HR: 0800h
AN: S31A-09    [Abstracts]
TI: Numerical Models of Oblique Rifting: Application to the Gulf of California
AU: * van Wijk, J W
EM: jolante@lanl.gov
AF: Los Alamos National Laboratory, MS D443, Los Alamos, NM 87545, United States
AB: The modern oblique rift system in the Gulf of California was preceded by a stage of orthogonal rifting. The change to oblique rifting occurred around break up, at ca. 6-8 Ma. Pre-breakup rift segments are found in the northeastern part of Baja California. They are characterized by alternating rift asymmetry and half graben systems, similar to structures of the western branch of the East African Rift system. Numerical models of continental lithosphere extension that study the rifting process when the extension direction changes from orthogonal to oblique, show that these characterizations are typical for oblique segments. Numerical results show that the segments that are formed during oblique extension are oriented more or less orthogonal to the oblique spreading direction and show an alternating asymmetric pattern. Together the segments follow the zone of deformation, but individually they show an en echelon or stairway pattern. When extension continues, the numerical models show that some segments become the loci of mantle upwelling and magma formation. This suggests a genetic relationship with the Gulf of California oceanic spreading ridges that show a similar segmentation; the distinct basins where deformation has localised may have provided a mould for initial mid-oceanic ridge segments. After break up, an oblique system is predicted with orthogonal spreading at the ridges, offset by long transform fault systems, much as the present-day Gulf of California rift system.
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8109 Continental tectonics: extensional (0905)
SC: Seismology [S]
MN: 2007 Joint Assembly