Palaeoenvironmental interpretation of Late Albian calcareous dinoflagellate cysts from the Kirchrode I borehole (Lower Saxony Basin, NW Germany)

Late Albian calcareous dinoflagellate cyst assemblages from samples of the Kirchrode I borehole contains 38 morphospecies, which represent a flora of moderate warm water conditions in an oceanic-controlled epicontinental regime. The vertical changes of cyst associations reflect sea level fluctuations. The regressive phases of the highstand are characterised by the exclusive occurrence of benthic resting cysts, while planktonic counterparts joined during transgressive phases. Floral exchanges via the water masses, which were influenced by the Tethys, were in progress only during phases of relatively strong currents, in particular during transgressions. In contrast, the highstand, during which water circulation decreased, can be characterised by autochthonous morphotypes, reflecting an epicontinental habitat. The corresponding cyclic, intraspecies change of cyst diameter is interpreted to reflect changes in productivity, which were probably controlled by eccentricity cycles.