STRUCTURAL ANALYSIS AND LATE CENOZOIC EVOLUTION OF THE HURRICANE FAULT, LOWER WHITMORE WASH, WESTERN GRAND CANYON

Lower Whitmore Wash in western Grand Canyon offers superb three-dimensional exposures of the Hurricane Fault over a distance of several kilometers. While the Hurricane fault has been the subject of many paleoseismic investigations upstream in Whitmore Canyon, this investigation is the first detailed structural analysis of the Hurricane fault within the Grand Canyon. The great extent and high quality of the exposures, both horizontally and vertically, allow a structural characterization of the fault zone at a level of detail not possible in the previously studied areas immediately north of the Grand Canyon. Field work and data analysis are currently ongoing.

The goals of the structural analysis are: 1) to describe the extensional style of the fault zone; 2) to evaluate the applicability of relay-ramp and other fault-growth models to the Hurricane fault in Grand Canyon and 3) to test the hypothesis that the Hurricane fault is a reactivated Laramide monocline. Several Quaternary basalt flows and alluvial terraces are cut by the fault within the study area. These flows and surfaces have been dated by other workers using a variety of techniques. New and published data from these surfaces are used to establish a framework chronology for the structural development of the Hurricane fault. These results also have implications for the hypothesis that Quaternary motion on the Hurricane and Toroweap faults has controlled canyon-cutting rates in the Grand Canyon.