B.A. Robison, 1983. "Low-Angle Normal Faulting, Marys River Valley, Nevada", 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 Tertiary history of the Basin and Range Province of the western United States is characterized by voluminous eruption of Eocene to Miocene age intermediate composition volcanic rock accompanied and/or directly post-dated by broadly distributed extensional tectonics (Lipman, Prostka, and Christiansen, 1972; Davis, 1980; Eaton, 1980; Zoback, Anderson, and Thompson, 1981). Within the last decade it has become increasingly recognized that much of the extension has been accommodated by low-angle and listric normal faulting (Anderson, 1971; Wright and Troxel, 1973; Proffett, 1977). The purpose of this paper is to illustrate and describe the subsurface geometry and evolution of one range-bounding low-angle normal fault and the associated sedimentary fill. It supplements seismic interpretations from the Basin and Range Province previously published by McDonald (1976) and Effimoff and Pinezich (1981).
Marys River Valley is located near the town of Wells in northeastern Nevada (Figure 1). The valley is bounded on the east by the Snake Mountains, a northeastward tilted range consisting of thrusted lower Paleozoic geosynclinal rocks unconformably overlain by upper Paleozoic strata (Gardner, 1968; Peterson, 1968). West of the valley lie outcrops of Tertiary age rhyolitic to andesitic flows, breccias, and tuffs as well as tuffaceous sedimentary rocks (Stewart and Carlson, 1978).
The reflection seismic profile presented here begins just west of the bounding fault of the Snake Mountains and trends approximately perpendicular to its near-surface trace. The profile extends west for 8.4 mi (13.4 km) and is relatively straight. High data quality and integration with additional seismic control and data from four nearby exploratory wells results in an internally consistent geologic interpretation.
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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.