Arquitectura estratigráfica, ambientes de depósito y geocronología de la Formación Olinalá (Pérmico tardío), noreste de Guerrero, México

The Olinalá Formation is a marine-continental Permian sedimentary succession of ~860 m thick, which is exceptionally exposed in the northeast of the Guerrero state, in southern Mexico. The depositional architecture of this sedimentary succession indicates a mixed carbonatesiliciclastic homoclinal ramp system. The U-Pb ages of detrital zircon grains set from two basal sandstones of the Olinalá Formation yielded a weighted mean maximum deposit age of 268±5 Ma, which agrees with a Wordian biostratigraphic age based on ammonoids collected at its base. Wide continental siliciclastic facies diversity was identified in this sedimentary succession that represents a prominent fluvial incision valley of 130 m depth, at least. Instead, the siliciclastic and carbonate marine facies indicate a ramp system developed in warm waters and normal salinity conditions. The superposition of different environments in the Olinalá Formation through time allows us to deduce sea-level changes of a different magnitude, which partly controlled the sedimentary evolution of this unit.