HR: 1340h
AN: GP43A-0839    [Abstracts]
TI: Using Rotation Boundary Deformation to Infer Mechanics of Vertical-Axis Rotation in Southern California
AU: * Onderdonk, N W
EM: nate.onderdonk@fys.uio.no
AF: Physics of Geological Processes, University of Oslo PO Box 1048 Blindern, Oslo, 0316 Norway
AB: Although vertical-axis rotation of crustal blocks has been recognized and studied in every type of tectonic environment, the driving mechanisms and mechanics of this process remain poorly understood. Both these aspects of rotational deformation in the upper crust can be addressed by looking at the boundaries of rotated areas where rotated crust abuts non-rotated crust. The geometry, diffusity, and kinematics of these boundary zones indicate the relative movement of crustal blocks, the relative strength of the blocks, the surficial stresses, and the nature of rotational accommodation at depth. New paleomagnetic and structural data from areas of Neogene rotation in southern California provide clues to the mechanics of vertical-axis rotation. In the western Transverse Ranges, recent data show that differential rotation occurred across dip-slip faults and folds rather than strike-slip faults. This observation suggests that: 1. rotation is accommodated at depth on discrete surfaces, and 2. rotation is driven by stresses in the upper crust rather than basal traction. Miocene rotation in the Mojave Desert was also primarily associated with dip-slip faulting and current work in the area is beginning to define and evaluate distinct rotation boundaries.
DE: 8020 Mechanics
DE: 8110 Continental tectonics--general (0905)
DE: 8164 Stresses--crust and lithosphere
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1527 Paleomagnetism applied to geologic processes
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting