ABSTRACT: Depositional Styles and Structural Controls of the Tertiary Section in the Magdalena Valley, Central Colombia

LAVERDE, F. E., HOCOL-Shell, Cartagena, Columbia, and ROBERT RESSETAR* and RICHARDSON B. ALLEN, University of South Carolina, Columbia, SC

The Upper and Middle Magdalena valleys of Colombia contain a Tertiary fluvial sedimentary sequence that was deposited in the ancestral foreland basin of the Northern Andes. These rocks represent the synorogenic detritus of the Cordillera Central. They include hydrocarbon reservoirs in the Magdalena Basin, and they are the proximal equivalents of deltaic reservoirs in the Llanos Basin to the east.

Recent mapping in the western Cordillera Oriental permits a refined interpretation of the stratigraphic and structural significance of these rocks. In the area southwest of Bogota, the Eocene Gualanday Group grades eastward from proximal alluvial fan deposits to

finer-grained fluvial rocks. Northwest of Bogota in the Middle Magdalena Valley, the Eocene Chorro Group contains similar facies, but direct correlation with the units to the south breaks down in the area of the Girardot fold belt. This suggests that the structural differentiation of the Upper and Middle Magdalena Valleys had occurred by middle Eocene time and that subsequent deposition was controlled by separate tectonic events. We suggest that the principal deformational phases in the northeastern Upper Magdalena Valley occurred during early Eocene, late Oligocene, and Miocene to Holocene times, whereas those in the southeastern Middle Magdalena Valley took place in the early Eocene, late Eocene, and Miocene to Pliocene.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)