HR: 0800h
AN: T11A-1232    [Abstracts]
TI: Neogene-Quaternary Volcanic Alignments in the Transantarctic Mountains and West Antarctic Rift System of Southern Victoria Land, Antarctica
AU: * Paulsen, T S
EM: paulsen@uwosh.edu
AF: Dept. Geology, Univ. Wisconsin Oshkosh, 800 Algoma Blvd., Oshkosh, WI 54901 United States
AU: Wilson, T J
EM: wilson.43@osu.edu
AF: Byrd Polar Research Center, Ohio State University, 130 Orton Hall 155 S. Oval Mall, Columbus, OH 43210 United States
AB: Neogene-Quaternary volcanism in southern Victoria Land, Antarctica, produced the Erebus Volcanic Province, a suite of alkaline volcanic rocks that extend from the Transantarctic Mountains rift-flank uplift to offshore localities within the West Antarctic rift system. We are mapping volcanic vent patterns in the province to detect alignments indicative of stress/strain patterns during rift evolution. In the southern sector of the Erebus Volcanic Province in the Royal Society Range Block of the Transantarctic Mountains, mapping shows that elliptical scoria cones, fissures, dikes, and linear vent arrays define volcanic alignments that have a dominant NNE trend, with subsidiary WNW trends. Age data for the alignments suggest that this pattern persisted from 14.6 to 0.25 Ma. We are currently completing mapping along an east-west transect crossing the rift margin, and results obtained so far within the rift region indicate a similar pattern of alignments. On the northern flank of Mount Morning, a large volcano just to the east of the Royal Society Range, elliptical scoria cones and linear vent arrays define volcanic alignments that have a dominant NE trend, with a subsidiary NNW trend. Available age data suggest that many of these cone alignments may be of Quaternary age. At Brown Peninsula, further east from the rift flank, cone alignments trend NNE and available ages range from 2 to 3 Ma. To the east of Brown Peninsula, cone alignments trend NW at Black Island, but are of uncertain age; age data on Black Island range from 11 to 3.4 Ma. At White Island, the farthest east into the rift, cone alignments trend NNE and available age data suggest volcanism as young as 0.2 Ma. Although some differences in cone alignment trends are apparent between the rift flank and the rift system across our transect, both regions appear to be dominated by NE trending alignments, which implies a WNW to NW minimum horizontal stress (Shmin) direction. This is oblique to the ENE Shmin Cape Roberts in situ contemporary stress direction determined from borehole breakouts and induced core fractures, and to a single volcanic stress alignment of Neogene age within the rift flank in that sector. In both regions the Shmin direction is perpendicular to the interpreted trend of the structural boundary of the rift. The stress directions inferred from volcanic alignments are thus consistent with spatial changes in the Neogene-to-contemporary stress field.
DE: 8100 TECTONOPHYSICS
DE: 8107 Continental neotectonics
DE: 8109 Continental tectonics--extensional (0905)
DE: 8110 Continental tectonics--general (0905)
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting