The San Juan Basin Archaeological Society invites the public to a presentation. At 6:30 we will have social time, then after a brief business meeting, Jeff Pigati and Kathleen Sringer with the U.S. Geological Survey will discuss " Evidence of humans in North America during the Last Glacial Maximum (Dating of White Sands footprints) " For log-in information go to SJBAS.ORG.

Archaeologists and researchers in allied fields have long sought to understand human colonization of North America. Questions remain about when and how people migrated, where they originated, and how their arrival affected the established fauna and landscape. Here, we present evidence from excavated surfaces in White Sands National Park (New Mexico, United States), where multiple in situ human footprints are stratigraphically constrained and bracketed by seed layers that yield calibrated radiocarbon ages between ~23 and 21 thousand years ago. Independent chronologic controls have recently confirmed these ages. This timing coincided with a Northern Hemispheric abrupt warming event, Dansgaard-Oeschger event 2, which drew down lake levels and allowed humans and megafauna to walk on newly exposed surfaces, creating tracks that became preserved in the geologic record. These findings confirm the presence of humans in North America during the Last Glacial Maximum, adding evidence to the antiquity of human colonization of the Americas and providing a temporal range extension for the coexistence of early inhabitants and Pleistocene megafauna.

Kathleen Springer is a research geologist with the U.S. Geological Survey in Denver, Colorado. She specializes in deciphering complex stratigraphic sequences and reconstructing paleoenvironmental conditions, and studies how springs and other hydrologic systems responded to climate change in the recent geologic past.

Jeff Pigati is a research geologist with the U.S. Geological Survey in Denver, Colorado. His research is focused on understanding the response of hydrologic systems in arid environments to past episodes of abrupt climate change. He is also an expert in radiocarbon dating.