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Integrated Geological, Geochemical, and Geophysical Studies of Big Bend National Park

Project Objectives

The objectives of this project are to conduct geological mapping as well as volcanogenic and environmental geochemical studies of Big Bend National Park (BBNP). The primary goal of the project is to produce a 1:100,000-scale digital geologic map for BBNP, but as part of that effort, we will be studying poorly understood eruptive histories of late Cretaceous and early Tertiary volcanic units. Geochemical studies of abandoned mercury mines in and around BBNP will be carried out to identify any adverse environmental effects to ecosystems in the region. In addition, we will be conducting geochemical and isotopic tracer studies of altered rock, mineral deposits (mined and unmined), and surface and ground water resources.

Landsat image of Big Bend National Park and surrounding area.

Relevance & Impact

The National Park Service (NPS) is funding the USGS to produce a geologic map of BBNP because the current map used by the park is outdated.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 need additional study, including (1) 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 will be a major 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 adjacent to BBNP. Mercury was mined in this area from the 1890's to the 1970's, and produced about 6,900 t (200,000 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 is to evaluate whether runoff from such mercury mines has affected water quality in surrounding ecosystems. Geochemical studies of mine wastes and surface and groundwater in these areas will help to understand any adverse effects to surrounding ecosystems. We will also be conducting geochemical studies in additional areas where there is altered and mineralized rock with potentially high concentrations of heavy metals.