Taphonomy of ichthyofauna from an Oligocene sequence (Tylawa Limestones horizon) of the Outer Carpathians, Poland

Abstract

Oligocene deposits at Rudawka Rymanowska (Silesian Nappe, Polish Outer Carpathians) contain abundant fish remains. Sandstones and shales, displaying features of low-density turbidity-current deposits, contain isolated fish bones and scales segregated as detrital elements. Fish skeletons occur in laminated Tylawa Limestones (taphonomic Assemblage A), considered to be pelagic in origin, and in laminated claystones (taphonomic Assemblage B), probably also pelagic. Assemblage A contains very well preserved skeletons; Assemblage B contains only 40 to 60% of well preserved skeletons, the rest being partially disintegrated. The very good state of preservation of skeletons in the Tylawa Limestones indicates cessation of decay soon after death. In the claystones, the fish carcasses had arrived at the sea floor in various stages of soft tissue decay, and the carcasses rested on the sea floor for variable lengths of time. Deformations of the vertebral columns in all specimens studied are considered to be natural post-mortem ones. Taphonomic analysis supplements sedimentary data to reconstruct an array of physical/biogenic agents and events that acted intermittently at the Oligocene sea floor in other parts of the Carpathians and of the Caucasus.