K. Hinz, 1983. "Line Bgr 76-11 from Central East Greenland Margin", 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 outstanding feature of the East Greenland continental margin between latitudes 67° and 72°N is a sedimentary wedge up to 5,000 m (16,400 ft) thick which unconformably overlies the top of the acoustic basement (sequence GR-5).
The top of the acoustic basement is marked by a flat to hummocky, continuous unconformity (labeled the top of rift phase or TRP-reflection horizon), often with subacoustic basement reflectors and diffractions beneath. This unconformity is interpreted to represent the end of a rift phase in the Oligocene. The irregular reflection pattern beneath this unconformity and the derived instantaneous velocity of about 4.5 km/sec (2.8 mi/sec) might represent a highly consolidated and faulted succession of Paleogene and even older sediments.
The overlying thick sedimentary wedge has been divided into the four depositional sequences GR-1 to GR-4. Sequence GR-4 is characterized by a subparallel bedding with some high amplitude reflectors and interval velocities which increase from about 2.5 km/sec (1.6 mi/sec) at the outer slope from 4 to 4.5 km/sec (2.5 to 2.8 mi/sec) beneath the present shelf. Sequence GR-4 is interpreted as representing a consolidated, interbedded succession of sandstones and shales of upper Oligocene to upper Miocene age.
The overlying and seaward-thinning sequences GR-3 and GR-2 have a prograding clinoform pattern suggesting strong outbuilding and upbuilding into a subsiding basin. Beneath the lower slope, a feature with a non-coherent pattern occurs within sequence GR-2 which is thought to represent a slumped mass. The uppermost sequence GR-1 is thin and is interpreted as representing mainly glacial and glacial-marine sediments.
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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.