North Sea
Country / Region: Germany
Begin of project: January 1, 2002
End of project: December 31, 2012
Status of project: September 10, 2007
General geological structure of near-surface sediments of the southern North Sea.
Source: BGR
In the past few years the utilisation of resources in the German North Sea sector has increased considerably.
The shallow continental shelf is being used increasingly for pipelines, offshore wind parks, cable lines, underground storage caverns, sand and gravel extraction, etc. Area-wide geological information on the upper >>100 m thick, intricately structured sediments and a detailed knowledge of the active geological processes involved are therefore indispensable for the long-term planning and management of the region.
See also: Continental Shelf (CONTIS) Information System
Aim of the North Sea project:
The main aims of the project are: (i) high-resolution geological mapping of the near-surface substratum/bedrock, and (ii) the compilation of digitally available geological maps.
Methods:
- Interpretation and evaluation of available analogue and digital datasets (boreholes / seismic data)
- BGR high-resolution multi-channel and boomer/sparker seismic data
- Connection of all data in digital interpretation systems (GeoQuest, ArcInfo)
- Sequence- and biostratigraphical interpretation of BGR vibrocores.
Project status:
In addition to compiling and evaluating seismic and borehole data deriving from the oil industry and previous scientific projects, several BGR cruises since 2003 allowed us to obtain specific seismic data and sedimentary cores:
| Ausfahrt mit | Akronym | Projektpartner |
|---|---|---|
| MV AURELIA 2003 | BGR03-AUR | GEUS Denmaek |
MV AURELIA 2004 | BGR04-AUR | University of Bremen |
FS HEINCKE 2005 | HE242 | University of Bremen |
FS ALKOR 2006 | AL278 CORTEC | University of Kiel |
| MV FRANKLIN | BGR07- Franklin | University of Bremen |
Furthermore, aero-gravimetric data were obtained for a large part of the German North Sea sector in the summer of 2007.
First interpretations of the seismic data obtained during BGR seismic cruises together with previously compiled seismic profiles have delivered new results that greatly improve our still fragmentary knowledge on the geological development of the southern North Sea since the middle Miocene.
Selected examples:
Subglacial valleys
Spatial model of subglacial valleys (3D seismics)
Source: BGR
The distribution of subglacial valley systems is being mapped and the generally complex process of valley erosion/incision followed by sedimentary infilling is being analysed in detail using a 3D dataset deriving from the oil industry.
Glacio-tectonics
Compressed and thrusted sediments formed at the edge of a former ice sheet (north of Helgoland).
Source: BGR
Compressed and thrusted sediments formed at the edge of former ice sheets were previously known only from one site to the north of Helgoland (Borth-Hoffmann, 1980; Figge, 1983). They were analysed systematically in high resolution and could be identified up to Sylt. However, the pursuance of thrusted sediments up to the Danish island Rømø has now been confirmed.
Faults in the area around a salt diapir
Spatial illustration of faults (3D seismics).
Source: BGR
The positions of fault systems above a salt diapir have been analysed in detail using a 3D seismic dataset from the oil industry.
Keystone faulting occurred above the top of a salt diapir due to salt doming. Synthetic faults are indicated in blue; antithetic faults are indicated in red, yellow and orange. The main fault is marked with MA. Crossed faults (SE1 & SE2, SE4 & MA1) show that fields/regions of stress must have changed during the raising process. Vertical axis = 1 second two-way-traveltime (TWT), representing approximately 1 kilometre.
Peats
Datable peat layers from the North Sea can be used for the reconstruction of sea-level rise since the end of the last glacial period, which in turn provides important insights into the variable crustal subsidence which has occurred in the region.
Project contributions:
- Cenozoic biostratigraphy from the G-11-1 borehole, German North Sea sector
- Sea-level curves of northwest Europe: Evidence for isostatic subsidence of the German North Sea coast
Literature:
- Andersen, L.T., 2004. The Fanø Bugt Glaciotectonic Thrust Fault Complex, Southeastern Danish North Sea. A study of large-scale glaciotectonics using high-resolution seismic data and numerical modelling. PhD Thesis, University of Aarhus and Geological Survey of Denmark and Greenland (GEUS), Aarhus, 143 pp.
- Borth-Hoffmann, B., 1980. Flachseismische Untersuchung geologischer Strukturen in der östlichen Deutschen Bucht. Diplomarbeit, Universität Kiel, 93+VII pp.
Figge, K., 1983. Morainic deposits in the German Bight area of the North Sea. In: J. Ehlers (Editor), Glacial deposits in North-West Europe. Balkema, A. A., Rotterdam, pp. 299-304.