Quaternary Expression of Northern Great Valley Faults and Folds: Accommodating North-South Contraction between the Sierran Microplate and Oregon Block

Abstract:

The Northern California Shear Zone accommodates North American intraplate right-lateral transpressional shear driven by the relative motion of the northwest translating Sierran microplate. Within this zone, between the latitudes of 40⁰ and 42⁰, 1 – 4 mm/yr of north-south geodetic contraction is observed and for the most part remains geologically unaccounted for. We are investigating the Quaternary expression of transpressional shear localized at the northern end of the Sierra Nevada and Great Valley to evaluate both the recency and rates of deformation across structures that may be accommodating the contractional deformation suggested in geodetic studies.

The northeast trending Inks Creek fold belt north of Red Bluff, CA consists of anticline-syncline pairs and dome structures that appear optimally oriented to accommodate northwest crustal shortening. The folds plunge to the southwest where they are incised and deflect the course of the Sacramento River. We will present preliminary geomorphic maps of fluvial terraces and drainage patterns associated with the folds constructed with standard field mapping techniques and aided by airborne LiDAR. It is anticipated that dating of deformed terrace strandlines with radiocarbon and OSL techniques holds the potential to quantify the lateral and vertical propagation rates of fold growth, as well as, constrain rates of regional contractional deformation.