Color data were measured every 2 cm for Cores 175-1082A-1H through 9H. Cores 175-1082A-10H through 49X and all of Holes 1082B and 1082C were measured at 4-cm intervals. At Site 1082, total reflectance values range between 25% and 65% (Fig. 5, Fig. 6).
The general trends in total reflectance, calcium carbonate, and magnetic susceptibility can be correlated to the lithostratigraphic subunits of Hole 1082A (Fig. 5). Higher values in the total reflectance are observed in the nannofossil-rich clay of Subunits IA and IB as well as in Unit II, whereas lower values are associated with the diatom-rich clay of Subunit IB. Downcore variations in the total reflectance are positively correlated to the calcium carbonate content. This suggests that calcium carbonate controls the total reflectance of the sediment in the diatom-rich intervals. The negative correlation between total reflectance and magnetic susceptibility indicates the dilution of the clay component by the carbonate component.
Total reflectance records for the three holes at Site 1082 are very similar (Fig. 6). Sediment recovered in the upper 200 mbsf at Holes 1082A, 1082B, and 1082C is of Pleistocene age (see "Biostratigraphy and Sedimentation Rates" section, this chapter) and has high total reflectance values, with a maximum of 55% at about 40 mbsf. This depth interval corresponds to marine oxygen-isotopic Stages 9, 10, and 11 (see "Biostratigraphy and Sedimentation Rates" section, this chapter) and may be caused by better preservation of the carbonate shells and/or enhanced carbonate productivity. Higher total reflectance values are also observed at all three holes at the Brunhes/Matuyama magnetic reversal (76 mbsf; see "Paleomagnetism" section, this chapter) and appear to correspond to marine oxygen-isotopic Stage 19.
Cores 175-1082A-5H through 7H contain several dark olive-brown and black clay layers intercalated in the pervasive olive-gray and olive clays (Fig. 2). In general, the bottom of the dark olive-brown layers is very sharp, whereas the upper boundary is gradational because of extensive bioturbation. The color cycles reflect sharp changes in concentrations of calcium carbonate, organic carbon, and total sulfur (Fig. 7A). The dark layers have high concentrations of organic carbon and total sulfur and low concentrations of calcium carbonate and biogenic opal. Over this depth interval, calcium carbonate is inversely related to organic carbon and total sulfur. The variation in total reflectance corresponds closely to changes in calcium carbonate content (Fig. 7B). These data strongly suggest that in these sediments the abundance of calcium carbonate exerts the strongest influence on total reflectance. This effect is further accentuated by the strong negative correlation between calcium carbonate and organic carbon, as high contents of organic carbon tend to decrease the total reflectance of sediments.