Origin of trace fossils in Polish Carpathian flysch

Fifteen features of trace fossils on flysch sandstone soles have been found useful in distinguishing between pre-depositional traces of mud-inhabiting animals and post-depositional traces of sand-dwellers. The Polish Carpathian flysch ichnofauna of 55 genera and 145 species, including 41 ichno-genera that occur at least in part on sandstone soles, is dominated both in number of taxa and number of specimens by traces of mud inhabitants, and most traces, both of mud- and sand-dwellers, were produced by infaunal deposit-feeders. Because mud was the temporally dominant substrate, the mud-dwellers were much more abundant over long periods of time, but the fauna of turbidites and similar sands may have been nearly as diverse and abundant at any given moment as the mud fauna at another. The currents depositing these sands eroded surficial layers of mud and excavated any burrow fillings in almost every case. The flysch ichnofauna differs from observed trace assemblages of modern deep-sea substrates in that the former consists almost exclusively of burrows, while surface traces dominate the latter.