TRANS-TENSIONAL CHAOS IN SOUTHEASTERN DEATH VALLEY: GEOLOGIC MAPPING AND DETRITAL-ZIRCON SPECTRA OF THE MIOCENE CHINA RANCH BEDS, CALIFORNIA

The Miocene China Ranch beds of southeastern Death Valley, California, are found throughout the fault-bound China Ranch Basin overlying with Precambrian basement units and interbedded with volcaniclastic and megabreccia deposits. This basin is bound by accommodational, SE-NW strike-slip faults, such as the dextral Sheephead and Willow Wash fault zones on the north, and the Meteor Rock fault zone on the south. The China Ranch Basin is one of several roughly contemporaneous Miocene sedimentary basins along a SE-NW striking zone between the Southern Death Valley fault zone and Sheephead, Grandview, and related fault zones. A fundamental question is whether these basins formed individually and were translocated into their present positions along a single dextral strike-slip system, as suggested by some authors, or are part of a larger basin that was completely disaggregated by a conjugate system of SE-NW and SW-NE strike-slip fault zones. Through field mapping efforts funded by the USGS EDMAP project with geochronology by ⁴⁰Ar-³⁰Ar radiometric dating of ash-beds and detrital zircon U-Pb analysis, this study aims to better understand the temporal and spatial evolution of the China Ranch beds and associated basin in the context of adjacent trans-tensional sedimentary basins of the area. Here we present preliminary interpretations on the overlapping depositional history of the China Ranch and surrounding basins through structural observations along with data from detrital zircon analysis of the China Ranch beds.