Tectonostratigraphic Evolution and Salt Tectonic Processes of the Isthmus Saline Basin, South-eastern Gulf of Mexico: Implication for Petroleum Systems and Exploration

The Isthmus Saline Basin (ISB) in the south-eastern Gulf of Mexico is part of an inverted foreland basin complex located on the Western Mexican rifted continental margin in front of the Sierra de Chiapas thrust belt. The contrasting structural architecture and a complex salt tectonic history are controlled by a combination of gravity-driven halokinetic processes, regional contractional tectonic processes and basement-involved strike-slip deformation as consequence of convergence between the Caribbean (Chortis Block) and North American plates. The aim of this research is the analysis of salt tectonic styles and kinematics of salt structures in the ISB. Regional 2D seismic lines and a 3D seismic survey have been combined with wells, outcrop data, gravity, magnetic and earthquake data from published maps to develop the first tectono-stratigraphic and kinematic analysis of the onshore Isthmus Saline Basin. Structural and stratigraphic interpretation results based on 2D and 3D seismic data provide: (1) Regional tectonic analysis, (2) insights into the salt tectonic processes and related depositional systems of the study area, and (3) basis for kinematic analysis using structurally balanced and restored cross-section. Contraction caused by the lateral movement of the Chortís block transformed the salt anticlines into tall contractional diapirs and created large intervening depocenters with up to 6 km thick. Contraction reached its peak deformation in Middle Miocene and Late Miocene times during strike-slip reactivation of basement faults due to sinistral transpression along the Sierra de Chiapas strike-slip fault system. Results of structural restoration shows that shortening varied from a minimum of 17% (7 km) to a maximum of 59% (24 km). This variation of shortening is controlled by the relationship between basement geometry and salt thickness which greatly influenced the size and style of salt structures. The reactivation of basement faults caused the development of reverse faults, thrust faults and positive flower structures which represent structural traps and new potential migration routes.