Paleoenvironment Development on the West Antarctic Margin


Montag, 19. Mai 2014 - 18:15 Uhr
GEO-Gebäude, Raum 1550 (Hörsaal)
Ansa Lindeque

Recently a massive iceberg (33 km x 20 km) broke loose from the Pine Island glacier on the Pacific margin of West Antarctica, whilst the Larsen ice shelf in the Weddell Sea largely collapsed. These are some of the events that mark unprecedented present day Antarctic ice sheet melting and as a result, placed even more urgent focus on having accurate models that quantify the impact of ice sheet changes on ocean circulation, sea-level rise and climate.
These models depend on our understanding of past changes in ice sheet formation, ocean-circulation, basin evolution, sediment transport processes, palaeotopography and palaeobathymetry through geological time. The offshore sedimentary record preserved such changes throughout the pre-glacial to glacial paleoenvironmental development of the West Antarctic Margin. Multichannel seismic reflection (MCS) data provide an image of this sedimentary record, which allows for its analyses. In combining existing MCS surveys with newly acquired data in the Amundsen Sea and Ross Sea, previously unknown sequences representing the pre-glacial, transitional and full glacial depositional processes were identified.
Sediment deposition centers formed by pre-glacial sediment processes, seemed to have changed near or after the Eocene/Oligocene boundary (~34 Ma) when the first major ice sheets advanced to and across the shelf. The full glacial sequences, from the middle Miocene (~16 Ma) onwards, indicate a new depocenter formed in front of the Amundsen Sea Embayment and smaller depocenters in the Bellingshausen Sea and Antarctic Peninsula basins, shifted eastward. Calculations using present-day drainage paths and source areas on the continent indicate that ~4.6 km of West Antarctica's landmass were eroded since the Late Cretaceous, which corresponds to ~10.2 million km3 sediments deposited in the Southern Pacific. This has implications for the palaeotopographic and paleobathymetric reconstructions, which feed back into the ice sheet and climate models, and our understanding of the past and future dynamics of the West Antarctic Ice sheet.




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