HR: 10:20h
AN: T32C-01 INVITED     [Abstracts]
TI: Interaction of Plume-Driven Tectonics with Antarctica Climate
AU: * Sleep, N H
EM: norm@pangea.stanford.edu
AF: Department of Geophysics, Stanford University, Stanford, CA 94305 United States
AB: Ice cloaks the geology of most of Antarctica, but ice-produced sediments provide much information on the timing and nature of the tectonics. Slowly eroding regions preserve ancient tills and hence geological record. Marine drilling provides key data. Mantle plumes produced the strongest climatic and tectonic effects outside the Palmer Peninsula. Overall, most intense rifting occurred earlier than glaciation and current feeble tectonics are plume driven. Beginning with East Antarctica, the ice-free elevation of the Gamburtsev Mountains is over 2000 m and the near Vostok highlands are over 1500 m. These regions are too broad to be rift-flank features. Their heights indicate relatively recent, probably Tertiary, uplift. This uplift triggered glaciation. Continental glaciation began with local glaciers in highlands draining into Lambert Graben by 34-37 Ma. I attribute the broad uplift to a plume head impinging at ~50 Ma. Plume material spread out beneath the lithosphere over a ~1000-km radius region causing a few hundred meters of uplift in less than 1 m.y. Subsequently, material from the plume tail thinned the lithosphere causing further uplift in the Gamburtsev-Vostok area. The base of East Antarctic lithosphere acted as an upside-down drainage pattern for the plume material. Some cascaded over the cratonal margin along the Ross Sea. Pressure-release melting supplied volcanism from 48 Ma to the present. The magmas and the buoyancy of the plume material concentrated rifting along the edge of the Ross Sea. Vigorous extensional tectonics ended at ~24 Ma. Lithospheric thinning by plume material contributed to the uplift of the Transantarctic Mountains. The Gamburtsev-Vostok and Transantarctic uplifts grossly control glacial drainage patterns. Pre-existing drainages and differences in erodability are regionally important. Further away, plume material modulated marine bathymetry, including the rifts and basins between Tasmania and Antarctica. With regard to West Antarctica, I suggest that the Vostok starting plume head entrained a second tail, which now impinges beneath Marie Byrd Land. Its dome rises to 2700 m, but the region has only 25-km thick continental crust. This feature was active by 30 Ma, but its earlier history is not evident.
DE: 8107 Continental neotectonics (8002)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8175 Tectonics and landscape evolution
DE: 8177 Tectonics and climatic interactions
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: Fall Meeting 2005