- Hood, William C.
- Granger, Darryl E.
- Kirby, Eric
- Donahue, Magdalena S.
- Asmerom, Yemane
- Aslan, Andres
- Polyak, Victor
- Karlstrom, Karl E.
- Kelley, Shari
- Crow, Ryan
|Abstract or Summary
- Cosmogenic-burial and U-series dating, identification of fluvial terraces and lacustrine
deposits, and river-profile reconstructions show that capture of the Gunnison River by
the Colorado River and abandonment of Unaweep Canyon occurred between 1.4-0.8
Ma. This event led to a rapid pulse of incision unlike any documented in the Rocky
Mountains. Following abandonment of Unaweep Canyon by the ancestral Gunnison
River, a wave of incision propagated upvalley rapidly through Mancos Shale at rates of
~90-440 km/Ma. The Gunnison River removed 400-500 km3 of erodible Mancos Shale
and incised up to 360 m deep in 0.17-0.76 My (incision rates of ~470-2250 m/Ma).
Prior to canyon abandonment, long-term (~11-1 Ma) Gunnison River incision averaged
The wave of incision also caused the subsequent capture of the Bostwick-Shinn Park
River by the ancestral Uncompahgre River ca. 0.87-0.64 Ma, at a location ~70 km
upvalley from Unaweep Canyon. This event led to similarly rapid (up to ~500 m/Ma)
but localized river incision. As regional river incision progressed, the juxtaposition of
resistant Precambrian bedrock and erodible Mancos Shale within watersheds favored
the development of significant relief between adjacent stream segments, which led to
stream piracy. The response of rivers to the abandonment of Unaweep Canyon
illustrates how the mode and tempo of long-term fluvial incision are punctuated by
short-term geomorphic events such as stream piracy. These short-term events can
trigger significant landscape changes, but the effects are more localized relative to
regional climatically- or tectonically-driven events.
- Aslan, A., Hood, W. C., Karlstrom, K. E., Kirby, E., Granger, D. E., Kelley, S., ... & Asmerom, Y. (2014). Abandonment of Unaweep Canyon (1.4–0.8 Ma), western Colorado: Effects of stream capture and anomalously rapid Pleistocene river incision. Geosphere, 10(3), 428-446. doi:10.1130/GES00986.1
|Funding Statement (additional comments about funding)