Palaeogene biostratigraphy of the Loburg I/90 cored borehole in Saxony-Anhalt, Germany

Report of the project:

• Micropaleontology of sedimentary sequences of Germany
• Mikropaläontologie des tieferen Untergrundes von Deutschland

Location of the Loburg I/90 borehole Source: BGR

The Loburg I/90 cored borehole is located in Saxony-Anhalt 40 km northeast of Magdeburg and south of Genthien and Tucheim. The borehole was drilled for hydrogeological investigation and for local water supply in 1990 by GFE Halle (Volkseigener Betrieb Geologische Forschung und Erkundung Halle). In 1991 the geological documentation and the samples were transferred from GFE Halle to the Landesamt für Geologie und Bergwesen Sachsen-Anhalt in Halle.

Upper Paleocene to Lower Oligocene sediments in the Loburg I/90 cored borehole were investigated looking at calcareous nannoplankton and organic-walled dinoflagellate cysts. All the samples contain dinoflagellate cysts, whereas the Upper Paleocene and Lower Eocene are barren of calcareous nannoplankton. The absence of calcareous nannoplankton is probably due to temporarily unfavourable facies conditions (near shore) and due to dissolution.

The investigated profile comprises Late Paleocene (dinoflagellate cyst subzones D4na, D4nb), Early Eocene (D5nb, D6na, D6nb, D7na), Middle Eocene (D9nb, D10, and calcareous nannoplankton zones NP15, NP16, NP17), Late Eocene (D12nc, NP21, „NP22“) and Early Oligocene (D13, D14na, D14nb, NP23, NP24). Three hiatuses were determined biostratigraphically: latest Late Paleocene to earliest Early Eocene (D5na), late Early Eocene to early Middle Eocene (D7nb–D9na), and late Middle to middle Late Eocene (D11–D12nb, NP18–NP19/20). A possible fourth short-term hiatus is thought to coincide with the Eocene/Oligocene boundary (Schönewalde Formation/Rupel Formation, D12nc/D13) because of an abrupt change in the dinoflagellate cyst assemblage.

A paleoecological interpretation of the dinoflagellate cysts shows good analogies with the Gorleben area about 100 km NNW. At Loburg, the changing facies conditions and the near shore environments are more distinctive than at Gorleben. Fully marine conditions prevail in the middle Middle Eocene (D9nb, NP15, NP16) and the late Early Oligocene (D14nb, upper part of NP23, NP24).

Literature:

Köthe, A. (2009): Calcareous Nannoplankton and Dinoflagellate Cysts Paleogene biostratigraphy of the Loburg I/90 cored borehole (Saxony-Anhalt, central Germany). - Zeitschrift für Geologische Wissenschaften, 37 (6): 381-425.