Geology of state-owned submerged lands.




McGowen, J.H.; Morton, R.A.

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University of Texas at Austin, Bureau of Economic Geology


A comprehensive geological investigation is being conducted of Texas-owned submerged lands which include the bays, lagoons, and inner continental shelf extending from the Gulf shoreline seaward for 10.3 miles. The study is a joint effort between the Bureau of Economic Geology and the U.S. Geological Survey with major funding from the Coastal Zone Management Program of the General Land Office of Texas. Data collection consists of 6700 bottom sediment samples and 4100 nautical miles of high-resolution seismic reflection profiles. Sediment samples were subsampled for textural and geochemical analyses and descriptions of benthic fauna. Practical applications include delineation of (1) potentially active faults and shallow diapiric structures, (2) high concentrations of heavy metals, (3) biologically productive areas, (4) bottom substrates with markedly different engineering properties and (5) environmental assessment of pollutants in the shelf and estuarine systems. Basic geological studies will include seismic stratigraphy as well as geometry, facies distribution, and chronology of Quaternary sediments. Sedimentological data will augment other efforts such as mapping of mineral resources and determination of sediment budget. Preliminary results include lithofacies maps of surface sediments based on a three component classification (sand, mud, shell). These maps show that fault related topographic features on the inner Texas shelf control sediment type in some areas. High concentrations of shell and relict sediments, as well as major faulting, are closely related to fluvial-deltaic systems such as the Holocene Rio Grande and Brazos-Colorado deltas. Relative rates of sedimentation and general directions of sediment dispersion are inferred from sediment types, thicknesses, textures, and trace element distributions.




wetlands; coastal zone; sediments; stratigraphy; geology; mineral resources; sedimentation