C.H. Bruce, 1983. "Shale Tectonics, Texas Coastal Area Growth Faults", 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 terms growth, contemporaneous, synsedimentary, and syndepositional have been used interchangeably to denote faults that formed simultaneously with sediment deposition. These faults are characterized by thickening of sediment on the downthrown side, where rollover (reverse drag) is common. Although several mechanisms, such as basement tectonics, deep salt or shale movement, slump across flexures, or slump at the shelf edge are often cited as causes for growth faults, the mechanisms that appear to have formed most structures in the southern and central Texas Coastal Area are differential compaction and gravitational sliding resulting from differential sediment loading.
In coastal Texas, where thick sections of high pressure shale are present in the deep Tertiary section and where salt diapirism is not dominant, extensive growth fault systems are developed that extend for several miles subparallel with the coast. The relation of these growth fault systems to the underlying thick high pressure shale section and the pre-Tertiary surface is illustrated in a diagrammatic cross section of the northern Gulf of Mexico basin (Figure 1). A seismic line (Figure 2; see also Figure 2 location map) illustrates three Miocene growth fault systems that are present under the continental shelf offshore from the central Texas Coastal area. These fault systems, along with scattered relatively small post-depositional faults, are characteristic of many structures found in this part of the Texas Coastal area. Growth fault systems 1 and 2 are typical of faults that are downthrown basinward.
Fault system 3 exemplifies faults formed primarily through gravitational sliding. Fault systems formed in this manner usually consist of one or more major faults that are downthrown basinward and are accompanied by several antithetic (adjustment) faults.
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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.