Regional Neogene Salt Tectonics in the Offshore Salina del Istmo Basin, Southeastern Mexico

Abstract

Compared with the northern Gulf of Mexico, little has been published on the tectonics of its southern equivalent in the Bay of Campeche, especially in English. A middle Miocene change in the Pacific plate kinematics created the southern Mexico Neogene belt. This is locally expressed as four main fold belts underlying most of the study area: the Agua Dulce, Marbella, Marbella Norte, and Catemaco fold belts. Each fold belt contains productive Upper Jurassic and Cretaceous sections and may be part of a much larger fold belt that merges with adjoining fold belts in the Chiapas and Campeche areas. During the final stages of folding, salt was squeezed from diapirs and extruded over the eroded and uplifted fold belts. The extruded salt coalesced to form the discontinuous Sal Somera canopy. The salt canopy or equivalent weld is roughly conformable with the underlying fold belts, indicating that the canopy extruded during the final stage of folding or soon after. Evacuation of the thickest parts of the salt canopy allowed the greatest Pliocene–Pleistocene subsidence and minibasin growth. Three counterregional minibasins formed by seaward evacuation of the underlying salt canopy in the Pliocene–Pleistocene. Counterregional systems dominate the study area, the largest of which forms the seaward boundary of the 100-km-long (62-mi-long) Pescadores minibasin. Some minibasins are floored by the allochthonous salt canopy or equivalent salt weld, others rest directly on the fold belts, and others are more deeply rooted.