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Book Chapter

Structure of the Mexican Ridges Foldbelt, Southwest Gulf of Mexico

R.T. Buffler
R.T. Buffler
University of Texas at Austin, Institute for Geophysics
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January 01, 1983


The Mexican Ridges foldbelt is an enormous belt of folded Tertiary strata that extends along the entire western Gulf of Mexico slope from about 25 N to about 19N lat. (Figure 1). The folds form long, linear, subparallel topographic features on the sea floor. The nature and origin of these folds has been the subject of debate since their discovery in the mid-1960s.

In 1975, the University of Texas collected a grid of multifold seismic data across the foldbelt in the southwestern Gulf (Figures 1 and 2). These lines were discussed in detail by Buffler et al (1979). The lines presented here are duplications of most of the figures included in this 1979 paper. The reader is referred to this paper for a more detailed discussion of (1) previous descriptions of the foldbelt, (2) descriptions of the University of Texas seismic data, and (3) conclusions regarding the origin of the foldbelt in light of the new deep-penetration seismic data. These figures are repeated again in this atlas because of the unique nature and origin of this large foldbelt. As far as we know, nothing quite like it has been described anywhere else in the world. in addition, this belt may have enormous petroleum potential, as deep-water turbidite sands probably occur within the deformed Mexican Ridges seismic unit (drilled in DSDP holes 90 and 91; Figure 1), and "bright spots," possible gas hydrates, and fluid contacts are observed on several lines in the crests of anticlines.

The main conclusion inferred from the seismic data is that the foldbelt is probably a huge late-Tertiary gravity-slide feature detached from flat-lying older Tertiary strata below along a decollement or deformed zone within weak, possibly geopressured, slope shales. It is characterized by a large growth-fault system at its upper limit at the present shelf-break. The folds and associated imbricate thrust faults indicate regional compressional stresses acting in an east to west direction. Deformation apparently began in Miocene time and probably is continuing today.

A much more detailed analysis of the entire southern Mexican Ridges foldbelt was completed recently (Pew, 1982) Pew analyzed a more extensive set of seismic data, including older singlechannel data in the area.

Details about the collection and processing of the University of Texas seismic data shown here are included as an Appendix.

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AAPG Studies in Geology

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
A. W. Bally
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American Association of Petroleum Geologists
ISBN electronic:
Publication date:
January 01, 1983




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