112-2 Comparison of Various Basement Depth Determination Approaches from Potential Field Data: A Case Study from the Rio Grande Rift and Big Bend Regions of SW Texas

Session: Geophysics in Investigating and Exploring for Mineral, Energy and Groundwater Resources (Posters)

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Abstract:

Determining a region’s basement depth is crucial for understanding its tectonic evolution, regional geology, geothermal resources, and mineral exploration potential. Presidio County, situated in the Rio Grande Rift and Big Bend regions of SW Texas, has been identified for its significant geothermal potential. However, a lack of deep drillhole data and limited geophysical studies in the study area make it challenging to characterize the deep subsurface for geothermal studies. This is also complicated by the presence of non-sedimentary rocks, such as volcanics and igneous dykes. Therefore, the present study estimates the basement depth by using multiple potential field data processing techniques (e.g., 3D gravity inversion, Euler deconvolution, and spectral analysis), and compares their results to borehole and outcrop data. 3D gravity inversion results indicate that deeper basement depths of ~5-6 km are found under Presidio Basin, Valentine Basin, and the eastern part of the Chinati Mountains, confirmed by borehole data. The Marfa Basin and Redford Basin characterize moderate basement depths of ~3 to 4 km, while shallower depths (~1-2 km) are observed beneath the Bofecillsos and Sierra Vieja Mountains. Euler solutions for basement depth mostly fall between 1 and 3 km in the study area. Relatively deeper depth solutions of ~3-4 km are identified along the southern margins of the Big Bend, the Chinati Mountains, and the western margin of the Valentine Basin. The deepest structural depths, exceeding 4 km, are observed within the Creshaw Mountains. Spectral analysis revealed that the average depths of the deepest, intermediate, and shallowest gravity sources are approximately 7 km, 3.5 km, and 1.5 km, respectively. Our comparative study recommends the spectral analysis tool as an effective method for fast, preliminary estimation of basement depth using coarse-resolution Bouguer anomalies. During the early-stage exploration, Euler deconvolution provides a suitable alternative for investigating depth to the top of the basement when reasonably high-quality Bouguer anomalies are available. For detailed basement depth mapping, employing a 3D inversion tool is preferable and recommended, particularly when high-quality Bouguer gravity anomaly data with good spatial resolution are available.

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

doi: 10.1130/abs/2025AM-7797

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