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This study is a reconstruction of the Coniacian palaeogeographic and palaeoenvironmental development in the North Sudetic Basin, a synclinal trough within the Late Cretaceous Central European seaway linking the Boreal and Tethyan marine provinces. The basin formed as an early side effect of the Alpine orogeny combined with the mid‐Cretaceous eustasy, and crucial stages of its evolution occurred during the Coniacian. The basin in the early Coniacian was a long and narrow shallow‐marine embayment with a hypothetical (non‐preserved) bayhead strait funnelling tidal currents. Coalescing tidal sand ridges formed a littoral platform that prograded from the bayhead zone along the basin axis, impinged on laterally by the basin‐margin shoreface and local river deltas. A mid‐Coniacian forced marine regression and closure of the bayhead strait, attributed to the Alpine tectonism combined with eustasy, brought about a dramatic change in the basin, whereby the basin‐wide littoral sand platform emerged and turned briefly into a denudated coastal plain. The late Coniacian eustatic marine transgression formed an in‐place growing coastal sand barrier at the outer edge of the former littoral platform, sheltering a paralic limno‐lagoonal plain with peat‐forming mires. The coastal barrier was eventually drowned by the sea and maximum marine flooding occurred, followed by a normal regression recorded as a rapidly upwards‐shallowing succession of offshore‐transition to fluvio‐deltaic deposits. This case study of the sedimentation pattern in an evolving, tectonically controlled marine embayment contributes to the existing facies models for estuarine embayments formed by a passive marine drowning of large fluvial or glacial valleys. [ABSTRACT FROM AUTHOR]

Abstract: The study is a qualitative and semi-quantitative analysis of calcareous nannofossils in marlstone and calcareous mudstone beds in a 4.6-m thick section of the Kropivnik Fucoid Marls (Late Campanian–Early Maastrichtian) in the Skole nappe of the Polish Outer Carpathians. This turbiditic succession is conspicuous by its short-term alternation of marlstone-rich and siliciclastic-rich packages, ca. 1m thick. A model for paleoceanographic control on sedimentation is proposed on the basis of nannofossil assemblages in the studied section. The nannofossils form assemblages of mixed synsedimentary taxa derived from diverse marine environments, differing in trophy, water temperature and distance from land. The mixing occurred due to submarine resedimentation processes. The nannofossils indicate that the siliciclastic-rich packages were deposited during periods of lowered water temperature, decreased calcareous nannoplankton production and oligotrophic to mesotrophic water conditions, which corresponded to the sea-level fall and lowstand. Anti-estuarine circulation and downwelling due to arising shelf-break front are inferred as the factors responsible for oligotrophy. In contrast, in the marlstone-rich packages, the calcareous nannofossils indicate sedimentation during periods of significantly increased calcareous nannoplankton production, which corresponded to the sea-level rise and highstand. The increased nannoplankton production is attributed to estuarine circulation and upwelling. The changes in sea level and water circulation conform to the climate changes postulated independently for the Late Campanian–Early Maastrichtian. [Copyright &y& Elsevier]