M UTTI & RICCI LUCCHI , 1972). METHODS INTRODUCTION The Tertiary clastic sequences bordering the SouthAlpine front and the Apennines provide fundamental information about the evolution of the Alpine chain between Eocene and Miocene Fig. 1 - Fig. 1 A detailed geological/structural map at 1:5000 scale has been realized. Val d'Aveto Formation is composed of five members: 1) basal calcareous-arenitic member; 2) pelitic- arenitic silicoclastic member with two para-conglomerates interbedded; 3) volcanoclastic para-conglomerate member; 4) volcanoclastic sandstone member; 5) calcareous sandstone member, with a paraconglomerate interbedded. Conglomerate facies of Val d'Aveto Formation (MUTTI & RICCI LUCCHI, 1972; G ELATI et alii, 1988; BERSEZIO et alii, 1993; ELTER et alii, 1999; SCIUNNACH & TREM OLADA, 2004; GARZANTI & M ALUSÀ, 2008; M ALUSÀ et alii, 2010). Our _________________________ (*) Dipartim ento di Scienze Geologiche e geotecnologie studi di M ilano Bicocca. (**) Istituto per la Dinamica dei Processi Am bientali CNR. Università degli Sezione di Milano, Fig. 2 Folds in the calcareous arenitic member On eight conglomerate bodies, three of which in the pelitic arenitic member, five in the conglomerate member and the last one in the upper calcareous sandstones member, statistical counting pebbles were concentrated. Statistical method has been used, which contemplates a counting of over a hundred of 36 DI C APUA ET ALII Gr aph. 1 Fieldwork counting results. Note that counting on the same bodies are shown as a single value derived from an average of counts. Bottom of stratigraphical sequence = 123; top of stratigraphical sequence = 175 + 176. pebbles in a 1.5 m² area. Fieldwork counting results are shown in Graph.1 with metamorphic minerals, in particular garnets, while heavy minerals from A41 sample is mainly composed of abundant associations epidote and light mineral (usually quartz), garnet Pebbles analysis has been integrated by two thin sections of samples collected into two microconglomerate levels (A1 and A2) located in the upper part of the pelitic-arenitic silicoclastic member and by heavy minerals analysis of the paraconglomerate' matrix (A41) interbedded in the upper calcareous sandstones. Results of the thin sections and heavy mineral analysis are shown in Graph. 2 and 3. DISCUSSION AND CONCLUSION The petrographical signal underlines a preponderant presence of metamorphic rocks, in particular quarzite, followed by gneiss and micaschists, and a constant presence of calcareous clasts, with two main pulses with an increasing trend of volcanoclastisc material and a very weak pulse of plutonic rock. Moreover, thin sections A1 and A2 show a preponderant content of plutonic/ortogneiss fragments plus feldspar and quartz fragments, Gr aph. 2 Thin section counting results. STRATIGRAPHIC TREND EVOLUTION OF THE SEDIM ENTARY PULSES OF VAL D AVETO FORMATION 35,0 Zircone incolore Rutilo giallo 30,0 CATANZARITI R., FERONI A. C., O TTR IA G. & LEVI N. (2009) The contribution of calcareous nannofossil biostratigraphy in Apatite incolore Apatite rosa 25,0 R.F. apatite inc+bt+L R.F. apatite rosa+TiO2+L 20,0 Epidoto incolore 15,0 Pistacite Epidoto granulare 10,0 Zoisite R.F. epidoto+L 5,0 R.F. epidoto+L+bt Granato incolore 0,0 R.F. granato+ti+L Miocene foredeep of the northern Apennines (Italy ), SEPM Special Pubblication 93, 309-321. E LTER P., CATANZATIRI R., GHISELLI F., M ARRONI M., M OLLI G., OTTRIA G. & PANDOLFI L. (1999) L'Unità Aveto (Appennino settentrionale): caratteristiche litostratigrafiche, biostratigrafia, petrografia delle areniti e assetto strutturale. Boll Soc Geol It. 118, 41 63. G ARZANTI E. &. M ALUSÀ. M. G. (2008) The Oligocene Alps: Domal unroofing and drainage development during early orogenic growth. Earth and Planetary Science Letters 268, 487 500. R.F. granato+epidoto HM Gr aph. 3 37 G ELATI R., NAPOLITANO A. & V ALDISTURLO A., (1988) A41 heavy minerals' content on percentage and epidote, and single crystals of epidote and apatite. To trace a plausible source area our results have been integrated available data available in literature (E LTER et alii, 1999, CATANZAR ITI et alii, 2009, MATTIOLI et alii, 2012). In particular M ATTIOLI et alii (2012) suggests a local Apennine source area, even if a detailed study of the sedimentary fraction of Aveto Formation is however highly needed to completely exclude or not the possibility derivation of the sedimentary succession from the Alpine chain. This work is still in progress: next steps will be the stratigraphical and petrological study of both the foredeep and Molassa Alpine Tertiary Formations, and to compare them with a modern and active case. La pino . Rivista Italiana di Paleontologia e Stratigrafia, 94, 285-332. M ALUSÀ M. G. & GARZANTI E. (2012) Actualistic snapshot of the early Oligocene Alps: the Alps-Apennines knot detangled. Terra Nova doi: 10.1111/j.1365-3121.2011.01030.x M ALUSÀ M. G., V ILLA I. M., VEZZOLI G. & GARZANTI E. (2011) Detrital geochronology of unroofing magmatic complexes and the slow erosion of Oligocene volcanoes in the Alps. Earth and Planetary Science Letters, 301(1-2), 324-336. Elsevier B.V. doi:10.1016/j.epsl.2010.11.019 M ATTIOLI M., LUSTRINO M., RONCA S. & BIANCHINI G. (2012) Alpine geochimical petrographic constrains and geodynmic implication from Early Oligocene Aveto Petrignacola Formatio (Italy). Lithos 134-135, 201 220 REFERENCES M UTTI E. & RICCI LUCCHI F. (1972) Le torbiditi dell'Appennino settentrionale: introduzione all'analisi di facies. Mem. Soc. Geol. It., 11, 161 199, 30 ff., 1 tab. BERSEZIO R., FORNAC IARI M., G ELATI R., N APOLITANO A. & V ALDISTURLO, A. (1993) The significance of the Upper Cretaceous to Miocene clastic wedges in the déformation history of the Lombardian southern Alps. Géologie Alpine, 1993, L 69, p. 320 S CIUNNACH D. & TREM OLADA F. (2004) The Lombardian Gonfolite Group in central Brianza (Como and Milano Province, Italy): calcareous nannofossils biostratigraphy and sedimentary record of neo alpine tectonics. Eclogae Geol. Helv., 97, 119-131, Basel. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 38-40, 2 figs. © Società Geologica Italiana, Roma 2012 Sedimentological and pedological study of some pedogenized intervals of the Plio-Pleistocene Upper Valdarno Basin FRANCESCO F IDOLINI (*) & ANNA ANDREETTA (**) Key words: facies analysis, palaeosols, sedimentary environments, Upper Valdarno basin, Plio-Pleistocene. INTRODUCTION The study of palaeosols, coupled with the classical methods of process sedimentology, is increasingly being recognized as an effective tool for evaluating landscape stability and evolution. The intrinsic complementarity of these two methods, which record the effects of processes developing over different periods of time, allows improving the information gained from palaeoenvironmental reconstruction. Even if the Upper Valdarno basin is one of the best-studied Plio-Quaternary continental basins of the Northern Apennines, only few works that include palaeopedological investigations have been published (M ANCINI & ROM AGNOLI , 1966; BERTINI et alii, 2010). The objective of this study was to document the existence of some important pedogenised stratigraphic intervals in the Upper Valdarno basin and to characterise their morphological features, with the aim to improve the understanding of landscape evolution in the basin by integrating stratigraphic and sedimentological data with palaeosol properties. We selected four representative stratigraphic intervals bearing pedogenised horizons, which are considered particularly useful to a complete palaeoenvironmental reconstruction in key phases of basin-fill accumulation. elongated in a NW-SE direction and drained by the Arno River, which flows to NW parallel to the main axis of the basin. The depression, which is widely interpreted as a half-graben with the main normal fault system located along the NE margin, is filled by 550 m of alluvial and lacustrine deposits accumulated during the Plio-Pleistocene. The basin-fill succession is subdivided into three synthems GEOLOGICAL OUTLINE The Upper Valdarno basin (Fig. 1) is a 15 km wide tectonic depression bounded by the Chianti Mountains and the Pratomagno Ridge, about 35 km SE of Florence. The basin is _________________________ (*) Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via G. La Pira 4, 50121, Firenze. (**) Dipartimento di Scienze delle Produzioni Vegetali, del Suolo e delle Cascine 15, 50144, Firenze. Fig. 1 Geological sketch map of the Upper Valdarno basin and location of the studied s ections (m odified from F IDOLINI & ANDREETT A, in press). 39 FIDOLINI & ANDREETTA (F IDOLINI et alii, in press), that are, from bottom up: Castelnuovo dei Sabbioni (CSB), Montevarchi (VRC) and Torrente Ciuffenna (UFF) synthems. A fourth one, Fosso del Salceto Synthem (OLC) is exposed only in the Palazzolo sub-basin and is partly coeval with the VRC Synthem. The four studied sections are distributed within the fill deposits as follows (Fig. 2): The San Cipriano section, hosting the oldest pedogenised deposits recognized in the basin, belongs to the youngest unit of the CSB Synthem. The Ricasoli section is located at the base of the VRC Synthem. Palaeosols found in this section are weakly developed and polygenic, locally incorporating erosional surfaces. The presence of Fe-oxide coatings around pores and the low chroma of the soil matrix suggest their classification as Gleysols or Infragleysols, developed in poorly drained conditions. Ricasoli section This section is made of vertically stacked, tabular sandy and muddy beds cut by subordinate sand lenses. Tabular beds represent overbank deposits and consist of sandy beds (5-40 cm) produced by expanding, turbulent flows during flood events and muddy intervals (20-100 cm), containing root traces and pedogenic evidence, accumulated by suspension settling in flood generated ponds. Sand lenses, which represent channel-fill deposits, may contain gravels and mud clasts at the base as lag deposits and are internally made of gently inclined or convexupward bedsets, made of plane-parallel or cross stratified beds, accumulated by lateral and longitudinal bars respectively. The overall palaeotransport direction is from SW (i.e. Chianti margin). Palaeosols are differ in the development of ped structure, showing abundant Mn-Fe spherical concretions and can be classified as Cambisols or Infracambisols. They show evidence of transitory waterlogging and periodical changes from poorly- to well-drained conditions. Francalanci pit section Fig. 2 Stratigraphic scheme for the Upper Valdarno basin. The stratigraphic position of the four studied sections is reported (from F IDOLINI & A NDREETT A, in press). The Francalanci pit section covers the mid part of the VRC Synthem. The Acquaborra pit section exposes gravelly to sandymuddy deposits of the UFF Synthem. STUDIED SECTIONS San Cipriano section It consists of sandy channelized deposits (up to 2 m thick and 8-12 m wide) incised into horizontally bedded floodplain mud, bearing root traces and pedogenic features, with sandy interbeds. Sandy channels, locally floored by lag deposits made of pebblesized gravels and mud clasts, consist of sets of gently inclined (10°-15°) beds (up to 20 cm thick) accumulated by the lateral migration of bars. Floodplain deposits consist of mud accumulated by suspension settling in flood-generated ponds, and sandy interbeds, which are up to 30 cm thick, representing deposition of crevasse splays. It consists of alternating, laterally persistent muddy and sandy tabular beds cut by subordinate sand lenses, which are more common in the lowermost and uppermost parts of the section, resulting in a fining-to-coarsening-upward trend. Tabular beds are commonly bioturbated and pedogenised, and consist of muddy layers (up to 3 m thick) accumulated by sediment fallout in standing water bodies developed after flood episodes, and sheet-like sandy beds (5-30 cm) representing overbank deposits produced by turbulent, unconfined flows expanding out of the channels. Dark grey muds (30 cm thick) with abundant fresh water bivalves, accumulated in small lakes, are locally present. Sand lenses, internally made of sets of gently inclined beds (5-40 cm thick) accumulated by the lateral migration of bars, represent channel deposits. Palaeotransport direction is mainly from SW (i.e Chianti margin). A composite soil located in the mid part of the section has been studied. It shows the co-occurrence of carbonate accumulation, vertic and hydromorphic pedofeatures, suggesting successive phases of soil development characterised by different conditions in terms of draining. It can be classified as a Calcic Gleyc Vertisol or Pedocalcic Infragleyc Vertisol. Acquaborra pit section This section shows a clear fining-upward trend, passing from gravelly to sandy and muddy deposits. Gravelly amalgamated PEDOGENIZED INTERVALS OF THE PLIO-PLEISTOCENE UPPER VALDARNO BASIN bodies (up to 6 m thick and tens of m wide), occurring in the lower part, represent fluvial channels and consist of wedgeshaped units made of large-scale inclined beds accumulated by the lateral migration of bars. In the upper part of the section, tabular beds represent floodplain deposits, consisting in muddy intervals (up to 3.5 m thick) accumulated by suspension fallout after floods, and sandy beds (20-150 cm thick) deposited by unconfined, turbulent flows as crevasse splays. Sand lenses (4-6 m thick and tens of m wide) cutting tabular deposits represent fluvial channels, made of large-scale inclined bedsets accumulated by the lateral migration of bars. Palaeosols occurring in this section are characterised by the coexistence in the same horizon of features that generally develop in different soil environments, and thus they are polygenic. Soils occurring in the lower part of the section show carbonate accumulation within argic horizons, testifying a transition from warm conditions, with alternating dry and wet seasons, to temporary hydromorphic and reducing conditions. Soils occurring in the upper part of the section are characterised by the presence of hydromorphic features superposed on vertic ones. 40 development, interrupted by depositional episodes, coherent with the vicinity to active channels. According to overall palaeotransport direction and sedimentary features, deposits exposed in the Francalanci pit can be referred to a transitional environment located between the distal portion of alluvial fans sourced by the Chianti Mountains and the lateral reaches of the axial floodplain. The superposition of gleyc features over carbonate accumulation and vertic features accounts for a significant stability of soil surface through time, possibly related to sediment starving and low accommodation Deposits exposed in the Acquaborra pit are referred to a fluvial environment developed under changing draining conditions. The lowermost part of the section represents a relatively sinuous, gravelly fluvial system, while the upper part represents a sinuous, mainly sandy fluvial system. Palaeosols show stagnic or gleyic features, superimposed on carbonate accumulation horizons and/or vertic features. These characteristics are more evident in the uppermost part of the pedostratigraphic sequence, in which channels appear to be more isolated and entrenched within floodplain deposits. REFERENCES RESULTS The main results of the study can be summarized as follows. According to the collected data, deposits exposed in the San Cipriano section can be referred to a fluvial environment characterised by overall poorly drained conditions. Pedological data attest for a general weak development of soils belonging to this stratigraphic interval. The presence of compound truncated sets and composite soils is coherent with unsteady depositional conditions (KRAUS , 1999), characterized by episodes of sediment accumulation and possible erosion and phases of soil development. Redoximorphic features indicate overall waterlogged conditions. Sedimentary features, architecture and palaeotransport direction suggest that deposits belonging to the Ricasoli section can be referred to a distal alluvial fan setting characterised by episodes of waterlogging. Palaeosols are weakly developed and show evidence of weak oxidized conditions, with weathered topmost horizons containing sparse organic matter. These characteristics attest for relatively short periods of soil BERTINI A., M AGI M., MAZZA P.A. & FAUQUETTE S. (2010) Impact of short-term climatic events on latest Pliocene land settings and communities in Central Italy (Upper Valdarno basin). Quat. Int., 225, 92-105. F IDOLINI F. & ANDREETTA A. (in press) Integrating sedimentological and palaeopedological data for palaeoenvironmental reconstruction: examples from the PlioPleistocene Upper Valdarno basin (Northern Apennines). It. J. Geosc. F IDOLINI F., G HINASSI M., M AGI M., P APINI M. & S AGRI M. (in press) - The Plio-Pleistocene Upper Valdarno Basin (Central Italy): stratigraphy and basin fill evolution. It. J. Geosc. K RAUS M.J. (1999) Paleosols in sedimentary rocks: their geologic applications. Earth Sc. Rev., 47, 41-70. M ANCINI F. & ROM AGNOLI L. (1966) - Primo contributo alla Geo-morfologia ed alla Paleopedologia del Valdarno superiore. Boll. Soc. Geol. It., 84 (7), 169-185. Rend. Online Soc. Geol. It., Vol. 20 (2012), p. 41. © Società Geologica Italiana, Roma 2012 Facies and geometries of carbonate platforms of the Dolomites after the Carnian Pluvial Event (CPE). G IOVANNI GATTOLIN (*), MARCO FRANCESCHI (**), ANNA BREDA (*) & NEREO P RETO (*) Key words: carbonate platform, Carnian Pluvial Event, depositional geometries, Dolomites, facies. Depositional geometries can be decisive in identifying the origin of sedimentary bodies because their spatial characters can be linked to the conditions in which sedimentation took place. We here present preliminary results of an ongoing quantitative study that aims at understanding the link between changes in depositional architectures and the processes of shallow water carbonate precipitation across the Carnian Pluvial Event (CPE). During Middle Triassic, the Western Tethys displayed a complex paleogeography, featuring isolated carbonate platforms and carbonate-siliciclastic deep basins. This complexity disappeared as a late Early Carnian global climatic event (CPE) increased significantly the terrigenous input to marginal basins and determined their infilling, leading to the formation of a epeiric sea where the large Dolomia Principale (DP) carbonate platform, deposited developing depositional geometries on the scale of hundreds to thousands of kilometers. The transition from isolated carbonate buildups to the epeiric DP platform is apparently abrupt, and seems to imply a major crisis of carbonate platform-depositional systems, during which the mode of carbonate precipitation changed dramatically. To investigate more in detail this transition, three dimensional acquisition techniques (laser scanner and photogrammetry) were applied to capture depositional geometries of sedimentary bodies deposited during and after the Carnian crisis. Contemporaneously, facies analysis was carried out to relate changes in depositional geometries to facies variations. The Early Carnian interval was surveyed on the southern walls of the Tofana di Rozes (Dolomites, Falzarego valley - Cortina d'Ampezzo, BL), that exposes a platform-to-basin transect of preand post-crisis platforms, and at Dibona hut where a ~ 30 m thick prograding carbonate body deposited during the Carnian crisis crops out. The Norian interval is being surveyed on the DP margin and slope cropping out at Portella Pass (Dolomites, Cave _________________________ (*) Dipartimento di Geoscienze, Università degli Studi di Padova, via Gradenigo 6, 35137 - Padova (**) Museo delle Scienze, via Calepina 14, 38122 - Trento del Predil, Tarvisio, UD). In these outcrops both depositional geometries and facies are preserved and consequently observations from larger to finer scale can be done. At the Tofana di Rozes, photogrammetric modeling of topography permitted positioning and visualization of geological features observed in the field into a three dimensional frame that was used to define a conceptual sedimentological model for the basal part of the Heiligkreuz Fm. (HK). It consists of numerous carbonate mounds, tens to hundreds of meter in size, grown on a pre-existing inclined surface, and intercalated with an alternation of skeletal carbonates (grainstones and packstones) and siltitesarenites. This system soon evolved into a carbonate-clastic ramp. A 3D model of the clinostratified body at Dibona was then realized on the basis of LiDAR and petrographic analysis to test if it fits in the larger scale conceptual model. The original inclination of clinoforms ( ~ 25°) and their amplitude ( ~ 30 m) point to a deltaic environment, deposited in a narrow passage between mounds. Facies (mainly mixed carbonate siliciclastic grainstones) are in agreement with this interpretation. These observations on depositional architectures and facies analysis seem to testify that a phase of complex intermediate sedimentation in which carbonate mounds and detrital processes coexisted, characterized the turnover of carbonate factory across the CPE. This implies that, at least in terms of carbonate factories turnover, the event has not to be considered strictly abrupt. Preliminary results presented in this work seem to point out that an integrated approach relying both on 3D characterization of geometries and facies analysis could greatly help to shed light on this critical interval of Late Triassic history. Facies mapping and geometry acquisition via photogrammetry are now being applied to the DP margin and slope at Portella Pass. Preliminary results suggest that microbialites might be the main character at play for the onset of the DP. ACKNOWLEDGEMENTS M. I. Sotton provided help during fieldwork, L. Tauro and E. Masiero realized thin sections. Thanks to G. Teza for GPS data elaboration, M. Belvedere, S. Castelli, F. Menna and 3DOM unit of FBK for basics on photogrammetry, G. Roghi and J. Dal Corso for discussion. foundation granted) with the financial contribution of Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 42-43, 2 figs. © Società Geologica Italiana, Roma 2012 Seep-carbonates as indicators of global cooling events (Miocene, northern Apennines). CLAUDIA G RILLENZONI (°), STEFANO CONTI (°), D ANIELA FONTANA (°) & ELENA TURCO (*) Key words: cooling events, Miocene, northern Apennines, seep carbonates. Recent studies in dating seep-carbonates suggest that their occurrence is controlled by climatic changes (TEICHERT et alii 2003). KIEL (2009) suggests that this correlation exists from the late Jurassic to Recent, and shows a statistically relevant correlations between the frequency of seep-carbonates in the past 150 Ma and low deep-water temperature and low sealevels. In the Miocene of the northern Apennines, the abundance and the extent of the seep-carbonates from different tectonic-sedimentary settings, foredeep to satellite basins, provide a rare opportunity to study the tectonic and/or climatic controls on seepage (CONTI & F ONTANA, 1999). The Vicchio outcrop in the Tuscan Apennines contains excellent exposures of a Miocene seep-system (more than 80 Fig. 1- carbonate body enclosed in marly sediments of the Vicchio Fm. _________________________ (°) Department of Earth Sciences, University of Modena and Reggio Emilia, Largo Eufemia, 19, 41121, M odena (*) Department of Earth Sciences , University of Parma, Parco Area delle Scienze, 157A, 43100 Parma carbonate bodies) enclosed in marly sediments (Fig. 1). A detailed stratigraphic and biostratigraphic study of carbonates and enclosing marls indicates that the stratigraphic horizon bearing seep-carbonates lies between the T. cf. T. quinqueloba AE (13.75 Ma) and the P. siakensis A1B (13.32 Ma) encompassing a time interval of about 400.000 years. Since the AE of T. cf. T. quinqueloba approximates the midMiocene global cooling event, we infer that the beginning of the seep-carbonate precipitation in the Vicchio Marls seems to be related to this climatic event (Fig. 2). We assume that the ascent and emission of methane-rich fluids may have been triggered by the pressure drop due to the eustatic fall associated with the Mi3b event, estimated in about 60 m (H ILGEN et alii, 2009). A drop of the hydraulic pressure on the plumbing system during sea level lowering in glacial phase could increase methane flows at seeps, inducing carbonate precipitation. SEEP-CARBONATES AS INDIC ATORS OF GLOBAL COOLING EVENTS 43 Fig. 2 - Geological map of the studied area showing the distribution of carbonate bodies and relationships with the Acme End (AE) of the T. cf T. quinqueloba. REFERENCES CONTI S. & FONTANA D. (1999) - Miocene chemoherms of the northern Apennines (Italy). Geology, 27, 927-930. HILGEN F.J., A BELS H.A., I ACCARINO S., KRIJ GSMAN W., RAFFI I., S PROVIERI R., TURCO E. & ZACHARIASSE W.J. (2009) The Global Stratotype Section and Point (GSSP) of the Serravallian Stage (Middle Miocene). Episodes, 32, 152166. KIEL S. (2009) - Global hydrocarbon seep-carbonate precipitation correlates with deep-water temperatures and eustatic sea-level fluctuations since the Late Jurassic. Terra Nova, 21, 279-284. TEICHERT B.M.A., EISENHAUER A., BOHRMANN G., H AASESCHRAMM A., BOCK B. & LINKE P. (2003) - U/Th Systematics and ages of authigenic carbonates from Hydrate Ridge, Cascadia Margin: Recorders of fluid flow variations. Geochimica et Cosmochimica Acta, 67, 3845-3857. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 44-45, 1 fig. © Società Geologica Italiana, Roma 2012 The subsurface record of hydrocarbon-charged fluids migrating through the Messinian sedimentary column (Maiella Basin, Central Italy) ANNALISA I ADANZA (*), G IANLUCA SAM PALMIERI (*), GIANLUCA FRIJIA (**), PAOLA CIPOLLARI (*, °), D OM ENICO COSENTINO (*, °), M ARCO MOLA (°) Key words: Messinian, Maiella basin, fluid migration pathways, brecciated buildups. INTRODUCTION During the Messinian Salinity Crisis of the Mediterranean Sea (MSC), the Western Mediterranean margins recorded a fluid migration event, possibly triggered by a major event of dissociation of gas hydrates (P IER RE & ROUCHY , 2004; CLARI et al., 2009; RYAN , 2009). In the Maiella Basin (Central Italy), in a marginal foreland setting, similar seep-related phenomena took place soon after the development of the Messian Erosional Surface (MES), as evidenced by the informal Brecciated Limestones unit, representing the early post-evaporitic (p-ev1) record in the basin. The investigation of the Brecciated Limestones unit was performed using a suite of sedimentological and geochemical techniques. The methodological approach chiefly encountered: facies analyses, carried out at the outcrop scale and on polished thin sections by means of optical, cathodoluminescence and electronic microscopic devices; compositional analyses (Ca, Mg, Mn, Fe, Sr); and stable isotopes analyses ( 13 C; 1 8O). The main seep-related geobodies in the study area, resting above the MES, are represented by: 1) widespread highly brecciated buildups (intraformational breccias) and concretions; 2) minor patchy concretions embedded in the surrounding host anoxic sediment; 3) localized metric fluid migration pathways (while cemented chimneys were detected only at the microscale in the host sediment). The fluid migration therefore presumably developed with major fluxes along neoformed channels and seepage through microchimneys in the host sediment. The brecciated bodies are bedding-retentive, devoid of gravity segregation and show scale-invariant brecciation. The related _________________________ (*) Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre (**) Institut für Erd- und Umweltwissenschaften, Universität Potsdam (°) Istituto di Geologia Am bientale e Geoingegneria (IGAG-CNR), Area della Ricerca Roma 1, Montelibretti. limestones consist of pyrite bearing clotted microbialites, microbrecciated at places, tar bearing (tar plagues and porefilling microtar), and accompanied by celestite. Along with the most remarkable fluid migration features represented by fluid migration pathways and microchimneys, the integrated microfacies analysis also revealed the occurre nce of fluidal microtextures and cross-cutting relationships. The main fluid migration pathways are commonly typified by channels filled by fluidized pelites. Nonetheless, the most spectacular fluid migration structure, observed in a quarry (Abbateggio Limestones Quarry, Fig. 1), is made up by carbonates. There, within a major brecciated buildup, a meandering brownish channelway mounding upward, at places impregnates laterally and upwardly the surrounding host rock, at other places cuts the main body. A single cylindrical calcitic concretion collected from this channelway, yielding remarkable microscale heterogenities and a complex history of cementation and localized microbrecciation, was chosen to perform chemical analyses, by microdrilling the most representative subsamples. Its facies framework at a first glance is made up by two portions, a pale cream core and a dark brown impregnated rim, separated by a milling impregnation front: on one hand, the dark brown impregnated portion is constituted by microbial fragments and fluid microchannels, on the other hand, the pale cream portion is typified by microbial fragments and pseudomorphs after gypsum affected by corrosion-reaction rims. The resulting fabric put in evidence that the brecciation event developed in multiple phases, accompanied by oil impregnation. Compositional analyses of this sample yielded preliminary results chiefly indicating: 1) a general strong Sr enrichment (up to 10340 ppm), possibly pointing to pristine aragonite phases or testifying the occurrence of Srenriched diagenetic fluids; 2) a local enrichment in Fe and Mg in correspondence to cemented microveins. The genetic relation of the Messinian Brecciated Limestones in the Maiella area with a hydrocarbon seep paleoenvironment is 13 also definitely stressed by w C data (down to Their presumable origin from the subsurface, within the sedimentary column, is herein inferred by the occurrence of widespread autobrecciation accompanied by fluid channels, together with the absence of chemosynthesisbased paleocommunities. HYDROCARBON-CHARGED FLUIDS M IGRATING THROUGH THE MESSINIAN SEDIM ENTARY COLUMN 45 Fig. 1 - Fluid m igration pathway (Brecciated Lim estones unit; Abbateggio Limestones Quarry, Maiella Basin) REFERENCES CLARI P., DELA PIER RE F., M ARTIRE L. & CAVAGNA S. (2009) The Cenozoic CH4-derived carbonates of Monferrato (NW Italy): A solid evidence of fluid circulation in the sedimentary column. Marine Geology, 265, 167 184. P IER RE C. & ROUCHY J.M. (2004) - Isotopic compositions of diagenetic dolomites in the Tortonian marls of the Western Mediterranean margins: Evidence of past gas hydrate formation and dissociation. Chemical Geology, 205, 469-484. RYAN W.B.F. (2009) - Decoding the Mediterranean salinity crisis. Sedimentology, 56, 95 136. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 46-47, 2 figs., 1 tab. © Società Geologica Italiana, Roma 2012 The role of the Backshore/Foreshore length ratio in short-term beach monitoring studies SERGIO G. LONGHITANO (*) Key words: beach equilibrium profile, backshore, foreshore. INTRODUCTION A straightforward conceptual method is proposed to quantitatively assess the inter-annual tendency of retreatment or advancement on microtidal beaches by using the backshore/foreshore length ratio. This method is based on measuring the profile of a beach when it passes through the 'transitional state' that separates the high- from the low-energy season, period during which the morphological characteristics of the beach are as similar as possible to its equilibrium profile. The B/F length ratio method postulates that foreshore and backshore lengths are equivalent in beaches that approximate to their state of morphodynamic equilibrium (B/F~1) (Fig. 1A). A backshore length exceeding the foreshore length is indicative of a state of beach recession, with a B/F length ratio >1 (Fig. 1b). When the foreshore length is greater than the backshore length, the shoreline is advancing or, alternatively, it is developing in a state of morphological confinement, i.e. due to the presence of a sea cliff, with a B/F<1 (Fig. 1c). This empirical method has been applied on a number of sand and gravel microtidal beaches from the coasts of Basilicata, southern Italy. The various beach states have been synthesised into seven classes (I-VII), each identified from specific value intervals of the B/F length ratio (Tab. 1). RESULTS The beach examples analysed in the present study pertain to two very different coastlines, including sand, gravel and mixed beaches. All these beaches lie in states of retreatment, advancement or stability depending on highly varying local conditions of sediment supply, morphological confinement and exposure to dominant winds and waves (Fig. 2). Fig. 1 Theoretical beach profiles defined on the basis of their respective backshore and foreshore lengths. _________________________ (*) Dipartimento di Scienze Geologiche, Università degli Studi della E-Mail: [email protected] Fig. 2 Beach profiles measured along the Tyrrhenian (a-c) and Ionian (d-g) coas tline of Basilicata. THE ROLE OF THE BACKSHORE/FORESHORE LENGHT RATIO IN SHORT-TERM BEACH MONITORING STUDIES The Tyrrhenian beaches are confined or semi-confined systems whose correspondent profiles have shown beaches that nearly approximate to the equilibrium. This state is confirmed by convex-up profile shapes and B/F lengt indicate that backshore and foreshore have quasi equivalent lengths (e.g., Acquafredda beach; fig. 2a). Profiles with B/F length ratio <1 indicate advancing beaches or back-confined evelop if compared to the foreshore (e.g., Cersuta and Spiaggia Nera beaches; figs. 2b and 2c). Thus, the beaches observed along the Tyrrhenian coastline are included in the classes III and IV of the Table 1. In the Ionian examples, the B/F ratio increases from the southern to the northern beaches, ranging from 1.75 to 4.11. The advancing receding lower values, somewhat >1, express quasi -equilibrium states, and this condition is also supported by the compound (concave- to convex-up) 2D profiles of the Policoro and Terzo Cavone beaches (Figs. 2f and 2g). These systems are in fact the bestpreserved beaches observed along the Ionian coast of Basilicata where, although the shoreline is generally affected by a long-term retreat, some beaches show short -term local advancement, due to their position adjacent to river mouths. B/F ratios >>1 indicates an extremely reduced foreshore and thus strong erosion for the Metaponto and Lido Quarantotto beaches (Figs. 2d and 2e), whose profiles maintain concave-up shapes also during the transitional state from the winter to the summer season. The beaches documented along this coastline are therefore included in the classes V, VI and VII of the subdivision proposed in Table 1. class beach state I II III st r on g l y ad van ci n g mo d erat el y ad v anci n g sl i g ht l y ad v anci n g stable (neither advancing nor receding) sl i g ht l y r e c e d in g mo d erat el y rec edi n g st r on g l y reced i n g IV V VI VII 47 B/F length ratio <0.5 0.5 0.8 0.8 - 1 1 1 -2 2 -3 >3 Tab. 1 - Subdivision into seven classes of advancing, receding and stable beaches on the base of their respective value intervals of B/F length ratio. FINAL REMARKS SIGNIFICANCE OF THE B/S RATIO The subdivision between backshore and foreshore detected in the subaerial beach on the base of their genetic significance and bi-dimensional volume, allow assessing quantitatively the state of equilibrium or disequilibrium at the time of the profile acquisition. Advancing, receding and stable beaches are identified into seven classes of beach states on the base of their respective values, or value intervals, of the B/F length ratio (Tab. 1 th (Tab. 1). The subaerial part of microtidal, wave-dominated beaches is thus considered as key in the short-term evaluation of their state of morpho-dynamic equilibrium. During the passage from the high-energy to the lower-energy season, a beach crosses through -equilibrium profile whose shape lies between the two endpoints of the winter and summer profiles. This intermediate state reflects more faithfully the mean dynamics of a beach that results in the dimension of its physical components forming the subaerial sector. Thus, backshore and foreshore, if properly detected and bi dimensionally measured, can be consistently related to the state of beach retreatment or advancement at the momen t of the observation. This very quick and low-cost method thus requires only one profile measurement per year, which has to be strategically acquired during the late spring, when a beach is expected to be in preserve the tracks of the advancing/retreating trend. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 48-50, 2 figs. © Società Geologica Italiana, Roma 2012 The problem of small footprints in paleoichnology related to extramorphologies: new data from the Early Permian Erpetopus LORENZO MARCHETTI (*), G IUSEPPE SANTI (**) & MARCO AVANZINI (°) Key words: critical size, Early Permian, extramorphologies, footprints, Erpetopus but the use of new techniques and the discovery of new well preserved specimens of this taxa in Italian Early Permian allow us to bring new important data on this matter. DISCUSSION INTRODUCTION The study of small footprints has always been difficult in paleoichnology, because small size seems to be more strictly linked to extramorphologies which could modify the true morphology of footprints. These extramorphologies have different origins and could be caused by granulometry and wetness of sediment, or by different kind of locomotion of trackmakers, so diagnostical characters could be misunderstood. Because of this, paleoichnolgists instituted a critical size (20 mm). Footprints smaller are too much affected by extramorphologies to allow reliable data. This fact, united with the technical difficulties to make drawings and measures on these specimens explains the lack of serious studies on footprints of this size, justifying in this way the institution of ichnotaxa with very poor data. In Early Permian paleoichnology this is the case of ichnotaxa Erpetopus willinstoni (MOODIE, 1929), firstly described by the ichnofauna of Castle Peak (Texas). The lack of data brought some confusion, especially when compared with the similar Camunipes cassinisi (CEOLONI et alii, 1987), found in Northern Italy. Italian ichnologists justified the separation from Erpetopus with a more distinctive rotation of V digit in Camunipes (S ANTI, 2007). American ichnologists rejected this supposition, considering it only an extramorphological feature, frequent for footprints under the "critical size". This discussion appears to be "philosophical", because reliable data to support one of the other hypothesis don't exist, _________________________ (*) Dipartimento di Geoscienze, Università degli Studi di Padova, via Gradenigo 6, 35131 Padova (**) Dipartimento di Scienze della Terra Studi di Pavia, via Ferrata 1, 27100 Pavia , Unirsità degli (°) Museo Tridentino di Scienze Naturali, via Calepina 14, 38100 Trento A real problem in the study of footprints smaller than 20 mm is the difficulty to find well-preserved specimen, with all the features of footprints displayed. Another is the measure of parameters, too small measures tend to increase human errors. In order to add reliable data on the knowledge of Erpetopus, the study of well-preserved trackways was improved by the use of photos and laser scanner techniques. Imprints clearly modified by extramorphological effects were not taken in account. The study was focused on the re-examination of the holotype of Camunipes cassinisi (specimen 10 pal_67, stored at Museum Fig. 1 Particular of trackway 3 (specimen 12465). To notice the high and regular divarication of digits, due to the soft mud. Scale bar 2 cm. of Natural Sciences of Brescia) and an exceptional new specimen with four complete trackways of Erpetopus (specimen 12465, stored at Museum of Natural Sciences "E. Caffi" of Bergamo ) (Figs. 1, 2). The holotype shows all the features of Erpetopus, plus marked divarication between digits IV-V (65° in manus, 82° in 49 NEW DATA FROM THE EARLY PERM IAN ERPETOPUS Fig. 2 Drawing of specimen 12465 (stored at Museum of Natural Sciences "E.Caffi", Bergam o). Scale bar 10 cm . pes) and I-V (181° in manus, 161° in pes). Pes appears parallel to midline and with central digits close to each other. These features appear also in the specimen 12465, in trackways 1 and 4, where we observe high divergences between digits IV and V (51-72° in manus, 99° in pes) and digits I and V (182-198° in manus, 193° in pes), and pes almost parallel to midline. This similitude appears to be not due to extramorphologies, because we observe the same characteristics in different substrates (silt in 10_pal 67 and mud in 12465), and in reptiles with different speed of locomotion (trackmaker of the holotype is slower) and size (holotype is bigger). On the contrary, trackways 2 and 3 seems to vary their features with speed of locomotion and wetness of substrate. The high total divergence in trackway 3 (184° in manus and 180° in pes) seems to be related with the difficult locomotion of the reptile, which opened the digits to have more grip on the ground. Trackway 2 instead has faster locomotion and appears more digitigrade: this probably caused the very low total divergence (76-89°) and low divergence between digits IV-V (15-37°). All these trackways seem to represent well the ichnotaxa Erpetopus willinstoni, but distinctive features not related with extramorphologies or ontogenetical stages are possible (trackways 1-4 of 12465 and 10 pal_67). These features may be due to different skeletal structures, in this case the presence of Camunipes would be confirmed, but we need further data. We can also see significant variations of parameters with characteristics of substrate and speed in trackways 2-3, this represents an extramorphological effect. All these new data improve our knowledge on footprints smaller than the critical size, proving that extramorphological features are recognizable but not so striking to prevent serious studies on footprints parameters, in particular for well-preserved and long trackways. REFERENCES A VANZINI M., CEOLONI P., CONTI M.A., LEONARDI G., MANNI R., MARIOTTI N., MIETTO P., M URARO C., NICOSIA U., SACCHI E., SANTI G. & SPEZZAM ONTE M. (2001) - Permian and Triassic tetrapod ichnofaunal units of Northern Italy, potential contribution to continental biochronology. Natura Bresciana, Monografia, 25, 89-107. BERNARDI M. & AVANZINI M. (2011) - Locomotor behavior in early reptiles: insight from an unusual Erpetopus trackway. Journal of Paleontology, 85 (5). 50 MARCHETTI ET ALII CEOLONI P., CONTI M.A., MAR IOTTI N., M IETTO P. & N ICOSIA U. (1987) - Tetrapod footprints from Collio Formation (Lombardy, Northern Italy). Memorie di Scienze Geologiche, 39, 213-233. HAUBOLD H. (1971) - Ichnia Amphibiourum et Retpiliorum fossilium. Enciclopedia of Palaeoherpetology, 18, 1-124. HAUBOLD H. (2000) - Tetrapodenfahrten aus dem Perm Kenntnisstand und progress 2000. Hallesches Jahrbuch für Geowissenschaften, 22, 1-16. HAUBOLD H. & LUCAS S.G. (2001) - Die Tetrapodenfährten der Choza Formation (Texas) und das Artinsk-Alter der Redbed Ichnofaunen des Unteren Perm. Hallesches Jahrbuch für Geowissenschaften, 23, 79-108. HAUBOLD H. & LUC AS S.G. (2003) - Tetrapod footprints of the Lower Permian Choza Formation. Paläontologische Zeitschrieft, 77, 247-261. LEONARDI G. (1987) - Glossary and Manual of Tetrapod Footprint Palaeoichnology. Depart. Nacional. Producao Mineral, Brasilia. 117 pp. M OODIE R. L. (1929) - Vertebrate footprints from the red bed of Texas. American Journal of Science, 97, 352-368. M OODIE R. L. (1930) - Vertebrate footprints from the red bed of Texas II. Journal of Geology, 38, 548-565. S ANTI G. & K RIEGER C. (2006) - A possible philetic relationship between Camunipes and Erpetopus, ichnogenera of the Lower Permian of Europe and North America. Giornate di Paleontologia 2006, Trieste. S ANTI G. (2007) - A short critique of the Ichnotaxonomic Dualism Camunipes-Erpetopus, Lower Permian Ichnogenera from Europe and North America. Ichnos, 14, 185-191. S ARJEANT W.A.S. (1971) - Vertebrate tracks from the Permian of Castle Peak, Texas Texas Journal of Science, 22, 344-366. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 51-52, 3 figs. © Società Geologica Italiana, Roma 2012 Geochemical characterization of sediment quality in the river basin of the Rio Grande Quequén (Argentina) EMANUELA M ARIN (*), LILIANA BEATRIZ TERUGGI (°), ELENA M ARROCCHINO (*) & CARM ELA VACCARO (*) Key words: heavy metals, Rio Quequén Grande, river sediments, XRF. ABSTRACT The hydrographic basin of Rio Quequén Grande (Argentine) occupies 10.000 Km2 of the south-east area of the Buenos Aires province, in the area "pampeana bonaerense", located in the bigger area of Argentine loess, between latitude 20° and 40°South. The area of the basin is for the 97,5 % flat and, thanks to the abundance of water resources and the fertility of the soil, it has been interested by the intensification of agriculture which made of it, in the last decades, one of the greater areas of food supplying on worldwide scale (FARENGA et alii, 2005; ROM ANELLI et alii, 2009; TERUGGI et alii, 2005b). Through sedimentological, chemical and petrographic analysis, this study provides data on the quality of river sediments, from source to mouth of Rio Quequén Grande. A comparison of the results with those obtained in the 2002 campaign, has allowed an assessment, after some time, about problems of pollution due to storage of heavy metals such as Pb, V and Zn, and salinity phenomena. Geochemical analysis were obtained by X-ray fluorescence (XRF) model ARL Advant'X spectrometer, while the development took advantage of the use of GIS mapping, with use of ArcGIS software, version 9.3. Chemical data reflect the uniformity of the river sediments derived by the rearrangement of aeolian sediments (loess Quaternary Argentines) in an area prevalently flat and not subject, from Mesozoic, to tectonic deformation events. Despite this macro-uniformity, on scale of detail, it can be observed variations in chemical and mineralogy composition, not only due to the presence of the sequence of carbonate horizons, _________________________ (*) Univers ità degli Studi di Ferrara, Dipartimento di Scienze della Terra, Via Saragat 1, 44121 Ferrara (Fe) (°)Università degli Studi di Firenze, Dipartimento di Ingegneria Civile ed Ambientale, Via di Santa M arta 3, 50139 Firenze (Fi) caliche, deposited during dry periods and persisted over time, due to the precipitation of carbonate waters, but also for the contributions of local deposits derived from the dismantling of the Paleozoic basement, that outcrops on the edge of the basin in the northern sector. Finally, some sediment samples, taken in the vicinity of the greater built -up areas of the centers of Necochea, Loberia and Quequén, showed an increase in metals that however are included widely within the limits recommended by the directives UNI and the Worldwide Organization of the Health. Rio Quequén Grande morphology From an environmental point of view, the impermeable beds of caliche (Fig. 1) represent aquitards that, confining the permeable sandy horizons, allow the development of the multi aquiferous system of the Pampa (TERUGGI et alii, 2005a). Fig. 1 Carbonate beds, caliche. These water resources serve not only for water supply, but also for the development of internal marshy areas with fresh and brackish waters, where protected plant and animal species can find hospitality, including migratory birds (Fig. 2). In Fig.3 we can see where, from the landscape of Argentine loess, particularly in the north west area, are visible outcrops of ancient Paleozoic basement. 52 MARIN ET ALII REFERENCES F ARENGA M.,TOM ÁS M., BERNASCONI M.V. & TERUGGI L.B. (2005) - Implementación de un Sistema de Información Geográfica en la Cuenca del Río Quequén Grande, Provincia de Buenos Aires, Argentina: Desde la Generación de la Cartografía Base hasta el Modelo Digital del Terreno. Revista Cartogràfica, 80/81, 107-115. Instituto Panamericano de Geografía e Historia, México. Fig.2 - Flock of flamingos in a marshy area of the Argentina Pampas on the Rio Quequén Grande. ROM ANELLI A., QUIROZ LONDOÑO O.M., MARTINEZ D.E. & BOCANEGRA E. (2009). - Caracterización hidrogeoquímica e isotópica de la laguna La Salada y su relación con el acuífero pampeano (Partido de Necochea, Provincia de Buenos Aires). VI Congreso Nacional de Hidrogeología y IV Seminario Hispano-Latinoamericano sobre temas actuales de la Hidrología Subterránea, Actas, II, 601-610. T ERUGGI L.B., M ARROCCHINO E., RAPTI-CAPUTO D. & V ACCARO C. (2005a) - Geochemical characterization of bed sediments of the Rio Quequén Grande Grande catchemnt, Argentina. Geologica Romana, 38, 19 - 23. T ERUGGI L.B., M ARTINEZ G.A, BILLI P. & PRECISO E. (2005b) Geomorphology and sediment transport in a very low relief catchment: R. Quequén Grande, Argentina. Geomorphological Processes and Human Impacts in River Basins. IAHS Publ. 299, 154-160. Fig.3 - Outcrops of the old basement. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 53-54, 1 fig. © Società Geologica Italiana, Roma 2012 The lagoon of Nador (Morocco): geochemical and petrographic analysis of sediments and environmental conditions EMANUELA MARIN (*), D RISS N ACHITE (**), MOHAM ED N AJ IH (°), G IORGIO ANFUSO (°°), ELENA M ARROCCHINO (*) & CARM ELA V ACCARO (*) Key words: ArcGis 9.3, anthropogenic pollution, lagoon of Nador, heavy metals, XRF. ABSTRACT The Nador lagoon is one of the most important ports on the coast of Morocco, and the second lagoon in North Africa by extension (1115Km2). The lagoon is bordered to the north-west by the volcanic products of the Gourougou volcano complex (887 m asl) and south-east by the Jurassic carbonate succession of marine environment belonging to the Complex of Kebdana (932 m asl); the rest of the area around the lagoon is flat and is characterized by arenaceous-pelitic deposits linked to the Miocene and Quaternary magmatic activities. The rocks outcropping in the hinterland are generally characterized by low concentrations of metals, and are no exception most of the volcanic rocks of the Gourougou Complex, constituted mainly by latitic tuffs and trachytes, and rare basalts and andesite of the promontory of Atalayoum that are not volumetrically significant. A natural potentially impacting source of heavy metals is located in the northwestern part of the lagoon, where outcrops skarn with magnetite mineralization, widely exploited since ancient times (EL ALAMI et alii, 1998; EL RHAZI & H AYASHI, 2002; G ILLA et alii, 2004). To fully describe the quality of Nador lagoon sediments, 49 samples along the banks and on the bottom of the lagoon were gathered and their distribution was analysed and compared with the patterns of water circulation in the lagoon. The samples were subjected to petrographic and geochemical characterization by x-ray Fluorescence (XRF) by means of an ARL Advant X Spectrometer model. Furthermore, data distribution was obtained using GIS tools (ArcGis software, ________________________ (*) Università degli studi di Ferrara, Dipartimento di Scienze della Terra, Via Saragat 1, 44121 Ferrara (Italy) (**) Faculté Polydisciplinaire de Larache. BP 745 Poste Principale, 92004, Larache (M orocco) (°) Centre régional de l'INRH à Nador B.P. 493 Nador principal, Nador (M orocco) version 9.3) and thematic maps were created. The data showed that, despite the prevalence of contributions from the Miocene-Quaternary sedimentary sequences, characterized by low content of heavy metals, the samples contained high quantities of heavy metals, evidencing diffuse human related pollution problems. Since sediments are predominantly composed by quartz and carbonate, the content in metals is extreme ly low and the only natural source of pollution is attributable to the mobilization of metals contained in ancient iron mines dumps located along the banks of the Gourougou Complex. Such sediments are exposed to weathering and leaching processes that produce in nearby areas the largest observed concentrations of iron, in this sense enhancing the importance of the anthropogenic pollution versus the natural one. Specifically, the points with higher rates in metals are found near the town of Nador, the main urban centre in the area. High concentrations are also observed south of Nador, close to the plain of Bou Areg, densely tilled and devoted to agricultural purposes carried out using massive quantities of fertilizers and unpurified wastewater for irrigation. It is not clear however if the Promontory of Atalayoum, located in the north of the lagoon, constitutes a natural supply area of heavy metals. In this sense, further investigation should be carried out to fully understand the role of basic volcaniclastic deposits in the pollution linked to Cr, Ni, V and Co. However, it is possible to state that the main anomalies concern Cu, Fe, Pb and Zn, whose contributions are typical of human impact. Along the banks of the Nador lagoon, are also located the towns of Beni Enzar and Kariet Arkmane, characterized by a dramatic increase in population over the past 30 years, because of the opportunities offered by the business linked to the construction of summer houses, hotels, etc. as well as to the enlargement of the local port. The rapid increase in population was not accompanied by the realization of services and, most importantly, there are no appropriate treatment facilities for wastewater, with the associated environmental problems. In addition, analyzing the obtained maps using a geochemical point of view, two distinct areas are observed and linked to water circulation patterns within the lagoon. It is possible to observe a preferential current along the banks and a secondary current that splits into two parts in the middle of the lagoon, this being related 54 MARIN ET ALII Fig. 1 Distribution of Pb concentrations in the lagoon of Nador: map was created using IDW interpolation and software ArcGIS 9.3. to the very specific geomorphologic characteristics of the lagoon; it may be also noticed that neither the streams that flow into the lagoon nor the inlet to the Mediterranean Sea create appreciable convective motions. The internal flows of the lagoon have low intensity; this fact and the shallow water depths determine an insufficient water supply and oxygenation (BLOUNDI et alii, 2008). For this reason, in recent years, it was started the building of an artificial inlet with the Mediterranean Sea. Specifically, the main aim of the construction of the Canal is to improve the water quality of some parts of the lagoon and mitigate the environmental problems, which were confirmed by the presented investigations. It would be useful, in a near future, to carry out further researches to evaluate the effects of the new inlet on water circulation and associated environmental problems. In conclusion, the study outlines how the quality of bottom sediments of Nador lagoon is deeply affected by the increasing anthropogenic pressure and the geochemical intrinsic characteristics of local sediments rich of heavy metals. FIGURES In Fig.1 example of thematic map describing the distribution of elements in the Nador lagoon: the areas characterized by a greater amount of Pb are located close to the cities of Nador and Beni Anzari and in the northern area along the banks of Gourogou Complex. Furthermore, the distribution of the presented element reflects the geomorphologic characteristics and the water current patterns in the lagoon. REFERENCES BLOUNDI M.K., FAURE P. & D UPLAY J. (2008) - Organic contamination identification in sediments from a Mediterranean coastal ecosystem: The case of the Nador lagoon (Eastern Morocco). C. R. Geoscience, 340, 840 - 849. E L A LAMI M., M AHJOUBI R., D AM NATI B., KAM EL S., ICOLE M. & TAIEB M. (1998) - Sédimentologie et géochimie organique des sédiments superficiels de la lagune de Nador (Maroc nord oriental). J. Africain Earth Sci., 26, 249 -259. E L RHAZI M. & HAYASHI K.(2002) - Mineralogy, Geochemistry, and Age Constraints on the Beni Bou Ifrour Skarn Type Magnetite Deposit, Northeastern Morocco. Resource Geology, 52, 25 - 39. G ILLA R.C.O., APARIC IO A., EL AZZOUZIC M., HERNANDEZD J., THIRLWALLA M.F., BOURGOISE J. & MARRINERA G.F. (2004) - Depleted arc volcanism in the Alboran Sea and shoshonitic volcanism in Morocco: geochemical and isotopic constraints on Neogene tectonic processes. Lithos, 78, 363 - 388. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 55-56. © Società Geologica Italiana, Roma 2012 Facies analysis and sequence stratigraphic interpretation of sandy deposits in the central part of the Siena Basin (Italy) I VAN MARTINI & F ABIO SANDRELLI (*) Key words: deltaic deposits, nearshore, Siena basin, sequence stratigraphy The Siena Basin is one of the post-collisional basins of the inner Northern Apennines, a collisional belt formed during the Cenozoic in response to the interaction between the Adria and the Corso-Sardinian microplates (CARM IGNANI et alii, 2001 and references therein). The structural origin and evolution of this basin is still a matter of debate (see BROGI, 2011 for a comprehensive review). Regardless of its structural origin, the Siena Basin was interested by a continental and marine sedimentation during Miocene and Pliocene time. In detail, the Pliocene marine succession is represented by nearshore marine deposits (sands and conglomerates) passing basinward to offshore silty clays. These deposits are generally considered as the expression of a single transgressive-regressive cycle (early Zanclean-late Piacenzian), characterized by a diachronous transgression from the southern to the northern sectors of the basin (BOSSIO et alii, 1992). A striking feature of the Siena Basin is the presence of thick (up to 80-100 m) sand-dominated bodies cropping out in its central sector. They were interpreted by the first authors who studied the Siena Basin (PANTANELLI , 1880; SIGNORINI, 1966) as the expression of a generic nearshore deposition. GANDIN & SANDRELLI (1992) reinterpreted the same deposits as turbiditic lobes related to the re-sedimentation of nearshore sands through gravity-driven processes, caused by sin-depositional tectonic activity. In this contribution these sandy bodies have been investigated focusing on component sedimentary facies and architectural geometries, integrated with micropalaeontological investigations in order to establish their depositional age and the palaeo-environmental conditions. The obtained results show that they are organized in coarseningand shallowingupward successions, _________________________ (*) Dipartim ento di Scienze della Terra, Università di Siena, via Laterina 8, 53100, Siena. representative of a deltaic deposition (i.e. shallow-water deltas). A typical sequence is composed of basal offshore mud, transitionally passing to alternations of muddy and sandy beds overlaid by thick sand bedsets. The latter are d ominantly composed of ungraded, structureless or plane-parallel laminated fine-grained sands. Subordinate normal graded (medium to fine-grained) sand beds, characterized by slight erosional bases, are also present. Continental plant fragments are common in both facies, testifying the genetic relation with land-derived flows. The sandy beds show tabular or slightly convex-up geometries at outcrop scale; lateral pinching-out and compensational stacking patterns are locally present. These deltaic deposits are the expression of two phases of deltaic deposition (the first one during the late Zanclean, the second one in the Piacenzian) separated by transgressive offshore mud. Therefore, they can be interpreted as lowstand deltas formed in response to two base-level falls. The same subaerial unconformities bounding depositional sequences (MARTINI et alii, 2010, 2011), thus allowing large scale correlations across the basin. REFERENCES BOSSIO A., CERR I R., COSTANTINI A., GANDIN A., LAZZAROTTO A., M AGI M., M AZZANTI R., M AZZEI R., SAGRI M., SALVATOR INI G. & SANDRELLI F. (1992) I Bacini distensivi Neogenici e Quaternari della Toscana. In: 76a Riunione Estiva SGI-Convegno SIMP, Guida Società Geologica Italiana, 198-227 BROGI A. (2011) - Bowl-shaped basin related to low-angle detachment during continental extension: The case of the controversial Neogene Siena Basin (central Italy, Northern Apennines). Tectonophysics, 499 (1-4), 54-76. CARM IGNANI L., D EC ANDIA F.A., DISPERATI L., FANTOZZI P.L., KLIGFIELD R., LAZZAROTTO A., LIOTTA D. & MECCHERI M. (2001) - Inner Northern Apennines. In: G.B. Vai & I.P. Martini (Eds) - Anatomy of an Orogen. The Apennines and Adjacent Mediterranean Basins, 197-214. 56 MARTINI & SANDRELLI GANDIN A. & S ANDRELLI F. (1992) - Caratteristiche sedimentologiche dei corpi sabbiosi intercalate nelle argille plioceniche del Bacino di Siena. Giornale di Geologia, 54, 55-65. (2010) The Pliocene deposits of the southeastern Siena Basin ( -Montisi area, Tuscany, Italy) revised through allostratigraphy. In: Abstract book GeoSed 2010, Torino, 47. MARTINI I., ALDINUCCI M., F ORESI L.M., M AZZEI R. & SANDRELLI F. (2011) - Geological map of the Pliocene succession of the Northern Siena Basin (Tuscany, Italy). Journal of Maps, 193-205, doi:10.4113/jom.2011.1176. P ANTANELLI D. (1880) Gli strati litorali e salmastri del Pliocene inferiore in Toscana. Atti Soc. Tosc. Sc. Nat., Proc. Verb. Vol. II, Pisa. MARTINI I., ARRAGONI S., A LDINUCCI M. & SANDRELLI F. S IGNORINI R. (1966) I terreni neogenici del Foglio Siena. Boll. Soc. Geol. It., LXXXV, Roma. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 57-58. © Società Geologica Italiana, Roma 2012 Coral patch reef in a Burdigalian mixed carbonate-siliciclastic coastal system (Cala Paraguano, Corsica) ANDREA M AZZUCCHI & LAURA TOM ASSETTI (*) Key words: Burdigalian, coastal system, corals, carbonatesiliciclastic mixing, Corsica. This study concerns facies analysis of a Burdigalian coralrich mixed carbonate-siliciclastic system developed in the western part of the Bonifacio Basin (Cala Paraguano, southern Corsica). The Miocene marine sediments of this basin are divided in two formations: Cala di Labra Fm. and Bonifacio Fm. (F ERRANDINI et alii, 2002). The deposits of Cala di Labra, related to the Burdigalian transgression, overly the hercynian basement and are characterized by different coral-rich episodes (GALLONI et alii, 2001; FERRANDINI et alii, 2002). Cala di Labra Fm., cropping out at Cala Paraguano, shows a very good exposure and offers the opportunity to report an example of coral patch reef development in costal settings, dominated by a mixed carbonate-siliciclastic sedimentation. At Cala Paraguano, the sea-cliff exposure allowed us to trace the stratigraphic surfaces, and identify stratal and coral bioconstruction geometries. The description of coral bioconstructions follows the terminology proposed by INSALACO (1998). Thin section analysis permitted a better definition of the biotic constituents. Finally, the carbonate content of the samples was determined through gasometric analysis using a Dietrich-Fruhling calcimeter. This deposits were assigned to four sedimentary facies: a) coral rudstone to floatstone in a siliciclastic matrix, b) coral floatstone, c) coral domestone, d) maerl. The coral rudstone to floatstone in a siliciclastic matrix is a roughly bedded facies gently dipping (up to 10°) to SW. Coral colonies are abundant in this facies, although they are mostly not in life position. Corals are predominantly small in size, with massive-globular morphology, although subordinate plate _________________________ (*) Dipartimento di Scienze della Terra, La Sapienza Università di Roma, P. Aldo M oro 5, I-00185 Roma. [email protected] and rare branching forms are also present. The inter-coral sediment is a hybrid sandstone with bivalves, ec hinoids and subordinate small benthic foraminifera, red algae and gastropods. The coral floatstone facies shows a massive to crude stratification, and locally a slightly ondulate lamination. Coral colonies are both in life position and reworked, often dispersed in the sediment, which is a grainstone-packstone consisting of abundant geniculate and non geniculate red algae fragments and subordinate bioclastic constituents. Coral domestone facies is characterized by coral colonies (Porites, subordinate Tarbellastrea and faviids) in living position. The dominant massive-globular and the less common platy colonies grow close one over another forming a dense bioconstruction, which results in a build-up of up to 5 m in height. The inter-coral sediment is represented by a moderately-poorly sorted bioclastic floatstone to packstone. The main components are red algae, bivalves, echinoids and larger benthic foraminifera (Miogypsina and subordinate Amphistegina). The maerl facies consists of poorly sorted floatstone to rudstone, in a packstone matrix, composite parallel beds, characterized by planar to slightly ondulate internal stratification. Red algae (Spongites, Sporolithon and melobesoids), often intensively bored by clionid sponges, are the major constituents of thi s facies. Other components include bryozoans, pectinids, serpulids, larger benthic foraminifera (Miogypsina, Amphistegina and rare Heterostegina) and echinoids. The reconstructed depositional model shows a wedgeshaped profile along the downdip direction. The coral rudstone to floatstone in a siliciclastic matix facies developed in a highly energetic environment under elevated terrigenous input, whereas the coral domestone facies was originated by small size patch reef in a moderate energetic and well-lit zone. These coral bioconstruction pass basinward to the coral floatstone facies. The more distal facies is represented by the maerl facies, which indicates deeper and less energetic environment in oligophotic condition. 58 MAZZUCCHI & TOMASSETTI REFERENCES FERRANDINI M., GALLONI F., BABINOT J.F. & MARGEREI J.P. (2002) - La plateforme carbonatée burdigalienne de Bonifacio (Corse du Sud): microfaunes et paléoenvironnements. Revue de Micropaleontologie, 45, 57-68. G ALLONI F., CORNEE J.J., REBELLE M. & F ERRANDINI M. (2001) - Sedimentary anatomies of early Miocene coral reefs in South Corsica (France) and South Sardinia. Géologie Mediterranéenne, 28, 73-77. I NSALACO E. (1998) - The descriptive nomenclature and classification of growth fabrics in fossil scleractinian reefs. Sedimentary Geology, 118, 159-186. Rend. Online Soc. Geol. It., Vol. 20 (2012), p. 59. © Società Geologica Italiana, Roma 2012 Mysterious Triassic ammonoids of Recoaro area: state of art PAOLO MIETTO , STEFANO MANFRIN (*) Key words: Ammonoid fauna, ceratitoid, Recoaro area, German basin, Alpine basis. During the 1800 and the beginning of 1900, several germanspeaking geologists (such as Beyrich, Mojsisovics, Tornquist) studied the Recoaro area, describing important ammonoid fauna characterized also by peculiar species of the Germanic B asin. This fauna, most of which is coming from the Nodosus Formation, consists in problematic species that are affected by provincialism and thus difficult to interpret under the taxonomic and biostratigraphic point of view. Unfortunately, most of the collected materials have been destroyed during the II World War, precluding a modern taxonomic revision. One of the unravelled _________________________ (*) Dipartimento di Geoscienze, Università degli Studi di Padova, via G. Gradenigo, 6, 35131 Padova [email protected] questions was related to the presence of a german ceratitoids in the alpine ammonoid association. Recent field work in the Recoaro area tried to complete the lost collection but only not well preserved specimens have been collected. Fortunately, an unexpected ammonoid fauna from the Recoaro area has been found in a small and old collection stored at the Museo Geologico e Paleontologico of the University of Padova. This small collection permitted to solve the open question since a typical species belonging to the Germanic Muschelkalk has been documented within the Alpine Basin. This finding is important for the Triassic ammonoid taxonomy and biostratigraphy, and plays an important role for the Triassic sequence stratigraphy. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 60-62, 3 figs. © Società Geologica Italiana, Roma 2012 Upper Miocene Lower Pliocene provenance changes in the Venetian Foreland G IOVANNI MONEGATO (*) & CRISTINA STEFANI (**) Key words: Provenance, alluvial deposits, Venetian Basin, Upper Miocene. INTRODUCTION The Upper Miocene clastic wedge of the Venetian Basin represents a regressive foreland succession recording the Neoalpine phase of the eastern Southalpine Chain, during the Serravallian-Messinian time bracket (CASTELLARIN et alii, 2006). The succession encompasses the Vittorio Veneto sandstone, related to offshore environment, and the Montello conglomerate, mostly made of continental sedimentary units (M ASSARI, 1975; MASSARI et alii, 1986); the latter is interpreted as the filling of the foreland during the acme of the Neoalpine tectonic phase (M ELLERE et alii, 2000). The facies associations, as well as the stratigraphy of the succession, was recently reviewed (STEFANI et alii, 2010) in order to delineate a better chronology of the sedimentary wedge and the correlation with comparable sedimentary units outcropping in the Friulian piedmont plain (ZANFERRARI et alii, 2008). The Upper Miocene succession of the Venetian Basin reflected the uplift and the progradation of the chain at its back, so changes in the drainage network within the chain are marke d by variations in sedimentary supply and provenance in the fluvial deposits of the related the foreland basin. Early analyses on pebbles (MASSAR I et alii, 1974) and on sandstones (STEFANI , 1987) were realized in the Montello conglomerate separating the unit between the Tortonian interval from the Messinian one, according to M ASSARI (1975) age boundary; only in M ASSAR I et alii (1994) a rough analysis on pebbles was performed along a composed stratigraphic section. The present study provides a new analysis on sandstones realized considering four main stratigraphic sections (marked in Fig. 1), in which some different units have been distinguished in the Tortonian-Messinian interval (STEFANI et alii, 2010). These analyses yielded a more detailed reconstruction on the drainage network feeding the Venetian Basin during the cited interval, compared also with samples of Pliocene age. METHODS Fig. 1 Sketch of the study area _________________________ (*) CNR - Istituto di Geoscience e Georisorse, Torino (**) Dipartimento di Geoscience, Università degli Studi di Padova This work is part of the Post-doc project CPR095351/09, Università degli Studi di Padova. One hundred and five suitable sandstone and sand samples were studied for quantitative analyses. They are relative to four stratigraphic sections, while data for present rivers have been included for comparison after MONEGATO et alii (2010). The entire sandy fraction (0.0625-2 mm) was examined. It was split and impregnated in an epoxy resin according to the methodology described by GAZZI et alii (1973). Thin sections were stained with alizarine-red solution for the determination of the carbonate phases. Sandstone and sand point counts were carried out following Gazzi -Dickinson procedures (INGERSOLL et alii, 1984). For each sandstone section 500 points were counted, 300 for the sand ones, using 0.5 mm grid spacing. In UPPER MIOCENE 61 LOWER PLIOCENE PROVENANCE CHANGES IN THE VENETIAN FORELAND order to improve the information, a separate count of almost 200 rock fragments was performed on each sample. The results were plotted in ternary diagrams and compared with the existent databases (GAZZI et alii, 1973; G ARZANTI et alii, 2006; MONEGATO et alii, 2010). RESULTS 5) The more recent Pliocene deposits, making group 5, are mostly related to the western sector and the composition points to an increase of fine-grained lithic fragments. Compared to the present day rivers, the analyses indicate that from the exhumation of the Southalpine basement onwards, the Brenta River catchment became to take shape, as shown by the comparison to the present sediments (G ARZANTI et alii, 2006; M ONEGATO et alii, 2010). In the eastern sector, the lack of a The results were plotted in ternary diagrams (Fig. 2), which evidence petrofacies clusters. Five groups were distinct from the stratigraphic succession, after STEFANI et alii (2010), and represented in figures 2 and 3. 1) The oldest of Tortonian age related to the Vittorio M 10 0 1 2 3 4 5 Brenta Piave 25 75 Q+F Q+F 50 10 0 1 2 3 4 5 Brenta Piave 25 75 1 2 3 4 5 50 75 25 50 10 0 50 10 0 75 50 25 V S 75 25 10 0 10 0 L 75 50 25 CE L CE Fig. 2 Ternary diagram of s andstone samples. Q: quartz, F: feldspars, L: fine-grained lithic fragments; CE carbonate fragments. 1: m, iddle Fig. 2 Ternary diagram of sandstone samples. lithic Q: quartz, F: feldspars L: Tortonian; upperfragments; TortonianCE keycarbonate level; 3: upper Tortonian; 4: M essinian; 5: fine-grained2:lithic lithic fragments. Pliocene (see text for details). Veneto sandstone and the basal Montello conglomerate, in this the petrofacies is well defined despite samples collected in different locations. 2) The second group is related to the horizon in which clasts of the Southalpine basement appear. This is well defined in the western portion of the study area, interested by an important supply from the basement outcrop area (M ONEGATO et alii, 2010), while it is smoothed towards the east. 3) The third group is related to a series of fluvial sedimentary bodies interbedded with transitional of marine facies. In this group differentiations in distinct source areas become clearer. The western source is distinguishable for the higher content in quartz and fine-grained lithic fragments. 4) The subdivision is maintained in the fourth group, which is related to the spread of the alluvial fans in the piedmont plain. A palaeoBrenta provenance is related to a different petrofacies (Fig. 2), rich in quartz and fine-grained lithic fragments. Fig. 3 Ternary diagram of the lithic component. M: metam orphic rock fragments , V: volcanic r.f., S: sedimentary r.f.. (see caption of figure 2 for color legend). clear trend and the overlapping to the present composition of the Piave River suggest a steady catchment within the Dolomitic area. Taking into consideration the lithic fragments (Fig. 3), these show how the boundary area between modern Brenta and Piave catchments had an independent development during the Messinian-Pliocene time. Actually, the presence of acidic volcanic fragments (Permian rhyolites) together with low-grade basement rocks points to the similarity to the present Cismon Stream. This can be observed in pebble composition in the correspondence of the modern outlet of the Piave valley. REFERENCES CASTELLARIN A., N ICOLICH R., F ANTONI R., CANTELLI L., SELLA M. & SELLI L. (2006) - Structure of the lithosphere beneath the Eastern Alps (southern sector of the TRANSALP transect). Tectonophysics, 414, 259-282. G ARZANTI E., ANDÒ S. & VEZZOLI G. (2006) - The continental crust as a source of sand (Southern Alps cross section, northern Italy). J. Geol., 114, 533 554. 62 MONEGATO ET ALII GAZZI P., ZUFFA G.G., G ANDOLFI G. & PAGANELLI L. (1973) Provenienza e dispersione litoranea delle sabbie delle inquadramento regionale. Mem. Soc. Geol. It., 12, 1 37. INGERSOLL R.V., BULLARD T.F., FORD R.L., GRIM M J.P., P ICKLE J.D. & SARES S.W. (1984) - The e ect of grain size on detrital modes: a test of the Gazzi Dickinson pointcounting method. J. Sediment. Petrol., 54, 103 116. (Italy). In: M. Marzo and C. Puigdefabregas (Eds) Alluvial Sedimentation Spec. Publ. Int. Ass. Sediment., 17, 501-520. M ELLERE D., STEFANI C. & ANGEVINE (2000) - Polyphase tectonics through subsidence analysis: the Oligo-Miocene Venetian and Friuli Basin, north-east Italy. Basin Res., 12, 159-182. MASSARI F. (1975) Sedimentazione ciclica e stratigrafia del Tortoniano superiore Messiniano tra Bassano e Vittorio Veneto. Mem. Ist. Geol. Min. Univ. di Padova, 31, 1-56. M ONEGATO G., STEFANI C. & ZATTIN M. (2010) - From present rivers to old terrigenous sediments: the evolution of the drainage system in the eastern Southern Alps. Terra Nova, 22, 218-226. MASSARI F., ROSSO A. & RADICCHIO E . (1974) - Paleocorrenti e composizione dei conglomerati tortoniano-messiniani compresi tra Bassano e Vittorio Veneto. Mem. Ist. Geol. Min. Univ. di Padova, 31, 1-20. S TEFANI C. (1987) - Composition and provenance of arenites from the Chattian to Messinian clastic wedges of the Venetian foreland basin (Southern Alps, Italy). Giornale di Geologia, 49, 155-166. MASSARI F., GRANDESSO P., STEFANI C. & JOBSTRAIBIZER, P.G. (1986) - A small polyhistory foreland basin evolving in a context of oblique convergence: the Venetian basin (Chattian to Recent, Southern Alps, Italy). In: P.A. Allen and P. Homewood, (Eds) - Foreland Basin Spec. Publ. Int. Ass. Sediment., 8, 141-168. S TEFANI C., M ONEGATO G., GRANDESSO P. & FORNAC IARI E. (2010) - Reconciling the Tortonian-Messinian stratigraphy of the Venetian foothills (NE Italy). GeoSed 2010, Torino, 19-25 settembre 2010. MASSARI F., MELLERE D. & DOGLIONI C. (1994) - Cyclicity in non-marine foreland-basin sedimentary fill: the Messinian conglomerate-bearing succession of the Venetian Alps ZANFERRARI A, AVIGLIANO R, G RANDESSO P, MONEGATO G, PAIERO G, POLI ME & STEFANI C. (2008) - Note illustrative APATRegione Autonoma Friuli Venezia Giulia. Rend. Online Soc. Geol. It., Vol. 20 (2012), p. 63. © Società Geologica Italiana, Roma 2012 Provenance of the Pleistocene fluvial deposits of the Ambra valley (central Tuscany): implication for palaeo-drainage evolution G IORGIA MOSCON (*) Key words: fluvial deposits, provenance analysis, Northern Appennines, Pleistocene . ABSTRACT The Plio-Pleistocene evolution of the most main Tuscan rivers has been outlined in 1981 by Bartolini and Pranzini. Those Authors showed as the Chianti Ridge at the boundary between the Siena and Upper Valdarno B asin (central Tuscany) was a key area for the Arno River drainage evolution. During the Middle Pliocene the Arno River flowed almost southward, from the Casentino to the Val di Chiana Basin. Subsequently, between Pliocene and Pleistocene, the Upper Valdarno Basin subsidence induced a piracy of the Arno river, which started to flow toward NE along the present-day tract. Recent studies (ALDINUCCI et alii, 2007; BOSCAINI 2011) showed the Chianti Ridge at the boundary between the Siena and Upper Valdarno Basin was drained by a Plio-Pleistocene southward -flowing fluvial system hosted in a N-S trending valley. Palaeohydrological studies (RONER, 2011) showed that the paleo-discharge of this river was comparable to that of the modern Arno River. The present study focuses on the composition of sandy and gravelly fluvial deposits, and aims at defining the meaning of this fluvial system in the frame of the paleodrainage evolution of the area. The study paleovalley was cut both on pre-Neogene bedrock forming the Chianti Ridge and Pliocene marine to transitional deposits of the Siena Basin. The infill have been dated at PlioPleistocene through regional geological evidences and fossil content (ALDINUCCI et alii, 2007). The valley fill consists of two intervals separated by an erosive surface. The upper interval is cut in the lower one in the northern and southern part of the study area. The lower interval (40 m thick) is mainly made of gravels. The upper interval is about 35 m thick and deposited across a sin-sedimentary normal fault dipping toward NE (i.e. upstream). This interval consists of organic-rich mud containing isolated channels passing downstream into channelized gravels. _________________________ (*) Dipartimento di Geoscienze, Università degli Studi di Padova, via G. Gradenigo, 6, 35131 Padova, Italy The present study focuses on the composition of sandy and gravelly deposits of the upper interval. Both these fractions appear to be rich in calcareous lithologies, which are relatively poorly exposed along the Chianti Ridge. In particular, the sandy fraction, which belongs to the sensu FOLK, 1974; ZUFFA , 1980) is rich in calcareous and marly clasts. Such a composition is very similar to that of the sand forming the Pleistocene terraces of the Arno River in the Upper Valdarno Basin. Compositional data highlight that the study paleovalley probably drained an area which was significantly wider than the Chianti Ridge. A preliminary hypothesis would suggest a correlation between the study drainage and the Paleo-Arno system, which passed through the study area before to enter the Upper Valdarno Basin. REFERENCES A LDINUCCI M., GHINASSI M. AND S ANDRELLI F. (2007) Climatic and tectonic signature in the fluvial infill of a late Pliocene valley (Siena Basin, Northern Appennines, Italy). SEPM, Journal of Sedimentary Research, 77, 398-414. BARTOLINI C., P RANZINI G. (1981) - Plio-Quaternary evolution of the Arno basin drainage. Z. Geomorph. N.F., 40, 77 91. BOSCAINI N. (2011) - I depositi plio-pleistocenici di valle incisa del Torrente Ambra (Toscana, Italia: interazione tra tettonica e sedimentazione). Master Thesis, unpublished. CIPRIANI C . (1961) - Ricerche sulle arenarie:III. La composizione mineralogica di una serie di rocce della Formazione del Macigno. Period. Mineral. 30, 23 59. F OLK R.L. (1974) - The petrology of sedimentary rocks. Austin, Tx, Hemphill Publishing Co. 182. RONER M. (2011) - I depositi ghiaiosi pleistocenici del paleoArno (Toscana centrale, Italia): facies sedimentarie ed architetture deposizionali. Master Thesis, unpublished. ZUFFA G.G. (1980) - Hybrid arenites: their composition and classification. Jour. Sed. Petrology, 50, 21-29. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 64-66, 4 figs. © Società Geologica Italiana, Roma 2012 Study and interpretation of some uncertain Triassic lithosomes at the base of the Lagonegro Basin succession: a key for a correct reconstruction of the Monte Facito Formation (Basilicata, southern Italy) GIUSEPPE PALLADINO & GIACOM O PROSSER (*) Key words: Gravity-induced deposits, Lagonegro Basin, Monte Facito Formation, southern Italy. discuss the tectono-stratigraphic significance of the Monte Facit o Formation. THE MONTE FACITO FORMATION INTRODUCTION In passive margins gravity-induced deposits are usually recognized at the hangingwall of the main extensional faults. These sediments often form thick bodies mostly composed of breccia and conglomerates, olistoliths, submarine slides etc. Commonly, after these rocks are incorporated into the orogens, their sedimentary nature is difficult to recognize due to the tectonic overprinting taking place during thrust activity. In fact, intense deformation in the correspondence of the main detachment levels may completely obliterate the original sedimentary fabric producing rock bodies with a block-in-matrix structure, interpreted as mélanges, broken formations, olistostromes, etc.. Consequently, discrimination of gravitydriven structures from those induced by later contractional tectonics is difficult. These problems are commonly encountered when a complete stratigraphic reconstruction of the Monte Facito Formation is attempted. This Triassic unit, largely cropping out at the base of the Lagonegro Basin succession, was deposited during the first stages of the Africa-Europe continental separation and later, during Miocene, was affected by contractional deformation during the development of the southern Apennine chain. As a consequence of this complex tectono-sedimentary history, the Monte Facito Formation consists of a series of equivocal, deformed lithosomes that can be interpreted to have either a tectonic or sedimentary origin. A significant example of this is provided by the genesis of pebbly mudstones, (paraconglomerate in the current literature), that have been interpreted both as Triassic gravity-flow deposits or as sheared levels related to contractional Miocene shear zones. A detailed study performed in well-exposed series of the Monte Facito Formation gave us the opportunity to document the sedimentological nature of these uncertain lithosomes and to _________________________ (*) Università degli Studi della Basilicata, Dipartimento di Scienze Geologiche, via dell'Ateneo Lucano, 10 - 85100 POTENZA The Monte Facito Formation represent a very peculiar stratigraphic unit of the southern Apennine thrust -belt. It records the first stages of the Africa -Europe continental rifting of EarlyMiddle Triassic age (SCANDONE , 1967; DONZELLI & CRESCENTI , 1970, WOOD, 1981; CIARAPICA et alii, 1990; P ANZANELLI F RATONI, 1991; MARSELLA et alii, 1993; CIARAPICA & PASSERI , 2000) (Fig 1). In particular, following Wood (1981), the deposition of the Monte Facito Formation records the initial break-up and the late extensional collapse of a previously emerged basement. Following this evolutionary scheme, the Monte Facito deposits can be subdivided, at first approximation, into two informal categories of lithofacies: - the first consists of Scithian to Anisian shallow-water lithofacies, essentially made up of massive carbonate build-ups, shelf rythmites and wave influenced shoreface sands (SCANDONE , 1967; DONZELLI & CRESCENTI , 1970, WOOD , 1981; CIARAPICA et alii, 1990; PANZANELLI FRATONI, 1991; CIARAPICA & PASSERI , 2000); - the second consists of deep-water lithofacies, made up of gravity-induced deposits alternating with-fine-grained sediments settled by fall -out mechanisms. In particular, most of the deepwater succession has been referred to a Ladinian olistostrome or mélange containing up to hectometric -sized carbonate olistoliths, breccias, conglomerates, etc. (W OOD, 1981; M ICONNET, 1988; M ARSELLA et alii, 1993; CIARAPICA & P ASSERI, 2000). The shallow-water lithofacies can be related to the first stage of basin opening, whereas the deep-water lithofacies testify the onset of a marked basin subsidence occurring after the continental collapse. In the field, the frequent occurrence of older shallow-water lithofacies juxtaposed on younger deep-water beds (PANZANELLI F RATONI, 1991) has been related to the presence of closely spaced thrust planes. Following this view CIARAPICA & PASSER I (2000) interpreted the paraconglomerate as resulting from fragmentation of more competent beds within a contractional shear zone. Alternatively, the paraconglomerate is regarded as the product of sedimentary processes as well as gravity-flow 65 RECONSTRUCTION OF THE MONTE FACITO FORMATION events occurred during the Triassic continental break-up (WOOD, 1981; PANZANELLI FRATONI , 1991). This work provides new field data indicating the sedimentary origin of some uncertain lithosomes in the Monte Facito Formation, improving the knowledge on the tectono-stratigraphic evolution of the southern tethyan domain during the Middle Triassic time. DESCRIPTION OF UNCERTAIN LITHOSOMES In this work two categories of uncertain lithosomes, respectively represented by folded slabs and pebbly mudstones (paraconglomerate) are considered. Folded slabs This lithosome consist of slabs made up of thinly-bedded Fig. 1 Folded strata slab consisting in a limestones /shale alternance. calcarenite/shale couplets, typical of the Early Triassic shallow water lithofacies (Fig.1). Slabs are generally isolated in a radiolaritc matrix. Internal structures include folds, normal faults and boudinaged beds. Commonly, limestone/shale slabs overlie a marked surface in the proximity of which deformation of the strata increases. We refer folded slabs to large slide bodies, consisting of exotic, semi-consolidate well-bedded material, along a planar basal shear surface, emplaced during the Middle Triassic extensional phase. A series of evidences support this hypothesis: i) folded slabs are commonly recognized in association with other gravity-driven deposits; ii) folded slabs are imbedded within a scarcely deformed Ladinian radiolarite host. Abrupt termination of individual slabs, their chaotic distribution and orientation, together with the close association with boulders, pebbles and cobbles of identical rock types as constituents of the adjacent gravity-driven deposits, indicate that the allochthonous masses have been emplaced by sedimentary processes; iii) the lack of structures typical of tectonic deformation, such as evidence of folding by flexural slip processes. Pebbly mudstones (Paraconglomerate) They consist of massively-bedded, matrix-supported, polygenic conglomerates and breccias. Clasts, very isolated in the matrix, vary in size from few centimeters to some decimetres. Isolated metre-scale blocks are also present. Often clasts exhibit a tabular shape. Angular to well-rounded clasts have also been recognized. A weak layer-parallel clast preferred orientation has been sometimes observed. Clasts mainly consist of massive or crossbedded calcarenites, micaceous arenites and quartzarenites deriving from Early Triassic shallow-water lithofacies. Matrix is commonly made up of brown-greenish shale. Pebbly mudstone bodies usually show irregularly-shaped geometries with a marked erosional basal surface and a convex - up geometry in the upper part. They may vary in thickness from few meters to some tens of Fig. 2 Lens -shaped pebbly mudstone body alternating to red radiolarites. Note at the base the undulating erosional surface. coloured meters. The accurate study of well-outcropping successions of the Monte Facito Formation reveal that pebbly mudstones are regularly alternated to relatively undisturbed Ladinian radiolarite deposits (Fig. 2). The above characters lead us to interpreted the pebbly mudstones as strongly dismembered slide masses or as debris flows. The observed pebbly mudstone/ radiolarite alternation is interpreted as a series of catastrophic events alternating with to quiet periods during which only fallout sedimentation took place. DISCUSSION Within the Monte Facito Formation, folded slabs and pebbly mudstone bodies are intimately associated everywhere. Often, packages of well-stratified folded strata gradually become brecciated laterally and vertically, resembling pebbly mudstones. Starting from these considerations we interpret the pebbly mudstones as the result of the progressive transformation of an 66 PALLADINO & PROSSER supported conglomerate with poorly-sorted tabular-shaped clasts. Only a slight imbrication can locally be observed. The massive interval is interpreted to derive by progressive deformation and fluidization of the overturned flank of the fold along a slide shear surface. Fig. 4 illustrates a carbonate breccia from the Monte Facito area. It should be noted that the original limestone strata have been plastically deformed and fragmented into cm-sized clasts. MAIN STRATIGRAPHIC IMPLICATIONS Fig. 3 portion. Calcarenite/shale folded slab showing a brecciated basal initially well-bedded calcarenite/shale slab during downslope sliding. In fact, it is well known that slides can initiate their downslope movements as coherent masses, successively evolving into debris flows (SPENCE & TUCKER, 1997). This process is particularly efficient when thin-bedded limestone/shales alternations are involved. Initially slide masses are folded, without exceeding their internal shear strength. Successively, the initially well-bedded masses progressively lose their cohesion because of the establishment of internal deformation mechanisms consequent to the outpacing of the shear strength. As a consequence, shale tends to make up a fluidized matrix, whereas single strata are broken into a series of isolated tabular clasts. The ultimate deposits produced through this process consist of a matrix-supported, poorly-sorted, flat-pebble conglomerates with clasts that exhibit both random or subparallel orientation. The above described process can be often documented in the field. If we analyze the folded slab in the Fig. 3, it is possible to separate a well-bedded upper portion from a nearly massive lower portion. In particular, this latter consist of a matrix- Fig. 4 Breccia deriving from the progressive folding and fragmentation of laminated calcarenite strata. Early Triassic lithosomes, widely recognized in the Monte Facito Formation, are here considered as gravity-induced sedimentary bodies produced during the Early-Middle Triassic extensional stages leading to the Africa-Europe continental separation. This interpretation can easily explain the observed older on younger contact s frequently recognized in the Monte Facito Formation. Concluding, the upper part of the Monte Facito Formation is made up of early Triassic rock bodies and clasts included in a Ladinian radiolarite matrix. REFERENCES CIARAPICA G., CIRILLI S., M ARTINI R., RETTOR I R., SALVINI BONNARD G. & ZANINETTI L. (1990) - Carbonate buildups and associated facies in the Monte Facito Fm. (Southern Apennines). Boll. Soc. Geol. It., 109 (1), 151-164. CIARAPICA G. & PASSER I L. (2000) - Le facies del Triassico inferiore e medio (Fm. di Monte Facito Auctt.) nelle aree di Sasso di Castalda e di Moliterno (Basilicata). Boll. Soc. Geol. It., 119 (2), 339-378. D ONZELLI G. & CRESCENTI U. (1970) - Segnalazione di una microbio facies permiana, probabilmente rimaneggiata, nella Formazione di M. Facito (Lucania Occidentale). Boll. Soc. Natur. Napoli,79, 13-19. M ARSELLA E., KOZUR H. & ARGENIO B. (1993) - Monte Facito Formation (Schitian-middle Carnian). A deposit of the ancestral Lagonegro Basin in the Southern Apennines. Boll. Serv. Geol. It., 110, 1991, 225-248. M ICONNET P. (1988) - Evolution mesozoique du secteur de Lagonegro. Mem. Soc. Geol. It., 41, 321-330. P ANZANELLI FRATONI R. (1991) - Analisi stratigrafica della «Formazione del M. Facito» Auctt. (serie di LagonegroAppennino Meridionale). Proposta di istituzione del Gruppo di Monte Facito. Tesi di Dottorato in Scienze della Terra, Università degli Studi di Perugia, 215 pp., Perugia. S CANDONE P. (1967) - Studi di geologia lucana: la serie calcareo-silico-marnosa. Boll. Soc. Natur. Napoli, 76, 1-75. S PENCE G. H. & TUCKER M. E. (1997) Genesis of limestone megabreccias end their significance in carbonate sequence stratigraphy model: a review. Sedimentary Geology, 112, 163-193. W OOD A.W. (1981) - Extensional tectonics and the Birth of the LagonegroBasin (Southern Italian Apennines). N. Jb. Geol. Palaont. Abh., 161 (1), 93-131. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 67. © Società Geologica Italiana, Roma 2012 New estimation of the post Little Ice Age sea level rise V INCENZO PASCUCCI (*), S TEFANO ANDREUCCI (*) & GABRIELA FRULIO (**) Key words: Little Ice Age, Medieval warm, late Pleistocene sandstones, Dimension stones, Maunder, Sardinia, Alghero. STATE OF ART Sea level rise is one of the main effects of climate changes. It is worldwide accepted that not only natural events have driven this processes, but also humans. Holocene is considered a high stand related to an Interglacial Stage. However climate and, therefore, sea level have experienced several fluctuations. It is well known that during the warm Medieval Period (9501350 AD) Vikings landed in Greenland and sailed through the NW passage. This warm time was followed by a relative cold one known as the Little Ice Age (LIA). During LIA, it has been estimated that temperature (N hemisphere) dropped down of at least 1 °C and that climate condition in Europe deteriorated to increase glaciers. This period started at about 1350 AD and ended 1850 AD and had three well defined minima temperatures associated to low solar activity: Wolf (12801350), Sporer (1450-1550) and Maunder (1645 1715). The new modern relative warm period started at about 1850 and is continuing now. Because of the strong emission of CO 2 due to industrial activities and related atmospheric pollution, it is not simple to discriminate which are normal from induced effects on this new climate warming. AIM Aim of this paper is to bring new information on the amount of post Little Ice Age sea level rise. We hope that the comparison of the emerged data with those relative to previous warming times (i.e. Medieval) may discriminate the amount of human contribution on climate changes. THE SPANISH QUARRIES The study area is located in NW Sardinia Island (Italy), _________________________ * DIPNET, Università di Sassari, Via Pandanna 4, 07100, Sassari, Italy, [email protected] ** TEXNH Project & Consulting, via Is M aglias 31, 09122 Cagliari, Italy Mediterranean Sea. Sardinia is considered stable since the late Pliocene with a negligible subsidence of about 0.01 mm/y. It is therefore normally used to reconstruct the Pleistocene and Holocene sea level curves. Our research focusses on the seafacing city of Alghero that since the 1353 to 1720 was under the Spanish government. During this time the city was renovated and new buildings edified. Dimension stones were quarried all around Alghero both in the nearby inland and along the coast. Coastal quarries were considered the most suitable both for rock quality and the easy way to transport the exploited material by boat. The quarried rocks are late Pleistocene dune and beach sandstones developed during the last Interglacial Stage (MIS5 Eemian). Sandstones crop out from few cm to 3m above the present sea level and underwent to several consolidation processes related to loading and marine weathering. This last favoured dissolution and circulation of calcium carbonate who cemented the rocks. It is reported that Spanish were looking for characteristics. Coastal quarries were active during the entire Spanish time. No documents indicate active costal quarries after the 17 th Century. Different rules were adopted through time for the size of dimension stones and this has allowed us to establish a quarry exploitation chronology. For example Alghero Cathedral dated at 1505-1593. Nowadays most of the coastal Spanish quarries are some centimetres below the minimum tide sea level (tidal range is 30 cm) and our measures have indicated that: 1) during low tide the max water high is of 20 cm; 2) during high tide the max water high is of 50 cm. CONCLUSIONS Data presented let us to infer that sea level from the apex of the Little Ice Age rose at least of 50 cm with an estimated rate of about 3 mm/y. If this were true and considering that sea level rise during Medieval warm period was of 0.6 mm/y over a period of about 400y, we may deduct that human influence is so strong to allow sea level rise five times higher than previous warm periods. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 68-70, 3 figs. © Società Geologica Italiana, Roma 2012 Late Holocene palaeohydrography in central and southern Venetian Plain: the role of petrographical sand analysis SILVIA PIOVAN (*), CRISTINA S TEFANI (**) & PAOLO MOZZI (**) Key words: sand, petrography, palaeohydrography. Recent studies of M OZZI et alii (2010) and PIOVAN et alii (2010) focused on the Late Holocene palaeohydrographical reconstruction of Padua surrounding areas (Fig. 1) and Adige-Po alluvial plain, respectively (Fig. 2). These works were based on remote sensing and DTM analysis (in particular, for DEMs _________________________ (*)University of Padua, Department of History, Padua, 35123, Italy (** ) University of Padua, Department of Geoscience, Padua, 35123, Italy analysis of Padua, see also N INFO et alii, 2011) and chronostratigraphical investigations. Padua lies on the Brenta River megafan (FONTANA et alii, 2008) and is encased within two meanders occupied, in the modern age, by the minor Bacchiglione River. The most ancient Holocene channel belt recognized in the study area is the Mestrino -Rubano (MR) one, which incised the alluvial plain formed during the Last Glacial Maximum. It was formed by the Brenta River between the Lateglacial and 6300 cal B stretch of 13 km in the northeastern part of the Padua alluvial plain; it probably was the last active river bed in the MR channel belt, between 8400 and 6300 cal BP. The present Bacchiglione Fig. 1 Geomorphological sketch of the alluvial plain around Padua with the location of petrography sand samples (m odified from Mozzi et alii, 2010). LATE HOLOCENE PALAEOHYDROGRAPHY IN CENTRAL AND SOUTHERN VENETIAN PLAIN Fig. 2 69 Geomorphological sketch of the Adige-Po alluvial plain with the location of petrography sand samples (m odified from Piovan et alii, 2010). River follows another, more recent, Brenta River channel belt, named Veggiano-Selvazzano (VS) channel belt. The meanders in the city centre of Padua most probably belong to this channel belt (M OZZI et alii, 2011). In the Padua southern area MiddleHolocene Brenta River deposits are present. In spite of the detailed stratigraphical information presented, the attribution of these channel bodies to a particular fluvial system has supported only by geomorphological and, for more recent times, by historical evidences. More to the south, the Brenta River megafan is bounded by the Adige-Po sedimentary system. This latter is characterized by a complex network of alluvial ridges pertaining to the Po and Adige rivers, which intersect and overlie one to another. These alluvial ridges are formed by the aggradation of sandy and silty channel deposits, natural levees and minor, proximal crevasse splays. Between them, that of the early Middle Ages. Another important alluvial ridge is the socalled direction to the southern Venice Lagoon (PIOVAN et alii, 2010). The Montagnana-Este alluvial ridge divides, near Pernumia, in three minor branches: Terrassa, Bagnoli and Conselve alluvial ridges. These two latter seem to join the Saline-Cona alluvial ridge in Agna and Concadalbero, respectively. Around 3000 cal BP the Saline-Cona was no more active but, in its distal part, the aggradation continued until Roman times due to sedimentation of the Bagnoli and Concadalbero palaeochannel (P IOVAN et alii, 2011). In particular, P IOVAN et alii (2010), thanks to petrographical sand analysis, linked the Fratta and Saline-Cona alluvial ridge to the Po basin, comparing the results with the data obtained from the modern Adige alluvial ridge in Pettorazza Grimani. Here we present new data from petrographical sand analysis performed on samples extracted by different corings located in the Padua city centre and its surrounding: among them, those from La Storta palaeochannel, Middle -Holocene Brenta River deposits, VR channel belt and from the modern Bacchiglione riverbed. A comparison of the results with those of PIOVAN et alii, (2010) and those recalculated from G AZZI et alii (1973) and S CETTRI (1991) has been carried out. The main objective of this contribution is to describe the results of petrographical analysis and to attempt a first attribution of channel belts in Padua alluvial plain to the appropriate fluvial basin (i.e. Brenta R. vs. Bacchiglione R .). The ternary plot (Fig. 3) evidences three clusters of samples, defined as petrofacies. All the Padua samples are in the lithic area while the Po samples shifted more to the quartz vertex. Sands from the modern Adige palaeomeander of Pettorazza Grimani seems to have an intermediate content of lithic grains compared to the other two clusters. In particular, Adige sands are characterized by a larger amount of carbonate and acidic volcanic rock fragments than the Po ones. Thanks to a different geological setting of the drainage areas, the Po sands are distinguishable from Adige ones also because the heavy mineral content, among which the glaucophane is regarded as diagnostic (GAZZI et alii, 1973). The modern Bacchiglione sands seems to have a very high 70 PIOVAN ET ALII content of lithic and carbonate grains but these data are not sufficient to distinguish them from the other sand bodies in Padua alluvial plain. However, their higher volcanic acid grain and heavy minerals content suggest that these latter could be related to the Brenta fluvial system. The composition of modern Adige, Po (G AZZI et alii, 1973) and Brenta rivers sands is reported for comparison. REFERENCES F ONTANA A., MOZZI P. & BONDESAN A. (2008) - Alluvial megafans in the Venetian-Friulian Plain (northeastern Italy): Evidence of sedimentary and erosive phases during Late Pleistocene and Holocene. Quaternary International 189, 7190. G AZZI, P., ZUFFA, G.G., G ANDOLFI, G., & PAGANELLI, L. (1973) Provenienza e dispersione litoranea delle sabbie delle Inquadramento regionale. Memorie Società Italiana, 12, 1-37. Geologica M OZZI P., P IOVAN S., ROSSATO S., CUC ATO M., ABBÀ T. & FONTANA A. (2010) - Palaeohydrography and early settlements in Padua. Il Quaternario - Italian Journal of Quaternary Sciences, 23(2bis), 387-400. N INFO A., FERRARESE F., MOZZI P. & FONTANA A. (2011) - High resolution DEMs for the analysis of fluvial and ancient anthropogenic, landforms in the alluvial plain of Padua (Italy). Geografia fisica e dinamica quaternaria, 34, 95-104. P IOVAN S., M OZZI P. & STEFANI C. (2010) - Bronze Age palaeohydrography of the Southern venetian plain. Geoarcheology, 25(1), 6-35. P IOVAN S., M OZZI P. (2010) - Recognizing avulsion events in the Adige River alluvial system. Il Quaternario - Italian Journal of Quaternary Sciences, 21, 120-122. Fig.3 Gross composition of the analyzed sands. Modern Po (green circle) and Adige (light blu circle) data are recalculated from Gazzi et alii, 1973. Q represents total quartz; F represents felds pars; L+CE represents fine-grained rock fragments and extrabasinal carbonates. S CETTRI F. (1991) - Studio geomorfologico e sedimentologico della pianura a Sud di Padova. Tesi di Laurea, Università degli Studi di Padova. Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 71-75, 3 figs. © Società Geologica Italiana, Roma 2012 New amber findings in Northeastern Italy: suggestions for an integrated view on fossil resin EUGENIO RAGAZZI (*), M ARCO AVANZINI (°), I GINIO D IENI (**), GUIDO ROGHI (°°) & CRISTINA S TEFANI (**) Key words: Amber, Eocene, fossil resins, FTIR INTRODUCTION New amber findings in the Northeastern Italy increase the palaeobotanical documentation of fossil resin occurrence in this part of Italy and confirm the Early Eocene as a particular "amber prolific" time interval. In Italy finds of amber have been reported since long time, from Tertiary rocks of the Northern Apennines (SKALSKI & VEGGIANI, 1990) and especially of Sicily, where the fossil resin simetite has been found near the river Simeto. From the Southern Alps, since recent times, the occurrence of amber has been cited only sporadically. Among first records is a letter, dated 1827, where Catullo informed Brugnatelli about a fossil forest, including fossil resin, discovered in a valley near Roana, on the Asiago Plateau (CATULLO, 1827). Stoppani (STOPPANI , 1886) reported that amber was collected from the Chattian beds at the base of the Monte Brione Formation, near Riva del Garda (Trento province). Anecdotal reports of amber from the Triassic of the Dolomites were from Koken (KOKEN , 1913), Zardini (ZARDINI, 1973) and Wendt & Fürsich (WENDT & FÜRSICH, 1980), but no thorough study was performed before 1998 (G IANOLLA et alii, 1998). During the last decade, more comprehensive investigations on amber findings in Italy have been conducted under geological and physico-chemical contexts. Here follows a list of these reports: 1. near Redagno and Pietralba (Bolzano province) some millimetric granules of amber from the Arenarie della Val Gardena Formation, Upper Permian (M AFFI & MAFFI, 1992); _________________________ (*) Departm ent of Pharmaceutical and Pharmacological Sciences, University of Padova, largo E. M eneghetti 2, I-35131 Padova (Italy). [email protected] (**) Department of Geosciences, University of Padova. (°) Trento M useum of Sciences, Geology section, Trento. (°°) CNR Department of Geosciences and Georesources, Padova. Badia (Bolzano province) amber from the Heiligkreuz Formation, Upper Triassic (Carnian) (GIANOLLA et alii, 1998; RAGAZZI et alii, 2003; ROGHI et alii, 2006; SCHM IDT et alii, 2006); 3. at Vernasso (Udine province) and at Ra Stua (near Cortina Santonian) and Lower Cretaceous (Albian) sites, respectively (ROGHI et alii, 2004); 4. at Cava Rossi quarry, Monte di Malo (Vicenza province), some centimetric amber nodules from the marly limestones of the Lower-Middle Eocene (BOSCARDIN & V IOLATI TESCARI, 1996; TREVISANI et alii, 2005); 5. amber from the world -famous fossil-Lagerstätte of Pesciara di Bolca (Verona province) in Lower Eocene sediments (TREVISANI et alii, 2005); this amber presents a strict similarity with Cava Rossi amber (TREVISANI et alii, 2005). On the basis of the physico chemical and palynological analysis of the site, some hypotheses were proposed about the palaeobotanical origin of the fossil resin. The close resemblance of the physico chemical properties of amber from Bolca with that of Monte di Malo (mainly FTIR spectra and thermal analysis behaviour), together with the biostratigraphical correlation obtained by means of larger foraminiferal biozones, permitted to hypothesize that the two amber layers are substantially isochronous (Middle Cuisian, Early Eocene), although with palaeoenvironmental differences; 6. in the Chiavon stream, near Salcedo (Vicenza province) some millimetric granules of amber from Oligocene beds (RAGAZZI & ROGHI, 2003); 7. similar fragments were collected also from the Upper Oligocene (Chattian) of Sedico (Belluno province) (RAGAZZI & ROGHI, 2003); in Belluno province some fragments of amber had been described by Arduino (ARDUINO , 1818), within fossil wood in molar stone quarries, possibly close to Tisoi church. Also Catullo (CATULLO, 1834, 1838, 1840) quoted some samples of amber together lignite in blue marl located in the Ardo river valley. Again Catullo (CATULLO, 1863-1864) described amber among lignite found within Tertiary molasses dug in quarries from Fregona (Treviso); similar sediment was found near Lamosano and Alpago church (loc. Pissa), Belluno Province; 72 RAGAZZI ET ALII 8. most recently, TREVISANI et alii (2011) published a note about amber found in the Eocene Belluno Flysch (Cuisian). Based on Infra-red spectroscopical analysis, the fossil resin was assigned to an Araucariacean source, possibly Agathis genus, not recorded during Eocene in the Northern hemisphere; therefore it should be older that Tertiary, suggesting an origin of the material from an older sediment (Cretaceous - Paleocene?). NEW AMBER FINDINGS The scenario of amber findings among different geological sites in the Northeastern Italy has been further expanded by three new samples (see map of Fig. 1) of which we aimed to present the main characteristics. Fig. 2 Image of the amber sample found near Pont village. FTIR ANALYSIS Fig. 1 Map of the area of discovery of the new amber samples. A) from flysch sediment of M ujè stream, near the village of Frisanco, Pordenone Province; B) from Pont village, Belluno Province; C) from Doss, Trento city. The new ambers are: A. some small and very fractured samples of fossil resin from Pordenone Province, found within flysch sediment of Mujè stream, near the village of Frisanco, in geological strata belonging to Eocene; this amber has been already quoted by RIMOLI & DREON (1998) but it still has not been fully investigated; B. a centimeter-sized amber (Fig. 2) from Belluno Province, near Pont village, belonging to Early Eocene, found by one of us (C.S.) during This fossil resin comes from the lowermost part of the flysch succession corresponding to the Discoaster lodoensis Nannoplancton Zone (GRANDESSO , 1976); C. some fractured samples of fossil resin from Doss Trento, (Trento city) (found by M.A.) in the Calcare di Chiusole formation, Early Eocene in age. The samples were analyzed under the physico-chemical point of view. The characteristics were typical of fossil resins (external aspect, color, hardness 2.5-3 of Mohs scale, no appreciable surface solubility in alcohol or acetone). A Fourier Transform Infrared Spectroscopy (FTIR) analysis (performed on powdered samples included in potassium bromide pellets with a Perkin Elmer 1600 series spectrophotometer) permitted to observe the pattern of absorption typical of amber (Fig. 3), although the spectra of both Trento and Mujè samples were very few informative due to low intensity of most bands, probably because of high degree of diagenetic alteration, as already observed with Belluno Flysch Eocene amber (TREVISANI et alii, 2011; see also Fig. 3). The sample from Pont village produced a very clear spectrum (Fig. 3). Among the several absorption bands detected, some are present in all fossil resin spectra, such as those around 3.5 µm (due to stretching of C -H bonds), 6.8 and 7.3 µm (due to bending of C-H bonds) and 5.8 µm (the of C=O double bonds). The bands in the upper region of the spectrum between 8 and 10 µm chemical structures of the resin, but are more useful than those in the lower region, since the former reflect changes in composition (LANGENHEIM & BECK, 1965) and may represent a comparison tool among different samples. As underlined by 73 NEW AMBER FINDINGS IN NORTHEASTERN ITALY LANGENHEIM & BECK (1965), identity of spectra can never be expected, even for samples obtained from a single specimen, since resins are very highly complex and heterogeneous mixtures of high molecular weight components. However, the presence of similarities, in particular in the "fingerprint" region of the spectrum, can suggest a structural similarity in terms of major constituents. DISCUSSION AND CONCLUSIONS FTIR spectrum of Pont amber did not show the typical the presence of succinic acid, although it is mostly in combined form: TONIDANDEL et alii, 2009) which presents the so called preceded by a flat shoulder, attributed to absorption of ester groups (see Fig. 3). The morphology of the fingerprint region of the spectrum of Pont amber however, although with differences in the intensity of absorption bands, presents similarities with that of Bolca and Monte di Malo amber (Fig. 3), which are of Eocene epoch as well, suggesting a common palaeobotanical origin. Also a close similarity can be detected with spectra of Sedico and Salcedo amber (RAGAZZI & ROGHI, 2003; see also Fig. 3), although belonging both to Oligocene epoch. Regarding the spectra of the other two samples of amber, found at Trento and in proximity of the Mujè stream, as above mentioned, the pattern of absorption bands is quite poor, and therefore no sure comparisons can be made. However, a similarity with a Belluno Flysch sample previously investigated (TREVISANI et alii, 2011, reported also in Fig. 3) is quite evident. Considering that it is difficult to attribute any palaeobotanical affinity to a fossil resin based only on infrared spectra, and in absence of an association with identified vegetal remains, however we might suggest that the newly investigated fossil resins can belong to a unique general cluster. A similarity with the spectrum produced by resins of the Araucariaceae family genus Agathis (LANGENHEIM & BECK, 1968; KOSM OWSKA -CER ANOWICZ , 1999) may suggest a link to this conifer group, as already suggested for the Belluno Flysch sample (Trevisani et alii, 2011). However, some features of the spectra (discussed in TREVISANI et alii, 2005, 2011), suggest that a link with an Angiosperm-type resin-producing plant cannot be excluded, but at present the key signatures are too scarce to provide a valuable palaeobotanical attribution. As suggested for Bolca amber (TREVISANI et alii, 2005), some similarity can be observed also with the spectrum of glessite (KOSM OWSKA -CERANOWICZ et alii, 1993; KOSM OWSKA -CER ANOWICZ , 1994, 2001), a dark-brown fossil resin found in Germany (Bitterfeld mine, Saxony-Anhalt, and Lusatia), which has been attributed to the family Burseraceae, and with fossil resin found in Borneo, attributed to the family Dipterocarpaceae (KOSM OWSKA -CERANOWICZ, 1994), but all remains in terms of speculation. However, it is of interest to underline the fact that amber in Italy has been found in many sediments of different geological age, dating from Mesozoic to Cenozoic. Amber occurrence during a strict time-interval in the Triassic (ROGHI et alii, 2006), presenting peculiar climate shifts, has suggested that amber production might be linked to climate-induced plant stress, documented also by palynological/palaeobotanical evidences. The occurrence of amber findings, although occasional, here reviewed, might suggest similar considerations regarding the process of amber production also during the Early Eocene in Italian area. In conclusion, the three new amber samples permitted to expand the knowledge concerning Northern Italy fossil resins of geological interest, and suggest to take into account the role of amber as a possible paleoclimatic/paleoenvironmental indicator. ACKNOWLEDGEMENTS The authors thanks to Dr. Angelo Leandro Dreon for providing the Mujè stream amber sample, and Dr. Giovanni Marzaro (Padova University) for performing FTIR spectra. REFERENCES A RDUINO G. (1818) - Risposta del Sig. Arduino alla premessa lettera del Sig. Dottore Gualandris. In: Catullo T. A., Osservazioni sopra i monti che circoscrivono il distretto di Belluno. Mainardi, Verona, p. 122. BOSCARDIN M. & V IOLATI TESCAR I O. (1996) - Gemme del Vicentino. Museo Civico G. Zannato, Montecchio Maggiore, Italy. CATULLO T.A. (1834) - Osservazioni sopra i terreni postdiluviani delle Provincie Austro-Venete. Minerva, Padova, p.54. CATULLO T.A. (1838) - Trattato sopra la costituzione geognostico-fisica dei terreni alluvionali o postdiluviani delle provincie Venete. Sicca, Padova, p. 57. CATULLO T.A. (1840) - Osservazioni geognostico-zoologiche sopra due scritti pubblicati nel tomo terzo delle Memorie . Nuovi saggi della Imperiale Regia Accademia di Scienze Lettere ed Arti in Padova, Sicca, Padova, vol. V, p. 230. CATULLO T.A. (1863-1864) - Discorrimenti sopra alcuni importanti fatti geognostico-paleozoici meritevoli di essere Veneto di Scienze, Lettere ed Arti, Antonelli, Venezia, p. 473. CATULLO T.A. (1827) - Scoperta di una foresta fossile. Squarcio di lettera del Prof. Catullo al Prof. Brugnatelli. Giornale di Fisica, Chimica, Storia Naturale Medicina ed Arti, Decade II, Tomo X, p.151. 74 RAGAZZI ET ALII Baltic Belluno Flysch Sedico Trento Salcedo Mujè Bolca Pont Monte di Malo Fig. 3. - FTIR spectra (absorption mode) of amber samples from Northeastern Italy; the spectrum of Baltic amber is also shown for comparison. Some of the reported spectra have been published in previous papers (RAGAZZI & ROGHI , 2003; TREVISANI et alii, 2005, 2011). NEW AMBER FINDINGS IN NORTHEASTERN ITALY GIANOLLA , P., RAGAZZI, E., & ROGHI, G. (1998) - Upper Triassic amber from the Dolomites (Northern Italy). A paleoclimatic indicator? Rivista Italiana di Paleontologia e Stratigrafia 104, 381 390. GRANDESSO P,. (1976) - Biostratigrafia delle formazioni terziarie del Vallone Bellunese. Bollettino della società Geologica Italiana, 94, 1323 1348. KOKEN E. (1913) - Kennitnis der Schichten von Heiligenkreuz (Abteital, Südtirol). Abhandlungen der KaiserlichKöniglichen Geologischen Reichsandstalt 16, 1 43. KOSM OWSKA -CER ANOWICZ B. (1994) - Bursztyn z Borneo . Geologiczny, 7, 576 578, 604. KOSM OWSKA -CER ANOWICZ B. (2001) - Wie Bernstein entsteht. In: Krumbiegel, G. & Krumbiegel, B. Eds., Faszination Bernstein. 17 35. Goldschneck-Verlag. KOSMOWSKA -CER ANOWICZ B., KRUM BIEGEL G. & V AVRA N. (1993) - Glessit, ein tertiäres Harz von Angiospermen der Familie Burseraceae. Neues Jahrbuch für Geologie und Paläontologie 187, 299 324. KOSM OWSKA -CER ANOWICZ B. (1999) - Succinite and some other fossil resins in Poland and Europe (deposits, finds, features and differences in IRS). Estudios del Museo de Ciencias Naturales de Alava, 14 (Num. Esp. 2), 73-117. LANGENHEIM J.H., BECK C.W. (1965) - Infrared spectra as a means of determining botanical sources of amber. Science, 149, 52 55. LANGENHEIM J.H. & BECK C.W. (1968) - Catalogue of infrared spectra of fossil resins (ambers): I. North and South America. Botanical Museum Leaflets Harvard University, 22,65-120. MAFFI D. & M AFFI S. (1992) - Le più antiche ambre delle Alpi. Paleocronache, 1, 39 48. RAGAZZI E. & ROGHI G. (2003) - Prima segnalazione di ambra nei sedimenti oligocenici di Salcedo (Vi) e di Sedico (Bl). Studi e Ricerche 2003, Associazione Amici del Museo, Museo Civico G. Zannato, Montecchio Maggiore, 19 22. RAGAZZI E., FEDELE P., GIANOLLA P. & ROGHI G. (2003) . Rivista Mineralogica Italiana, 1, 21-22. 75 RIMOLI G. & D REON A.L. (1998) - Notizie mineralogiche dell'area del Pordenonese con particolare riguardo ai minerali della Val Cellina e della Val Colvera. Boll. Soc. Naturalisti "Silvia Zenari" Pordenone, 22, 45-62. ROGHI G., RAGAZZI E. & FEDELE P. (2004) delle Dolomiti e delle Prealpi Giulie (Italia). Giornate di Paleontologia S. P. I., Meeting of the Italian Palaeontological Society, Bolzano (Italy) 21-23 May 2004, Abstract book, p. 52. ROGHI G., RAGAZZI E. & G IANOLLA P. (2006) - Triassic Amber of The Southern Alps (Italy). Palaios, 21, 143-154. S CHM IDT A.R., RAGAZZI E., COPPELLOTTI O. & ROGHI G. (2006) - A microworld in Triassic amber. Amber as old as the first dinosaurs captured the diversity of microbial life 220 million years ago. Nature, 444, 835. S KALSKI A. & V EGGIANI A. (1990). Fossil resin in Sicily and the Northern Apennines: Geology and organic content. Praze Muzeum Ziemi 41, 37-49. S TOPPANI A. (1886) rapporti colle origini e collo svolgimento della civiltà in Europa. Fratelli Dumolard editori, Milano. T ONIDANDEL L., RAGAZZI E. & TRALDI P. (2009) - Mass spectrometry in the characterization of Ambers. II. Free succinic acid in fossil resins of different origin. Rapid Communications in Mass Spectrometry, 23, 403-408. TREVISANI E., RAGAZZI E. & ROGHI G. (2011) - First report of amber from the Early Eocene Belluno Flysch (Southern Alps, Northern Italy). Boll. Soc. Paleontologica It., 50, 2328. TREVISANI E., P APAZZONI C.A., RAGAZZI E. & ROGHI G. (2005) - Early Eocene amber from the Pesciara di Bolca (Lessini Mountains, Northern Italy). Palaeogeography, Palaeoclimatology, Palaeoecology, 223, 260 274. W ENDT J. & FÜRSICH F.T. (1980) - Facies analysis and palaeogeography of the Cassian Formation, Triassic, Southern Alps. Rivista Italiana di Paleontologia e Stratigrafia, 85,1003 1028. ZARDINI R. (1973). Geologia e fossili attorno a Cortina . Rend. Online Soc. Geol. It., Vol. 20 (2012), pp. 76-77, 1 fig. © Società Geologica Italiana, Roma 2012 Connections between glacial and fluvial systems in the lower Astico Valley and the piedmont plain (NE Italy) SANDRO ROSSATO (*), PAOLO M OZZI (*), G IOVANNI M ONEGATO (°), M AURIZIO CUCATO (^), BARBARA G AUDIOSO & ANTONELLA M IOLA Key words: glacial collapse, glacial transfluence, Last Glacial Maximum, plain evolution, south-eastern Prealps, Venetian Plain. INTRODUCTION This work concerns the Late Quaternary evolution of the Astico Valley, with a focus on the relations between the glacial complex hosted in the terminal valley tract and the piedmont alluvial fans. The Astico valley is located in the Venetian Prealps (eastern-southern Alps), NW of the city of Vicenza (Italy). The Astico River flows into this valley, initially N/S and then NW/SE. This river has its source between the Sommo Alto and the Plaut peaks and flows on the valley bottom as far as the town of Piovene Rocchette, where it enters a narrow and 50-m deep gorge until reaching the Venetian alluvial plain, about 10 km downstream. The valley incise mostly limestones and dolostones (Triassic to Cretaceous) and volcanic rocks (Triassic and Cenozoic). The Cenozoic lithologies can be found in the final tract of the valley, which is carved almost entirely in Oligocenic volcanic rocks, both intrusive and effusive. The whole area is interested by two main deformative systems, related to the neoalpine tectonic phase (CASTELLARIN & CANTELLI SE/NW), which cuts the previous one with a left-strike-slip cinematic. In addition, a third system (oriented roughly E-W) is _________________________ (*) University of Padua, Departm ent of Geoscience, Padua, 35123, Italy (°) National Research Council, Institute for Geoscience and Earth Resources, Turin, 10123, Italy (^) Province of Bolzano, Geology and material tests Office, 39053, Cardano (BZ), Italy ( University of Padua, Department of Biology, Padua, 35131, Italy related to the thrust propagation front of the eastern Southern Alps towards SSE. The stratigraphy of the Quaternary successions at the outlet of the Astico Valley shows different sedimentary episodes, including glacial advances, related to the Middle and Late Pleistocene (BARTOLOMEI, 1976; 1984; CUCATO, 2001; 2007). Three distinct glacial events are considered here. The last event created the terminal moraine system of Cogollo del Cengio, whose outwash apron filled the lower part of the Astico Valley and built a fan in the piedmont plain. Two incised sandur channels are still recognizable in front of the outer terminal moraine (BARTOLOMEI, 1976). This glacial advance is attributed to the Last Glacial Maximum (LGM). BARTOLOMEI (1976) and CUCATO (2001) report various small outcrops of glacial deposits (lodgment and ablation till and erratics) at various elevations on both valley flanks of the lower Astico valley. These glacial deposits belong to lateral moraines of a glacier whose front was further downstream of the Cogollo del Cengio end moraines, and relate them to a preLGM glaciation. The presence of a lodgement till about 5.5 km downstream of the terminal LGM moraines, along with some pollen analyses run on lacustrine deposits outcropping along the fluvial scarp of the present Astico River, point to another preLGM glaciation. Along the upper Astico Valley and at the margins of surrounding plateaus, several glacial deposits have been recognized and related to the glacial transfluence of the Adige glacier through several saddles; these sediments are ascribed to different glaciations, according to their weathering degree and geomorphological position (CUCATO , 2007). Local glacial units in the Sette Comuni Plateau were also described and mapped (TREVISAN , 1939; BARTOLOMEI, 1984) according to CUCATO (2007) During the LGM these minor glaciers remained separated from the Astico glacier. Remote sensing, field survey, stratigraphic measurements and reconstructions, sand petrography, radiocarbon datings and pollen analyses confirmed the attribution of the last glaciation CONNECTION BETWEEN GLACIAL AND FLUVIAL SYSTEMS IN THE LOWER ASTICO VALLEY AND THE PIEDIMONT PLAIN to the LGM, the previous one probably to the MIS 6 and the oldest to an undefined glaciation during the Middle Pleistocene. Sand petrography analyses confirm that all these glacial deposits contain rock fragments that reach the Astico Valley through a transfluence of the Adige glacier. During LGM, this glacial stream entered the Astico Valley from the North through the Carbonare saddle (1075 m a.s.l.), as it probably happened also in previous major glaciations. The chronostratigraphy of two cores drilled near the towns of 77 Vicenza and Villaverla shows that the outwash stream changed its way to the piedmont plain at the end of LGM, as a response to rapid glacial collapse. This switch led to the deactivation of the north-western sector of the plain (Thiene fan) in favour of the south-eastern one (Sandrigo fan). The lower and middle Astico Valley preserved significant evidence of minor glacial fluctuations during the LGM in response of subtle climatic changes, namely an early glacial withdrawal at 23-24 cal ka, which may be difficult to distinguish in major Alpine glaciers. Fig. 1 Evolution of the m iddle-lower Astico Valley since the M iddle Pleistocene; PR: Piovene Rocchette; Ca: Caltrano, I: M IS 6 (?), maximum advance; II: MIS 6 (?), initial of the withdrawal; III: interglacial; IV: LGM, maxim um advance; V: LGM: glacial pulse; VI: LGM: the glacial transfluence stops; VII: pre sent situation) (source: R OSSATO et alii, 2012). REFERENCES BARTOLOMEI G. (1976) - Cause dello spostamento del corso del . Quaderni del Gruppo di Studio del Quaternario Padano, 3, 151-159. BARTOLOMEI G. (1984). Evoluzione fisica e biologica dal Pliocene ai giorni nostri. In: Aspes, A. (Eds.) - Il Veneto nell'antichità, preistoria e protostoria, Banca Popolare di Verona, Verona, Italy, 113 -136. CASTELLARIN A. & CANTELLI L. (2000) - Neo-Alpine evolution of the Southern Eastern Alps. Journal of Geodynamics, 30, 251 274. CUCATO M. (2001) - Rilevamento della media Val d'Astico (Provincia di Vicenza): saggio per l'applicazione della normativa sulla cartografia geologica del Quaternario continentale, Boll. Serv. Geol. It., 115, 99-130, (1996) 1 tav. f.t. CUCATO M. (2007) - La successione continentale pliocenico?quaternaria. In: Barbieri, G. & Grandesso, P. (Eds.) - Note Dipartimento Difesa del suolo - Servizio Geolo alia, 60-94. ROSSATO S., MONEGATO G., MOZZI P., CUC ATO M., GAUDIOSO B. & MIOLA A. (2012) - Late Quaternary glaciations and connections to the piedmont plain in the prealpine environment: the middle and lower Astico Valley (NE Italy). Quat. Int., doi:10.1016/j.quaint.2012.03.005. TREVISAN L. (1939) dei Sette Comuni (Vicenza). Bollettino del Comitato Glaciologico Italiano, 19, 1-19. Norme di stampa per la pubblicazione sui RENDICONTI della Società Geologica Italiana I Rendiconti della Società Geologica Italiana, editi in volumi quadrimestrali, escono nei mesi di Dicembre, Aprile ed Agosto. 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