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

The Gulf of Mexico (GOM) has been subject of numerous geological studies as a major petroliferous basin and a key puzzle piece in the tectonic evolution of North America. The structural and stratigraphic evolution of early Mesozoic rift basins in E and S Mexico has variably been related to back-arc extension or GOM opening during Pangea break-up. The Huayacocotla Uplift in Hidalgo exposes early Mesozoic siliciclastic strata similar to those in Huizachal or Todos Santos rift basins. New field observations and detrital zircon (DZ) U-Pb data resolve the temporal and stratigraphic evolution of Huayacocotla basin. Stratigraphically, it exposes Permian (~268 Ma) volcanoclastic turbidites of the Tuzancoa Fm, unconformably overlain by marine sandstone and conglomerate of the Sinemurian-Pliensbachian (~194-182 Ma) Huayacocotla Fm and fluvial arkosic sandstone and conglomerate of the Callovian-Oxfordian (161-165 Ma) Cahuasas Fm. New chrono- and lithostratigraphic constraints and the marked angular unconformity between the Huayacocotla and the Cahuasas Fms imply two distinct rift pulses separated by ~20 Myrs and major depositional changes during Early to Middle Jurassic rifting. DZ U-Pb age spectra of the Tuzancoa, Huayacocotla, and Cahuasas Fms from Huayacocotla elucidate the local depositional evolution of the Jurassic syn-rift sequences and reveal a tectonic unroofing sequence characterized by a dominant initial presence of Permian age component in the basal Huayacocotla Fm and a distinct switch to mainly Proterozoic and Paleozoic ages in the Cahuasas Fm with a pronounced first-cycle Middle Jurassic arc signal. The youngest DZ ages point an initial phase of Early Jurassic rifting, linked to the syn-rift Huayacocotla Fm, prior to GOM opening, Yucatan Block translation, and GOM salt deposition (166-169 Ma). This early phase of rifting, predating the GOM, was likely linked to back-arc extension due to early Jurassic subduction roll-back. In contrast, the younger Callovian-Oxfordian Cahuasas Fm strata in the Huayacocotla Uplift are coeval with strata in the Huizachal basin and GOM opening, pointing to a regional second pulse of extension that was linked to GOM opening and Yucatan translation. The Huayacocotla basin appears to be a composite rift basin recording the protracted extensional evolution of E Mexico.