HR: 0800h
AN: T11A-1242    [Abstracts]
TI: Passive Margin Uplift in Antarctica Possibly Controlling the Global Climate Change
AU: Yamasaki, T
EM: yamasaki@cp.dias.ie
AF: Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin, 2 Ireland
AU: * Miura, H
EM: miura@nipr.ac.jp
AF: National Institute of Polar Research, Kaga 1-9-10, Itabashi-ku, Tokyo, 173-8515 Japan
AB: The basement uplifts on the continental margin in Antarctica is important for the development of ice sheet and its movement. If there was no uplift in Antarctica, a large amount of ice sheet might flow into the sea, and the present amount of ice sheet might not be maintained. Since the amount of ice on the land and that flowing into the sea are very important factors controlling the Earth_fs climate, the passive margin uplift in Antarctica may partly play an important role in the global climate change. Therefore, to reveal the mechanism of uplift of the passive margin in Antarctica relates to the study on the development of ice sheet and the global climate change. Although the lack of geological data makes it difficult to expect the importance of the passive margin uplift in Antarctica for the Earth_fs climate, we propose a possibility that the passive margin uplift in Antarctica partly controls the climate of the Earth. In order to investigate the hypothesis we first have to examine the origin of the elevated mountain chains on the margin in Antarctica. This study is a first step in the investigations of the linkage between the passive margin uplift in Antarctica and global climate change. In this study we mainly discuss the mechanism of Gondwana breakup and its associated marginal uplift. Based on a two-dimensional thermo-mechanical finite element model, we examine the response of the continental lithosphere to extensional tectonic force, and the dependence of the magnitude of the uplift on the initial lithospheric structure is evaluated. We also estimate the initial lithospheric structure leading to the continental breakup due to the horizontal tectonic forces, and discuss the mechanism of Gondwana breakup. Our numerical results indicate that larger amplitude of the uplift can be obtained for the stronger lithosphere, in which the uplift is an intrinsic consequence of the necking process and is supported by the flexural strength. It is also found that there is a critical strain rate leading to the continental breakup and it seems difficult to obtain the Gondwana breakup by the currently accepted magnitude of the tectonic force for the initial rheological condition inferred beneath the East Antarctica. The breakup may require the dynamic effects of rising plume. However, the dynamic interaction between the convective asthenosphere and strong lithosphere has never clarified well yet, and the passive margin uplift should be affected by the thermal buoyancy and subsequent cooling. Our future studies to deepen the understanding of the mechanism of Gondwana breakup and passive margin uplift will address these important issues.
DE: 8109 Continental tectonics--extensional (0905)
DE: 1824 Geomorphology (1625)
DE: 1827 Glaciology (1863)
DE: 1236 Rheology of the lithosphere and mantle (8160)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting