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Title: Recently discovered overthrusting northeast of Llano uplift along extension of San Marcos platform: new exploration frontier in central Texas

Abstract

TJB Resources recently completed gravity, magnetotelluric, and seismic geophysical surveys in San Saba and Mills Counties north of the Llano uplift, west of the Ouachita Disturbed belt. Significant results show overthrusting has occurred 60-70 mi west of the Ouachita Disturbed belt. Earliest thrusting could have occurred in the Silurian-Devonian from south or southeast. Faulting reoccurs during Pennsylvanian Ouachita thrusting and again in the Late Cretaceous. The primitive Llano uplift buttressed the allochthonous rocks moving north and west. Magnetotelluric and gravity data indicate the Llano uplift is a separate and distinct isolated remnant or terrain, with numerous igneous intrusions reaching to great depths. Associated with this thrusting is a major tectonic northwest-southeast lineament located parallel to the termination of the Cretaceous rocks, outcropping on the western edge of Mills and Lampasas Counties. This lineament is documented by east-west seismic lines displaying a 0.3-sec displacement and farther southwest a 1.1-sec displacement. Paleozoic fossils were found near the surface trace of the northwest-southwest lineament as observed on the east-west seismic line. This area was previously mapped as Cretaceous. Surface inspection found Paleozoic rocks containing crinoids, spirifers, and rugose corals, with beds dipping to 45/sup 0/, contrasted with the N2/sup 0/ regional dip surroundingmore » the lineament area. Well-log correlations from Marble Falls to Ellenberger range from 350 to 600 ft from east to west near the Llano uplift. The 60 to 70-mi frontal edge of the thrusting provides potential hydrocarbon traps along a north to northeast trend from central Texas to Oklahoma.« less

Authors:
; ; ; ;
Publication Date:
OSTI Identifier:
5160974
Report Number(s):
CONF-860624-
Journal ID: CODEN: AAPGB
Resource Type:
Conference
Journal Name:
Am. Assoc. Pet. Geol., Bull.; (United States)
Additional Journal Information:
Journal Volume: 70:5; Conference: American Association of Petroleum Geologists annual meeting, Atlanta, GA, USA, 15 Jun 1986
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; PETROLEUM DEPOSITS; EXPLORATION; TEXAS; CRETACEOUS PERIOD; DEVONIAN PERIOD; FOSSILS; SEISMIC SURVEYS; SILURIAN PERIOD; WELL LOGGING; FEDERAL REGION VI; GEOLOGIC AGES; GEOLOGIC DEPOSITS; GEOPHYSICAL SURVEYS; MESOZOIC ERA; MINERAL RESOURCES; NORTH AMERICA; PALEOZOIC ERA; RESOURCES; SURVEYS; USA; 020200* - Petroleum- Reserves, Geology, & Exploration

Citation Formats

McMurdie, D S, Bryan, J G, Gibson, M, King, T, and Sill, W. Recently discovered overthrusting northeast of Llano uplift along extension of San Marcos platform: new exploration frontier in central Texas. United States: N. p., 1986. Web.
McMurdie, D S, Bryan, J G, Gibson, M, King, T, & Sill, W. Recently discovered overthrusting northeast of Llano uplift along extension of San Marcos platform: new exploration frontier in central Texas. United States.
McMurdie, D S, Bryan, J G, Gibson, M, King, T, and Sill, W. 1986. "Recently discovered overthrusting northeast of Llano uplift along extension of San Marcos platform: new exploration frontier in central Texas". United States.
@article{osti_5160974,
title = {Recently discovered overthrusting northeast of Llano uplift along extension of San Marcos platform: new exploration frontier in central Texas},
author = {McMurdie, D S and Bryan, J G and Gibson, M and King, T and Sill, W},
abstractNote = {TJB Resources recently completed gravity, magnetotelluric, and seismic geophysical surveys in San Saba and Mills Counties north of the Llano uplift, west of the Ouachita Disturbed belt. Significant results show overthrusting has occurred 60-70 mi west of the Ouachita Disturbed belt. Earliest thrusting could have occurred in the Silurian-Devonian from south or southeast. Faulting reoccurs during Pennsylvanian Ouachita thrusting and again in the Late Cretaceous. The primitive Llano uplift buttressed the allochthonous rocks moving north and west. Magnetotelluric and gravity data indicate the Llano uplift is a separate and distinct isolated remnant or terrain, with numerous igneous intrusions reaching to great depths. Associated with this thrusting is a major tectonic northwest-southeast lineament located parallel to the termination of the Cretaceous rocks, outcropping on the western edge of Mills and Lampasas Counties. This lineament is documented by east-west seismic lines displaying a 0.3-sec displacement and farther southwest a 1.1-sec displacement. Paleozoic fossils were found near the surface trace of the northwest-southwest lineament as observed on the east-west seismic line. This area was previously mapped as Cretaceous. Surface inspection found Paleozoic rocks containing crinoids, spirifers, and rugose corals, with beds dipping to 45/sup 0/, contrasted with the N2/sup 0/ regional dip surrounding the lineament area. Well-log correlations from Marble Falls to Ellenberger range from 350 to 600 ft from east to west near the Llano uplift. The 60 to 70-mi frontal edge of the thrusting provides potential hydrocarbon traps along a north to northeast trend from central Texas to Oklahoma.},
doi = {},
url = {https://www.osti.gov/biblio/5160974}, journal = {Am. Assoc. Pet. Geol., Bull.; (United States)},
number = ,
volume = 70:5,
place = {United States},
year = {Thu May 01 00:00:00 EDT 1986},
month = {Thu May 01 00:00:00 EDT 1986}
}

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