Provenance of Carboniferous-Permian sedimentary units in southern Mexico: evidence for peri-arc basin evolution during the Pangea assembly.

The Oaxacan Complex Carboniferous-Permian sedimentary cover in southern México records provenance shifts through time, reflecting the collision between Gondwana and Laurentia to amalgamate Pangea. The integration of petrological analysis and LA-ICP-MS U-Pb zircon geochronology from Santiago, Ixtaltepec and Yododeñe formations compared with adjacent terranes suggests that: (1) during the Early Mississippian, the Santiago Formation received sediments mainly from local sources such as the Oaxacan Complex and Tiñu Formation, with minor contributions from adjacent peri-Gondwana sources. The magmatic activity may have started during this time (~359–346 Ma) (2) during the Late Mississippian (Ixtaltepec Formation), detrital zircon grains of Ediacaran-Cambrian age are dominant, derived from sediments either related to the Pan-African/Brasiliano orogeny or the opening of the Iapetus Ocean; (3) during the Late Mississippian-Middle Pennsylvanian, intercalated marine volcaniclastic sandstone (Ixtaltepec Formation) provides the first record of Carboniferous arc-related volcanism reported in southern Mexico, dated between 330 and 308 Ma; (4) the early Permian Yododeñe Formation records the exhumation and erosion of the sedimentary cover during the final stage of Pangea assembly. Rhyodacitic subvolcanic sills and lavas dated at ~282–270 Ma are present throughout the succession. Volcanism and ca. 360–308 Ma detrital zircon grains could be associated with a Carboniferous magmatic arc formed by subduction of the Rheic oceanic plate beneath Gondwana. Slightly younger detrital zircon and subvolcanic rocks dated at ~300–270 Ma are linked to a western Pangea arc developed in response to the subduction of the Paleo-Pacific Ocean following Pangea assembly. Our results suggest that the Carboniferous-Permian units were deposited in a peri-arc basin, sharing sediment provenance with the Maya and Coahuila blocks, the Sierra de Juárez Complex, and northwestern South America. [ABSTRACT FROM AUTHOR]