Cenozoic biostratigraphy from the G-11-1 borehole, German North Sea sector
Report of the project:
Ditch cuttings from Neogene and Paleogene sequences of the G-11-1 borehole from the German North Sea were analysed for dinoflagellate cysts and calcareous nannoplankton.
The record displays several time gaps (Late Thanetian to Middle Ypresian, Bartonian to Middle Priabonian, earliest Oligocene, within the Middle Rupelian, Chattian to earliest Aquitanian, Middle Burdigalian and Late Tortonian to Early Zanclean). These time gaps can be traced for at least 30 kilometres in seismic lines. There is apparently no hiatus around the Cretaceous/Paleogene boundary because the youngest Maastrichtian calcareous nannoplankton zone (CC26) and the oldest Paleocene dinoflagellate cyst zone (D1) were determined.
One of the most prominent seismic features in the Cenozoic sequences of the North Sea Basin is the Mid-Miocene Unconformity (MMU). The age of the MMU in the G-11-1 borehole can be narrowed as early Middle Miocene (dinoflagellate cyst zone DN5, calcareous nannoplankton zone NN5 for sediments below the MMU) to early Late Miocene (dinoflagellate cyst zone DN8 for sediments above the MMU).
Below the MMU, the sedimentary pattern is strongly influenced by numerous time gaps (erosions or condensed sections), whereas above the MMU, prograding deltas are the main features.
The left figure above shows the time migrated seismic line (normal polarity), the gamma-ray log (provided by BEB Erdgas und Erdöl GmbH) and the ages of the sediments in terms of dinoflagellate cyst zones. The yellow lines separate intervals of different ages respectively time gaps (hiatuses or condensed sections), the red line indicates the MMU. The right figure shows the Cenozoic record of the G-11-1 borehole. Yellow intervals are proven biostratigraphically; grey intervals are time gaps (hiatuses or condensed sections), grey shaded intervals are of unsure biostratigraphy.
Literature:
Köthe, A. (2007): Cenozoic biostratigraphy from the German North Sea sector (G-11-1 borehole, dinoflagellate cysts, calcareous nannoplankton). – Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 158(2): 287-327; Stuttgart.
Köthe, A., Gaedicke, C. & Lutz, R. (2008): Erratum: The age of the Mid-Miocene Unconformity (MMU) in the G-11-1 borehole, German North Sea sector. - Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 159(4).