Dsdpodp Drilling Dates Initiation of Antarctic Ice Sheet

By this time, the ODP had approved two further Antarctic legs, one in the Weddell Sea (DSDP 113) and one in Prydz Bay (ODP 119), seeking a glacial history from other sectors of the Antarctic margin. The Weddell Sea leg cored thick continuous Paleogene deep-sea sediments between 60° and 71°S, recording a relatively warm climate, cooling sufficiently for cold deep water formation and some limited ice to form on land in the early Oligocene (Barker, Kennett et al., 1988). However, ODP 119 was able to drill several

Figure 3.5: A comparison of the deep-sea isotope record of Miller et al. (1987), the eustatic sea level curve of Haq et al. (1987), and the record from cores from the Eastern and Victoria Land Basins and Prydz Bay (from Barrett and Davey, 1992). Both the isotope record and the eustatic sea level curve were considered by their proponents to be sound Ice volume proxies, but showed significant differences in early Cenozoic times. Reproduced from Barrett and Davey (1992), with permission from the Royal Society of New Zealand.

Figure 3.5: A comparison of the deep-sea isotope record of Miller et al. (1987), the eustatic sea level curve of Haq et al. (1987), and the record from cores from the Eastern and Victoria Land Basins and Prydz Bay (from Barrett and Davey, 1992). Both the isotope record and the eustatic sea level curve were considered by their proponents to be sound Ice volume proxies, but showed significant differences in early Cenozoic times. Reproduced from Barrett and Davey (1992), with permission from the Royal Society of New Zealand.

shelf sites in Prydz Bay, coring offshore-dipping strata, ranging from Cretaceous terrestrial sediments near the coast to thick late Eocene-early Oligocene diamictite mid-shelf to Neogene diamictites in the outer shelf (Hambrey et al., 1991). No better age has been extracted from these fossil-poor sediments, but the result was sufficient to make it clear that continental-scale ice sheets on Antarctica were delivering ice to the shelf edge beyond the limits of the modern ice sheet at least from early Oligocene times. ODP Leg 120 that followed was able to both confirm this physically through the occurrence of ice-rafted debris at the Eocene-Oligocene boundary and provide a better deep-sea isotope record from continuous Paleogene cores from the edge of the Kerguelen Plateau to the north (Zachos et al., 1992). The timing of the first of the big Antarctic-wide ice sheets had now been established (Wise et al., 1991).

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