Spit bar deposits from the Upper Cretaceous (Cenomanian) transgressive sequence in NE Bohemia (Czechia)

Abstract

We propose a spit bar setting as the possible palaeoenvironment of the basal Late Cretaceous transgressive sequence in NW Bohemia. A new Cenomanian transgression model for the Bohemian Basin is also proposed. The uppermost Devět Křížů Sandstone, which has been conventionally referred to the Bohdašín Formation, probably represents the middle or lower upper Cenomanian (Upper Cretaceous), not the Triassic as previously supposed. We assume that this controversial unit was deposited before the main latest Cenomanian–early Turonian transgression. The spit bars were likely overgrown by vascular plants during their emergence in the late Cenomanian, and then inundated during the latest Cenomanian and early Turonian transgressive phases. The studied deposits had been intensively bioturbated, and the cf. Taenidium suite was recognized for the first time in them alongside the Thalassinoides assemblage (T. paradoxicus, T. suevicus, Thalassinoides isp., cf. Thalassinoides), which are characteristic of the Scoyenia and Glossifungites ichnofacies, respectively. The bioturbated, rhizolith-bearing horizon was presumably a paleosol.