Author	Heilmann-Clausen, C. and Thomsen, E.
Year	1995
Journal	Geologisches Jahrbuch, Abhandlungen 141: 257-365Geologisches Jahrbuch, Abhandlungen 141: 257-365
Title	Barremian-Aptian dinoflagellates and calcareous nannofossils in the Ahlum-1 borehole and the Otto Gott clay pit, Sarstadt, Lower Saxony Basin, Germany

Abstract Heilmann-Clausen, C. and Thomsen, E., 1995; Barremian-Aptian dinoflagellates and calcareous nannofossils in the Ahlum-1 borehole and the Otto Gott clay pit, Sarstadt, Lower Saxony Basin, Germany. Geologisches Jahrbuch, Abhandlungen 141: 257-365 Abstract: The Ahlum 1 borehole, situated east of Hannover in the Lower Saxony Basin, includes a very complete uppermost Lower Barremian to Upper Aptian sedimentary sequence. The distribution of dinoflagellates and calcareous nannofossils in this section and the dinoflagellates in a Barremian section from the Otto Gott clay pit at Sarstedt near Hannover is described. Some general aspects of biostratigraphical correlation based on dinoflagellates are discussed. The two sections are then correlated on the basis of dinoflagellates, and correlation is established to previously studied Barremian and Aptian sections in the Lower Saxony Basin, the North Sea and in southern and eastern England. Dinoflagellate events that are useful for correlation within the North Sea Basin are recognized and calibrated to belemnite and ammonite zones. The distribution of calcareous nannofossils is compared with results from previously studied sections in the North Sea area, the Tethyan Realm, and the eastern Atlantic Ocean. The stratigraphic distribution of several species is refined, and useful biostratigraphic markers are identified. The most important dinoflagellate and calcareous nannofossil events in Ahlum 1 are calibrated, and their occurrence at various levels in Ahlum I is discussed. Many of the dinoflagellates and calcareous nannofossil taxa are described or discussed. Four new species and two new subspecies of dinoflagellates are established.