--> ABSTRACT: A Salt-Related Domic Structure Postdating Thrust Tectonics: An Example from the Cordillera Oriental, Colombia, by Camilo Montes, Mauricio Baquero, Daniel Castillo, Martin Cortes; #91020 (1995).

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A Salt-Related Domic Structure Postdating Thrust Tectonics: An Example from the Cordillera Oriental, Colombia

Camilo Montes, Mauricio Baquero, Daniel Castillo, Martin Cortes

Detailed geological mapping and a comprehensive structural analysis revealed a remarkable set of extensional features never recognized before within the characteristic compressive structural domain of the Cordillera Oriental. These extensional structures are defined by slightly radial jointing and faulting, step-like block faulting, and bridge faults in a gently dipping domic structure. Older thin-skinned thrust faults and joints in the area of the dome were rotated to almost vertical whereas thrust-related structures not far from it show no later folding. Left-lateral, strike-slip fault surfaces were also reactivated by normal faulting, and were slightly rotated in a radial fashion.

Two phases of deformation were interpreted to exist: the first one would be characterized by northwest verging thrust faulting and an associated left-lateral fault system. Later extensional activity would be the responsible for the extensive reactivation of the pre-existing, near-vertical planes of weakness, and for the rotation of originally, near-horizontal thrust fault surfaces. The style of the latter event is characterized by step-like normal faulting with moderate to non-existent folding associated. Two main rotation axis were identified for particular domains of the domic structure converging towards its center.

These observations indicate that the activity of an intrusive salt body beneath the study area postdates the main phase of deformation in the Cordillera Oriental. Interestingly enough this possible salt body matches a trend of salt occurrences in the area which does not coincide with the main structural trend of this part of the Cordillera. Such a salt trend might be the expression of a preorogenic structure beneath the main detachment faults of the Cordillera.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995