USGS Open-File Report 01-425: The Internal Structure of Sand Bars on the Colorado River, Grand Canyon, as Determined by Ground-penetrating Radar

The Internal Structure of Sand Bars on the Colorado River, Grand Canyon, as Determined by Ground-penetrating Radar

By Walter Barnhardt, Robert Kayen, David Rubin, and Diane Minasian

Abstract

High-resolution, subsurface imagery from ground-penetrating radar (GPR) has revealed the internal structure of sand bars at seven sites on the Colorado River, Grand Canyon. Based on reconnaissance-level surveys, we recognized three stratigraphic units and several intervening unconformities. Unit A, which exhibits hyperbolic reflections and always occurs at the base of the section, is interpreted as bedrock and/or talus. Unit B is a commonly observed sand deposit that overlies unit A and is characterized by reflections that gently dip down toward the river axis. Unit C is a sand deposit up to 2 m thick that always occurs at the top of the section and may represent a flood deposit from 1983. This study demonstrates the utility of GPR for non-destructive investigation of sand-bar thickness and the stratigraphic record of flood events in the Grand Canyon.

First posted November 27, 2001

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Pacific Coastal & Marine Science Center
U.S. Geological Survey
400 Natural Bridges Drive
Santa Cruz, CA 95060

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Suggested citation:

Barnhardt, Walter, Kayen, Robert, Rubin, David, Minasian, Diane, 2001, The Internal Structure of Sand Bars on the Colorado River, Grand Canyon, as Determined by Ground-penetrating Radar: U.S. Geological Survey Open-File Report 01-425, https://pubs.usgs.gov/of/2001/0425/.