Stable isotope compositions of waters and sulfate species therein, Death Valley, California, USA: Implications for inflow and sulfate sources, and arid basin climate

In this study, 95 water samples were collected in Death Valley between May 1992 and March 1994. The isotope compositions of these waters range from −15.2‰ to +2.8‰ for δ18O and from −109% to −21% for δD. Rain, snow, and shallow spring waters derived from melting snow on the mountains fall on the meteoric water line (MWL). Salt pan brines fall on a local evaporation line with a slope of 3.6, indicating strong evaporation. Regional spring waters have low δ values, reflecting a different origin from the modern precipitation in Death Valley. At least three major sulfate sources were identified by the isotope data from sulfate in these waters: (1) atmospheric sulfate in precipitation; (2) dissolved sulfate from the local spring flow system; (3) dissolved marine sulfate from Paleozoic carbonate rocks in the regional groundwater system. The isotopic variations of these waters and sulfate therein reflect changing and/or mixing of sources in the basin.