Overview of the Cenozoic geomorphic evolution of the Colorado River through Glen Canyon and Upper Colorado River Corridor and how it relates to the age and origin of Grand Canyon, Colorado Plateau, USA

The overall purpose of this paper is to integrate the geomorphic evolution of Glen Canyon and Upper Colorado River Corridor with that of Grand Canyon in order to address two key enigmas: why did the Colorado River not arrive at the mouth of Grand Canyon until 5.5 Ma, and how did the Colorado River cross the Kaibab arch high? This evolution was approached from three different perspectives: (1) by reviewing geologic investigations in the Glen Canyon area from the late 1800s to the present; (2) by explaining how a paleo-Colorado River constrained within a lake or a chain of lakes on the Colorado Plateau is necessary for the Colorado River to have arrived at the mouth of Grand Canyon ca. 5.5 Ma; and (3) by proposing how the incision rates in Marble Canyon, Glen Canyon, and central Colorado Plateau may be related to a prolonged base-level fall at the Confluence of the ColoradoLittle Colorado rivers starting at similar to 5.5 Ma, to a karst-connection model of a Colorado River crossing under the Kaibab arch, or to a lake-overflow model. An attempt was made to find field and analytic evidence for a pre-5.5 Ma Miocene lake along the north to west sides of Navajo Mountain, Utah, where high pediment surfaces still remain along the Colorado River, but from field investigations, Al-26-Be-10 cosmogenic dating, and SEM analysis, no direct evidence for a past lake was substantiated. However, a number of lines of indirect evidence are discussed supporting the possible existence of a Miocene lake or chain of lakes along Glen Canyon and Upper Colorado River Corridor. A lake-overflow model is compared with a karst-connection model as to how the Colorado River might have crossed the Kaibab arch.

Automated summary

The purpose of this paper is to study the geomorphic evolution of Glen Canyon, Upper Colorado River Corridor, and Grand Canyon in order to address the mystery of why the Colorado River did not reach the mouth of Grand Canyon until 5.5 million years ago and how it crossed the Kaibab arch high. The paper reviews geologic investigations in the Glen Canyon area, explains the importance of a paleo-Colorado River constrained within a lake or a chain of lakes for the river to reach Grand Canyon at 5.5 million years ago, and proposes different models to explain the incision rates in Marble Canyon, Glen Canyon, and central Colorado Plateau. The paper also discusses the possibility of a Miocene lake or chain of lakes along Glen Canyon and Upper Colorado River Corridor and compares different models for the river's crossing of the Kaibab arch.