Abstract

Lake response to climate forcing is commonly regarded as being controlled by within-lake processes. We present a case from the northern Great Plains in which Holocene drought response recorded in lake sediments was determined by changes in chemical characteristics of source ground water. Middle Holocene ostracode assemblages were dominated by halophylic Limnocythere staplini, indicating increased lake-water salinity, yet the oxygen isotope values in this period decreased by 2‰ to 3‰, contrary to expectations of evaporative dominance. We infer from these proxy records and ground-water flow-model results that the paleoclimatic record in the lake was mediated by changes in ground-water catchment area and by reduction in evapotranspiration accompanying desiccation of peripheral lake basins.

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