Fossils from the Silesian-Subsilesian series of the Polish Western Carpathians: the implications for changes in sea-level and the marine environment during the Albian-Turonian

Abstract

Fossils and exotics from the Albian-Cenomanian deposits of the Western Polish Carpathians are discussed in relation with changes in depositional environments. Environmental conditions were controlled by geotectonic activity, sea-level changes and also anoxic and biotic events. During the Albian-the Early Cenomanian, and in the Turonian the fall in sea level led to increased supply of coarse-grained material rich in siliceous and sometimes calcareous bioclasts and exotics. This cyclic process has contributed to changes in the marine biota. In the Albian monogenic foraminiferal assemblages with the surficial epifauna corresponding to the organic influx and oxygen deficiency (OAE 1b) were evolved into more variable associations including deep infauna, which indicated more aerobic conditions. Under these conditions also preserved planktonic and calcareous benthic fossils, which indicated the supply of terrigenous material from shallow-water environments and land. During the Albian-Turonian transition intensive subsidence and volcanic activity associated with eustatic sea-level rise led to intensive production of phytoplankton. The sea-surface productivity and enhanced upwelling resulted in expanded short-term oxygen minima at the end of the Albian (OAE 1d) and the Cenomanian (OAE 2). In the latter interval benthic forms almost extinct while siliceous and calcareous plankton survived. In the Turonian changes in sea-level and sedimentary regime led to re-colonization of the basin bottom.