Provenance analysis and thermochronology of the Chivillas Formation, Mexico: a record of basin formation and inversion in the southern Sierra Madre Oriental during the Early Cretaceous-Palaeogene

Sandstone petrography, zircon and apatite U-Pb geochronology, and apatite geochemistry of Early Cretaceous siliciclastic turbidites interbedded with basalt (Chivillas Formation) in the southern Sierra Madre Oriental, Mexico, indicate local provenance from westerly basement sources. Three main detrital populations were observed in both the zircon and apatite geochronology: Meso-Neoproterozoic, Carboniferous-Permian, and Early Cretaceous. Apatite Sr/Y vs light rare earth element discrimination diagrams indicate that most Precambrian grains have affinity with high-grade metamorphic rocks and most Phanerozoic grains with igneous rocks. These results are consistent with derivation from exposed crystalline sources within the Acatlan-Oaxacan block including the Grenvillian Oaxacan Complex, the East Mexico Arc, and the Early Cretaceous continental arc. The compositional disparities observed in individual samples reflect differences in source of individual turbiditic flows comprising the Chivillas Formation. We surmise that various rivers from the northern and southern Acatlan-Oaxacan block drained into the basin during the Early Cretaceous. Furthermore, detrital apatite fission-track analyses of Chivillas sandstones yielded mostly 42-40 Ma ages (Eocene) that post-date the shortening of the Mexican orogen in the southern Sierra Madre Oriental. Thermal models calculated based on track lengths indicate rapid exhumation of Chivillas rocks at 46-36 Ma, which is the time of the development of the Tehuacan Valley and reactivation of the Oaxaca Fault System as a normal fault.