HR: 0800h
AN: T11A-1237    [Abstracts]
TI: Aeromagnetic and Gravity Data Reveal Crustal Structure and Tectonic History of the Central Transantarctic Mountains Region
AU: * Goodge, J
EM: jgoodge@d.umn.edu
AF: Univ. of Minnesota, Dept. of Geological Sciences, 1114 Kirby Dr., Duluth, MN 55812 United States
AU: Finn, C
EM: cfinn@usgs.gov
AF: U. S. Geological Survey, Box 25046, M.S. 964, Denver Federal Center, Denver, CO 80225 United States
AU: Damaske, D
EM: D.Damaske@bgr.de
AF: Federal Inst. for Geosciences and Natural Resources, Stilleweg 2, Hannover, 30655 Germany
AU: Abraham, J
EM: jdabraha@usgs.gov
AF: U. S. Geological Survey, Box 25046, M.S. 964, Denver Federal Center, Denver, CO 80225 United States
AU: Moeller, H
EM: h-d.moeller@bgr.de
AF: Federal Inst. for Geosciences and Natural Resources, Stilleweg 2, Hannover, 30655 Germany
AU: Anderson, E
EM: ericanderson@usgs.gov
AF: U. S. Geological Survey, Box 25046, M.S. 964, Denver Federal Center, Denver, CO 80225 United States
AU: Roland, N
EM: nw.roland@bgr.de
AF: Federal Inst. for Geosciences and Natural Resources, Stilleweg 2, Hannover, 30655 Germany
AU: Goldmann, F
EM: f.goldmann@bgr.de
AF: Federal Inst. for Geosciences and Natural Resources, Stilleweg 2, Hannover, 30655 Germany
AU: Braddock, P
EM: akaloa@xtra.co.nz
AF: Akaloa, 284 Rathbone Ave., Columbus, OH 43214 United States
AU: Rieser, M
EM: ries0109@d.umn.edu
AF: Univ. of Minnesota, Dept. of Geological Sciences, 1114 Kirby Dr., Duluth, MN 55812 United States
AB: Near complete coverage of the East Antarctic shield by ice hampers geological study of the crustal architecture important for understanding global tectonic and climate history. Limited exposures in the central Transantarctic Mountains, however, show that Archean and Proterozoic rocks of the shield as well as Neoproterozoic-lower Paleozoic sedimentary successions were deformed during oblique convergence associated with Gondwana amalgamation. Subsequently, the area was overprinted by Jurassic magmatism and Cenozoic uplift. To extend the known geology of the region to ice-covered areas, we conducted a draped aeromagnetic survey flown by helicopters over the Transantarctic Mountains and by fixed-wing aircraft over the adjacent polar plateau. We flew $>$32,000 line km covering an area of nearly 60,000 $km^{2}$ at an average altitude of 600 m (average line spacing 2.5 km over most areas and 1.25 km over basement rocks exposed in the Miller and Geologists ranges). Additional lines flown to true north, south and west extended preliminary coverage and tied with existing surveys. Broad, moderate amplitude magnetic highs and lows over the ice-covered plateau resemble those inferred for Precambrian shield provinces to the north, suggesting a similar origin. Additionally, seismic tomographic models and a ground-based gravity profile show that the region is underlain by thick, cold lithosphere. Exposed high-grade metamorphic rocks, representing lower crust exhumed from $\sim$25-30 km depth during the Ross orogeny, show variable magnetic anomalies, with pronounced central highs and a linear, SE-trending corrugated fabric that correlates with ductile shear structures and regional folds. The magnetic highs correlate with retrogressed mafic eclogites in exposed layered gneiss and are in line with trends of high-amplitude magnetic highs and lows over the adjacent polar plateau. The parallelism of these anomaly trends with those farther to the west suggests that rock types exposed in the surveyed ranges extend beneath the polar plateau. Outboard lower Paleozoic siliciclastic rocks show uniformly quiet magnetic character, whereas Jurassic Ferrar sills and inferred dike swarms yield magnetic highs. Distinctive magnetic lows are associated with exposed Ross-age granitic plutons and indicate several large bodies hidden beneath the ice. A prominent thrust system exposed north of Nimrod Glacier, which places Neoproterozoic-Cambrian platform rocks upon Cambrian-Ordovician molasse deposits, can be traced magnetically several 10's of km to the south, including places previously mapped erroneously as an unconformity boundary.
DE: 9310 Antarctica
DE: 8040 Remote sensing
DE: 8110 Continental tectonics--general (0905)
DE: 8125 Evolution of the Earth
DE: 0925 Magnetic and electrical methods
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting