Radiolarian faunas from the Late Callovian and Early Oxfordian deposits of the Kraków-Wieluń Upland, South Poland
Abstract
Promienice w osadach górnego keloweju i dolnego oksfordu Wyżyny Krakowsko-Wieluńskiej
This paper presents the result o f research on radiolarian faunas from the Upper Callovian and Lower Oxfordian deposits o f 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 o f specimens this association is dominated by the spherical, oval and conical forms o f the Nassellaria group. Assemblage II is associated with the Lower Oxfordian deposits and it is characterised by the dominance o f 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 o f 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 o f the basin.
This paper presents the result o f research on radiolarian faunas from the Upper Callovian and Lower Oxfordian deposits o f 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 o f specimens this association is dominated by the spherical, oval and conical forms o f the Nassellaria group. Assemblage II is associated with the Lower Oxfordian deposits and it is characterised by the dominance o f 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 o f 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 o f the basin.