Publication Date

April 2018


Suzanne O'Connell


Earth & Environmental Sciences


English (United States)


Creating an accurate age model for Antarctic sediment is difficult due to a general lack of preserved carbonate. Core 693A-2R, from the Ocean Discovery Program (ODP) Leg 113, is an exception. Cored in 2560 m of water, this 9.5 m long core contains abundant foraminifera. Site 693 is located adjacent to Dronning Maud Land in the Southeast Weddell Sea on an upper slope bench near Wegener Canyon. Based on the shipboard timescale, it appears that Core 2R ranges from 0.25 to 0.95 Ma, placing it across the Brunhes-Matuyama reversal. Here we use the planktonic foraminifera species N. pachyderma (sinistral), to create a downcore stable oxygen isotope record for Core 2R. The downcore variation in ice rafted detritus (IRD) was also calculated to help determine ice flow during the Pleistocene. Lastly, from the IRD, hornblendes and biotite were picked for 40Ar/39Ar analysis in order to determine IRD provenance at Site 693 during the Pleistocene. High IRD during glacial periods is witnessed at Site 693 which is characteristic of the North Atlantic, but not the Southern Ocean. IRD provenance at Site 693 suggests little or no icebergs from the immediate Grunehoga Craton, which is the dominant source today. This difference indicates that the calving and travel of icebergs was likely different in the past. Lastly, our planktonic d18O curve appears to work well for determining temperature changes in the Weddell Sea during the Pleistocene, but not on a global scale. Looking at the results together, Core 2R points to a very dynamic East Antarctic ice sheet during the Pleistocene.



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