Facies sequence of Triassic-Jurassic red beds in the Sierra Madre Oriental (NE Mexico) and its relation to the early opening of the Gulf of Mexico

Abstract

The configuration of Upper Triassic grabens in the Gulf of Mexico rift system is pointed out by the suture zones of late Palaeozoic plate convergence. Rifting particularly started on both sides of the ancient magmatic arc. The taphrogenic red beds of the Huizachal Formation in the Sierra Madre Oriental represent the western parts of this system. The early syn-rift sediments are characterized by fining upward cycles of a fluvial environment with a low-sinuosity channel pattern. Later on, decreasing of relief intensity caused the change to a rather meandering system. Climate was evidently semiarid during that time. The petrographic composition of the clastic rocks suggests a nearby sedimentary-metamorphic basement. The transition to early post-rift sediments is marked by an angular unconformity. Its formation approximately coincides with the first emplacement of oceanic crust in the central parts of the Gulf basin. The early post-rift sediments of the La Joya Formation show, within a single fining upward megacycle, the transition from terrestrial to marine conditions that persisted up to the beginning of Cenozoic time.