K. Hinz, 1983. "Reflection Seismic Record Across the Northwest Sulu Basin", 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 Sulu Sea is a marginal sea which is bordered in the northwest by the island of Palawan and in the southeast by the Sulu Archipelago. The northeast trending volcanic Cagayan Ridge divides the Sulu Sea into the Northwest Sulu basin and the Southeast Sulu basin.
A seismic line across the Northwest Sulu basin is shown. Between the Palawan shelf and an acoustic basement high of unknown nature lies a northwest-trending sedimentary basin. The thickness of the sediments is about 8,000 m (26,247 ft) in the center of the basin according to refraction seismic measurements and gravity modeling. A middle Miocene age is assumed for the distinct unconformity between 2.5 and 3 secs (two-way traveltime).A chaotic-diapiric zone about 25 km (15.5 mi) wide exists in the center of the basin which can be followed over a length of about 150 km (93 mi). The configuration and the internal structural style of the chaotic-diapiric zone have some similarities with diapiric structures of the oil-bearing province of West Sabah. The observed chaotic-diapiric zone within the Northwest Sulu basin is interpreted to represent a melange, formed in pre-middle Miocene time and which was reactivated by strike-slip motions of the North Palawan block along the Ulugan Bay fault in the late Neogene to Recent.
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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.