K. Hinz, 1983. "Line Bgr 78-19 (24-Fold Stack) from the Continental Margin of Queen Maud Land / Weddell Sea—Antarctica", 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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Two units are recognizable on the reflection seismic records within the continental margin of Queen Maud Land, Antarctica: 1) a buried lower unit the top of which is marked by the distinct Weddell Sea "continental margin unconformity"; and 2) an upper sedimentary unit.
The dominant features of the lower unit beneath the "Weddell Sea unconformity" are a suite of oceanward-dipping reflectors (sequence WS-4 and called "EXPLORA Wedge,") which has a similar seismic pattern and velocity distribution as the wedge of oceanward-dipping subacoustic base ment reflectors off Norway and an outer basement high.
Four depositional sequences (sequence WS-1 to WS-3A) are recognizable within the upper unit. Since no boreholes have been drilled on the continental margin of Queen Maud Land, an attempt was made to assess the age of the regional unconformities by assuming that the Antarctic glacification was the dominant short-period mechanism in the Neogene which causes relative changes of eustatic sea level. Under this assumption, the lower boundary of sequence WS-1 has been correlated with the middle Miocene Antarctic ice cap formation. The lower boundary of sequence WS-2 was correlated with the development of an unrestricted Circum Antarctic Current in the late Oligocene.
The erosional unconformity between sequence WS-3B and WS-3A is thought to represent a major climatic-glacial threshold at the Oligocene/Eocene boundary.
The "Weddell Sea unconformity" is interpreted to mark the end of the Jurassic tectonicmagmatic/volcanic regime, which preceded the opening of the Weddell Sea.
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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.