Stratigraphy and Geomorphology of Late Pleistocene Moraine at the Mouth of Taylor Valley, Antarctica: Implications for the Melting History of the West Antarctic Ice Sheet During the Last Deglaciation
Abstract
The nature of the West Antarctic Ice Sheet margin at its maximum late Pleistocene extent in the McMurdo Dry Valleys region is controversial. The prevailing view sees the WAIS margin abutting deep proglacial lakes which implies anomalously warm climate and significant effect on the ice margin. This is problematic because GPR profiles in and around Taylor Valley reveal mainly fluvial, not glacilacustrine deposits. We examined a 5 km-scale sediment ridge that forms the divide at the mouth of Taylor Valley, focusing on a 200 m wide, 15 m deep channel system that meanders across it. We collected more than 15 km of GPR at multiple frequencies and 3 cores that provide 38 m of sediment. The GPR shows several widespread undulating reflectors that likely were caused by passage of a grounded lobe of the WAIS into Taylor Valley in the late Pleistocene. Several channels were eroded into the uppermost buried surface, the deepest of which is 100 m wide and 20 m deep. The channels are filled with stratified fluvial and some lacustrine sediment to an elevation that corresponds to that of the highest deltas found using GPR in the interior Fryxell basin, today at 82 m above sea level. The surface channel system was eroded into these stratified sediments. During its last retreat from Taylor Valley, the WAIS was fronted by a shallow glacial lake implying that melting was limited and retreat was largely terrestrial. When the ice cleared the valley, WAIS meltwater carved the buried channels in the valley-mouth ridge lowering the threshold below its current altitude of 74 m asl. This precludes a deep, valley-wide proglacial lake. Further in deglaciation, WAIS melting changes caused fluctuations in channel and lake-level, filling and eroding sediment from the channel. The evidence forms the basis for a melting history of the WAIS margin during the last deglaciation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.C31C0504P
- Keywords:
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- 0726 Ice sheets;
- 0746 Lakes (9345);
- 4207 Arctic and Antarctic oceanography (9310;
- 9315);
- 4914 Continental climate records;
- 9310 Antarctica (4207)