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 ( approximately 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 approximately 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. We generated plots of factor scores downhole at Sites 1165 and 1167 to determine trends in temporal changes. At Site 1165 Factor 1 predominates above approximately 540 mbsf, Factor 2 is important above approximately 280 mbsf, and Factor 3 is high from 25 to 350 mbsf. Factor 4 exhibits two zones of high values from 20 to 50 mbsf and 540 to 750 mbsf. Factor 5 is important from 0 to 95 mbsf. In the HiRISC Section of Hole 1165B (0-54 mbsf), Factors 1 and 2 exhibit high scores through most of the section, with the exception of a low in both factors centered at approximately 30 mbsf. Factors 3 and 4 exhibit high values primarily below 30 mbsf, and Factor 5 exhibits higher-frequency variation than the other factors. Despite apparent similarities in their downhole patterns, few of the factors are highly correlated to each other. In Hole 1167A Factor 1 is important only in the top 5 mbsf, whereas Factor 2 is important throughout the entire hole. Factor 3 is important only from 210 to 227 mbsf, Factor 4 exhibits a few high values in the uppermost 30 mbsf, and Factor 5 is most important from 30 to 210 mbsf. Regression of factor scores vs. X-ray diffraction percentage values for the various minerals downhole indicates minor correlations of Factor 1 to pyrite and Factor 2 to hornblende. No other factors exhibited a correlation >0.1 for any of the minerals analyzed.