Late Eocene signals of oncoming Icehouse conditions and changing ocean circulation, Antarctica

The end of the Eocene greenhouse world was the most dramatic phase in the long-term Cenozoic cooling trend. Here we use 75,000 km of multi/single channel seismic reflection data from offshore Prydz Bay, Antarctica, to provide new insight on the Paleogene stratigraphic transition from greenhouse to icehouse conditions and reorganizing the ocean circulation changes that were invigorated by the cooling and glaciation. We identify a new prominent Paleogene transitional phase (Greenhouse to Icehouse) preserved in the deep-water sedimentary record by correlating from shelf to the continental slope. The occurrence of mega-Mass Transport Deposits (MTDs) on the slope during an early stage in the transition suggests significant instability and collapse of the upper part of the continental margin. A second stage of the transition is represented by the growth of a well-defined set of continental slope clinoforms. We estimate the formation age of the MTDs and clinoforms to be around Eocene-Oligocene Transition. The formation of the clinoforms in the transitional phase indicates sea level has risen, and large volumes sediment delivered to the margin by marine-terminating glaciers on the shelf. Finally, a subsequent marked migration of the margin depocenter toward the west and northwest, attests the onset of drift sedimentation and full glacial conditions, suggesting a more vigorous ocean circulation as the Earth entered the icehouse conditions after the Eocene-Oligocene boundary.

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