HR: 0830h
AN: T31E-0875    [PDF]
TI: High Resolution Aeromagnetic Survey of the Big Bend National Park Region, Texas
AU: * Drenth, B J
EM: bjdrenth@utep.edu
AF: University of Texas at El Paso, Department of Geological Sciences, 500 West University, El Paso, TX 79968 United States
AU: Finn, C A
EM: cfinn@usgs.gov
AF: USGS, Federal Center, Denver, CO 80225 United States
AB: The Big Bend National Park region of west Texas has experienced a complex geologic history, including such events as the Paleozoic Ouachita orogeny, Laramide compression, Tertiary magmatism, and Basin and Range/Rio Grande rift extension. During late fall of 2002, a high resolution aeromagnetic survey was flown over this region for the purposes of improving present geologic maps and developing a better understanding of igneous stratigraphy in the region. Total-field anomaly data was acquired with a 400 meter flight-line spacing and continued to a draped surface at a constant level of 400 meters above the ground surface. Reduction to pole, pseudogravity, and analytic signal filters were applied to the total-field anomaly grid, revealing many features that correlate well with mapped geology and many additional, unmapped features. A set of northeast trending, long wavelength anomalies correlate well with mapped trends of rocks of the Ouachita orogenic belt, especially a magnetic low that correlates with the Ouachita interior zone. A prominent magnetic and pseudogravity high indicates the presence of a large (30 by 25 km) igneous body underlying the Chisos Mountains. Superimposed on this anomaly is a set of smaller anomalies that correlate with mapped locations of the Pine Canyon and Sierra Quemada calderas. Numerous short wavelength anomalies correlate with mapped locations of Tertiary volcanoes and intrusions, plus many similar anomalies indicate the presence of unmapped and buried intrusions. In the Christmas Mountains, a large negative anomaly indicates that a magnetic reversal is recorded in the rocks of this area. Northwest-trending normal faults produced by Tertiary extension produce magnetic anomalies where they cut and offset magnetic rocks of the South Rim and Chisos Formations, most notably within the Terlingua Abaja and Punta de la Sierra fault belts. These faulting trends are enhanced in the analytic signal map, which will allow delineation of unexposed faults by extrapolation from their surface exposures. Future fieldwork to collect magnetic rock property data will allow detailed modeling to take place.
DE: 0905 Continental structures (8109, 8110)
DE: 0925 Magnetic and electrical methods
DE: 8110 Continental tectonics--general (0905)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting