Gunnison River
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 (&gt;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.