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The Role of Inherited Salt Structures of the Isthmian Saline Basin Province on the Northern Deformation Front of the Sierra de Chiapas, Southeastern Gulf of Mexico


The Isthmian Saline Sub-basin in the Southeastern Gulf of Mexico is part of a foreland basin complex. These pre-existing salt structures exert a strong control on the regional tectonic styles and kinematics of the fold belts in the Chiapas and Campeche areas. Parts of the salt basin are already incorporated in the Chiapas fold belt and adjoining fold belts. The Isthmian Saline Sub-basin and the front of Sierra de Chiapas Range provinces represent a major exploration challenge due to their structural complexity, which is partly controlled by the distribution of Jurassic salt sediments and present-day salt structures. The salt distribution, the evolution of the diapirs and minibasins since the Jurassic and their impact on the regional tectonic evolution of the deformation front of the fold belts are still poorly understood. Regional tectonic analysis based on 3D seismic reflection data, well data and geological maps provided by PEMEX give insights in the tectono-stratigraphic evolution of the salt basin and adjacent mountain front. The N-S trending, E-vergent “Cerro Pelon” anticline, which is located just North of the modern deformation front allows to study the salt basin extend and controls of pre-salt basement structures on salt deposition and regional tectonic evolution. In the Oligocene and Miocene foreland basin, the fold core exposes Middle Jurassic sediments (Todos Santos Formation) time-equivalent to the salt sediments and Eagle Milles Formation of the Northern Gulf of Mexico. Towards the northern portion of the anticline some of the exploration wells reported the presence of diapir salt, whereas none of the wells south of the anticline have encountered salt. Preliminary seismic interpretation results show that the onshore salt basin is characterized by spectacular salt structures including 10 km tall salt diapirs and minibasins with up to 6 km thick Paleogene-Miocene sediments sourced from the near by mountain ranges. Early salt anticlines, salt walls and pillows formed during early Cretaceous times. Contractional deformation in Paleocene to Miocene times caused by the lateral movement of the Chortís block transformed the salt anticlines into tall contractional diapirs and salt tongues and created large intervening depocenter with up to 6 km thick sediment fill.