Palaeoceanographic regime during the O xfordian– K immeridgian in the W estern T ethys recorded by radiolarian assemblages in the siliceous sediments of the P ieniny K lippen B elt, C arpathians

Water temperature and productivity patterns during the middle Oxfordian through the late Kimmeridgian on the intrabasinal high in the Pieniny Basin, a part of the Western Tethys, have been identified by qualitative and quantitative analyses of radiolarian assemblages. These analyses have been conducted on cherts (radiolarites), siliceous limestones, and shales from the Polish part of the Pieniny Klippen Belt, Carpathians, in order to establish the habitat of radiolarian groups and use them to evaluate temperature and productivity changes over the time interval characterized by abundant siliceous deposition. A significant enrichment of well‐diversified radiolarians, dominated by a thermocline radiolarian species group, was recognized within the middle Oxfordian–earliest Kimmeridgian interval. This coincides with a decrease in deeper dwelling radiolarian taxa, high radiolarian diversity, and fluctuating values of the thermocline surface radiolarian index, as a consequence of a shallowing thermocline and more intense nutrient supply from deeper water masses. This was interpreted to record a prevailing upwelling regime in this area. We suggest that it might have been induced by seasonal changes in direction and position of trade and monsoon winds in the western sector of the Tethys, and we propose a model of oceanic circulation during this time interval.