Behaviour of the oyster Rhynchostreon suborbiculatum assemblages in a Cenomanian-Turonian river dominated marginal-marine environment: multidisciplinary study from the Pieniny Klippen Belt (Western Carpathians, Slovakia)

Abstract

ABSTRACT The tens of metres thick shell accumulations within the Cenomanian-Turonian strata of Western Carpathians enabled a complex study of ecological and geochemical proxies in relation to behavioural patterns of oyster Rhynchostreon suborbiculatum. Integration of geological and palaeobiological approaches enabled comparisons between one of the most famous fossil oyster species and several Recent bivalves. The analysis of grain size (Qz) and major oxides, together with taphonomic and population analysis, reveals a high-energy marginal-marine environment in the sedimentation area of the Orlové Sandstone. The life conditions of the association of bivalves, gastropods and polychaetes were influenced by the fluctuating influx of freshwater due to climatic changes that occurred during a dynamic period of the Late Cretaceous. A shift in the prominent control of biological production caused a massive increase in α-diversity, in conjunction with a change in the trophic structure of the studied system. The ecological responses of organismal association were also analogous to Recent representatives inhabiting marginal-marine environments. Size and allometric analyses of oysters forming monospecific assemblages show that their high density correlates with smaller shell sizes, indicating that intraspecific competition for food and space most intensified at times of the lowest salinity.