Day 1 : Stop 1

DAY 1 (9/26/2025) - STOP 1

"Salt Flat"

COORDINATES:  31.75271° N, 104.98735° W

Fig. 1 View of the Guadalupe Mountains from the salt flat

Fig. 2 Mudcracks compared to 5.8 cm rock

Our first site lies within the Salt Basin (fig. 1) on the western side of the Guadalupe Mountains, a depression that formed when regional uplift and normal faulting during the Miocene caused the adjacent Guadalupe block to rise while the basin floor subsided. It’s located in an enclosed drainage system with no outlet, allowing runoff from surrounding uplands to accumulate on the basin floor as shallow, ephemeral lakes (NPS, 2022). Due to the region’s arid climate, these water bodies evaporated rapidly, concentrating dissolved ions and promoting the precipitation of evaporite minerals such as gypsum, halite, and other evaporites, which form the present salt-flat surface (NPS, 2022). The presence of mud cracks demonstrates repeated wetting and drying cycles as fine-grained sediment contracts during evaporation, documenting the intermittent nature of water coverage across the basin floor. Although the present geomorphology reflects recent Quaternary processes, the setting is linked to the deeper geologic history of the Permian Basin, which underwent evaporite deposition as marine connections diminished and evaporation exceeded inflow during the late Permian. Thick subsurface beds of gypsum, anhydrite, and halite formed during this period record the transition from a marine basin to a restricted, evaporitic one. The modern salt flat represents the latest stage in this long environmental evolution, shaped by internal drainage, climate variability, and ongoing cycles of flooding, evaporation, and salt precipitation (Boyd, Kreitler, 2021).

External References:

Salt Basin Dunes - Guadalupe Mountains National Park (U.S. National Park Service). (2022). Nps.gov. https://www.nps.gov/gumo/planyourvisit/dunes.htm

‌Boyd, F. M., & Kreitler, C. W. (2021). Hydrogeology of a Gypsum Playa, Northern Salt Basin, Texas. Utexas.edu; The University of Texas at Austin, Bureau of Economic Geology. https://www.beg.utexas.edu/publications/hydrogeology-gypsum-playa-northern-salt-basin-texas

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