Geophysical Constraints on Extensional Models for the Death Valley Region of California and Nevada

Project funded by the National Science Foundation,
Geophysics Program

Principal Investigator: John N. Louie
Seismological Laboratory, The University of Nevada, Reno


Research Products:


PROJECT SUMMARY

This project will test Cenozoic extension models for the southern Great Basin with large- and small-scale, multidisciplinary geophysical investigations. It will develop geophysical methods to characterize the development of small alluvial and lacustrine basins, which can constrain the timing and nature of regional tectonic activity. In addition, this project will provide geophysical field experience to three classes of undergraduate and graduate geological sciences students, enhancing several degree programs. Additional funds are requested to partially support a graduate student who will coordinate field efforts, perform regional studies, and interpret and report on the small- and regional-scale results in combination.

Regional tectonic models suggest the mode and timing of the development of several small sedimentary basins east of Death Valley, California. Although hidden, the stratigraphy of each basin may be diagnostic of the mode and timing of extension. Three years of geophysical field course exercises out of the Penn State University and the University of Nevada, Reno; conducted by Dr. Louie in the Amargosa and Chicago Valleys have revealed early basin histories and distinct formational geometries. The use of several small-scale survey methods on the same profiles resulted in sufficient structural and stratigraphic control to date initial basin formation and describe a major boundary in regional extensional character.

Datasets on a regional scale provide additional constraints on tectonic models. A non-linear inversion of first-arrival travel time picks from the extensive COCORP Death Valley lines 9 and 10, combined with regional surface wave group arrival times, show few differences in overall crustal velocity structure when comparing the southern Great Basin with surrounding tectonic provinces. This observation suggests broadly similar crustal histories despite great differences among the provinces in the amounts of Cenozoic extension interpreted. This project will continue this analysis by developing constrained velocity models from all available regional seismic survey and earthquake travel-time data. It will also provide for the reprocessing of the COCORP lines for shallow basin structure, to extend features surveyed in detail to wider regions; and evaluate seismic data for fault reflections and constraints on fault geometries.

The proposed further small-scale efforts will characterize the Tecopa and Chicago Valley basins in three dimensions, and will extend basin analysis east across Pahrump Valley to the Spring Mountains. This project will continue these efforts as yearly geophysical field course exercises, involving students of diverse backgrounds in a project each carries from the planning through the reporting stages. Constrained by mid- and upper-crustal characterizations of velocity structure, these results will test the geophysical and sedimentary features proposed by differing Cenozoic tectonic models.

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