Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2011-2012
LASER SCANNER CYCLOSTRATIGRAPHY: A NEW APPROACH TO REFINE NUMERICAL
ASTRONOMICAL SOLUTIONS AND THE GEOLOGICAL TIME - SCALE
Ph.D. candidate: Luca Penasa, II course
Tutor: Prof. Nereo Preto
Cycle: XXVII
Abstract
Laserscannig and photogrammetric methods permit to capture three dimensional models of outcrops. These methods
demonstrated high potential in the reconstruction of long time-series for stratigraphic purposes. A new technique for
laserscanner data processing, based on Computer Vision and Data Mining techniques, has been developed with the specific
aim to automate the lithology recognition task. A photogrammetric survey of a quarry in Calcare Massiccio Fm., (Jurassic)
has been carried out for testing applicability of these techniques in a context where laserscanning is not easily applicable.
Thanks to ad-hoc code, we produced a simplified stratigraphic log of the series, and a color-based time-series that revealed
strong periodicity and a possible orbital-forcing of facies succession. Results suggest that the extraction of geological data via
Computer Vision algorithms from laserscanning and photogrammetric models is the key for long time-series reconstruction
from outcrops.
Introduction
Quasi-periodic changes in the Earth’s orbit and tilt produce cyclic variations in the solar insolation,
influencing the global climate. These cycles, especially those in the the Milankovitch band of frequencies
(periods from 20 to 400 kyrs), are of stratigraphic interests since many sedimentary systems may have the
ability to record them. In appropriate circumstances, these climatic oscillations are imprinted in sediments
as periodic alternations of lithologies (see House, 1995; Hinnov, 2000; Hinnov and Ogg, 2007). Once
these cycles are unequivocally observed in stratigraphic sequences, they can be used for placing the
sequence in the time domain, with absolute chronological value if the sequence is linked to present (or
additional dates are available) or as floating time-intervals.
Recent numerical simulations (Laskar et al., 2004, 2011a, 2011b) of solar system dynamics proved its
chaotic nature and highlighted how the models themselves cannot provide consistent estimations of past
(>50 Ma) climatically-forced periodicities. Disambiguation between different numerical solutions may be
provided by observation of the long periodicities (∼1.2 Ma) that may be recorded in sediments.
Observing long-period cycles require the construction of long stratigraphic logs in the form of timeseries representing how some property of the sedimentary system changed over time. These time-series
are then analyzed with spectral methods seeking for known periodicities. Building time-series of
appropriate sizes is a challenging task that requires detailed logging of outcrops (and possibly sampling
and subsequent analysis of the samples), resulting in a highly time-consuming task.
Terrestrial remote sensing methods, as laserscanning and photogrammetry, provide an alternative way
to produce such long time-series, once to the observed property has been attributed a geological
significance. Main goal of this doctoral research is to develop quantitative methods for remote sensing of
stratigraphic series, their processing, data extraction, and management of digitized stratigraphic
information. These problematics have been faced through:
• the development of specific software for point cloud data management and processing,
• the individuation and testing of specific algorithms for the automation of data extraction,
• the application of the results to real case studies.
All the code developed is now hosted on www.github.com and accessible to everyone. Recent developments
includes more generic facilities for geologic interpretation of Virtual Outcrop Models, including part of
the codes used for the processing of the Gola della Rossa quarry.
Automation of data extraction
Remote sensing methods are able to produce large amounts of data that need to be processed in order to
extract geological information. This requirement has been faced by identifying algorithms for automated
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Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2011-2012
data extraction from laserscanner-derived point clouds. This work, currently under review (Penasa et al.,
2013), demonstrated the efficiency of Data Mining techniques (as Support Vector Machine classifiers and
texture and geometric descriptors) in solving a concise but otherwise complex stratigraphic problem, i.e.,
mapping chert nodules and beds on an outcrop. We were able to demonstrate that chert shows a peculiar
behavior at IR wavelength (reflectance lower than limestone), separate rock from vegetation on the
outcrop, and isolate chert from its host rock. Chert abundances can thus be precisely plotted against
stratigraphy, and interpreted in paleoclimatic or lithostratigraphic studies.
Extending the data sources: photogrammetry
During a one-month stage at ENSG1, the use of photogrammetric techniques for long time-series
generation have been investigated. A new and simplified approach for stratigraphic logging on
photogrammetric models has been developed with the precise aim to apply it to a case study. The software
for photogrammetric reconstruction, developed by Dr. Marc Pierrot-Deseilligny and his team
(MICMAC), has permitted to test a specific solution for digitizing stratigraphic-elements.
Gola della Rossa quarry: a case study
For testing the photogrammetric approach, a full scale photogrammetric survey has been carried out on
the Gola della Rossa quarry (Central Italy). The quarry is active and is 200 meter height and ∼500 meters
wide. The dimensions of the quarry and the impossibility to reach the rock wall (for safety issues) made
of this quarry the ideal case for a remote sensing approach.
The quarry is entirely composed of Calcare Massiccio Fm. (Early Jurassic) that is an alternation of
subtidal to supratidal limestones. Subtidal and intertidal facies are characterized by white and light colors,
while supratidal facies are darker. This feature has been used as key for a preliminary interpretation in a
small portion of the quarry. The interpretation has been carried out tracing the beginning of each
supratidal and sub and intertidal interval directly on the picture used for the photogrammetric
reconstruction. Thanks to ad-hoc developed software we demonstrated the possibility to translate this 2Figure 1: Spectral analysis revealed the presence of spectral power concentrations that
might be correlated to precession. Following this interpretation, sedimentation rates of
180 m/Myr (150 to 200) are suggested. These rates well fit those of a nearly drowning
platform during Jurassic extensional tectonics. Green area (and dashed line) represent
the noise level; the gray area is a spectral estimation of the Gola della Rossa Quarry time
series. Peaksexceeding the noise level are significant periodicities; Black line:
astronomically calculated ETP spectrum, tuned to a sedimentation rate of 180 m/Myr.
1 École Nationale des Sciences Géographiques
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Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2011-2012
dimensional information to the 3D domain. From this last 3D dataset we obtained a simplified
stratigraphic column representing main alternations of facies.
A time series representing the color variations along stratigraphic height has been also produced and
used for spectral analysis. A wide set of spectral estimation techniques has been employed to assess if the
supra-to-subtidal oscillations might be in tune with known Milankovitch periodicities. Also a new
technique has been developed for estimating the signal-to-noise ratio in an independent way. This
technique takes advantage of the full point-cloud dataset: a set of surrogate time-series are drawn directly
from the dataset and then employed for estimate the noise baseline. This noise-modeling technique,
although still to be formalized, discloses the full potential of data redundancy of point-clouds.
An extract of the results is shown in Figure 1, together with a preliminary cyclostratigraphic
interpretation.
These two case studies demonstrate that remote sensing of outcrops, through laserscanning or
photogrammetry, coupled with Data Mining and Computer Vision techniques for the extraction of
geological data, allow the recovery of long time series and their efficient exploitment for stratigraphic
purposes. This approach will be now applied to a long cyclic succession for the identification of long
(Myr-scale) periodicities.
Research plan for the next year
A new lasercanner survey is planned for December. The scans will be collected in Central Italy in the
Contessa road quarry. The selected outcrop is one of the longest stratigraphic sequences of the Italian
Mesozoic, comprising a time span > 20 Ma.
From January, 2014, I’ll spend 6 months at the Geoscience Dpt. of Rennes (Fr). During this period I’ll
work in close collaboration with the Quantitative Geomorphology Equipe, supervised by Dr. Dimitri
Lague, head of the research group. The main goal will be the formulation of an appropriate algorithm for
the automatic extraction of coherent stratigraphic information from point clouds. The result will be an
important part of the generic Virtual Outcrop Model practice. The algorithms that will be developed will
be tested on a real case study, with the final aim to produce the longest possible time-series for
investigating long-term cyclicities in the geologic record.
The results of photogrammetric surveys at the Gola della Rossa quarry and the methods developed for the
specific case will be the subject of a poster at AAPG conference (Naples), in March.
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Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2011-2012
References
LINDA A. HINNOV. New perspectives on orbitally forced stratigraphy. Annual Review of Earth and
Planetary Sciences, 28 (1): 419–475, 2000.
LINDA A. HINNOV and JAMES G. OGG. Cyclostratigraphy and the Astronomical Time Scale.
Stratigraphy, 4 (2/3): 239–251, 2007.
M.R. HOUSE. Orbital forcing timescales: an introduction. Geological Society, London, Special
Publications, 85 (1): 1, 1995.
J. LASKAR, P. ROBUTEL, F. JOUTEL, M. GASTINEAU, A. C. M. CORREIA, and B. LEVRARD. A long-term
numerical solution for the insolation quantities of the Earth. Astronomy and Astrophysics, 428 (1):
261–285, December 2004.
J. LASKAR, A. FIENGA, M. GASTINEAU, and H. MANCHE. La2010: a new orbital solution for the longterm motion of the Earth. Astronomy & Astrophysics, 532: A89, 2011a.
J. LASKAR, M. GASTINEAU, J. B. DELISLE, A. FARRÉS, and A. FIENGA. Strong chaos induced by close
encounters with Ceres and Vesta. Astronomy & Astrophysics, 532: L4+, July 2011b.
PENASA L., FRANCESCHI M., PRETO N., TEZA G., and POLITO V. Integration of intensity textures and
local geometry descriptors from Terrestrial Laser Scanner to map chert on outcrops. ISPRS Journal
of Photogrammetry and Remote Sensing, Submitted, 2013.
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Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2011-2012
SUMMARY OF ACTIVITY IN THIS YEAR
Courses:
VITTORIO MASELLI (CNR Bologna). “Seismic and sequence stratigraphy”, Geosciences Department of Padova
DIERNA M. “JRC Reconstructor” , Gexcel SRL, Brescia
ROBERTO CARNIEL (University of Udine). “Spectral Analysis and Dynamics of Time Series” , Geosciences Department of
Padova
PERTICONI S., PISCAGLIA F., GHELLER C., CALORI L., MUSCIANISI G., ANGELI D., BRIA A. DELLI PONTI F.,
IMBODEN S., QUADRANTI P, NEGRI A. “Advanced School on Scientific Visualization”, CINECA (Bologna)
LYDIA GULIK. “Advanced Scientific English”, Geosciences Department of Padova
Posters:
PENASA L., Franceschi M., and Preto N.. Mapping chert on outcrops with terrestrial laser scanner, 29th IAS Meeting of
Sedimentology (2012)
PENASA L., Franceschi M., Preto N., 2012 - Terrestrial laser scanning for high resolution cyclostratigraphy of chert in
pelagic limestone series. EGU General Assembly, Vienna, Austria, April 22-27, 2012.
Franceschi M., PENASA L., Preto N., 2012 - Mapping chert on outcrops with terrestrial laser scanner. 29th IAS Meeting of
Sedimentology, Schladming, Austria, September 10-13, 2012.
PENASA L., Girod L., Preto N., Montanari S., Gattolin G., Franceschi M., High resolution stratigraphic logging of Lower
Jurassic peritidal carbonates with open-source photogrammetric software, submitted to AAPG Conference, Naples, Italy, 2526 March 2014.
Publications:
PENASA L., FRANCESCHI M., PRETO N., TEZA G., and POLITO V. Integration of intensity textures and local geometry descriptors
from Terrestrial Laser Scanner to map chert on outcrops. ISPRS Journal of Photogrammetry and Remote Sensing, Submitted,
2013.
Other:
Stage at ENSG “Application of LIDAR and photogrammetry to cyclostratigraphy ”, at Ecole Nationale Des Sciences
Géographiques (ENSG), under the supervision of Dr. Marc Pierrot-Deseilligny .
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