Cobbold, Peter R.1, Luis A. Gomez2
(1) Rennes University, 35042 Rennes, France
(2) ECOPETROL, Bogota, Colombia
ABSTRACT: Style and Timing of Andean Contraction, Middle Magdalena Basin and Cordillera Oriental, Colombia
In Colombia, the Cordillera Oriental and adjacent Middle Magdalena Basin have developed
mainly in a contractional tectonic setting since Mid-Cretaceous times. Using selected data
from surface and subsurface, we describe the style and timing of deformation, paying
attention to three-dimensional aspects and incidence on petroleum systems.
The style of contractional deformation is strongly influenced by fault reactivation. Mesozoic extensional faults have reactivated as reverse or strike-slip faults, contributing to inversion of deep rift basins. Paleozoic thrusts have reactivated repeatedly in compression. Basement-involved structures have caused uplift on both flanks of the Cordillera Oriental. Above them, detachments in organic-rich mudstones and Early Cretaceous evaporites are associated with emerald-bearing veins. More generally, thin-skinned folds, thrusts and detachments are common within Mesozoic strata. In three-dimensions, structures reflect interference between faults of various lengths and orientations. For example, constriction has developed in the apex of the Cordillera Oriental. Positive flower structures are common almost everywhere. Triangular basins provide challenging opportunities for exploration, especially in the Magdalena Basin and central parts of the Cordillera Oriental.
The timing of deformation reflects plate motions. Aptian to Oligocene phases of compression, due to oblique convergence of the Nazca and Caribbean plates with South America, resulted in right-lateral motions along N-S faults. Neogene phases, reflecting collision of Panama and convergence of oceanic plates, resulted more in crustal thickening. Foreland basins have developed since the Aptian. Timing is of vital importance to hydrocarbon trapping and preservation. In the Magdalena Basin, the critical moment is typically Paleogene.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.