Detrital modes of Permian sandstones in southern Italy

During Permian, the Pangea supercontinent experienced the most critical and dramatic restocking of its configuration. Meanwhile, in the Mediterranean region, the occurrence of late Paleozoic siliciclastic strata experienced peculiar tectonic and climatic environment. Here, we detail the Permian sedimentary succession types displayed in some portions of the circum-Mediterranean region, providing new insights about the composition of Permian siliciclastic strata of the basal Apulian Unit, in Puglia 1 well log, and the Sosio Valley succession in Sicily. Permian sandstones, and related mudrocks, record a synchronously phase of post- Variscan collision and subsequent final closure of Paleotethyan ocean. Sedimentological and stratigraphic framework, also associated to the distribution of mineralogical composition of sandstones and mudrocks, are pivotal factors to reconstruct the sedimentary evolution of the Permian paleogeography. The Apulia Unit played a critical role because it stood relatively still in the Mediterranean paleogeographical contest and received a great Permian sedimentary load. Nowadays these strata were intersected in Puglia 1 well between 7070 m to 6110 m in depth, for 960 m in thickness, with sandstone, mudstone and breccia mostly. Meanwhile a Sicily Permian succession (the San Calogero Formation) is well preserved, outcropping around the Sosio Valley (northwestern Sicily), by few tens of meters of marine sandstones and clays strata. Sandstones of the Puglia 1 Well are quartzolithic, with abundance of quartz and metasedimentary lithic fragments (mainly phyllite and schist). Feldspars are minor. Sandstones of the San Calogero Fm. in Sicily, are more variable in composition, from quartz-rich sandstone, to hybrid arenites and calclithite, and include abundant extrabasinal carbonate fragments and metasedimentary lithic fragments, as such as important contributions of intrabasinal carbonate grains. Interbedded volcanic and volcaniclastic layers are also present. These siliciclastic strata experienced a diverse burial history. The Puglia 1 succession presents moderate carbonate cements, that are dominant, and consist of crystals of dolomite, ankerite and calcite (related to dedolomitization/calcitization processes of the first carbonates. Mudrocks display K-enrichments, intense paleoweathering under a hot, episodically humid, climate with a prolonged dry season, and sediment recycling processes. Meanwhile Sicily succession is pervaded by carbonatic poikilotopic cements mostly, siliciclastic matrix and less iron cements. Quartz overgrowths are locally present. In terms of provenance, sandstone detrital modes are typical of quartzolithic sandstones, hybrid arenite and calclithite: that should be related to the erosion of upper crustal levels of the Variscan orogenic terranes , with most of metasedimentary and sedimentary rocks occurring in Calabria-Peloritani, southern Alps and in internal domains of the Circum-Mediterranean orogens.