Central Mineral and Environmental Resources Science Center
Project status is complete. Please check the CMERSC project list for currently active projects.
The objectives of this project were to conduct geological mapping as well as volcanogenic and environmental geochemical studies of Big Bend National Park (BBNP). The primary goal of the project was to produce a 1:100,000-scale digital geologic map for BBNP, but as part of that effort, we also studied poorly understood eruptive histories of late Cretaceous and early Tertiary volcanic units. Geochemical studies of abandoned mercury mines in and around BBNP were also carried out to evaluate any adverse environmental effects to ecosystems in the region. Geochemical and isotopic tracer studies were also carried out on altered rock, mineral deposits (mined and unmined), and surface and ground water resources.
The National Park Service (NPS) funded the USGS to produce a geologic map of BBNP because the current map used by the park is outdated. There are a number of geologic complexities in BBNP that were studied, including (1) the superimposition of Ouachita, Laramide, and Basin-and-Range style tectonic regimes, (2) well exposed but poorly understood Tertiary mafic to silicic, alkaline to peralkaline magmatism, (3) several newly discovered calderas, (4) late Cretaceous to early Tertiary sedimentary rocks with unique dinosaur and early mammal fossils, and (5) late Cenozoic regional uplift and erosion. Geologic mapping and geochronological, geochemical, paleontological, and petrological studies of BBNP were a significant contribution to the understanding of the geologic history of the Trans-Pecos region.
There are a number of inactive and abandoned mines within and adjacent to BBNP with high concentrations of potentially toxic heavy metals. For example, mines at Terlingua are part of a large mercury district located in and around BBNP. Mercury was mined in this area from the 1890's to the 1970's, and produced about 5,000 t (150,000 flasks) of mercury. Terlingua ranks as the 4th largest producer of mercury in the United States. Mercury is a heavy metal that is toxic to all organisms, including humans. An important contribution to the study of BBNP and the surrounding area was evaluation of runoff from such mercury mines that potentially affects water quality in surrounding ecosystems. Geochemical studies of mine waste and surface and groundwater in these areas were carried out to evaluate any adverse effects to surrounding ecosystems. Geochemical studies in additional areas were also carried out where there is altered and mineralized rock with potentially high concentrations of heavy metals.