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Peleoecological and Sedimentological Characteristics of Sarmatian Sediments from the Hrvatsko Zagorje Basin (Croatia)

Miocene deposits of the Hrvatsko zagorje Basin belong to the south-western marginal belt of the Pannonian Basin System. Sedimentological, paleontological and mineralogical investigations were performed on three outcrops of Sarmatian deposits located on the North- western part of Hrvatsko zagorje. Sarmatian sediments of this area were deposited in two depositional environments of reduced salinity: near shore deposits composed of conglomerates, sandstones, biocalcirudites, biocalcarenites and marls, and offshore deposits with local input of clastic material represented with marls and silts with sand intercalations. The mineral association of the sands and silts which consists of garnet, dolomite, glauconite, tourmaline, zircon and rutile indicate a local origin of the material. Marls predominantly consist of calcite and clay minerals, while quartz and feldspars are less abundant. The calcite content varies from 20 to 80 %. Among clay minerals, in the less than 2 μm insoluble residue fraction, smectite, illite, chlorite and kaolinite were determined. Furthermore, the deposits of these facies associations contain numerous fossil species. The deposits determined as near shore are rich with typical Sarmatian macrofossils: Ervilia dissita dissita, Ervilia dissita podolica, Irus (Paphirus) gregarius dissitus and Mactra vitaliana eichwaldi. The association of foraminifera which consists of Anomalinoides dividens and Elphidium reginum indicates a Lower Sarmatian age. Besides typical Sarmatian fossils, in these deposits numerous microfossils redeposited from Badenian, Lower Miocene and Eocene sediments are present as well. Offshore deposition characterised by Elphidium hauerinum and Porosononion granosum association of foraminifera indicates the Upper Sarmatian age. Dinoflagellate cysts Polysphaeridium zoharyi, Lingulodinium machaerophorum and Spiniferites spp. of the open marine environment and prasinophytes phycomas Tytthodiscus mecsekensis and Hidasia racemosa, from restricted environments indicate Polysphaeridium zoharyi – Lingulodinium machaerophorum Zone (Pzo-Lma) of Sarmatian age. The development of the Sarmatian from the North-western part of the Hrvatsko zagorje Basin is in accordance with the developments in other parts of the Central Paratethys.

Sarmatian; Hrvatsko Zagorje Basin; near shore deposits; offshore deposits

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