MONTES, CAMILO¹ and ROBERT D. HATCHER, Jr.^2
1University of Tennessee, Knoxville, TN
²Department of Geological Sciences, University of Tennessee, Knoxville, TN; and Environmental Sciences Division, Bldg. 1509, MS-6400, Oak Ridge National Laboratory, Box 2008, Oak Ridge, TN 37831

Abstract: Three-Dimensional Structure of the Girardot Belt: A Sample of the Structure of the Cordillera Oriental, Colombia

The three-dimensional structure and deformation of a segment of the Cordillera Oriental of Colombia is analyzed using detailed geologic mapping, strain analysis, subsurface information, and remote sensing. The Girardot belt, a complex area along the western flank of the Cordillera Oriental, shares structural and stratigraphic features with the Upper Magdalena Valley and the Cordillera Central. This deformed belt contains faults that further north are thought to accommodate much of the northwestward displacement of the Cordillera Oriental, as well as large dextral strike-slip faults from the Cordillera Central. In addition, this belt is the only place where Jurassic intrusive bodies (not basement) belonging to the Cordillera Central domain are present in the western foothills of the Cordillera Oriental. This unique overlap facilitates the study of the relationship (both in space an time) between a strike-slip dominated orogen (Cordillera Central), and a thrust dominated one (Cordillera Oriental). Also, syntectonic deposits and neotectonic features allow to accurately date the relative timing of events.

The study of three dimensional deformation and structural geometry in the Cordillera Oriental will help solve the inconsistency that exists between regional balanced cross-sections, and tectonic models of the Caribbean. Balanced crosssections assume that no deformation has taken place along the strike; about 100 km of NW-SE horizontal shortening has been estimated invoking a doubly vergent fold-thrust geometry. This implies that deformation paths are perpendicular to the trend of the Cordillera (NW-SE dip-slip). On the other hand, kinematic plate tectonic reconstructions predict that the Cordillera Oriental of Colombia experienced oblique convergence throughout the Cenozoic as a result of its location between the Caribbean and South American plates. This contradiction may introduce significant errors and distortions in estimates of horizontal shortening, hydrocarbon maturation and migration histories, and basin reconstructions.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas