Abstract

The described succession crops out close to the Sasso di Castalda village (PZ). It is made up by Calcari con Selce fm (late Ladinian-Rhaetian) and Scisti Silicei fm (Rhaetian-Late Jurassic). The Calcari con Selce fm (Alaunian-Rhaetian) contains well bedded cherty micrites, some calcarenites and shales horizons that become important in the upper part (Transitional interval). The Scisti Silicei fm is divided in 4 members: 1) Buccaglione m., with siliceous shales, radiolaritic cherts and calcarenites, mainly in the upper part (Rhaetian); 2) Nevera m., with grey shales, calcarenites and black cherty layers (Rhaetian-Liassic); 3) Serra m:, made or red shales, cherty radiolarites and calcarenites (lower Liassic); 4) Acqua Sulfurea m., with well bedded green and whitish cherts (Middle to Late Jurassic). This new study allows us to define the biostratigraphy or each member. The evolution or this succession demonstrates: a) the deepening of the basin from Norian to Middle Jurassic; b) tectonic activity at the platform margins mainly from the Rhaetian to the Lower Jurassic, documented by the increasing amount of calcarenites and cirudites with fossils of different ages; c) the existence of anoxic conditions around the Triassic/Jurassic boundary; 4) the connections or the Lagonegro basin with the oriental Tethyan paleobiological province and its separation from the Proto-Atlantic domain during the Late Triassic.

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