Pre-glacial to glacial sedimentation of the Amundsen Sea Embayment shelf, West Antarctica, from seismic surveying


Contact
Karsten.Gohl [ at ] awi.de

Abstract

Studies of the sedimentary architecture and characteristics of Antarctic shelves provide clues of past ice sheet advance-retreat cycles and help improve constraints for paleo-ice dynamic models since early glacial periods. A first seismostratigraphic analysis of the Amundsen Sea Embayment shelf and slope of West Antarctica reveals insights into the structural architecture of the continental shelf and slope and shows stages of sediment deposition, erosion and transport history from pre-glacial times to early glaciation and to the last glacial periods. The shelf geometry consists of a large pre- and syn-rift basin in the middle shelf region between outcropping basement of the inner shelf and basement ridge and highs of the outer shelf. A middle shelf sub-basin exists which can be associated with motion along an early West Antarctic Rift System branch. At least 4 km of pre-glacial strata has been eroded from the present inner shelf and coastal hinterland since the onset of glaciation by ice sheet advances. Parts of the eroded sediments deposited as a progradational wedge extending the outer shelf by 25 to 65 km oceanward of the pre-glacial shelf-break. Comparing the observed seismic characteristics with that of other Antarctic shelf sequences, we assign an Early Cretaceous age for bottom sedimentary unit ASS-1, a Late Cretaceous to Oligocene age for unit ASS-2, an Early to Mid-Miocene age for unit ASS-3, a Mid-Miocene age for unit ASS-4, a Late Miocene to Early Pliocene age for unit ASS-5, and a Pliocene to Pleistocene age for the top unit ASS-6. The survival of buried grounding zone wedges in the upper part of unit ASS-5 of the outer shelf is consistent with the onset of a long warming phase and a retreated ice sheet in the early Pliocene as observed for the Ross Sea shelf and predicted by paleo-ice sheet models. Our data also reveal that the paleo-paths of central Pine Island Trough system have remained in stationary positions across the middle and outer shelf since early glacial advances. This study and its stratigraphic constraints will serve as a basis for future drilling operations required for an improved understanding of processes and mechanisms leading to West Antarctic Ice Sheet retreats as presently observed in high rate for the Amundsen Sea Embayment.



Item Type
Conference (Poster)
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Peer revision
Not peer-reviewed
Publication Status
Published
Event Details
International Polar Congress / Internationale Polartagung, 18 Mar 2013 - 22 Mar 2013, Hamburg.
Eprint ID
32214
Cite as
Gohl, K. , Uenzelmann-Neben, G. , Hillenbrand, C. D. , Larter, R. D. and Nitsche, F. O. (2013): Pre-glacial to glacial sedimentation of the Amundsen Sea Embayment shelf, West Antarctica, from seismic surveying , International Polar Congress / Internationale Polartagung, Hamburg, 18 March 2013 - 22 March 2013 .


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