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 (~0.13 wt%) also suggest a harsh environment and/or poor preservation in coarse (>2 µm) sediments that were extensively bioturbated below the oxygen minimum zone.
1Reusch, D.N., 2002. Oligocene-Miocene terrigenous and pelagic sediments, Skiff Bank, Kerguelen Plateau (ODP Leg 183, Site 1139). In Frey, F.A., Coffin, M.F., Wallace, P.J., and Quilty, P.G. (Eds.), Proc. ODP, Sci. Results, 183 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/183_SR/010/010.htm>. [Cited YYYY-MM-DD]
2Department of Geological Sciences, 5790 Bryand Global Sciences Center, University of Maine, Orono ME 04469-5790, USA. Present address: Department of Natural Sciences, University of Maine at Farmington, 173 High Street, Farmington ME 04938, USA. reusch@maine.edu
Initial receipt: 3 September 2001
Acceptance: 14 May 2002
Web publication: 22 October 2002
Ms 183SR-010
