Abstract
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS,
VOL. 11,
Q0AA05,
18 PP., 2010
doi:10.1029/2009GC002611 [Citation]
BMPix and PEAK tools: New methods for automated laminae recognition and counting—Application to glacial varves from Antarctic marine sediment
Institute of Geology and Mineralogy, University of Cologne, Zuelpicher Strasse 49a, D-50935 Cologne, Germany
Institute of Geology and Mineralogy, University of Cologne, Zuelpicher Strasse 49a, D-50935 Cologne, Germany
Alfred-Wegener-Institute for Polar and Marine Research, Am Alten Hafen 26, D-27568 Bremerhaven, Germany
Institute of Geology and Mineralogy, University of Cologne, Zuelpicher Strasse 49a, D-50935 Cologne, Germany
Helmholtz-Institut fuer Strahlen- und Kernphysik, University of Bonn, Nußallee 14-16, D-53115 Bonn, Germany
Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK
Institute of Geology and Mineralogy, University of Cologne, Zuelpicher Strasse 49a, D-50935 Cologne, Germany
We present tools for rapid and quantitative detection of sediment lamination. The BMPix tool extracts color and gray scale curves from images at pixel resolution. The PEAK tool uses the gray scale curve and performs, for the first time, fully automated counting of laminae based on three methods. The maximum count algorithm counts every bright peak of a couplet of two laminae (annual resolution) in a smoothed curve. The zero-crossing algorithm counts every positive and negative halfway passage of the curve through a wide moving average, separating the record into bright and dark intervals (seasonal resolution). The same is true for the frequency truncation method, which uses Fourier transformation to decompose the curve into its frequency components before counting positive and negative passages. The algorithms are available at doi:10.1594/PANGAEA.729700. We applied the new methods successfully to tree rings, to well-dated and already manually counted marine varves from Saanich Inlet, and to marine laminae from the Antarctic continental margin. In combination with AMS14C dating, we found convincing evidence that laminations in Weddell Sea sites represent varves, deposited continuously over several millennia during the last glacial maximum. The new tools offer several advantages over previous methods. The counting procedures are based on a moving average generated from gray scale curves instead of manual counting. Hence, results are highly objective and rely on reproducible mathematical criteria. Also, the PEAK tool measures the thickness of each year or season. Since all information required is displayed graphically, interactive optimization of the counting algorithms can be achieved quickly and conveniently.
Received 8 May 2009; accepted 30 December 2009; published 19 March 2010.
Citation: (2010), BMPix and PEAK tools: New methods for automated laminae recognition and counting—Application to glacial varves from Antarctic marine sediment, Geochem. Geophys. Geosyst., 11, Q0AA05, doi:10.1029/2009GC002611.
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