Radiolarian faunas from the Late Callovian and Early Oxfordian deposits of the Kraków-Wieluń Upland, South Poland

This paper presents the result of research on radiolarian faunas from the Upper Callovian and Lower Oxfordian deposits of the Kraków-Wieluń Upland (South Poland). The studied material comes from boreholes Wodna 1, Trzebionka 2 and Trzebionka 3, and from outcrops at Górka near Trzebinia and Grojec. Two radiolarian assemblages, differing markedly in their species contents, I and II, have been identified. Assemblage I occurs in the Upper Callovian deposits. It has been found within Q. lamberti ammonitic Zone. In the number of specimens this association is dominated by the spherical, oval and conical forms of the Nassellaria group. Assemblage II is associated with the Lower Oxfordian deposits and it is characterised by the dominance of spongy radiolarians belonging to the Spumellaria group. Assemblage II has been found within Q. mariae and C. cordatum ammonitic zones. A correlation with the Tethyan radiolarian zones indicates that both assemblages can be assigned to U.A.Z. 8 (Late Callovian trough Early Oxfordian age). The radiolarians show features of Tethyan faunas which spread over epicontinental seas when communication with the Tethys Ocean opened. A change in the character of the radiolarian assemblage in the Lower Oxfordian suggests boreal influences as well as gradual shallowing of the basin.