11 Future Voices in Geoscience- Undergraduate Research Posters

This session is for two-year college and four-year college and university students presenting research posters in any subdiscipline of geosciences. Posters and presentations will be judged for awards.

Monday, 18 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Using basin analysis to better understand Miocene extension in the Lake Mead Region: stratigraphic and structural analysis in the western Bitter Spring Valley, southern Nevada

Paper number: 11-6
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Exposed faulting in the region surrounding Lake Mead records Miocene large-scale continental extension. Previous studies focused on this faulting suggested deformation occurred in stages and shifted from extensional to transtensional. The main faulting stages were active between 17 to 12 Ma. Our study aims to build upon this prior work and refine our understanding of the nature and chronology of faulting via detailed basin analysis within the western Bitter Spring Valley, Nevada. Mapping occurred within the lowest member of the Horse Spring Formation, the Thumb Member. We worked only in the uppermost Thumb Member, which consists of repeating homogenous units of red sandstone, siltstone, and conglomerate. To identify the location and magnitude of faults, we used tuffaceous units as marker beds. By measuring section and conducting petrographic, geochemical, and lithologic analyses of tuffs, we identified six distinct, tuffaceous marker beds. The base of the upper Thumb is defined by a six- to ten-meter-thick tuffaceous sequence dated at 15.34 +/- 0.007 Ma. A second marker tuff is dated at 15.08 +/- 0.05 Ma. We determined the upper Thumb in the western Bitter Spring Valley is much thicker than the same subunit to the east: this will help refine paleogeographic models of the entire Thumb basin. Using mapped fault patterns and kinematic analysis, we recognize four sets of faults: northwest (NW), north-northwest (NNW), north-south (NS), and northeast (NE) striking faults. We define small faults as spanning zero to 100 m, medium faults 100 to 400 m, and large ones greater than 400 m. The NW faults show strike-slip to oblique strike-slip motion and range in all sizes. NNW and NS faults have normal to oblique-normal motion and range in all lengths. We have a few NE faults, and all are small to medium. Their relative motion could not be determined. Kinematic analysis using FaultKin yields an overall extension axis of 261°, 5°. Due to the narrow age range of our units, it’s hard to determine the exact timing of faulting within our area. However, our fault sets have similarities to those mapped to the north and southwest and thus support previous models of deformation. Our area may also contain syndepositional faulting, but additional fieldwork is required to conclusively determine this.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410628

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