HR: 0800h
AN: T11A-1239    [Abstracts]
TI: Isostatic Rebound due to Glacial Incision within the Transantarctic Mountains
AU: * Stern, T A
EM: tim.stern@vuw.ac.nz
AF: School of Earth Sciences, Victoria University of Wellington, Wellington, 6005 New Zealand
AU: Baxter, A K
EM: ainsliebaxter@yahoo.com
AF: School of Earth Sciences, Victoria University of Wellington, Wellington, 6005 New Zealand
AU: Barrett, P J
EM: peter.barrett@vuw.ac.nz
AF: Antarctic Research Centre, Victoria University of Wellington, Wellington, 6005 New Zealand
AB: In temperate climates about 25% of peak elevations in mountain ranges can be created by isostatic rebound as a response to incisional erosion. Significantly more relief generation and peak uplift is, however, possible for glacial erosion in a polar climate. Here we us a 3D flexure study to show that up to 2000 m or 50% of peak elevation in the central Transantarctic Mountains (TAM) is due to isostatic rebound as a response to glacial incision. Maximum rebound is predicted for the Beardmore-Nimrod region. Here peak elevations are about 800 m higher than elsewhere along the range and we show that this elevation difference can be ascribed to the rebound response to deep incisional erosion by the Nimrod and Beardmore glaciers. Comparable global localities for relief on the scale of the central TAM are only seen in the Himalayas where fluvial erosion has cut gorges of similar magnitude. But such strong relief in the Transantarctic Mountains is possible because of the special conditions afforded by a polar climate and adjacent ice sheet. In particular, the combination of freezing conditions at high elevations, which acts to preserve the peaks, and wet based glaciers at lower elevations produce optimal conditions for enhanced glacial incision. Based on our knowledge of the glacial history of the TAM, the likely time for creating relief, and hence rebound, is probably mid-Miocene when the East Antarctic ice cap became fully developed. As glacial incision is an easily quantified, negative-load, we use this loading to test different rheological models for the central, Transantarctic Mountain front. What is clear from the minimal disturbance of seismic stratigraphy in the adjacent Ross Embayment, is that if any shear stresses are transmitted across the front they are relatively minor and restricted to be within 40 km of the front. Finally, because isostatic rebound results in permanent peak uplift this mechanism provides an explanation of why the Transantarctic Mountains are one of the higher and more long-lived continental rift-margins on Earth.
DE: 9310 Antarctica
DE: 8159 Rheology--crust and lithosphere
DE: 5415 Erosion and weathering
DE: 5416 Glaciation
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting