Calcium carbonate content, brightness and color reflectance of ODP Site 188-165 and Hole 188-1167A

We measured and analyzed near-ultraviolet/visible/near-infrared spectral data from core samples recovered from Ocean Drilling Program Sites 1165 (Wild Drift) and 1167 (Prydz Channel Trough Mouth Fan) using our laboratory-grade spectrophotometer to help determine temporal mineralogical changes downhole. These measurements included closely spaced (~10 cm) samples for the section from 0 to 54.17 meters below seafloor (mbsf) in Hole 1165B, which is the Pliocene-Pleistocene age interval being studied in detail by the High-Resolution Integrated Stratigraphy Committee (HiRISC). We also determined calcium carbonate content for all samples in this HiRISC interval. The Pleistocene and uppermost Pliocene sediments (0-10 mbsf) show wide carbonate fluctuations ranging from 0 to 37 wt%; however, below 10 mbsf, the carbonate content is generally zero. To examine the major components that contribute to spectral variability in the holes, the first-derivative values for all samples from Sites 1165 and 1167 were assembled into a single matrix and the matrix was then factor analyzed after being subject to a varimax rotation. For Sites 1165 and 1167, factoring first-derivative values from 255 to 745 nm produced the most easily interpretable results, with five factors that explain ~92.5% of the total variance in the data set.
Factor 1 incorporates both goethite and chlorite, meaning that scores for this factor will be high where these two minerals covary.
Factor 2 is interpreted as organic matter.
Factor 3 appears to be a combination of clay minerals, possibly montmorillonite and illite.
Factor 4 is interpreted as the mineral maghemite, a polymorph of hematite.
Factor 5 is the mineral hematite.