Pliocene East Antarctic ice sheet retreat in the Wilkes subglacial basin

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Author(s): Cook, C.; van de Flierdt, Tina; Williams, Trevor; Hemming, Sidney R.; Pierce, E. L.; Iwai, M.; Kobayashi, M.; Jimenez-Espejo, F.; Escutia, C.; González, J.; Patterson, Molly O.; McKay, Robert M.; Passchier, S.; Tauxe, L.; Sugisaki, S.; Bohaty, S. M.; Riesselman, C. R.; Sangiorgi, F.; Brinkhuis, H.
Author Affiliation(s): Primary:
Imperial College London, Department of Earth Science and Engineering, London, United Kingdom
Lamont-Doherty Earth Observatory, United States
Columbia University, United States
Kochi University, Japan
University of Granada, Spain
Victoria University of Wellington, New Zealand
Montclair State University, United States
Scripps Institution of Oceanorgaphy, United States
University of Southampton, United Kingdom
U. S. Geological Survey, United States
Utrecht University, Netherlands
Volume Title: AGU 2012 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2012; American Geophysical Union 2012 fall meeting, San Francisco, CA, Dec. 3-7, 2012. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Polar ice sheets are an important component of the climate system, affecting global sea level, ocean circulation and heat transport, marine productivity, and albedo. However, there is considerable uncertainty in the response of the polar ice caps to predicted future warming. Warm intervals during the Pliocene Epoch (5.33-2.58 Ma) may provide insight on the sensitivity of ice sheets when atmospheric carbon dioxide levels were similar to today and temperatures were elevated by a few degrees Celsius. Global sea level during this time has been estimated to lie about 20m above modern, requiring not only Greenland and West Antarctica, but also the large East Antarctic ice sheet (EAIS) to have lost mass. Direct evidence for ice retreat around East Antarctica is, however, sparse. Here we present results of neodymium (Nd) and strontium (Sr) isotope analyses of detrital clay and silt-sized sediments from Integrated Ocean Drilling Program Leg 318 Site U1361 (64°24.57'S, 143°53.19'E), drilled offshore of the Wilkes Subglacial Basin, where large areas of the EAIS lie below sea level. Early Pliocene (5.33 to 3.3 Ma) detrital sediments from this location reveal two distinct endmembers. The first endmember is defined by epsilon Nd values of -11 to -14.5 and Sr isotopic compositions of 0.720 to 0.730, and the second endmember is characterized by more radiogenic values of -5.9 to -9.5 and 0.713 to 0.719, respectively. While the first endmember is consistent with siliciclastic material sourced from early Paleozoic bedrocks exposed in Oates Land and the western region of northern Victoria Land to the east of the study site, the second endmember requires a significant contribution (95-70%) from the Jurassic-Triassic Ferrar Large Igneous Province (FLIP), which today is only regionally exposed in volumetrically significant quantities in the Transantarctic Mountains. For this area to be an important source to IODP Site U1361 sediments, significant retreat of outlet glaciers and collapse of the Ross Ice Shelf would be required, as well as transport of detritus over more than 3000km from the Ross Sea by icebergs and/or by bottom currents. While we cannot fully exclude this possibility, we render it unlikely, as provenance analyses on sediments deposited during the early Pleistocene "super-interglacial" Marine Isotope Stage 31 (1.08 to 1.06 Ma) deposited at IODP Site U1359 show little indication of FLIP signatures. Instead we suggest that FLIP material at IODP Site U1361 is eroded from within the Wilkes Subglacial Basin during times of retreat of the EAIS. This interpretation is supported by aerogeophysical surveys implying that FLIP intrusions and sedimentary infill are present within the Wilkes Subglacial Basin. Times of predominance of a FLIP signature in IODP Site U1361 detrital sediments correlates with Pliocene episodes of pronounced warmth in the Southern Ocean, identified by changes in sedimentology, physical properties, bulk geochemistry and micropaleontology. In summary, our results indicate that the Wilkes Subglacial Basin was a key location of EAIS destabilization during warm intervals of the Pliocene, with implications for both Pliocene and future climate change.
Year of Publication: 2012
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctic ice sheet; Antarctica; Cenozoic; Deglaciation; East Antarctic ice sheet; Expedition 318; IODP Site U1361; Integrated Ocean Drilling Program; Neogene; Paleoclimatology; Pliocene; Southern Ocean; Subglacial processes; Tertiary; Wilkes Land
Coordinates: S642434 S642434 E1435312 E1435312
Record ID: 2015005630
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