OWENS LAKE DUNE FIELDS: COMPOSITION, SOURCES OF SAND, AND TRANSPORT PATHWAYS

Analysis of the mineral and chemical composition of aeolian sands, as well as those from potential fluvial, alluvial, or lacustrine sources can provide valuable information on sand sources and transport pathways, as demonstrated for dune fields in many areas. The results of such analyses can also be used to constrain the conditions in which dune construction occurred. We describe the mineral and grain size composition of sand from the major dune areas adjacent to the now dry Owens Lake, California and compare it with sand from potential sources including washes draining the Inyo and Coso ranges to the east and south of the basin, as well as to the Owens River and washes draining the Sierra Nevada, which lies to the west of the Owens Valley and Owens Lake.

The compositional data indicate that the dune sands are all very similar and are composed of an average of 47% quartz, 33% plagioclase and 13% K-feldspar, with minor amounts of calcite and other minerals. The relative proportions of quartz, plagioclase, and K-feldspar indicate that the sands are derived from granodioritic source rocks. It is therefore considered that the primary source of sand for dune fields in the Owens Lake basin is sediment derived from the Sierra Nevada Mountains, via the Owens River from the north, together with minor additions from the Coso Range to the south.

Sediment from fluvial and alluvial sources reached the dune fields in the northeastern sector of the basin by wind transport across the exposed bed of Owens Lake during periods of low lake levels. The pathway by which sand reached the Olancha Dunes located to the south of the lake is less clear, but probably involved transport from the South Sand Sheet, via the former Dirty Socks Dunes. The source of sand for the South Sand Sheet area is hypothesized to be the adjacent Coso Wash system draining the Coso Range.