Sediment colour analysis from digital images and correlation with sediment composition
Alexandra J. Nederbragt, Robert B. Dunbar, Anthony T. Osborn, Adrian Palmer, Jürgen W. Thurow, Thomas Wagner, 2006. "Sediment colour analysis from digital images and correlation with sediment composition", New Techniques in Sediment Core Analysis, R. G. Rothwell
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Sediment colour records can be extracted from digital images of sediment core surfaces, which provide the spatial resolution needed to measure colour in laminated sediments. Digital cameras sample colour in three broad wavelengths, red, green and blue, which are subsequently translated into the CIE L*a*b* colour space. Methods to extract calibrated colour values are discussed in this paper. L*, a* and b* values are correlated with geochemical analyses of cm-scale bulk sediment samples. The sediments are from a suite of laminated and homogenous sections containing organic matter, carbonate, biogenic opal and lithogenic material in variable proportions. Total organic carbon (TOC) content has the dominant effect on sediment colour. Results show that there is a strong correlation with lightness (L*) for TOC values between 0.5 and 10%, but that sediment lightness becomes saturated at higher TOC concentrations. Biogenic opal content cannot be resolved using the L*a*b* colour space. Biogenic opal in itself has a light colour but it tends to occur in darker coloured sediments because of a positive correlation between opal and TOC content. Carbonate content in the measured sections is generally less than 25%, at which values its effect on colour is obscured by the other sediment components.
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Marine sediment cores are the fundamental data source for information on seabed character, depositional history and environmental change. They provide raw data for a wide range of research including studies of climate change, palaeoceanography, slope stability, oil exploration, pollution assessment and control, seafloor survey for laying cables, pipelines and construction of seafloor structures. During the last three decades, a varied suite of new technologies have been developed to analyse cores, often non-destructively, to produce high-quality, closely spaced, co-located downcore measurements. These techniques can characterize sediment physical properties, geochemistry and composition in unprecedented detail. Palaeoenvironmentally significant proxies can now be logged at decadal, and in some cases, annual or sub-annual scales, allowing highly detailed insights into climatic history and associated environmental change. These advances have had a profound effect on many aspects of the Earth Sciences and our understanding of the Earth's history.
In this volume, recent advances in analytical and logging technology and their application to the analysis of sediment cores are presented. Developments in providing access to core data and associated datasets, and advances in data mining technology in order to integrate and interpret new and legacy datasets within the wider context of seafloor studies are also discussed.