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:

1. Interpretation and evaluation of available analogue and digital datasets (boreholes / seismic data)
2. BGR high-resolution multi-channel and boomer/sparker seismic data
3. Connection of all data in digital interpretation systems (GeoQuest, ArcInfo)
4. 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 Leg 1+2	University of Bremen TNO-NITG the Netherlands
FS HEINCKE 2005 and FK SENCKENBERG	HE242 Leg 1+2 SENCK05	University of Bremen MPI (Marine Microbilogy) Senckenberg Institut
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.