Integrated Surface and Subsurface Geological Mapping of the Valley of the Missions, San Antonio, Texas

A multistrand fault zone beneath Mission Concepción, San Antonio, Texas, may have facilitated the ascent of warm waters through thick Upper Cretaceous mudstone, contributing to the formation of a spring deposit (tufa) used in constructing two historic missions. This finding emerges from an integrated surface and subsurface geological mapping project conducted at a 1:24,000 scale across the Valley of the Missions. The study leverages well control data drilled for the Edwards Aquifer to infer fault locations and bedrock outcrops or subcrops, addressing the scarcity of surface outcrops in the area. Additionally, the research identifies mappable transitions from clay to sandy soils, correlating with thin Poth sandstones and related siltstone units recognized subsurface. This work aims to deepen understanding of the missions' setting, their resource utilization, and to inform conservation efforts while guiding metropolitan development.

Ewing, T. E. (2020). INTEGRATED SURFACE AND SUBSURFACE GEOLOGICAL MAPPING OF THE VALLEY OF THE MISSIONS, SAN ANTONIO, TEXAS. Geological Society of America Abstracts with Programs. https://doi.org/10.1130/abs/2020sc-343520