Stephen Schwarz

Publication Date



Suzanne O'Connell


Earth and Environmental Sciences (E&ES)




To better understand the past stability of the Antarctic ice sheet, grain size and geochronology analyses were completed on Eocene to Early Pliocene samples from Ocean Drilling Program Sites 693, 694, and 696 within the Weddell Sea. These analyses are compared to similar studies from other areas of Antarctica, further illuminating the past ice sheet dynamics.

The grain size analysis shows that the first glacial evidence occurred during the Lower Oligocene in the Eastern Weddell Sea and that the West Antarctic Ice Sheet had been fully formed by the Middle Miocene. The 40Ar/39Ar ages of detrital hornblendes and U-Pb ages of detrital zircons show shifting source areas for the Weddell Sea icebergs from the Middle Miocene to the Early Pliocene. These analyses lead to the conclusion that most of the ice rafted debris is sourced from East Antarctica, even after the formation of the West Antarctic Ice Sheet. There is also evidence for a destabilization event, similar to an event observed by previous studies (Williams et al., 2010), during the Late Miocene and Early Pliocene. Age provenance indicates that distant icebergs arrived and that there was a shift in the method of coarse material deposition from ice rafting to turbidites.



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