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How Deep is the Sandbox?
Tara Gregg
Whitman College, Walla Walla, WA 99362
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A system of geologically young grabens has developed in the Needles District
of Canyonlands National Park, Utah. In this region, Pennsylvanian and Permian
sandstones overlie evaporites of the Pennsylvanian Paradox Formation. The creation
of a deep canyon by the erosion of the Colorado River has removed lateral support
for these rocks, producing a series of normal faults whose movement is facilitated
by the low-strength evaporite layer. Fault displacement can be inferred based
on the thickness of sediment fill within these grabens. Gravity surveys performed
in coordination with seismic studies indicate that sediment in Cyclone Graben
exceeds 30 meters in thickness and may possibly be as thick as 100 meters. These
results indicate that fault displacement exceeds previously reported estimates
by at least a factor of 1.5. Faculty Sponsor: Kevin Pogue
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