Ancient human footprints at White Sands National Park

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. Excavated surfaces in White Sands National Park (New Mexico, United States) revealed multiple in situ human footprints that are stratigraphically constrained and bracketed by seed layers that yield calibrated radiocarbon ages between ~23 and 21 thousand years ago. 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. The White Sands footprints chronology has remained controversial, however, because of potential old carbon reservoir effects that could have compromised the accuracy of the seed ages. Here, we present new calibrated radiocarbon ages of terrestrial pollen collected from the same stratigraphic horizons as the seeds, along with optically stimulated luminescence ages of sediments from within the human footprint-bearing sequence, to evaluate their veracity. The new ages show that the chronologic framework originally established for the White Sands footprints is robust and reaffirm that humans were present in North America during the Last Glacial Maximum.

Speakers: Kathleen Springer and Jeff Pigati, USGS