Karl Butzer was one of the first prehistorians to think about and write about people, ancient and modern, on the landscape. Moreover, as a geomorphologist he knew that past 29 landscapes were as dynamic and varied as they are today-not static entities that formed the 30 backdrop for human activity. That viewpoint is critical in understanding the physical 31 environment faced by humans during the early peopling of the Americas (~13,500 to ~10,000 cal 32 YBP). North America was undergoing rapid environmental changes as the continent was coming 33 out of the last Ice Age. In the southwestern part of the continent large paleolake levels were 34 falling and smaller playa basins were aggrading as the area was occupied by Paleoindian groups 35 such as Clovis, Folsom, and later groups of First Americans. The paleolakes would have provided some resources, but modern gypsum deposits indicate that lake waters were unpotable. Numerous small depressions (playas) scattered around the floor of the Tularosa Basin contain muddy fills that span the Holocene and terminal Pleistocene, indicative of fresher water at least seasonally. Paleoindian sites tend to be clustered around these small basins and along drainages off of the mountains that flank the basin, as well as settings with good viewsheds rather than the main paleolake margins. Paleolakes were dramatic components of the late Pleistocene landscape in the Southwest, but likely were not the primary attractions to the First Americans.

The White Sands dune field is the largest gypsum dune system in the world, derived from deflation of paleo-Lake Otero deposits. Understanding the timing of initial dune construction, and therefore lake deflation, is critical for understanding regional landscape evolution, including the history of lake desiccation. The onset of dune construction is currently estimated at ~8000 to 6500 cal yr BP, but numerical age control is limited. Archaeological evidence reported here indicates two older phases of gypsum dune construction. An archaeological site draped over a parabolic dune south of the main dune body contains artifacts dating to >12,200 cal yr BP, providing an upper age limit for the landform. Another site buried within a remnant of the main dune field yielded six statistically identical radiocarbon dates averaging ~8770 cal yr BP. The initial phase of terminal Pleistocene deflation and parabolic dune construction was perhaps localized but correlates with a period of regional aridity. Barchans and crescentic ridges comprising the main dune body developed in the Early Holocene in response to elevated salinity in local ground water and extensive exposures of gypsum available for deflation, likely due to aridity.

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