Title

The River of Rock: Evolution of the Albion-Raft River-Grouse Creek (ARG) Metamorphic Core Complex of Idaho-Utah-Nevada and Implications for the Miocene Colorado River

Presentation Type

Poster

Abstract

Evidence suggests that the present southerly course of the Colorado River was not possible until the Pliocene. Despite this, geologic evidence suggests erosional processes due to river flow occurred 20 million years earlier in the upper reaches of the Grand Canyon. The proposed ancient course of this river went north to the Labrador Sea, traversing the ARG region. The tectonic chronology of the ARG metamorphic core complex of the Utah-Idaho-Nevada tristate region is preserved in the minerals and deformational structures of the rocks exposed today. This timeline reveals peak metamorphism related to regional plutonic deformation during the Eocene and Oligocene and subsequent extensional exhumation during the middle Miocene. The proposed northerly path of the prehistoric Colorado River follows a course that traverses the present day range that formed due to extensional normal faulting related to the exhumation of the ARG core complex. The geomorphic evolution of the river suggests these events were critical to impeding the northerly direction of flow, resulting in the internal drainage of the Great Basin that we observe today. Using age datasets already established, previous field notes, and our own field observations we can establish a timeline that connects the extensional tectonic events that resulted in the exhumation of the ARG core complex to the diversion of flow of the Miocene Colorado River. The ARG metamorphic core complex has been well studied and documented but the timing of events as of yet has not been related to geomorphic processes in the evolution of the former path of the Colorado River. This connection is vital to justify the timing of events and to better understand the landscape evolution of this region.

Category

Physical Sciences

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Apr 17th, 3:00 PM Apr 17th, 4:00 PM

The River of Rock: Evolution of the Albion-Raft River-Grouse Creek (ARG) Metamorphic Core Complex of Idaho-Utah-Nevada and Implications for the Miocene Colorado River

South UC Ballroom

Evidence suggests that the present southerly course of the Colorado River was not possible until the Pliocene. Despite this, geologic evidence suggests erosional processes due to river flow occurred 20 million years earlier in the upper reaches of the Grand Canyon. The proposed ancient course of this river went north to the Labrador Sea, traversing the ARG region. The tectonic chronology of the ARG metamorphic core complex of the Utah-Idaho-Nevada tristate region is preserved in the minerals and deformational structures of the rocks exposed today. This timeline reveals peak metamorphism related to regional plutonic deformation during the Eocene and Oligocene and subsequent extensional exhumation during the middle Miocene. The proposed northerly path of the prehistoric Colorado River follows a course that traverses the present day range that formed due to extensional normal faulting related to the exhumation of the ARG core complex. The geomorphic evolution of the river suggests these events were critical to impeding the northerly direction of flow, resulting in the internal drainage of the Great Basin that we observe today. Using age datasets already established, previous field notes, and our own field observations we can establish a timeline that connects the extensional tectonic events that resulted in the exhumation of the ARG core complex to the diversion of flow of the Miocene Colorado River. The ARG metamorphic core complex has been well studied and documented but the timing of events as of yet has not been related to geomorphic processes in the evolution of the former path of the Colorado River. This connection is vital to justify the timing of events and to better understand the landscape evolution of this region.