Upcoming Lectures


When: Thursday, May 9th, 2024 at 7:00 pm

Who: Jeff Pagati and Kathleen Springer (USGS)

Kathleen Springer and Jeff Pigati are research geologists with the U.S. Geological Survey in Denver, Colorado where they investigate geologic deposits associated with springs and desert wetland hydrologic regimes to determine how they responded to past episodes of abrupt climate change. Their work has focused on developing stratigraphic and chronologic frameworks throughout the Mojave Desert and southern Great Basin, which serve as hydroclimate roadmaps for these groundwater-dependent ecosystems. They have established that they are incredibly sensitive to changes in climate at multi-decadal to centennial timescales and that they expanded and contracted in near lockstep with changes in climate recorded in the Greenland ice cores over the past 40,000 years. Their results demonstrate that springs and wetlands in the southwestern U.S. disappeared altogether during abrupt warming events due to rapid groundwater lowering associated with these megadrought episodes. Their findings have tremendous implications for extant springs in arid environments in light of projected future warming.
Recently, Kathleen and Jeff have combined detailed stratigraphic analyses and cutting edge dating techniques with their intimate understanding of past climate events to establish the age, geologic context, and paleoenvironmental setting of ancient human footprints discovered at White Sands National Park – including the link to abrupt climate change that allowed the human and megafaunal footprints and trackways to be created and preserved. Their results show that humans were present in North America during the Last Glacial Maximum, upending traditional models regarding the peopling of the Americas and fundamentally changing the very foundation of North American archaeology.


Title: Ancient Human Footprints at White Sands National Park

Abstract: 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.


      • IN-PERSON PARTICIPANTS: 2520 55th St, Boulder, CO 80301 
        *Please note that the door will be locked when you arrive. Please call or text the number listed at the door to be let into the building.”

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Cost: Free & Open to the Public



February 2024: Justin Bautista (ERO Resources):  research and analysis of a prehistoric Middle Ceramic Period (655-555 BP) bison processing camp located in Douglas County. 

October 2023: Kenneth Vernon, PhD: A core-periphery approach to defining community boundaries

September 2023: Ethan Gannett: Investigating the Cherokee and Overland Trails in Colorado

May 2023: Kim Biela: Ceramics Patterning in Rio Blanco County, Colorado

April 2023: Beth Parisi: Archaeological Site Stewardship

February 2023: Sam Bock: The Sand Creek Massacre: The Betrayal that Changed Cheyenne and Arapaho People Forever

January 2023: Harold Henke, PhD: The Metal Detector: As Useful a Tool as a Shovel or Trowel for the Historical Archaeologist

November 2022: Spencer Little: Unbelievably Deep: A Reanalysis of the Hells Midden Site (5MF16)

April 2022: Michael J. Prouty: “Through This Tangled Mass”: Identification and Recordation of Historical Trails in Colorado

February 2022: Chris Johnston: Projectile Points, Chronology, and the Oshara Tradition in the San Luis Valley

January 2022: Anna Cordova: Stewardship of Colorado Springs’ Archaeological Resources

December 2021: Devin Pettigrew, PhD: Lessons from Realistic Experiments with Archaeological Weapons

November 2021: Dr. Holly Norton: Archaeology for a Changing Colorado

May 2021: Claire Novotny, PhD: Games of Change and Fate: Patolli at the Ancient Maya Site of Gallon Jug

April 2021: Vicki Twinde-Javner: Excavation of the Lessard Site, Prairie du Chien, Wisconsin



Is there a particular speaker that you would like to see? Email the IPCAS Vice President to suggest a speaker.