PLIOCENE AND PLEISTOCENE TEPHROCHRONOLOGY AND PALEOENVIRONMENTS OF THE KIT FOX HILLS, DEATH VALLEY, CA

The Kit Fox Hills in northern Death Valley contain a relatively complete Pliocene through Pleistocene sedimentary sequence. Tephrochronologic analyses and geologic mapping indicate that the Kit Fox Hills are a relatively unfaulted stratigraphic sequence ranging in age from ~3.5-0.76 Ma. The lowest or oldest part of the section is fine-grained playa lake and distal fan deposits that contain the ~3.34 Ma tuff of Zabriskie Wash along with the 3.28 Ma Nomlaki Tuff Member of the Tuscan and Tehama Formations, the ~3.1 Ma tuff of Artists Drive, and the informally named 3.28 -~3.1 Ma tuff of Kit Fox Hills. The base of the section is not exposed; however, deposition rates suggest a maximum age of ~3.5 Ma for the sequence. The fine-grained deposits grade upward into >200 m of coarse alluvial-fan deposits that contain the 2.89 Ma tuff of Benton Hot Springs. Laterally (north), the ~3.5-3.28 Ma fine-grained deposits grade to coarse alluvial-fan deposits. Further north, the alluvial-fan deposits vertically grade back to playa lake deposits that contain the 1.2-0.8 Ma tuffs of upper Glass Mountain. These tephra layers straddle the Jaramillo reversed polarity subchron and underlie the 0.76 Ma Bishop Ash bed. The older playa lake sequence in the Kit Fox Hills of Death Valley terminates at ~3.28 Ma in contrast to the lake sequence in the KM-3 core of Searles Valley that terminates at ~2.5 Ma. We attribute the difference in lake termination to the influence of glacial runoff from the Sierra Nevada into Searles Valley. In contrast, the ~1.2-0.8 Ma younger lake deposits in Searles and Death valleys roughly correspond.