Quaternary Expression of Northern Great Valley Faults and Folds: Accommodating North-South Contraction in the Northeastern California Shear Zone

Stephen J. Angster, Thomas Sawyer, & Steven G. Wesnousky

Submitted August 15, 2016, SCEC Contribution #6892, 2016 SCEC Annual Meeting Poster #094

The Northern California Shear Zone accommodates North American intraplate right-lateral transpressional shear driven by the relative motions of the northwest translating Sierran microplate and clockwise rotating Oregon Costal block. Within this zone, between the latitudes of 40 and 42, 1 – 4 mm/yr of north-south oriented contraction is geodetically observed and for the most part remains unaccounted for in the geology. The northeast trending Inks Creek fold belt north of Red Bluff, CA consists of anticline-syncline pairs and a dome structure that appear optimally oriented to accommodate northwest crustal shortening. The anticlines plunge to the southwest where they are incised by and appear to deflect the course of the Sacramento River. Geomorphic mapping and profiling of fluvial terraces along the Sacramento River are interpreted to record tectonic uplift through the fold belt. Dating of elevated fluvial terraces on the anticlines with radiocarbon, terrestrial cosmogenic nuclide, and OSL dating techniques is currently underway to quantify the vertical incision rate of the river as a result of tectonic uplift. The ultimate goal is to combine these geomorphic observations with structural observations and models to estimate the rate of contraction being accommodated by the folds.

Citation
Angster, S. J., Sawyer, T., & Wesnousky, S. G. (2016, 08). Quaternary Expression of Northern Great Valley Faults and Folds: Accommodating North-South Contraction in the Northeastern California Shear Zone. Poster Presentation at 2016 SCEC Annual Meeting.


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