60-59 Interpreting Extensional Detachment Tectonics in North American Cordillera, Beaver Dam Mountains, Southern Utah

Session: 2YC and 4YCU Geoscience Student Research Poster Showcase

Presenting Author:

Authors:

Abstract:

The Beaver Dam Mountains are part of the boundary between the Basin and Range and the Colorado Plateau provinces and are proposed to have been affected by low-angle normal faulting. The mountain range is composed of Pre-Cambrian metamorphic rock and a succession of Cambrian-Triassic, dipping homoclinally to the east. Uplift of basement and Paleozoic strata in the Beaver Dam Mountains has been interpreted as a product of isostatic uplift of the footwall of a low-angle normal fault. We conducted new geologic mapping to investigate whether this area was affected or in addition, by earlier shortening that may be partly responsible for its structure.

Field data indicates clear evidence of thrust fault structures and cleavage development in the Cambrian Bonanza King formation and younger units. These structures include exposures of the thrust and fault propagated folding and an area where Devonian Muddy Peak Fm thrusted on top of Mississippian Redwall Fm. Exposures of the thrust transition along strike into anticline-syncline pair with geometries suggestive of fault propagation folding.  Our mapping shows the presence of a fold-and-thrust belt striking ~N-S, cutting through the Beaver Dam Mountains, which is congruent with the orientation of the stress subjected on the area during the Sevier Orogeny. Our re-examination of the area suggests that the western edge of Utah underwent shortening before the onset of Basin and Range extension which likely has re-oriented the strata that was previously deformed by the Sevier thrust-belt system.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9236

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