Early Senonian radiolarian microfauna and biostratigraphy from the Western Vardar Zone (Western Serbia)

Abstract

Early Senonian radiolarian microfauna and biostratigraphy from the Western Vardar Zone (Western Serbia)The studied deposits represent the sedimentary cover of ophiolitic mélange of the Western Vardar Zone Belt. An association of sediments that correspond to a primary pyroclastic material occurs in the Upper Cretaceous carbonate sediments near the village of Struganik (Western Serbia). This is an interlayer within mainly carbonate sediments represented by limestone, clayey limestone and marlstone. It is made of the following succession: a lamina made of crystalline quartz, sanidine, plagioclase and biotite and a layer of clay. The clay is of the smectite type, highly crystalline. The age of the radiolarian assemblage from the clay layer is assigned to Early Senonian, based on the co-occurrence of radiolarian taxa:Dictyomitra formosaSquinabol,Dictyomitra koslovaeForeman,Dictyomitra torquataForeman,Alieviumsp. cf.A. superbum(Squinabol) andPseudoaulophacussp. cf.P. venadoensisPessagno. The pyroclastic material was brought into the water environment by a cloud that was formed after an explosive eruption whose exact location cannot be determined at the moment. According to geological data, there are no indications of volcanic activity before the Late Cretaceous in the wider studied area. Marine sedimentation continued after gravitational differentiation of pyroclastic material. The results of petrological and sedimentological investigations reveal that Struganik Limestone originated in a deep-water environment and that the sedimentation area was on the continental slope.