Offshore to onshore transition in the Upper Viséan paleontological record from the Paprotnia section (Bardo Mts., West Sudetes)

Abstract

This report provides detailed information on the taphocenosis succession from the Paprotnia series exposed in the western part of the Bardo Mts. (West Sudetes) and regarded as a temporal equivalent of the pelagic crenistria Limestone (cd III a, Upper Viséan). Five taphocoenoses have been recognised in the investigated section, which is composed of claystone and mudstone shales, greywackes and subordinately by carbonates. They differ mainly in terms of the relative frequency, size and state of preservation of specimens, and less in terms of their taxonomical composition. Changes in their vertical succession are coincidental with changes in the lithological record. Analyses of their taxonomical composition and various parameters of their paleontological record, reviewed herein, were used to estimate the paleoenvironment. Taphocoenosis I was deposited under low-energy conditions, probably in oxygen-deficient waters below the wave base. Taphocoenosis II was most likely accumulated in the environment located between the storm wave and fair weather wave bases, in oxygenated water. The fossils of assemblage III developed in a turbulent environment of well-oxygenated and relatively high-temperature shallow water. The organisms of taphocoenosis IV reflect renewed settling of the shallow seafloor during a short period of low energy conditions interrupted by the rapid delivery of a large quantity of terrigenic deposits. The uppermost part of the section, composed mainly of greywackes, which contain only the remains of terrestrial plants (taphocoenosis V) may suggest proximity to land. Both the paleontological and lithological features of the Paprotnia series indicate gradual environmental changes from offshore to onshore conditions. Consequently, the Paprotnia series represents the shallower facies equivalent of the pelagic crenistria Limestone, which is widespread in the Kulm facies of Variscan Europe.