Friday, 31 August 2007
5.PS-151
Complex exposure history of pre-LGM glacial drifts in Terra Nova Bay (Victoria Land), using a multiple cosmogenic nuclide approach
Luigia Di Nicola1, Stefan Strasky2, Christian Schlüchter3, Maria C. Salvatore4, Peter W. Kubik5, Susan Ivy-Ochs6, Rainer Wieler2, Naki Akçar3, and Carlo Baroni7. (1) Dipartimento di Scienze della Terra, Università di Siena, Siena, Italy, (2) Institute of Isotope Geochemistry and Mineral Resources, ETH Zurich, Zürich, Switzerland, (3) Institute of Geological Sciences, University of Bern, Bern, Switzerland, (4) Dipartimento di Scienze della Terra, Università La Sapienza, Roma, Italy, (5) Paul Scherrer-Institute, c/o Institute of Particle Physics, ETH Zurich, Zürich, Switzerland, (6) Institution of Particle Physics, ETH Zurich, Zurich, Switzerland, (7) Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
Glacially scoured morphology characterizes coastal piedmonts in the Terra Nova Bay area. Rounded mountain tops occur below the highest erosional trimlines on the flanks of glacial troughs draining the East Antarctic Ice Sheet (EAIS) and in intervening reliefs. Complex older drifts rest on deglaciated areas above the younger late Pleistocene glacial drift. The authors use geomorphological and glacial geological surveys and surface exposure dating to reconstruct a local chronology of pre-Last Glacial Maximum (LGM) variations of the EAIS and related outlet glaciers. Glacially transported erratics, as well as bedrock surfaces were sampled for cosmogenic-nuclide analysis (10Be and 21Ne). Bedrock samples show consistent 10Be and 21Ne exposure ages indicating exposure since at least 4 Ma with an erosion rate of about 17 cm/Ma; the erratic boulders show an excess of cosmogenic neon over cosmogenic beryllium that is interpretated as complex exposure histories with substantial periods of burial by cold-based ice.