SEDIMENTOLOGY AND PROVENANCE ANALYSIS OF UPPERMOST PALEOZOIC-MESOZOIC FLUVIAL SUCCESSIONS ORIGINALLY MAPPED AS THE MATZITZI FORMATION, MEXICO

During Permian time, the continental masses amalgamated to form Pangea the last supercontinent in the Earth history. The Matzitzi Formation in southern Mexico is a unit interpreted as the record of a fluvial system draining western equatorial Pangea. The age of the Matzitzi Formation is controversial. Paleontological data indicates that this unit was deposited during Late Permian time. However, in the last few years, U-Pb zircon dates from sandstone and felsitic peperite samples revealed that the Matzitzi Formation is a mixture of different fluvial successions that were deposited from the Late Permian consolidation of Pangea to its early Mesozoic breakup. Considering this scenario, the Matzitzi Formation is not a single unit, but rather a mixture of different formations that were deposited at different times and in different tectonic settings. In this work, we present new sedimentological and provenance analysis data for the different fluvial deposits previously grouped within the Matzitzi Formation. Our data show that the different fluvial successions originally grouped within the Matzitzi Formation display differences in the sedimentary facies, architectural elements, and provenance. Therefore, a detailed sedimentological characterization and provenance analysis of these fluvial deposits will permit an exhaustive redefinition of the latest Paleozoic-early Mesozoic stratigraphy of southern Mexico . The analyzed sandstones of Matzitzi Formation are metamorphiclastic and associated to an anastomosed fluvial system, meanwhile, rocks originally mapped as Matzitzi Formation are metamorphi-vulcaniclastic in composition and deposited in a braided river. Finally, considering that the biggest mass extinction on Earth (The Great Dying) occurred during the Permian-Triassic boundary, this stratigraphic reassessment will help paleontological studies in understanding the effects of this global extinction event on subaerial environments, by easily determining what was deposited before and what after the Permian-Triassic boundary.