Volcanic Rifted Margin along the TX LA Gulf of Mexico

http://gsa.confex.com/gsa/2008AM/finalprogram/abstract_148893.htm

Volcanic Rifted Margin along the Texas-Louisiana Gulf of Mexico Transitional Lithosphere
2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 289-6
Presentation Time: 9:50 AM-10:05 AM
Potential Field Evidence for a Volcanic Rifted Margin along the Texas-Louisiana Gulf of Mexico Transitional Lithosphere
MICKUS, Kevin, Dept. of Geosciences, Missouri State University, Springfield, MO 65897, kevinmickus@missouristate.edu, STERN, Robert, Department of Geosciences, Univ of Texas at Dallas, P.O. Box 830688, MS FO21, Richardson, TX 75083-0688, KELLER, G. Randy, School of Geology and Geophysics, University of Oklahoma, 100 East Boyd, Norman, OK 73019, and ANTHONY, Elizabeth Y., Geological Sciences, University of Texas at El Paso, El Paso, TX 79902
Volcanic rifted passive margins (VRMs) are characterized by the eruption of large quantities of lavas, seaward-dipping reflectors consisting of a mixture of volcanic and sedimentary deposits, and high velocity lower crust; VRMs form at some transitions between oceanic and continental crusts. Because the transitional crust of the Gulf of Mexico passive margin is buried beneath thick sediments (including seismically opaque salt) the nature of this transitional crust is poorly known. Because of the abundance of dense and magnetic mafic igneous rock, gravity and magnetics are powerful tools for identifying VRMs where other techniques cannot. Regional aeromagnetic data indicates that a large amplitude magnetic maximum over land parallels the Texas-Louisiana coastline from the Mexican border to Lafayette, LA. The Bouguer gravity anomaly map is less distinctive with either a small amplitude, positive anomaly or no significant anomaly. More distinctive on the Bouguer gravity anomaly map is a gravity maximum 150 km seaward of the magnetic anomaly which also parallels the coastline. There is a corresponding magnetic maximum, however the width and amplitude is smaller than the land-based magnetic anomaly. To quantify the sources of both the magnetic and gravity anomalies, a 2.5-D model was constructed along a profile from Mesoproterozoic crust of the Llano uplift to probable oceanic crust in the Gulf of Mexico. Constrained by results from geological and seismic refraction studies, the best fitting model indicates that a highly magnetized/dense layer up to 24 km and 240 km wide can explain the observed magnetic and gravity anomalies. The preferred model indicates that the transition from the unextended craton to the oceanic crust consists of two zones: 1) nonmagnetic inner zone of gradually thinning crust and 2) a highly magnetic and dense outer zone of seaward-thinning crust corresponding to a VRM similar to that along the Vøring margin of Norway.
2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM
General Information for this Meeting
Session No. 289
Lithospheric Structure and Geologic Evolution of the Gulf of Mexico Passive Margin
George R. Brown Convention Center: 322AB
8:00 AM-12:00 PM, Wednesday, 8 October 2008
Geological Society of America Abstracts with Programs, Vol. 40, No. 6, p. 445
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© Copyright 2008 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.  http://gsa.confex.com/gsa/2008AM/finalprogram/abstract_148893.htm

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