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Abstract: The Sevier Desert Basin, West-Central Utah: Re-examining the Geological and Geophysical Evidence

WILLS, STEWART, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY

The Sevier Desert basin -- a Tertiary depression in west-central Utah that contains greater than 4 km of lacustrine sediments in its deepest areas -- is generally viewed as the result of regional low-angle normal faulting, a model based almost entirely on seismic interpretation, tied with data from scattered industry wildcats. Recent study of material from near the supposed fault contact casts doubt on the detachment hypothesis and underscores the need for alternative models. One potentially attractive working hypothesis is that the basin sediments collected in a broad, gently subsiding saline lake, created during the Oligocene by thermal subsidence or sublithospheric loading and substantially deepened since the Miocene by basin-bounding high-angle normal faults. Under this hypothesis, the detachment geometries observed on area seismics stem not from movement on a rooted low angle fault, but from local withdrawal and re-emplacement of salt in a basin known to contain significant evaporites.

Testing the viability of this and other candidate models requires a better understanding of the three-dimensional basin geometry. My work will provide that understanding through an integrated reconstruction drawing on all available seismic, well, and gravity data and on field observations. The data set includes both published and previously unpublished industry seismic profiles, some of which provide crucial along-strike control and delineation of the basin's northern and southern margins that was not available to earlier researchers. The study will also take into account evidence from several deep industry wells for which data have only recently been released. Mapping and field reconnaissance of high-angle faults in surrounding mountains will attempt to constrain better the timing and kinematics of uplift of the basin-bounding ranges.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid