Seismic reflection and electrical resistivity imaging reveal
pre-Quaternary glaciation in the Rocky Mountains (Unaweep Canyon,
Colorado)
Abstract
Unaweep Canyon (Uncompaghre Plateau, Colorado) represents an enigmatic
landscape with a complex evolution. Interpretations for its origin have
ranged from ancestral fluvial erosion in the late Cenozoic to glacial
erosion in the Paleozoic, or some combination thereof, with significant
implications for global climatic and large-scale tectonic
reconstructions. To address the conflicting interpretations, we acquired
a high-resolution seismic reflection profile to investigate the depth,
structure, and sedimentary infill in the canyon. The dataset is further
complemented with a high-resolution electrical resistivity survey.
Integrated with other geophysical and geological data, the results
unambiguously demonstrate an overdeepened Precambrian basement with
pronounced transverse U-shape and corroborate the hypothesis of a
pre-Quaternary glacial origin. Our data constitute the first detailed
and high-resolution image of a buried pre-Quaternary glacial valley in
North America, and thus have far-reaching implications for our
understanding of global ice houses as well as the tectonic conditions
enabling preservation of such systems.