A. Thomson, 1983. "Salt Rollers—East Texas Salt Basin", 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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This seismic line, as interpreted, illustrates salt "rollers" or "anticlines" as they appear on the west flank of the East Texas salt basin. The rollers occur in a belt approximately 32 km (20 mi) wide parallel to structural and depositional contours. Downdip (east) of the zone of salt rollers is a zone of piercement salt domes, which represent the maximum original thickness of salt in the basin. The piercement salt domes are described on a seismic line edited by Engleman and Kemmer (this volume); the line continues eastward from the east end of this line. Updip (northwest) the salt thins to a feather edge within 64 km (40 mi) of the northwestern end of this line. Salt deformation in this zone is restricted to a few low relief pillows. An extensional fault system, the Mexia-Talco Fault Zone, is located approximately 9.5 km (6 mi) northwest of the northwestern end of this line. This fault system is believed to represent a regional pull-apart, from which salt moved downslope (east) following deposition of the Jurassic carbonates. This movement, in addition to overburden loading is thought to have been largely responsible for the anticlinal forms seen here. Timing of salt movement is complex, and appears to be episodic in some areas and continuous in others.
Salt can be observed to have withdrawn almost completely on both flanks of the roller at shot point 425, as well as on the eastern flank of the roller at shot point 625. The up-turn of the Jurassic carbonates at the extreme eastern end of this line may represent the west flank of a "turtle" structure.
Hydrocarbon production is associated with many of the rollers, where it is obtained principally from Jurassic carbonates. The well at shot point 425 produces from a structure in the Smackover Limestone overlying a well-developed roller. Structures over rollers may persist high in the stratigraphic section, as exemplified by the well at shot point 620 which produces from Lower Cretaceous carbonates.
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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.