A.W. Bally, 1983. "Tectonics of Compressional Provinces - Introduction", 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
Download citation file:
Following the outline given by Harding and Lowell (1979, reprinted in atlas volume 1), we now include seismic profiles across structural provinces that are characterized by dominant horizontal compression.
Section 321 on crustal profiles includes two contrasting tectonic settings. The first illustrates basement deformation in the inner zones of collisional fold belts. Such deformation is directly associated with decollement folding and thrusting in the adjacent outer portion of the same folded belt. The second structural setting deals with foreland deformation that involves the basement.
Section 322 focuses on the details of the basement involved foreland deformation. Most of the profiles are from the Colorado-Wyoming Rocky Mountains. The structures of that area have, for some years, been the subject of considerable controversy (Berg, 1962; Stearns, 1971, 1975; Sales, 1968; V. Matthews, 1978; and Gries, 1968). The COCORP profile shown in atlas volume 2 (Allmendinger et al) clarified a number of aspects, and the seismic profiles presented here seem to reinforce the notion that the boundary faults of a significant number of uplifts in the Wyoming-Colorado Rockies are reverse or thrust faults that involve the basement. These contrast with the well-known decollement thrust faults of the adjacent Wyoming fold belt (see section 341 on decollement tectonics).
Section 33 shows a number of examples of inverted extensional features. The main thought here is that basins or half-graben and graben systems are to varying degrees turned inside out by compressional forces that reverse the deformation along pre-existing normal faults (see Drozdzewski, part 341, for an additional example). It appears that in most cases, inversions are associated with strike-slip (wrench) faults systems and, in a different setting, with salt tectonics.
In all cases, a detailed three-dimensional kinematic analysis of inversion structures, based on reflection seismic documentation, has yet to be undertaken.
Note also that inversion structures may occur in quite diverse structural settings. Some of the best known examples occur in northeast Europe (see paper by Ziegler, section 33, and Ziegler, 1982). Other examples occur in a back-arc basin setting (see Harding, section 33), on Atlantic-type margins (see Davis, section 33; Petrobras, Potiguar Basin, section 223, atlas volume 2), and finally the section across the north flank of the Uinta Mountains (Clement et al, section 322) can also be viewed as a Laramide inversion of a Proterozoic rift system.
Profiles in the following major subdivision - 34, detached sediments - are grouped into decollement tectonics related to the subduction of continental lithosphere (A-subduction) and decollement tectonics related to the subduction of oceanic lithosphere (B-subduction). This subdivision has been discussed by Bally and Snelson (1980).Section 341 contains a number of profiles illustrating A-subduction related decollement and the associated foredeep basins. For additional information on decollement tectonics in folded belts the reader is referred to Bally et al (1966), Dahlstrom (1969, 1970), Dixon (1982), Harris et al (1981), Price (1981), Roeder et al (1978), Royse et al (1975), and Suppe and Namson (1979). For the relationship of foredeeps to folded belts, we refer to Beaumont et al (1982).
Note that foredeeps are also illustrated in a more stratigraphic context in section 123 (atlas volume 1) by Curnelle and Marco, and in section 125 (atlas volume 1) by Kirschner et al.
In section 342, we have combined sections that illustrate accretionary wedges associated with B-subduction zones, as well as some sections illustrating features associated with fore-arc basins and with back-arc basins. For an introduction into the tectonics of active margins, we suggest Dickinson and Seely (1979), Isacks and Baranzangi (1977), Ringwood, (1977), Sholl et al (1980), and Hayes ed., (1980).
Note that active margin tectonics are also illustrated in section 13 by Suzuki (atlas volume 1), and in section 42 (this volume) in the papers by Harding on Andaman Sea, by D'Onfro et al on southeast Asia, and by Roberts on Palawan.
Figures & Tables
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.