Sabkha deposits in the geologic record are commonly used to interpret the environmental conditions of deposition. Implicit in this use is the assumption that the solute system is chemically closed, that is, the authigenic minerals represent the composition of the fluids in their environment of origin. Thermodynamic and mass-balance calculations based on measurements of water and solute flux of contemporary Abu Dhabi coastal sabkha system, however, demonstrate that the system is open for sodium and chloride, where nearly half of the input is lost, but closed for sulfur, where nearly 100% is retained. Sulfur and chloride isotopes were consistent with this observation. If these sabkha deposits were preserved in the geologic record, they [...]
