HR: 1340h
AN: T53A-0476    [Abstracts]
TI: Sedimentary Basin Inversion Without Lithospheric Compression
AU: * Pearse, J
EM: pearse@physics.utoronto.ca
AF: Dept. of Physics, University of Toronto, 60 St. George St., Toronto, ON M5S 1A7 Canada
AU: Bailey, R C
EM: bailey@physics.utoronto.ca
AF: Geology and Physics Depts., University of Toronto, 60 St. George St., Toronto, ON M5S 1A7 Canada
AB: The inversion of sedimentary basins, because of its implications for petroleum generation and trapping, has received attention in recent years. Because of the common use of lithospheric extension models of basin formation (e.g. Mckenzie, 1978 etc), it is not surprising that models of inversion mechanics have concentrated on the inverse of lithospheric extension, namely compression. Such models of inversion have no direct mechanism of localizing uplift (and thus inversion) at the site of the original basin. It is necessary to postulate mechanisms by which the presence of the basin weakens the lithosphere locally (e.g. by elevated geotherms cuased by the thermal blanketing of the basin). However, such mechanisms are variable in their effectiveness (Sandiford 1999). In this paper, we examine a different context for basin formation and inversion, in which the inversion is automatically localized at the original basin. Specifically, we examine the case where basin formation is driven by intra-crustal anomalous density loads induced subsidence of the elastic upper crust in response to elastic thickness reduction driven by sublithospheric heating. In such a case, if elastic thinning is sufficient, the density load can detach from the elastic upper crust and sink, by ductile flow, rapidly (Glazner, 1994) into the deep crust. The resultant relief permits the elastic upper crust to rebound upwards over the site of the prvious basin. Strikingly, such rebounds can be as much as 7 km (locally erasing a huge part of the detrital record). We demonstrate this by both semi-analytic modelling using an extended version of Kaufman and Royden's (1994) elastic-beam over ductile channel model, and with a full thermal and viscoelastic finite element model. Finite element modelling shows that in this type of inversion, surface horizontal stresses in the basin are compressive during basin formation, and become more tensional during inversion, in direct contrast to the lithospheric extension-compression models.
UR: http://www.physics.utoronto.ca/~bailey/
DE: 8100 TECTONOPHYSICS
DE: 8105 Continental margins and sedimentary basins
DE: 8110 Continental tectonics--general (0905)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting