S. A. Kelley, C. E. Chapin, K. E. Karlstrom, D. Stockli, M. Hoffman, J. Lee, R. McKeon and R. V. Garcia

A regional compilation of apatite fission-track (AFT) and (U-Th)/He (AHe) data from surface and subsurface samples from the Colorado Plateau/ Rocky Mountain/ Rio Grande rift region reveals a multi-stage, episodic, exhumational history with Laramide (80-40 Ma), middle Cenozoic (35-25 Ma), middle to late Cenozoic (25-10 Ma), and late Cenozoic (110°C during subsequent tectonic events. Waning of extensive volcanism, elevated heat flow, and modification of crustal density structure following the ignimbrite flare-up (35-25 Ma) is recorded in cooling ages from S Colorado and New Mexico. Buoyancy caused by crustal modification lingered into the 25-10 Ma time frame, enhancing exhumation on the Colorado Plateau and High Plains. Extensional ranges along the margins of the Plateau also exhumed during this time interval. The 5- 10 Ma cooling ages in SW Colorado lie above profound low wave-speed anomalies in the uppermost mantle and are interpreted to place an upper bound on the timing of formation of these anomalies.

2011 New Mexico Geological Society Annual Spring Meeting April 15, 2011, Macey Center, New Mexico Tech campus, Socorro, NM Online ISSN: 2834-5800

Pages: 36