Arizona Geological Society
2026 Speaker Series
Tuesday, 5 May 2026 | 5:30 - 8:00 PM
Location: Hexagon Mining Division Office
40 East Congress Street, Suite 150, Tucson, Arizona 85701
Parking: On the street or parking garage (Old Pueblo Parking)
Social Hour - Sandwiches from Beyond Bread (5:30-6:20 PM MST), Presentation (6:25 PM MST)
NOTE: This event will be live-streamed.
Link will be provided at a later date
AGS and SEG Publications will be available
for sale at the meeting.
Will need cash or check (no credit cards)
For those planning to attend the event, please register by 6:00 PM on Sunday, May 3, 2026. Please register early so we have an accurate number of attendees to order the right amount of food.
The Arizona Geological Society thanks Hexagon
for generously providing the venue and drinks
The Role of the Bidahochi Basin in the Integration of the Colorado River and the formation of the Grand Canyon
Ryan Crow, U.S. Geological Survey
Flagstaff, Arizona
Abstract: A long-standing question and controversy has been the timing and mechanism of integration of the Colorado River through Grand Canyon. New U-Pb dating of ashes and detrital grains sheds light on this problem by indicating that the upper Bidahochi Formation was deposited by the Colorado/Green River starting around 6.6 million years ago. This change in Bidahochi sediment provenance coincides with an order-of-magnitude increase in depositional rate, an increase in carbonate 87Sr/86Sr ratios, and the appearance of large fish species characteristic of fast-flowing waters that have affinities with fish from the Snake and Sacramento Rivers. It now seems clear that the Colorado River pooled in Bidahochi basin until at least 6 million years ago before integrating through what is now Grand Canyon, likely by spillover.
Bio: Ryan Crow is a Research Geologist with the U.S. Geological Survey in Flagstaff, Arizona. He specializes in geologic mapping, understanding landscape evolution of the southwestern United States, and the long-term evolution of the Colorado River. Crow holds degrees from the University of Colorado and the University of New Mexico, where he focused on the tectonic geomorphology of the Grand Canyon. He joined the USGS as a Mendenhall Postdoctoral Scholar in 2014, became a Research Geologist in 2018, and currently leads the Lower Colorado River Geologic Mapping Project. The work Crow will be presenting was the result of a large collaborative project with staff from the U.S. Geological Survey, University of California at Los Angeles, Paradise Valley Community College, Arizona Geological Survey, and other academic institutions. Collaborators include John He, John Douglass, Chris Holm-Denoma, Jorge Vazquez, Brian Gootee, Marsha Lidzbarski, Laura Pianowski, Harrison Gray, Emma Heitmann, Phil Pearthree, Kyle House, and Shannon Dulin.
Hexagon Mining Division Office - 40 East Congress Street,
Suite 150, Tucson, Arizona 85701
