Biostratigraphy and paleoenvironmental analysis of benthic foraminifera and radiolarians in Paleogene Variegated Shales in the Skole Unit, Polish Flysch Carpathians

Abstract

Analiza biostratygraficzna i paleośrodowiskowa paleogeńskich pstrych łupków w jednostce skolskiej (Karpaty fliszowe), w oparciu o otwornice bentoniczne i radiolarie We studied Paleocene to middle Eocene variegated shales in the Skole Unit of the Polish flysch Carpathians at the Dylągówka sections in order to understand their depositional environments, using data on agglutinated foraminifera, Radiolaria and mineralogy. These deposits have been placed in the Paleocene Rzehakina fissistomata foraminiferal Zone, and in the lower through middle Eocene Glomospira spp. Assemblage Zone, Saccamminoides carpathicus Zone, and Reticulophragmium amplectens Zone of Geroch and Nowak ( 1984) which we correlate with the Buriella clinata, Phormocyrtis striata striata and Theocotyle cryptocephala radiolarian zones. The deposition of variegated shales took place below the calcite compensation depth in the lower bathyal zone. The foraminiferal morphogroup and radiolarian faunal analyses indicate that paleoenvironmental changes during the Paleocene through middle Eocene caused changes in sedimentation rates, in nutrient supply, and oceanic circulation. The “Radiolaria Flood” in lower and middle Eocene deposits may have been caused by a change of surface circulation in the Carpathian basins, emphasised by the relatively slow rate of sedimentation below the CCD, and the mineralogy of fine-grained sediments were conducive to the preservation of radiolarian sceletons.