Mixed terrigenous-pelagic sediments from the Oligocene-lower Miocene interval of Hole 1139A accumulated on the flank of an eroded alkalic volcano, Skiff Bank. In this study, I explore relationships among sediment fluxes, especially of organic carbon and the clay mineral by-products of silicate weathering, and lithologic, tectonic, climatic, and biologic forcing factors. Benthic foraminifers indicate that Skiff Bank had subsided to lower bathyal depths (1000-2000 m) by the Oligocene. Two prominent maxima in noncarbonate concentration at 28 and 22 Ma correspond to peaks in the terrigenous flux; also, high noncarbonate concentrations are associated with larger grain sizes (silt) and higher opal concentrations. These and higher-frequency variations of noncarbonate concentration were probably controlled by glacioeustatic/climatic changes, with higher noncarbonate concentrations caused by increased erosion during glacial lowstands. Around 27 Ma, benthic foraminiferal 18O values decreased 0.7 as the noncarbonate concentration decreased after the 28-Ma maximum. A paucity of clay-sized sediment and clay minerals suggests that physical erosion, by waves and/or ice, predominated under weathering-limited conditions. Low organic carbon concentrations ( approximately 0.13 wt%) also suggest a harsh environment and/or poor preservation in coarse (>2 mu m) sediments that were extensively bioturbated below the oxygen minimum zone.