198-2 Geoheritage Without Borders: Exploring the Ancient Landscapes of South Texas

Session: Geoheritage Without Borders: International Perspectives on the Conservation and Celebration of Geodiversity, Part II

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Abstract:

The Lower Rio Grande Valley (LRGV), comprising the four southernmost counties of Texas and home to approximately 1.7 million residents, along with an additional 150,000 seasonal visitors, is often portrayed through narrow and problematic lenses, primarily associated with poverty, narco-trafficking, and undocumented migration. In response, the "Ancient Landscapes of South Texas" Geoheritage Trail was developed as a regional initiative to generate positive visibility, foster geoscience education, and promote sustainable tourism. This interpretive trail brings to light the underappreciated geologic, natural, and cultural heritage of the LRGV, spanning a 60-kilometer-wide corridor from the Gulf of Mexico westward to the historic city of Roma, a distance of 215 kilometers. The LRGV is a majority-Hispanic region (87%) with deep cultural ties to the land. The trail highlights a geologic narrative extending over 43 million years, illustrated through accessible outcrops and features such as the ancestral shoreline of the Gulf of Mexico, massive oyster reefs, a 20-meter-thick volcanic ash deposit, and remnants of a petrified forest. It also incorporates objects of natural significance and aesthetic value, including the 40-pound La Villa Meteorite, a 900-year-old Montezuma cypress, and biologically unique wind-tidal flats with resilient algal mats. Human-environment interactions are also emphasized, from the prehistoric exploitation of salt flats and El Sauz Chert for toolmaking, to evidence of late Pleistocene megafauna, including large game and giant tortoises. The trail concludes with historic norias, hand-dug wells that penetrated ~10 meters of caliche, critical to the establishment of cattle ranching in this semi-arid region. Despite the region's shared geologic history, modern restrictions on cross-border collaboration limit scientific and cultural understanding of its full geoheritage potential. Before the late 20^th century, the Rio Grande seldom functioned as a true boundary. While a few of these sites are long-recognized landmarks, the majority remain largely unknown to the public. This initiative seeks to reframe the LRGV through its geodiversity, promoting a sense of place, scientific value, and cross-cultural appreciation.

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

doi: 10.1130/abs/2025AM-7867

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