Evidence for late Pleistocene hydrologic and climatic change from Lake Otero, Tularosa Basin, south-central New Mexico

Abstract

Stratigraphic relations, lithofacies, and radiocarbon chronology of deposits that accumulated in and around the margins of late Pleistocene Lake Otero in south-central New Mexico provide evidence for the timing and relative magnitude of episodes of lake expansion that occurred in the basin during the last ice age. The lower few meters of stratified sediment in exposures along the margins of the winddeflated floor of Tularosa Basin contain gypsiferous lithofacies, sedimentary structures, and fossils indicating deposition along the margins of a shallow saline lake. Radiocarbon dates indicate that these basal nearshore lake deposits accumulated from about 45,000–28,000 14C yrs b.p. A widespread erosional episode removed at least 2 m of lake-margin deposits between 28,000 and 25,000 14C yrs b.p. Lakebeds overlying the erosional unconformity contain a relative abundance of siliciclastic sediment and aquatic fossil organisms suggesting repeated episodes of increased precipitation, surface runoff, and freshening of the lake system. These inferred episodes of increased precipitation and enhanced fluvial activity in the basin began ca. 24,500 14C yrs b.p. and lasted for at least 9 millennia. Highstands of the lake during this period appear to have reached an elevation of ~1,204 m. Details of the history of Lake Otero after 15,500 14C yrs b.p. remain sketchy due to wind deflation of the basin floor and wholesale removal of lacustrine deposits during the Holocene. The evidence from Lake Otero for the onset of maximum pluvial conditions during the late Pleistocene appears to be in good temporal agreement with lacustrine reconstructions from neighboring lake basins to the north and south. Additional study of the deposits associated with Lake Otero, including their abundant and diverse assemblages of aquatic fossil organisms, is clearly warranted.