A hypersaline ichnoassemblage from the Middle Triassic carbonate ramp of the Tatricum domain in the Tatra Mountains, Southern Poland

Abstract

The Middle Triassic of the Tethyan domain contains heavily bioturbated carbonates known as vermicular limestones. In the Tatricum domain in the Tatra Mountains, Western Carpathians, these were deposited on a restricted carbonate ramp below the fair-weather wave base. Sedimentological and geochemical evidence points to a hypersaline depositional environment. The vermicular limestones contain an impoverished ichnoassemblage of the Cruziana ichnofacies dominated by Planolites. Small size Thalassinoides is less common, ? Balanoglossites and Rhizocorallium are rare, and Helminthopsis, ? Phycosiphon and Taenidium are very rare. The ichnoassemblage points to environmental stress, related foremost to hypersaline conditions and less so to lowered oxygenation. Trace fossil diversity and abundance diminishes from totally bioturbated limestones to dolomitic limestone and dolostones, and disappears in the dolostones, probably due to an increase in salinity to values in which burrowing fauna is eliminated. The repetitive occurrence of the vermicular limestones and associated facies reflects partly fluctuations of salinity, which were probably climatically controlled.