Unaweep Canyon
Encyclopedia
Unaweep Canyon is a geologically unique canyon that cuts across the Uncompahgre Plateau
in western Colorado
. It is unique because two creeks, East Creek and West Creek, flow out of opposite ends of the canyon, separated by the almost imperceptible Unaweep Divide.
or Gunnison
river. Many others have also suggested it was carved by either the Gunnison or Colorado Rivers, but evidence for gravel deposits characteristic of these rivers was elusive, and the existence of the divide remains difficult to explain. Several have suggested that Plio-Pleistocene uplift caused diversion of the (Colorado and/or Gunnison) river(s) and abandonment of the canyon. But rates of river incision typically exceed those of tectonic uplift, making this unlikely. The many apparent glacial-like features of the canyon's inner gorge have led some to suggest a Pleistocene
glacial origin for the canyon, but the low elevation of the canyon, and lack of Pleistocene glacial deposits, make this problematic. More recently, documentation of gravels characteristic of the Gunnison River and located at the western mouth of Unaweep Canyon provide evidence for occupation of the canyon by an ancestral Gunnison River Hence, the ancestral Gunnison River may have carved the canyon. However, another hypothesis holds that the ancestral Gunnison River did not carve the canyon, but exhumed a pre-existing (paleo) canyon. This hypothesis of an ancient age for the inner gorge of Unaweep Canyon comes from dating of sediments recovered in a core through the canyon fill. This core proved the existence of a thick (>300 m) sediment fill in the canyon, an idea first proposed in the 1970s on the basis of a geophysical study. Related to the proposed ancient age for the canyon is the hypothesis that the canyon was glaciated during the Late Paleozoic, roughly 300 million years ago. The hypotheses of a Paleozoic age and glacial origin for the canyon, remain debated, like many other hypotheses for the origin of this scenic canyon.
runs inside Unaweep Canyon between Whitewater
and Gateway
, one segment of the Colorado designated Unaweep Tabeguache Scenic Byway. The Unaweep Divide, elevation 7008 ft (2,136 m), is near mile marker 135 on SH 141.
Uncompahgre Plateau
The Uncompahgre Plateau in western Colorado is a distinctive large uplift part of the Colorado Plateau. Uncompahgre is a Ute Indian word that describes the water: "Dirty Water" or "Rocks that make Water Red"....
in western Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
. It is unique because two creeks, East Creek and West Creek, flow out of opposite ends of the canyon, separated by the almost imperceptible Unaweep Divide.
Hypotheses of origin
There are multiple explanations for the origin of Unaweep Canyon. In the late 19th century, members of the Hayden Survey recognized the oddity of a canyon with two outlets, and suggested it was carved by the ancestral ColoradoColorado River
The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...
or Gunnison
Gunnison River
The Gunnison River is a tributary of the Colorado River, long, in the Southwest state of Colorado. It is the fifth largest tributary of the Colorado River, with a mean flow of 4320 ft³/s .-Description:...
river. Many others have also suggested it was carved by either the Gunnison or Colorado Rivers, but evidence for gravel deposits characteristic of these rivers was elusive, and the existence of the divide remains difficult to explain. Several have suggested that Plio-Pleistocene uplift caused diversion of the (Colorado and/or Gunnison) river(s) and abandonment of the canyon. But rates of river incision typically exceed those of tectonic uplift, making this unlikely. The many apparent glacial-like features of the canyon's inner gorge have led some to suggest a Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
glacial origin for the canyon, but the low elevation of the canyon, and lack of Pleistocene glacial deposits, make this problematic. More recently, documentation of gravels characteristic of the Gunnison River and located at the western mouth of Unaweep Canyon provide evidence for occupation of the canyon by an ancestral Gunnison River Hence, the ancestral Gunnison River may have carved the canyon. However, another hypothesis holds that the ancestral Gunnison River did not carve the canyon, but exhumed a pre-existing (paleo) canyon. This hypothesis of an ancient age for the inner gorge of Unaweep Canyon comes from dating of sediments recovered in a core through the canyon fill. This core proved the existence of a thick (>300 m) sediment fill in the canyon, an idea first proposed in the 1970s on the basis of a geophysical study. Related to the proposed ancient age for the canyon is the hypothesis that the canyon was glaciated during the Late Paleozoic, roughly 300 million years ago. The hypotheses of a Paleozoic age and glacial origin for the canyon, remain debated, like many other hypotheses for the origin of this scenic canyon.
Access
State Highway 141Colorado State Highway 141
State Highway 141 is a long state highway in far western Colorado. Though nominally oriented north–south, SH 141 winds around a considerable amount due to the rugged terrain and ultimately forms a giant S shape.-Route description:...
runs inside Unaweep Canyon between Whitewater
Whitewater, Colorado
Whitewater is an unincorporated community with a U.S. Post Office in Mesa County, Colorado, United States, just south of Grand Junction. The Whitewater Post Office has the ZIP Code 81527...
and Gateway
Gateway, Colorado
Gateway is an unincorporated town and a U.S. Post Office located in Mesa County, Colorado, United States. The Gateway Post Office has the ZIP Code 81522.-Tourism:...
, one segment of the Colorado designated Unaweep Tabeguache Scenic Byway. The Unaweep Divide, elevation 7008 ft (2,136 m), is near mile marker 135 on SH 141.