CLIMATIC AND TECTONIC LINKS TO PALEOGROUNDWATER SYSTEMS FROM SURFICIAL DEPOSITS MAPPING, DARWIN HILLS 1:100,000, INYO COUNTY , CALIFORNIA

The Darwin Hills 1:100,000 quadrangle includes the northern and central Panamint Valley, the southeasternmost Owens Valley as well as perched basins between the Coso and Argus Ranges. Surficial deposits in the Darwin Hills area include the active arid basin system of alluvial fans, washes and playas, as well as paleolacustrine and wetlands deposits. This is a desert area characterized by sporadic localized, but often intense rainfall and frequent wind and dust storms. The surface characteristics of the alluvial deposits are strongly influenced by eolian activity which tends to dominate fluvial/alluvial processes on surfaces that have been abandoned due to wash incision. This is especially favored where tectonic processes enhance incision.

Paleolacustrine, wetlands and spring deposits are found throughout the region and can be correlated with late Quaternary climate events. Chronostratigraphic constraints from 14C, 36Cl, OSL/TL, tephra correlation and amino acid analysis, combined with paleoenvironmental constraints from ostracode and molluscan assemblages provide additional information about the paleohydrologic conditions during the varying climate regimes in the late Quaternary. Particular emphasis has been given to determining the paleohydrology and landscape evolution during the last 75,000 years.

The paleohydrologic setting is also influenced by tectonic activity, particularly by major active fault zones. Basin bounding faults tap the deeper thermal groundwater systems. The amount of discharge from these deep aquifer systems appears to fluctuate with respect to climate controlled recharge. In addition, active fault zones locally form hydraulic barriers that have generated perched paleo-discharge areas in the middle of otherwise gently sloping pediments and(or) alluvial fans.

The chronostratigraphic information derived from the surficial deposits and the correlative climatically controlled geomorphic datums are also used to constrain the slip rate on active faults, the incision rate of active washes, and the deposition rate of alluvial fans, all useful parameters for modeling landscape evolution.