Title

Receiver Function Study of the Rifted Margin of the Gulf Coast Plain: A Pilot Project

Abstract

The Gulf Coast Plain (GCP) is one of the deepest sedimentary basins in the world; as a result little is known about the basement structure beneath this region. The few refraction seismic investigations of the GCP found sediment depths of 15 to 20 km, underlain by severely attenuated continental or transitional crust. A 2-D refraction investigation along the Texas-Louisiana Border, found the crystalline continental crust to be as little as 10 km thick, underlain by an anomalous lower crust/upper mantle body interpreted to be depleted mantle; a "rift pillow" developed during the Late Paleozoic through Early Mesozoic rifting. This rift pillow coincides with the magnetic high that parallels the coast line along the entire Texas GCP. This poster will present new receiver functions (RF) results using data from stations of the EarthScope Backbone array throughout the GCP and a temporary pilot deployment of five broadband instruments between Junction, TX and San Antonio, TX that took place in 2008. The stations at Kingsville, TX (KVTX) and Hockley, TX (HKT) are close to the coast. Receiver functions for KVTX have a very strong P20s phase that is likely from the sediment-basement contact and a Moho Ps phase at about 45 km deep. This depth to the Moho is greater than might be expected for a coastal setting. The 45 km depth is, however, similar to that found for the base of the "rift pillow" observed in the Northern GCP. KVTX is located in the magnetic high anomaly that was associated with the rift pillow in the Northern GCP. The station at Junction (JCT) appears to have about a 42 km depth to the Moho which is typical of a station from the stable continental (cratonic) setting. The station at Nacogdoches, TX (NATX) is situated in older Gulf Coast sediments in a similar position relative to GCP rifting as would be expected a few km outboard of San Antonio. The 36 km depth to the Moho estimated for KVTX appears shallower than those Moho depths estimated for JCT and KVTX which could be the result of attenuated, rifted continental crust that is inboard of the anomalous "rift pillow". Receiver functions (RFs) computed for the temporary deployment between JCT and San Antonio appear to have a uniform depth to Moho of about 45 km. These stations probably did not reach the point at which rifting thinned the crust. Refraction results from a line shot by Cram (1962) found about a 34 km depth to the Moho at a point about half way between San Antonio and the coastline. So the severe crustal attenuation appears to be outboard of San Antonio.

Meeting Name

AGU Fall Meeting (2009: Dec. 14-18, San Francisco, CA)

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Body waves; Lithosphere; Continental margins: divergent; Continental tectonics: extensional

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2009 American Geophysical Union (AGU), All rights reserved.

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