A diverse deep‐marine Ichnofauna from the Eocene Tarcau sandstone of the Eastern Carpathians, Romania

Abstract

The Paleocene to Middle Eocene Tarcau Sandstone at Buzau Valley, eastern Carpathians, Romania, records sedimentation in a turbidite system. These strata contain a diverse and abundant pre‐ and postdepositional ichnofauna consisting of 35 ichnogenera and 54 ichnospecies. The predepositional assemblage is rich in graphoglyptids and ornate grazing trails; simple grazing trails, resting traces, and feeding structures also occur. The predepositional assemblage includes Acan‐thorhaphe, Belorhaphe, Cardioichnus, Circulichnus, Coch‐lichnus, Cosmorhaphe, Desmograpton, Fustiglyphus, Gordia, Helicolithus, Helminthopsis, Helminthorhaphe, Lorenzinia, Megagrapton, Paleodictyon, Paleomeandron, Protopaleodictyon, Scolicia (S. strozzii), Spirorhaphe, Spirophycus, Treptichnus, and Urohelminthoida. The ich‐nodiversity, composition, ethology, and morphologic complexity of the predepositional association are indicative of the Nereites ichnofacies. The postdepositional association essentially consists of dwelling, feeding, and grazing traces, and is represented by Chondrites, Glockerichnus, Halopoa, Nereites, Ophiomorpha, Phycodes, Planolites, Polykampton, Scolicia(S. prisca. S. striata), Taenidium, Thalassinoides, and Zoophycos. Palaeophycus occurs in both assemblages. Allochthonous Teredolites is present in wood fragments, The postdepositional association includes elements of the Skolithos ichnofacies and facies‐crossing forms that are commonly present in deep‐marine deposits, Elements of the Skolithos ichnofacies are present not only in the most proximal parts of the turbidite system, but also in distal parts. The number of predepositional forms greatly exceeds postdepositional ones, reflecting a dominance of K‐selected over r‐selected population strategies in a stable environment. High levels of ichnodiversity in the Tarcau Sandstone are comparable with deep‐sea ichnofaunas from the Polish Carpathians and with other flysch trace‐fossil assemblages of similar age. This abundant and diverse Eocene ichnofauna supports the idea of extremely rich deep‐sea ichnofaunas in the Cenozoic.