Stable isotope geochemistry of aeolian sediment at Owens Lake, California



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Texas Tech University


The purpose of this study is to describe the occurrence of evaporitic dust produced on Owens (dry) Lake and transported by aeolian processes varying in stable isotope (carbon and oxygen) values by height and date above the lake bed surface. The samples analyzed in this study were collected at heights of 10, 20, 50, 60, and 100 cm above the playa lake surface during three storm events in March 1993. The dust was collected in dust tiaps along a 1.2 km transect on the lake floor. Carbonate dust samples were found to be more enriched in '^C and '^O isotopes and more tightly grouped with each successive storm. This study addresses this geochemical observation and possible explanations. Wide stable isotope variation within the same source evaporite minerals does not seem to be a normal occurrence. The minerals were not altered between storms and no new mineral formation was observed. The evaporitic mineral component of Owens (dry) Lake is produced primarily from brine evaporation and the dissolution and concentration of salts by rain and snow. These samples were collected during the early spring, when no precipitation occurred and conditions are not conducive to evaporation. The reason for isotopic variation is not clear, but this seems to be caused by mineral morphology and aeolian processes, preferential enrichment of heavy isotopes in the evaporation process or in the formation of minerals and/or both and or a combination of all three.