HR: 0800h
AN: T11D-1297    [Abstracts]
TI: Integrated Geophysical Methods to Examine the lithosphere beneath the of the Southern High Plains
AU: Ozyavas, A
AF: Texas Tech UNiversity, Dept. of Geosciences, Texas Tech, Lubbock, TX 79409 United States
AU: * Gurrola, H
EM: harold.gurrola@ttu.edu
AF: Texas Tech UNiversity, Dept. of Geosciences, Texas Tech, Lubbock, TX 79409 United States
AB: The high plains of west Texas have a more complex basement structure than the flat featureless surface would imply. This region is subject to some of the largest gravity anomalies in the continental U.S. Analysis of gravity data suggests that mafic intrusions, uplifts, lower crustal upwarps and shallower layers in the upper mantle are responsible for most of the small wavelength (less than 150 km) gravity anomalies in this region. Anomalies of this wavelength have been modeled by several previous investigators. We focus here on modeling the long wavelength anomalies that have previously been filtered out as regional anomalies. Regional gravity anomalies still show a tremendous gradient from a gravity low in the west and high gravity in the east. To try to model deep lithospheric structure we apply long wavelength pass filters to focus on regional anomalies. The entire gravity anomaly for wavelengths greater then 400 km could be modeled as a layer then this to about 90 km beneath the Rift and deepens to 115 km at the Texas New Mexico boarder and then thins slightly to the east. We then filtered these data to analyze adapt with 250 km wavelengths and longer. We did not allow the depth to this previous 90 to 120 km layer to change and found the Moho to be 35 km deep beneath the Rio Grande Rift thickening to 56 km beneath Lubbock, Texas (these depths were derived from receiver function analysis and are consistent with LaRistra images) but this did not account for a gravity low across most of western New Mexico. To match this long wavelength gravity anomaly it was necessary to place a thick "rift pillow" beneath the Rio Grande rift that is thickest near the rift but gradually thinning and pinching out near the Texas boarder. The geometry of these layers are consistent with tomographic results form the LaRistra project.
DE: 8110 Continental tectonics--general (0905)
DE: 7205 Continental crust (1242)
DE: 1219 Local gravity anomalies and crustal structure
DE: 1299 General or miscellaneous
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting