Compressional Features Across the Caribbean Margin of Colombia
J.W. Ladd, M. Truchan, 1983. "Compressional Features Across the Caribbean Margin of Colombia", 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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Lamont-Doherty seismic Line &130 is one of a suite of seismic lines shot by R/V ROBERT D. CONRAD across the Caribbean margin of Colombia. This margin, which Case (1974) called the South Caribbean basin, is part of a zone of convergence between the oceanic Colombian basin and the continent of South America. This zone of northwest to southeast convergence extends to the southeast onshore where thrusting and uplift of the Sierra Santa Marta occurs (Kellogg and Bonini, 1982). While there is great variability in detail from one seismic section to another, the main features of this margin are illustrated by Line C-130 — the continental slope is underlain by a thick, mildly deformed sediment section. Near the toe of the slope a highly deformed wedge of sediments which forms the South Caribbean Deformed Belt abuts the deep undeformed oceanic sediments of the Colombia basin. A map view of this region is best depicted on the Caribbean tectonic map by Case and Holcombe (1980).
Whereas other seismic sections more clearly show oceanic crust beneath the deformed toe of the slope, Line C-130 is particularly expressive of the similarity of this region to more generally recognized subduction zone complexes. The setting and internal structure of the deformed toe with the numerous diffraction hyperbolae suggesting landward dipping reflectors is similar to many accretionary prisms around the world. Adjacent seismic sections confirm the imbricate nature of the landward dipping reflectors. The thick, mildly deformed sediments of the Rancheria basin are similar to accumulations in basins that form the forearc regions of many subduction zones worldwide.
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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.