COMPARISON OF MIDDLE PLEISTOCENE RECORDS IN DEATH, PANAMINT, AND TECOPA VALLEYS, CALIFORNIA: IMPLICATIONS FOR REGIONAL PALEOCLIMATE

A long held hypothesis is that during Quaternary pluvial periods lakes successively filled basins along the Owens, Mojave and Amargosa River systems of California and Nevada ending in Death Valley. To test this hypothesis, we examined the stratigraphic evidence for pluvial lakes in three adjoining basins (Death Valley, Panamint and Tecopa) between ~1 to 0.6 Ma. Lake volume and surface area are climate proxies, thus the stratigraphic record of lakes along these paleo-river systems elucidates paleohydrologic connections and mid-latitude paleoclimate. Age control is provided by the 0.8-1.2 Ma Upper Glass Mountain, 0.76 Ma Bishop and 0.62 Ma Lava Creek B ash beds. In Death Valley, evidence of perennial water is found from ~1 Ma to >0.76 and between <0.76 and 0.62 Ma. Limited data makes distinguishing among a contiguous lake or several smaller lakes difficult. Interbedded carbonates are inconsistent with a deep contiguous lake. In Panamint Valley, a robust wetlands/lake environment is found at ~1 Ma, a playa with possible spring discharge is observed at 0.76 Ma, and perennial lake environment is present after <0.62 Ma. In the Tecopa basin, along the ancestral Amargosa River valley, perennial lakes existed from ~1 Ma to >0.76 Ma, from 0.76 to <0.62 Ma, and at least twice after 0.62 Ma. By surface area, the greatest lake existed just prior to 0.62 Ma.

Evidence from previous work suggests overflow from Searles to Panamint valleys between ~1 and 0.6 Ma; overflow from Panamint to Death valley during this time is plausible but not demonstrated by available data. Lake level and sedimentological data have not verified overflow from Tecopa to Death Valley between ~1 and 0.6 Ma. Alternatively, we propose that some combination of precipitation/evaporation and groundwater flow may be more influential than previously thought in supporting lakes and wetlands in topographically disconnected lake basins in the southwestern Great Basin during Middle Pleistocene pluvial periods.