M.A. Norton, 1983. "Kemmerer Area, Lincoln County Wyoming", 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 Kemmerer area seismic line is in T22N, R114 and 115W, Lincoln County, Wyoming. The line is an east to west traverse across the Hogsback Thrust plate which is the youngest and most eastern major thrust fault of the Idaho-Wyoming-Utah thrust belt salient. The Hogsback thrust carries an imbricated sequence of sediments ranging from the Upper Cretaceous through the Mississippian Madison Limestone in the upper plate. The footwall of the Hogsback thrust is the western margin of the Green River basin. The Green River block consists of a complete stratigraphic sequence ranging in age from Cretaceous to Cambrian. Drilling has confirmed the imbricate structure of the upper plate. Repeat sections of the Permian Phosphoria through Mississippian Madison were encountered in the upper plate in Well Nos. 1 and 2. Well No. 2 penetrated the Hogsback thrust and drilled a normal sequence of Lower Cretaceous through Jurassic Nugget in the Green River block. Surface geologic features consist of several north to south trending folds and a north to south normal fault. The upper plate folding is related to the ramping of the overthrust plate and subsequent imbricate faulting which results in a stacked section in the core of the fold.
The depth conversion of the seismic section illustrates one of the classic problems in overthrust exploration. The apparent seismic time structural rollover in the subthrust Green River block is a velocity anomaly produced by the higher velocity Paleozoic rocks thrust over the lower velocity Mesozoic strata. The overthrust belt of Western Wyoming has been the scene of numerous discouraging attempts to interpret and drill subthrust structure. This example points up the need for good quality seismic data and meticulous velocity studies to make more reliable structural interpretations of subthrust structures in the overthrust belt.
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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.