Depositional environment and biofacies characterization of the Upper Pennsylvanian–Lower Permian deposits of the San Salvador Patlanoaya section (Puebla, Mexico)

Abstract

The San Salvador Patlanoaya section (Puebla State of Mexico) has been subdivided into seven informal members labeled A–F. Members C–F have been dated as Missourian to Leonardian (equivalent to Kasimovian to Kungurian, i.e. lower Upper Pennsylvanian to upper Lower Permian). Members C–E display a shallowing-upward trend as does member F. The biodiversity of these carbonate deposits outcropping in the San Salvador Patlanoaya section is relatively low, although multiple microfossils (algae, small foraminifera, fusulinids and fish remains) are represented. Member C consists of calcarenitic limestone interpreted as distal tempestites interbedded with shaly limestone facies. These storm beds are composed mainly of silt, sand-sized quartz grains and bioclasts. Member D corresponds to coarse bioclastic limestones represented by calcareous tempestites and channel beds with erosional bases. Member E is composed of green shales and cross-bedded sandstones and gravelly conglomerates. Member F corresponds to a condensed package of limestones and interbedded siliciclastics and is Cisuralian (Early Permian) in age. Member G consists of condensed black shales and limestone nodules. The results of the study have significant implications for recognition of climatic and/or sea-level fluctuations in bioclastic–siliciclastic facies during the Late Pennsylvanian–Early Permian. The skeletal limestones and channel sandstones, common throughout the Pennsylvanian–Permian section, provide a constraint on palaeobathymetry, with the water depth fluctuating frequently around a position below, but near, the storm wave base.