10. Identification of the Glacial Signal from the Antarctic Peninsula since 3.0 Ma at Site 1101 in a Continental Rise Sediment Drift1

Ellen A. Cowan2

ABSTRACT

Sediment drifts on the continental rise west of the Antarctic Peninsula received fine-grained sediment and ice-rafted debris (IRD) directly from the continental shelf and thus indirectly record the history of West Antarctic glaciation. Site 1101 contains a 218-m-thick, nearly continuous section extending from the late Pliocene to the Holocene. To assess the presence of calving glaciers at sea level in the Antarctic Peninsula region, the mass accumulation rate (MAR) of IRD was calculated using the weight percent terrigenous sand fraction (250 Ám to 2 mm). IRD MAR is cyclic throughout, with small peaks alternating with periods of low or no IRD. Many cycles have a sawtooth pattern that increases gradually to the peak then abruptly decreases to zero. This pattern is consistent with rapid disintegration of ice streams and release of icebergs from the continental shelf. Three unusually large peaks (three to five times the size of other peaks) occurred at approximately 2.8, 1.9, and 0.88 Ma and indicate periods of intense ice rafting.

Lithofacies were described in detail using X-radiographs and core descriptions for the interval from 1.34 to 0.54 Ma. Glacial units are represented by thickly laminated mud deposited by distal turbidites and meltwater plumes. Less commonly, thinly laminated sediment formed by contour currents and diamicton by intense ice rafting. Interglacials are represented by foraminifer-bearing mud with IRD. Ice rafting appears to have increased in the later part of the glacial period and remained high in the interglacial period.

1Cowan, E.A., 2001. Identification of the glacial signal from the Antarctic Peninsula since 3.0 Ma at Site 1011 in a continental rise sediment drift. In Barker, P.F., Camerlenghi, A., Acton, G.D., and Ramsay, A.T.S. (Eds.), Proc. ODP, Sci. Results, 178 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/178_SR/chap_10/chap_10.htm>. [Cited YYYY-MM-DD]

2Department of Geology, Appalachian State University, PO Box 32067, Boone NC 28608, USA. cowanea@appstate.edu

Initial receipt: 8 August 2000
Acceptance: 5 April 2001
Web publication: 24 July 2001
Ms 178SR-206

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