Pliocene - Middle Pleistocene biostratigraphy in the Central Danish North Sea wells E-1, P-1 and TWB-12

Abstract

Six foraminiferal assemblage zones and 6 subzones have been identified in the boreholes TWB-12, P-1 and E-1. The zones cover the interval from the Pliocene to the Middle Pleistocene. In TWB-12 and E-1 the Pliocene /Pleistocene boundary is placed at the first common occurrence of the species Elphidium oregonense. This species was not found in P-1, and the boundary is here, tentatively, placed above the last local occurrence of Cibicides grossus. The palaeoecological variations indicated by the Pleistocene assemblages, suggest several oscillations both in water depth and in palaeotemperature. A cold, shallow water interval with Elphidium oregonense at the Pliocene/Pleistocene boundary is followed by a Early Pleistocene warm, deep water interval with a high content of the genera Stainforthia and Bulimina. These deposits are probably from the warm Tiglian stage. The succeeding Early Pleistocene fauna! assemblages indicate a cold, upwards shallowing environment, and in this interval the arctic species Elphidiella gorbunovi often has a short ranged occurrence. The fauna! assemblages of the overlying deposits are characterized by the species Elphidium ustulatum and Elphidium albiumbilicatum, and indicates nearshore/ deltaic conditions. This part of the sequence probably includes the Early /Middle Pleistocene boundary. The uppermost assemblages in the examined sequence indicate arctic, shallow water conditions. They are, probably, of Saalian age, and are referred to Middle Pleistocene.