Compositional Variability of Dust-Producing Landforms in the Mojave Desert of Southern California

The Mojave Desert in southern California has many landforms which are potential sources of dust. In this study three landforms with the highest propensity to emit dust were chosen to determine their compositional variability, with the ultimate goal of trying to pinpoint dust sources. The landforms sampled included a distal alluvial fan that drains the Providence Mts., Kelso Wash, and Soda Dry Lake. Samples were collected along transects and were analyzed to determine grain size distribution and major and trace element composition using ICP-MS. Our data support the following hypotheses: 1) the alluvial fan unit has the least amount of compositional variability because of a single source area, 2) Kelso Wash changes composition downstream based on inputs from tributaries (although not in a predictable manner), and 3) Soda Lake has the largest compositional variability because it is a mixing pot of sediments from numerous sources. Additionally, we tested the degree to which Soda Lake mixes sediments during its wet phases by comparing compositions on west, central, and east transects, along with local bedrock samples. Compositional data suggest that Soda Lake sediments can be differentiated along these transects; however, local sources appear to have minimal influence on the overall composition of the playa sediment. Comparison of the three landforms reveal that Soda Lake is compositionally distinct, having higher concentrations of elements such as Ba, Ca, and Mg compared to the wash and alluvial fan. This research sheds some insight into mixing of sediment via transportation mechanisms and compositional variability of landforms, and on the compositional variability of dust from landforms.