Cocorp Deep Seismic Reflection Traverse Across the Southern Oklahoma Aulacogen
R. Good, L. Brown, J. Oliver, S. Kaufman, 1983. "Cocorp Deep Seismic Reflection Traverse Across the Southern Oklahoma Aulacogen", Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces, A. W. Bally
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The Consortium for Continental Reflection Profiling (COCORP) recorded deep seismic profiles across the Southern Oklahoma aulacogen. The profiles run from the Hardeman basin, across the Wichita Uplift, and into the northern part of the Anadarko basin. The location of the COCORP lines and major geologic features are shown on Figure 1. The three major findings of the survey include evidence for: (1) an extensive Proterozoic basin lying south of the Wichita Mountains; (2) thrusting of the Wichita Mountains over the Anadarko basin by several kilometers; and (3) anticlinal structures within the Anadarko basin that can be interpreted as cored by blind listric thrust faults. These features are illustrated on the two seismic lines and the generalized geologic cross section. The following summary is abstracted from more detailed description published by Brewer et al (1981, in press).
The Southern Oklahoma aulacogen is a major tectonic element of the southern midcontinent. The exact definition of the aulacogen and even the time of the initiation is unclear, with some authors using the term for the deep Paleozoic Anadarko basin (the most obvious manifestation), while others suggest it also includes the Wichita Mountains and Hardeman basin to the south. The Southern Oklahoma aulacogen was placed within a plate tectonic framework by Burke and Dewey (1973) and Hoffman et al (1974), who suggested that the aulacogen may represent a "failed" rift arm which was reactivated by Pennsylvanian deformation associated with closure of an ocean to the southeast.
Initially, subsidence was thought to have started in the Late Cambrian with transgression of the basal Reagan sandstone over Precambrian basement. However, extensive studies by Ham et al (1964) showed that thick sequences of pre-Reagan sandstone, rhyolites, basalts, and metagraywackes are also present in this area. Ham et al (1964) suggested that major downwarping of the whole area occurred in the Late Precambrian or Early Cambrian, followed in the middle Cambrian by outpouring of basalts over the graywackes and intrusion by gabbros. Faulting and differential erosion was followed in the middle Cambrian by extrusion of silicic volcanic fields and intrusion of granites, forming what is now the Wichita Mountain block. Paleozoic subsidence and sedimentation was then concentrated in the Anadarko basin with deformation culminating in the Pennsylvanian.
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Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces
Until a few decades ago, structural and regional geology were traditionally the preserve of field geologists. They usually mapped areas of outcropping deformed rocks and supplemented their work by laboratory studies of rock deformation and by theoretical work. Structural geology became tied to the geology of uplifts, folded belts, and underground mines, all of which were accessible to direct observation. Since World War II we have witnessed a tremendous development of geophysics in oceanography and in petroleum geology. Academic geophysicists in oceanography led their geological colleagues into modern plate tectonics and industry geophysicists developed reflection seismology into a superb structural mapping tool that penetrated the subsurface.
Today we are facing a situation where instruction and textbooks in structural geology are almost entirely dedicated to rock deformation, analytical techniques in detailed field geology and summaries of plate tectonics. Illustrations based on reflection seismic profiles are virtually absent in textbooks of structural geology. These texts illustrate only the parts of the proverbial elephant, together with some conjecture, but without ever offering a glimpse of the whole elephant.
Some of the reason cited for the relative scarcity of published reflection profiles are: 1) the confidentiality of exploration data; 2) difficulties in the photographic reduction and reproduction of seismic profiles for a book format; 3) the two-dimensional nature of vertical reflection profiles; and 4) the obvious distortions in reflection profiles that are typically recorded in time.
The AAPG leadership felt that it was time to attempt to correct the situation and to produce this picture and work atlas. The first volumes, of what may become a series of volumes, are addressing an audience that includes: petroleum geologists concerned with structural interpretations; exploration companies that provide in-house training; the AAPG continuing education program; and academic colleagues interested in updating their curricula in structural geology by inclusion of reflection profiles from the “real world” in their teaching.
The atlas is not meant to be a textbook in reflection seismology (instead we listed some at the end of this introduction) nor a text in structural and/or regional geology. Our intent is simply to provide a teaching tool.