Courtesy, 1983. "Melville—Northwest Territories, Canada Line No. 7 by Texaco Canada Resources Ltd.", 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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Line No. 7 was recorded as a part of a large reconnaissance seismic survey on Melville Island in the Canadian Arctic in April of 1973. The survey was designed to add subsurface definition of features defined from surface geology studies (see attached location plats).
Melville Island is situated mainly within the Arctic Fold Belt, a 483-km (300-mi) long structural province dominated by east to west trending folds. This fold belt is flanked by the Sverdrup basin to the north and the stable shelf bordering the Canadian Shield to the south.
During the early Paleozoic this was the site of the Franklinian Geosyncline with mio geosynclinal sediments being deposited throughout the area from Early Ordovician to Mid-Devonian time. Prior to the development of the miogeosyncline peneplanation occurred and, during the Cambrian, clastics and carbonates were likely deposited on a broad shelf.
In Early Ordovician time a broad stable shelf persisted with the shelf edge located along the present northern coast of Melville Island. Thick carbonate buildups along the shelf edge ponded the shelf to the south and east causing restricted conditions and the deposition of evaporites (Baumann Fiord and Bay Fiord formations). By Late Ordovician time, evaporite deposition had given away to extensive shallow shelf carbonates with some localized lagoonal evaporite deposition on the shelf interior. The shelf carbonates thicken northward and seaward to the shelf edge (Thumb Mountain Formation).
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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.