Late Miocene-Pliocene ice sheet dynamic of the west antarctic Peninsula region: A sedimentary and oceanographic view
|Location||International Geological Congress,oslo 2008|
|Author||Hepp, Daniel A.; Moerz, Tobias|
|Holding Date||08 October 2008|
Ice has been present on Antarctica since the Eocene/Oligocene transition. Since the late Miocene the West Antarctica has been covered by a waxing and vanishing ice-sheet that periodically extends to the shelf edge. The late Miocene-early Pliocene is known as a period of warm climate conditions but the response of the Antarctic ice-sheets to these conditions is still a matter of controversial discussion. The late Miocene-early Pliocene is also thought to be a period of global enhanced primary productivity, possibly as a consequence of major tectonic, oceanographic and cryosphere events, which alter the strength and flow direction of the global overturning circulation, and also affect the meridional partitioning in the ocean of nutrients essential to opal-producing organisms. The Pacific margin off the West Antarctic Peninsula is very sensitive to climate and ice-sheet volume changes. The geometric framework of a relatively narrow continental shelf area and an oversteepened continental slope interacts with long-term variations in the polar regime, glacial cyclicity and regional climatic and oceanographic conditions.
Climatic variations on the Antarctic Peninsula continental shelf control regional sedimentary depositional processes and affect the build-up of giant deep-sea sediment drifts. These drifts are widespread features along the continental rise of the Antarctic Peninsula Pacific margin. Our study is focussed on sediment cores of ODP Site 1095 located on the distal part of one of the largest sediment drifts (Drift 7) in this region. The drift build-up is nourished by glacially driven turbidite currents and interglacial pelagic settling. The sediment cores of ODP Site 1095 comprise a continuous record of the ice sheet history from the late Miocene to the Holocene (~10 Ma). In our sedimentary and oceanographic study we present new X-ray core images, a multitude of existing and new gained sediment physical and geochemical proxy data, and compiled a new late Miocene-early Pliocene record of cyclic magnetic susceptibility losses to (1) describe and characterize glacial and interglacial intervals, (2) find parameters for the definition of glacial-interglacial boundaries, (3) quantify the Pliocene ice sheet dynamic via slope failure frequencies, (4) estimate the time offset between ice sheet controlled slope loading and slope failures resulting in turbidite depositions, (5) outline the mode and the impact of a high dynamic West Antarctic ice sheet with massive ice sheet collapses on primary productivity and bottom water ventilation, and (6) discuss the imprint of global climate signals on our local West Antarctic record. Our study describes the complex interaction of Antarctic ice sheet behavior and ocean conditions in warmer late Miocene-Pliocene climate and may serve as an outlook for upcoming changes in the Circum-Antarctic realm in the course of recent global warming.