T15 The Structure and Evolution of the North American Lithosphere: An Integrated Perspective

Sunday, 27 October 2013
8:00 AM - 12:00 PM
Room 401

CRUSTAL AND UPPER MANTLE STRUCTURE OF THE SOUTHERN OKLAHOMA AULACOGEN AND SURROUNDING REGIONS BY THE ANALYSIS OF RECEIVER FUNCTIONS, PN TOMOGRAPHY AND GRAVITY DATA

Paper number: T15-11
Program: Technical Sessions
Time: 10:30 AM – 10:45 AM

Authors

Abstract

The Southern Oklahoma Aulacogen (SOA) is a major tectonic feature in the south-central United States is characterized by a large intrusion of mafic igneous material and a series of northwest-trending faults in the Early Cambrian. These structures were reactivated in the late Paleozoic. Receiver function (RF) modeling and Pn tomography of EarthScope transportable and backbone seismic data together with gravity modeling were used to determine if features related to the Early Cambrian tectonic events are still present in the crust and upper mantle today. The RF analysis identified three discontinuities within the crust and upper mantle: 1) upper crust-middle crust (the base of the Paleozoic sedimentary layer, thickness 4-11km), 2) crust-mantle (Moho) and 3) the Hales discontinuity in the upper mantle. The thickest sedimentary sections occur within the Anadarko and Hollis-Hardeman basins with an underlying possible Proterozoic basin southeast of the Amarillo-Wichita uplift. Moho depths ranged from 36-48 km with the deepest sections along the Amarillo-Wichita uplift and the shallow sections under the Anadarko and Hollis-Hardeman/Proterozoic(?) basins. The thick crustal sections under the Amarillo-Wichita uplift can mostly be explained by accretion of mantle material depleted during rifting. The Hales discontinuity is deepest (90 km) under the Amarillo-Wichita uplift and this feature may be related to the early Cambrian rifting that formed the SOA. Pn tomography and gravity modeling helped confirm the location of the low velocity zone under the Amarillo-Wichita uplift. If the low velocity zone under the Amarillo-Wichita uplift is indeed related to the extraction of iron during formation of the SOA and relic features related to ancient rifts are preserved in the crust and upper mantle, more detailed geophysical studies can be used to determine the detailed nature of these features and the true origin of the SOA.