Calpionellid biostratigraphy and sedimentation of the Biancone limestone from the Rudnica Anticline (Sava Folds, eastern Slovenia)

Abstract

Mt Rudnica in eastern Slovenia structurally belongs to the Sava Folds. The mountain itself is an exposure of the Mesozoic core of the Rudnica Anticline. The major part of the core is composed of Triassic rocks deposited on the NE margin of the Dinaric (Adriatic) Carbonate Platform, overlain locally by deep-marine Berriasian Biancone limestone. The latter formation was logged in a newly discovered section on the northern slopes of Mt Rudnica near the village of Loka pri Žusmu. The Biancone limestone of Mt Rudnica is mostly monotonous, calpionellid-bearing limestone with only minor up-section differences in colour, chert presence, and clay content. It is characteristic pelagic facies for the entire Tethyan Realm of the time. Using calpionellid as well as dinocyst biostratigraphy, the formation was subdivided into Early Berriasian Calpionella Zone - Alpina and Ferasini Subzones, Middle Berriasian Calpionella Zone - Elliptica Subzone and upper Berriasian Calpionellopsis Zone - Oblonga Subzone. Within the Early Berriasian part of the formation a synsedimentary slump was documented, whereas the largest increase in clay content is observed in the topmost, i.e. Late Berriasian part of the formation.