An Exhumed Late Paleozoic Canyon in the Rocky Mountains: A Reply

Abstract

We thank William Hood for his discussion of Soreghan et al. (2007). We recognize that our interpretation of the events leading to the formation of Unaweep Canyon, particularly our proposed Paleozoic age of the (ancestral) canyon, represents a significant departure from established models. Validation of our hypotheses regarding its age and origin would force revision of several longaccepted models, ranging from the Cenozoic tectonic and geomorphic evolution of this region to the climatic and perhaps tectonic framework of the Permo-Pennsylvanian tropics represented by this system. Accordingly, our work deserves close scrutiny, and Hood’s discussion provides such an opportunity. Hood (2009) begins his discussion by stating that Soreghan et al. (2007) presented the hypothesis that Unaweep Canyon is a Permian glacial valley that was filled by Paleozoic sediment and subsequently exhumed by Cenozoic rivers. To clarify, the focus of Soreghan et al. (2007) is the hypothesized Paleozoic age of the canyon, although we posed the question of a possible glacial origin in the final sentences of the article. A more complete analysis of the evidence for a glacial origin, however, appears in Soreghan et al. (2008), although only abstracts of this aspect (e.g., Soreghan et al. 2004) were published at the time that Hood submitted his discussion. Nevertheless, here we address all of the points raised by Hood; we treat each of his points using the subheadings he provides. Reexamination of the Field Evidence and Paleomagnetic Data