Identifying Structural Styles in Colombia

Wayne P. Wilson, Robert E. Van Nieuwenhuise, Mark R. Steuer, and German Ojeada

Much of our understanding of the earth is from the study of surface geology and seismic, but many surface structures are responses to deformation which occurred below sedimentary layers. The practice within the petroleum industry is to use top-down processes of analyzing the surface to understand the subsurface, and observed surface structural styles tend to influence seismic interpretations. Yet many conditions which influenced the structural styles seen at the surface are different at depth. Since seismic is a time representation of the earth, many interpretation pitfalls may exist within areas of complex geology. Also, its reliability decreases with depth and with increasing geologic complexity. Forward modeling and pre-stack depth migration technologies are used to pr vide true depth images of the seismic data. Even with these advances in seismic imaging technology, the interpreter needs to incorporate additional data into the interpretation. Accurate structural identification requires the interpreter to integrate seismic with surface geology, remote sensing, gravity, magnetic data, geochemistry, fault-plane solutions from earthquakes, and regional tectonic studies. Incorporating these types of data into the interpretation will help us learn how basement is involved in the deformation of overlying sediments.

A study of the Eastern Cordillera of Colombia shows the deformation to be dominantly transpressional in style. Euler deconvolution of the areomagnetic data shows a highly fractured basement, steep fault lineaments, en echelon structures, and complex fault patterns, all of which would be typical of wrench-type deformation. Available surface geology, regional studies, earthquake data, and forward modeling support this interpretation.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California