HR: 1330h
AN: T53A-11    [Abstracts]
TI: The Margins of the Eastern Woodlark Basin: The Birth and Death of an Ocean Basin
AU: Taylor, B
AF: SOEST, University of Hawaii,
AU: * Goodliffe, A M
EM: amg@ua.edu
AF: Department of Geological Sciences, University of Alabama,
AU: Martinez, F
AF: SOEST, University of Hawaii,
AB: In Oct/Nov 2004 we surveyed the margins of the eastern Woodlark Basin on the R/V Kilo Moana, revealing details of its earliest rifting history and modern subduction. Initial stretching affected the borders of the Solomon Sea basin to the north and the Louisiade Plateau to the south. The NE end of the Pocklington Trough, formerly interpreted as a paleo-trench, is a segmented rift >200 km long that borders the south side of a 25-40-km-wide region of faulted blocks contiguous with the Pocklington Rise. The oldest oceanic crust in the Woodlark Basin formed during the reversed interval prior to magnetic chron 3. Spreading propagated westward to 158^o and then virtually simultaneously to 157^o. Spreading at 156^o and 155^o began prior to and during, respectively, chron 2A. The transform at ~155^o 10' developed after seafloor spreading had begun, cutting through rifted crust and truncating the northern limb of an overlapping spreading center. The strike-slip fault system separating the Solomon Sea and the eastern Woodlark Basin includes two major strands that splay to the NE and bound a widening wedge of intervening crust of the northern Woodlark Rise that is stretched along NW-trending normal faults. A small, right-stepping pull-apart basin on the northern fault provides further evidence for the right-lateral motion on this transform fault system. A new magnetization inversion and magnetic chron identification have allowed a revised interpretation of the triple junction region adjacent to the Solomon Islands. Although spreading may have ceased, Simbo Island sits on Brunhes ages crust. The current Simbo Transform Fault, linking the eastern end of segment 5 with either the Simbo spreading segment or the trench, appears to comprise right-stepping en echelon faults offsetting short volcanic/spreading segments. A volcano in the southern San Cristobal Trench axis is partially subducted beneath the forearc SW of the Russell Islands, uplifting the lower slope. A reentrant in, and uplift of, the lower forearc slope south of the eastern tip of Tetipare appears to have been caused by more complete subduction of another volcano. Further NW, subduction of the rifted northern margin fault blocks has created a serrated trench axis, uplifted the Treasury Islands and collapsed adjacent portions of the forearc.
DE: 3025 Marine seismics (0935)
DE: 3035 Midocean ridge processes
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 8105 Continental margins and sedimentary basins
DE: 8109 Continental tectonics--extensional (0905)
SC: Tectonophysics [T]
MN: 2005 Joint Assembly