Deformation and Uplift of the Santa Cruz Mountains: Re-evaluating and Augmenting the Restraining Bend-Advection Model
Abstract
The Santa Cruz mountains are located along a restraining bend in the San Andreas fault and hosted the Loma Prieta earthquake of 1989. Investigators have since focused on the distribution of topography surrounding the restraining bend and on the deformation of proximate stratigraphic units to understand the formation of the range and assess the future seismic hazard it poses to the San Francisco Bay Area. Current theories for range formation posit that recent deformation and the distribution of topography observable today resulted from the advection of material into and through the restraining bend in the San Andreas Fault. Though elegant in its simplicity, this bend-advection model is inconsistent with preliminary observations and results. Structural cross sections spanning the width of the Santa Cruz mountain range suggest that deformation since 7ma is localized within structural sub-blocks in the Santa Cruz mountains. Deformation in the Santa Cruz mountains thus appears influenced by both the mechanical properties of juxtaposed sub-blocks and the location of the restraining bend relative to the parcel of deforming crust. We retrodeformed a 3D geologic model of the Santa Cruz mountains to quantify fault-perpendicular displacements, and how these displacements correlate with restraining bend and sub-block locations and geometries. The rate and tempo of exhumation related to these deformations are imaged using the apatite (U-Th)/He and 4He/3He systems. Initial results suggest that the bend-advection model alone cannot fully account for the observed exhumation histories and so deformation in the Santa Cruz mountains is likely attributable to both restraining bend tectonics and regional margin-normal convergence and strain localization.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMEP11B1000B
- Keywords:
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- 1130 Geomorphological geochronology;
- GEOCHRONOLOGYDE: 8040 Remote sensing;
- STRUCTURAL GEOLOGYDE: 8107 Continental neotectonics;
- TECTONOPHYSICSDE: 8175 Tectonics and landscape evolution;
- TECTONOPHYSICS