Litholog generation with the StratigrapheR package and signaldecomposition for cyclostratigraphic purposes

Sebastian Wouters, Anne-Christine Da Silva, Michel Crucifix, Matthias Sinnesael, Miroslav Zivanovic, Frederic Boulvain, Xavier DeVleeschouwer

Research output: Contribution to journalMeeting abstract (Journal)

Abstract

To establish an astronomical time scale, it is useful to perform a visual inspection of the lithological evolution,together with proxies record. It allows to have a clear understanding of the expression of Milankovitch cyclicity.However, performing such an inspection can be challenging due to the large amount of data and high spatialresolution required to perform a sound cyclostratigraphic analysis.To address this problem we present the StratigrapheR package in the free software environment R(https://CRAN.R-project.org/package=StratigrapheR). This package is designed to generate lithologs and todeal with stratigraphical information. StratigrapheR takes advantage of the repetitive nature of sections usedfor cyclostratigraphic purposes to automate as much as possible the litholog generation while still allowing thevisualisation of discrepancies (e.g. lateral variations of thickness and irregular stratification boundaries) and ofany particular features (e.g. fossil content, sedimentary structures, stratigraphical intervals, etc.). The packagefurthermore allows to import vector graphics as SVG files, to export the lithologs in PDF and SVG form, tomanipulate stratigraphic interval data and to visualise oriented palaeomagnetic data.The lithologs made in StratigrapheR can be plotted at high resolution directly along the results of time seriesfiltering and/or decomposition methods. This is particularly useful for high-frequency components inspection.Empirical Mode Decomposition (EMD) in particular can be used for visual inspection. It allows to computedifferent components -also called modes- by iteratively subtracting from the signal the mean envelope curves,defined by local minima and maxima. In the isolated modes, each contiguous local extrema are separated by azero-crossing. This property furthermore allows the determination of instantaneous frequency and amplitude, usingfor instance the Hilbert transform. EMD typically decomposes standard cyclostratigraphic time series in maximum15 modes, which allows all the instantaneous ratios of the modes frequencies - taken two by two- to be calculatedin a realistic computational time. These instantaneous ratios of frequencies can then be used to find the signatureof Milankovitch cycles by identifying relatively higher ratios distributions at values characteristic of the orbitalcycles. Specific ratios intervals can then be isolated and linked back to the parts of the signal that are at their source.
Original languageEnglish
Article numberEGU2019-5520
Number of pages1
JournalGeophysical Research Abstracts
Volume21
Issue numberEGU2019-5520
Publication statusPublished - 10 Apr 2019
EventEGU General Assembly 2019 - Vienna, Austria
Duration: 7 Apr 201912 Apr 2019
https://www.egu2019.eu/

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