EGU21-13136, updated on 04 Mar 2021
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Sedimentary signature of past West Antarctic Ice Sheet and ocean dynamics from deep sea drill cores in the Amundsen Sea (IODP Expedition 379)

Delaney E. Robinson1, Julia S. Wellner1, Karsten Gohl2, Benedict T.I. Reinardy3, and the IODP Expedition 379 Scientists*
Delaney E. Robinson et al.
  • 1Department of Earth and Atmospheric Sciences, University of Houston, Houston, USA
  • 2Department of Geoscience, Alfred Wegener Institute Helmholtz—Center for Polar and Marine Research, Bremerhaven, Germany
  • 3Institutionen för Naturgeografi, Stockholm University, Stockholm, Sweden
  • *A full list of authors appears at the end of the abstract

Modern observations of the West Antarctic Ice Sheet (WAIS) show relatively warm ocean water causing negative changes in ice-sheet mass. The largest ice mass loss in the WAIS occurs in the Amundsen Sea region, where warm water flows onto the shelf and melts the marine-based ice shelves, a process with the potential to lead to full collapse of the WAIS. Geologic records from similar and warmer climate conditions than today are required to understand the role of changes affecting the Amundsen Sea drainage sector in steering past WAIS dynamics. International Ocean Discovery Program (IODP) Expedition 379 successfully recovered sediment drill cores from two sites on the continental rise in the Amundsen Sea, West Antarctica. Both sites are located on a large sediment drift that provides a continuous, long-term record of glacial history in a drainage basin that is fed exclusively by the WAIS. Sediments at both sites are associated with depositional processes related to glacial extent on the shelf. Repeated alternations of two major facies groups composed of dark-gray laminated silty clay and massive/bioturbated greenish-gray, clast-bearing mud are interpreted to represent cycles of glacial and interglacial periods. High-resolution sedimentological analyses define characteristics that vary within the two broad sedimentary facies, helping provide constraints on depositional processes of the sediments and controlling WAIS dynamics.

Detailed investigations were conducted on Miocene to Pliocene strata using grain size and shape analysis, combined with X-Ray Fluorescence data and computer tomography scans, as well as detailed thin section analysis. Laminated silty clay intervals contain consistently fine-grained sediments dominated by terrigenous components that were supplied by downslope transport during glacial periods. Massive/bioturbated muds with ice rafted debris (IRD) display variable grain size trends accompanied by changes in particular elemental ratios indicating increased supply of biogenic components and possibly reduced delivery of terrigenous detritus during interglacial periods. The boundaries between massive, interglacial facies and laminated, glacial facies are usually sharp; although occasionally, a more gradual interglacial-glacial transition is observed. Different sedimentation patterns suggest fluctuations in downslope transport and bottom current intensities that are connected to ice sheet extent on the West Antarctic continental shelf. Further analysis may reveal facies characteristics that vary with glacial-interglacial cycles and allow improved interpretation of past WAIS dynamics and Southern Ocean circulation.

IODP Expedition 379 Scientists:

Bauersachs, Thorsten; Bohaty, Steve; Courtillat, Margot; Cowan, Ellen; De Lira Mota, Marcelo; Esteves, Mariana; Fegyveresi, John; Frederichs, Thomas; Gao, Liang; Halberstadt, Ruthie; Hillenbrand, Claus-Dieter; Horikawa, Keiji; Iwai, Masao; Kim, Ji-hoon; King, Theresa; Klages, Johann; Passchier, Sandra; Penkrot, Michelle; Prebble, Joe; Rahaman, Waliur; Renaudie, Johan; Scherer, Reed; Siddoway, Christine; Wu, Li; Yamane, Masako

How to cite: Robinson, D. E., Wellner, J. S., Gohl, K., and Reinardy, B. T. I. and the IODP Expedition 379 Scientists: Sedimentary signature of past West Antarctic Ice Sheet and ocean dynamics from deep sea drill cores in the Amundsen Sea (IODP Expedition 379), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13136,, 2021.

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