A 2-MYR HISTORY OF SLIP ALONG THE GARLOCK FAULT ZONE, EASTERN CALIFORNIA

The Garlock fault zone (GFZ) is an intracontinental transform that initiated in Miocene time (~11 Ma) and subsequently accommodated ~64 km of left-lateral displacement at average rates of 5-7 mm/yr. Ongoing dextral shear along the Eastern California Shear Zone (ECSZ), however, passes smoothly across the GFZ, and ECSZ faults do not cross-cut the active trace of the GFZ. Although slip rates along the GFZ determined from displaced Late Pleistocene and early Holocene alluvial deposits appear to match the long-term average (5-7 mm/yr), there are no estimates of slip during the past ~4 Myr of accumulated shear along ECSZ structures. Employing a range of chronologic techniques, including 40Ar/39Ar dating of detrital sanidine, this study develops new slip rates at timescales ranging from ~15 ka to ~2 Ma to evaluate the pace of slip along the Garlock fault through time.