NEW GEOLOGIC MAP AND STRUCTURAL CROSS SECTIONS OF THE DEATH VALLEY EXTENDED TERRAIN: TOWARD 3D KINEMATIC RECONSTRUCTIONS

Tectonic reconstructions for the Death Valley extended terrain have evolved to include a growing number of offset markers for strike-slip fault systems but are mainly map view (2D) and do not incorporate a wealth of additional constraints. We present a new 1:300,000 digital geologic map and structural cross sections, which provide a geometric framework for stepwise 3D reconstructions of Late Cenozoic extension and transtension. 3D models will decipher complex relationships between strike-slip, normal, and detachment faults and their role in accommodating large magnitude extension/rigid block rotation. Fault coordination is key to understanding how extensional systems evolve with changing boundary conditions. 3D kinematic analysis adds necessary strain compatibility unavailable in 2D reconstructions.

The stratigraphic framework of Fridrich and Thompson (2011) is applied to rocks outside of Death Valley. Cenozoic basin deposits are grouped into 6 assemblages differentiated by age, provenance, and bounding unconformities, which reflect Pacific-North American plate boundary events. Pre-Cenozoic rocks are grouped for utility, for example: Mesoproterozoic aulogocen fill, Neoproterozoic-Cambrian clastic wedge, Cambrian carbonates, Ordovician-Mississippian carbonates are all separate groups. Offset markers are summarized in the associated tectonic map. Other constraints include fault geometries and slip rates, age, geometry and provenance of Cenozoic basins, gravity, cooling histories of footwalls, and limited seismic/well data.

Cross sections were constructed parallel to net-transport directions of fault blocks. Surface fault geometries were compiled from previous mapping and projected to depth using seismic/gravity data. Cooling histories of footwalls guide geometric interpretation of uplifted detachment footwalls. Mesh surfaces will be generated from 2D sections lines to create a framework for stepwise 3D reconstruction of extension and transtension in the study area.

Analysis of all available data in a seamless 3D framework should force more unique solutions to outstanding kinematic problems, provide a better understanding of the Cordilleran thrust belt, and constrain the mechanisms of strain localization between the upper and lower crust.