A karst hydrology model for the geomorphic evolution of Grand Canyon, Arizona, USA
Download Full Text
The evolution of Grand Canyon started ~85 Ma when the southwestern Hualapai Plateau section of the Colorado Plateau began uplifting. This uplift initiated a northeast-trending drainage/canyon system (“Laramide paleo-Grand Canyon”) that was to constrain all later routes, including that of the Colorado River. This drainage proceeded down dip but up the stratigraphic section so that northward incision intersected progressively younger Paleozoic to Mesozoic rock. We propose a capture of groundwater by the karstic Redwall Limestone at RM 197 that shifted the drainage direction of this early canyon along a N60°E-trending section to RM 130. Uplift of the Kaibab arch at ~80–65 Ma forced Coconino Plateau drainage to divert around the west side of the arch rather than northeast across it. In the Mid-Tertiary an “Arizona River” in the western Grand Canyon transported Shinumo clasts to the California Sespe Formation, and a magmatism-tectonic-volcanism episode occurred on and south of the Hualapai Plateau. By ~17 Ma, Basin and Range down-faulting furthered earlier Miocene canyon headward erosion eastward and then northward into Utah, causing a complete regional drainage reversal southward; this “Miocene western paleo-Grand Canyon” river incised into the Redwall-Muav karst aquifer so as to supply the 12–6 Ma Hualapai Limestone with high 87Sr/86Sr carbonate spring water. A ~6.0–5.5 Ma “final connection” between the east and west sides of the Kaibab arch was accomplished by karst-piracy drainage traversing under the arch. This complexity of origin – separate canyon sections joined, drainage reversals, and a final karst connection – is why Grand Canyon remains enigmatic to geologists.
Digital Object Identifier (DOI)
Hill, Carol A. and Polyak, J., "A karst hydrology model for the geomorphic evolution of Grand Canyon, Arizona, USA" (2020). KIP Articles. 6883.