Abstract:
Two optical methods of modeling calcium carbonate concentrations within oceanic sediment cores were explored in Ocean Drilling Program Legs 138, 154 and 162. Utilizing multiple regression analysis, the dynamics between light reflectance and carbonate content within Leg 162 were empirically explored. The resulting equations that predicted CaCO (sub 3) concentrations based on light reflectance were tested on Legs 138 and 154. The conclusions from this work are that first, equations correlating calcium carbonate to reflectance are responding primarily to carbonate fluxes and only secondarily to other minerals. Secondly, a large suite of reflectance terms across the spectrum can accurately model calcium carbonate concentrations. Finally, reflectance equations can successfully predict CaCO (sub 3) contents far from the areas in which they were developed, since the primary influence of the non-carbonate matrix is to uniformly offset carbonate predictions. Using grayscale analysis, the dynamic between sediment color and calcium carbonate was investigated in Leg 162 cores. A new methodology for correcting for light distortions was introduced. It was found that there is a linear correspondence between sediment color and calcium carbonate concentration. Secondly, equations that accurately predict carbonate content based on grayscale values were developed. Both grayscale and reflectance equations produce overestimated predictions at low carbonate concentrations and underestimated predictions at high carbonate concentrations. In summary, both grayscale and reflectance analysis have value in calcium carbonate prediction within oceanic sediment cores.