HISTORICAL AND LATEST HOLOCENE RECORD OF AEOLIAN DEPOSITION IN RESPONSE TO LOWSTANDS OF OWENS LAKE, EASTERN CALIFORNIA

Many dune fields in the southwestern U.S. have their sources of sand from either active alluvial, fluvial, lacustrine or all three depositional environments. Studies of the chronology and stratigraphy of beach ridges and dune fields that encompass Owens Lake basin coupled with analysis of the composition and sources of sand for the dune fields, provide a robust record of the geomorphic response and spatiotemporal relations between low lake levels and the formation of dunes and sand sheets, either by natural or anthropogenic forcing.

Radiocarbon and luminescence analyses were used to date shoreline and dune deposits in the northeastern sector of the lake basin near Swansea and Keeler. The latest Holocene lake-level record of the now dry Owens Lake shows seven periods of lowstands from 1.96–1.62, 1.56–1.42, 1.37–1.21, 1.14–0.80, 0.79–0.49, 0.45–0.33 cal ka, and as recently as from AD 1700–1871. These lowstands had water levels that were ~4–11 m below the historical highstand in AD 1872–1878. The pre-historical lowstands were controlled by persistent and higher hydroclimate variability in the region, whereas historical lowstands in AD 1884–1921 followed by desiccation in AD 1931 were the result of anthropogenically-forced water diversions. The ages of naturally-forced lowstands have strong temporal correspondence with the age of aeolian depositional events at 1.65, 1.23, 1.07, 0.67–0.56, 0.36–0.34 ka, and as recently as from AD 1717–1871. Recent sand sheet deposits near Keeler have ages from AD 1930–1976 coinciding with desiccation of the lake.

The mineral and grain size compositions of sand from the major dune fields indicate they are all very similar. The relative proportions of quartz, plagioclase, and K-feldspar indicate the sands are derived from granodioritic source rocks found in the Sierra Nevada and Coso Range, and not from metasedimentary rocks in the Inyo Mountains. It is therefore considered that the primary source and transport pathway of sand is sediment from the Sierra Nevada via the Owens River in the north and from the Sierra Nevada and Coso Range via distal alluvial fans in the south. Sediment from alluvial and fluvial sources reached the dune fields in the northeastern to southern sectors of the lake basin by wind transport across the exposed bed of Owens Lake during lowstands and desiccation.