MCA Pilot PUI: Developing new and novel research into the Miocene to Quaternary geomorphology of the upper Gunnison Basin, Colorado

Western Colorado University, Gunnison CO

Investigators

Abstract

The Colorado River and its tributaries have carved some of the largest canyons in the United States. Millions of Americans see these iconic landscapes in national parks like Grand Canyon, Canyonlands and Black Canyon of the Gunnison. When these canyons were cut and the processes driving river incision are areas of active research in geology. The Upper Gunnison River near Gunnison, Colorado has had much less river incision and canyon cutting over the last 10 million years than most other Colorado River sites. This project will study why river incision is so slow around Gunnison and the effect that slow incision has had on hazards and resources important to local and regional economies. This research will provide a more complete understanding of the Gunnison River aquifer, which provides fresh water to the City of Gunnison as well as private landholders and small industry around the Gunnison Valley. Additional public benefits include: research experiences for students at Western Colorado University, K-12 curriculum development with Gunnison Watershed School District educators and dissemination of results at public lectures, meetings and various publications. This project will accomplish three main scientific goals and test hypotheses regarding the landscape evolution of the upper Gunnison River drainage basin and apparent slow incision rates since the Miocene: 1) further mapping and study of paleo-Gunnison River gravels preserved under the 10 Ma basalt capped Flat Top and Red Mountains using clast provenance and detrital sanidine Ar-Ar dating, 2) dating the deposition of alluvial fill under the City of Gunnison using cosmogenic burial isochron techniques and 3) document the late Quaternary incision history of the Gunnison River from dating river terraces near Almont, Colorado using multiple techniques (soils, OSL, depth profile 10Be). This work will test hypotheses pertinent to the incision of the upper Colorado river basin including: relationship of slow incision rates over the past 10 Ma to mantle velocities suggesting dynamic topography and faster rates, the nature of high elevation basin sedimentation between the late Miocene/Pliocene to middle Pleistocene, and test the hypothesis of climate (glaciation) driven alluviation, river terrace planation and subsequent incision in a headwater basin. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.