Using a coupled geochemical/physical mass balance model to gain insights into the deposition of subrecent evaporites: Searles Valley, California, USA

Abstract

Modern and ancient saline lakes are important sites for the deposition of carbonates and evaporites. Here we describe a generalized computer model of chemical sediment production in a closed-basin lake subject to: (1) variable inflow sources through time; (2) variable volumes of these inflows; (3) variable temperature, and; (4) variable evaporation rates through time. We then apply our model to gain insights into some aspects of late Pleistocene evaporite deposits beneath Searles Lake, California, a well-described chemical sedimentary deposit. We tuned our model to match the masses and proportions of the major saline minerals trona and halite deposited in layers circa 32 ka to 24 ka. However, we could not reproduce the thicknesses of mixed siliciclastic, carbonate and organic layers sandwiched between the evaporites. The model is useful for interpreting and constraining the environmental conditions in and around any ancient saline lakes during evaporite deposition where the amounts, mineralogies, and vertical distribution of chemical sediments are known.