The Unit I mineral assemblages at Site 1146 display an increase in the chemical weathering product kaolinite with increasing depth, concomitant with a decrease in the primary minerals quartz and plagioclase and physical weathering proxies illite and chlorite. Taken together, a classic pattern of source region aridification from the middle Pliocene through the Pleistocene is indicated. The mineral variability in this interval suggests glacial-interglacial variability; the time resolution in this study is insufficient at present to quantify this assertion, and higher-resolution analyses are under way. Liu et al. (2003) conducted a high-resolution mineralogy study for the upper Pliocene through Pleistocene sediments at this site, and clear glacial-interglacial mineral variability is well documented in the younger sediments. The mineralogy of sediments recovered at Site 1146 suggests relatively constant sediment sources and source area weathering regimes throughout Unit II (upper Miocene through middle Pliocene), as indicated by low variability and relatively constant mineral concentrations through this interval.