engleski

Evidence of Early Sarmatian volcanism in the Hrvatsko Zagorje Basin, Croatia - mineralogical, geochemical and biostratigraphic approach

A bentonite clay layer is documented in Sutla-II column in the Hrvatsko Zagorje Basin, which belongs to south-western marginal belt of the Pannonian Basin System. The origin of the clay is attributed to the alteration of felsic to intermediate volcanic ash, deposited between horizontally laminated marls in a marine environment. Provenance analysis indicates that the marls were sourced from mixed, dominantly felsic, source rocks. Smectite present in marls is therefore not solely of terrigenous origin and may be also related to volcanic ash weathering. Based on the fossil content an inference has been made suggesting Early Sarmatian age of the sediment hosting the bentonite clay intercalation. The sedimentological and palaeontological data are in favour of the sedimentation at an inner shelf area marked by unstable palaeoenvironmental conditions. The upper part of Sutla-II column was deposited in the high-energy environment that consists of impure biocalcarenite and biocalcrudite coupled with fossiliferous litharenite, which all mark an intensive redeposition of older rocks and fossiliferous formations. The bentonite clay likely originated from distant volcanic eruptions, presumably located in the Apuseni Mts. or Eastern Carpathians within the Carpathian-Pannonian Region during the post-rift stage of the back-arc Pannonian Basin System development.

Carpathian-Pannonian Region, Sarmatian volcanism, bentonite, provenance, biostratigraphy

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