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Lakes in one form or another have characterized the western Mojave Desert since at least Miocene time. The most recent of these, Lake Thompson, developed in the late Pleistocene, when it covered as much as 950 km2 and rose to at least 710 m above sea level. During Holocene time, the lake desiccated, and is now represented by Rogers, Rosamond, and Buckhorn dry lakes, which may flood up to 200 km2 during unusually wet phases. The spatial dimensions of the former lake are defined by modest geomorphic and lithostratigraphic units, mostly exposed lake beds and beach ridges interbedded with and later mantled by fluvial and eolian deposits. The lake's temporal devolution is revealed by four cores, and ages are constrained by accelerator mass spectrometry 14C dating of organic sediment. These cores show a deep perennial lake from before 36 ka to at least 34 ka, a shallow but variable perennial lake from before 26 ka to 21 ka, followed by lowering and at least partial exposure of the lake floor to deflation and alluviation. A shallow perennial lake returned during the terminal Pleistocene, from around 16.2 ka to at least 12.6 ka, forming distinctive beach ridges beyond the margins of the present dry lakes, and it may have reappeared in the early Holocene. During subsequent Holocene desiccation, lake segmentation occurred as waves and currents generated lower sequences of beach ridges around contracting lakes. These ridges became mantled with eolian sand, but, as fluvial sediment inputs diminished with increasing aridity, these dunes were degraded, and their roots survive today as indurated yardangs.

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