MULTI-STAGE JURASSIC RIFTING IN EASTERN MEXICO AND IMPLICATIONS FOR GULF OF MEXICO OPENING

The Gulf of Mexico (GOM) is a major petroliferous basin and a key piece in the tectonic evolution of North America. The architecture and stratigraphy of early Mesozoic rift basins in Mexico have been related to the break-up of Pangea and the opening of the GOM. In the Sierra Madre Oriental of eastern Mexico, early Mesozoic marine and continental siliciclastic strata are exposed in the Huayacocotla Uplift that are structurally juxtaposed against Mesoproterozoic Oaxaquian (Grenville) basement by normal faults, subsequently reactivated as thrust faults within the Mexican orogen. New stratigraphic, petrographic provenance and detailed detrital zircon (DZ) U-Pb geochronology data presented in this study clarify the stratigraphic, depositional, and temporal evolution of this syn-rift basin strata and their relationship to the GOM. The Huayacocotla Uplift exposes Permian turbidite deposits of the Tuzancoa Fm that are overlain by Sinemurian-Pliensbachian marine syn-rift sandstone and conglomerate of the Huayacocotla Fm. These syn-rift strata are unconformably overlain by Oxfordian fluvial sandstone and conglomerate of the Cahuasas Fm. The lithologies, and angular unconformities between these formations document two discrete Early to Middle Jurassic rift pulses. The petrography suggest progressive unroofing of extensional fault blocks composed of volcanic and crystalline basement rocks. The DZ U-Pb data point to initial local unroofing of a Permian volcanic arc rocks – likely associated with the E Mexican Arc - during deposition of the early the Huayacocotla Fm, transitioning to more dominant sourcing Mesoproterozoic rocks during progressive footwall exhumation. Paleozoic and early Mesozoic grains become characterize the Cahuasas Fm. The maximal depositional ages for the rocks in the Huayacocotla Uplift document an Early Jurassic Huayacocotla rift pulse associated with subduction rollback and back-arc extension during the Sinemurian-Pliensbachian. In contrast, Cahuasas Fm deposition during late Callovian- Oxfordian rifting appears to correspond to GOM opening and Yucatan Block translation. These new detailed data indicate a multi-phase rift evolution with distinctly different tectonic drivers – early Jurassic back-arc extension followed by late Jurassic diffuse extension along the shear margin of the western GOM.