Deep Structure of The Eastern North German Basin, Possible Scenarios of Formation Modelled and Discussed On The Basis of Seismic and Potential Field Data
Abstract
The North German Basin (NGB) straddles a part of NW Europe where the underlying crust is formed by parts of the buried SW Baltica margin, Caledonian crustal units and part of the Variscides. The up to 9 km thick Permian to Cainozoic sedimentary cover of NGB is well known from a large number of boreholes and commercial re- flection seismic lines. However, most of the seismic energy in the commercial data is reflected by a strong reflector at the base of the Zechstein evaporites, masking the deep crust below NGB. The NS oriented DEKORP 9601 deep reflection seismic profile that traverses the eastern part of NGB over a distance of about 350 km from the Rügen Is- land to the Hartz Mountains offers a rare glimpse of the sub-Permian reflectivity. The sub-Permian structure is dominated by south dipping, low angle (< 30) reflectivity truncated by a sub-horizontal Moho at a depth of around 30 km. The top of Baltica is well constrained towards the north in the Rügen area and can be correlated, dip- ping towards the south, to at least a lower crustal level, below the centre of NGB. The most notable feature of the observed potential field pattern is the so called Pritzwalk Anomaly (PA), centred approx. in the middle of the profile, which has a width (in profile) of ca. 130 km and an amplitude of 30 mGal / 200 nT. Two relative potential field troughs are present on either side of PA and separate it from the sharp positive Flechtingen High anomaly to the south and the Rügen High anomaly in the North. In map view the PA seems to be part of an elongated positive NWUSE striking potential
field anomaly continuing NW-wards from the eastern NGB into the Danish area and the North Sea. Earlier potential field models of the PA proposed that vast amounts of magmatic rocks in the basin centre together with a central Moho uplift could explain the anomaly. The lack of Moho reflectivity in the central part of the profile could be explained by the presence of a high density crustal unit thrusted onto Baltica during the closure of the Tornquist Ocean. In view of the observed crustal reflection pattern in the DEKORP profile 9601 we suggest that an explanation of PA should take the Cale- donian to Variscan crustal evolution into account. Most of the PA may be explained 1 in the context of a Caledonian to Variscan orogenic thrust complex that may include slabs of high density and magnetic oceanic crust, accreted onto the margin of Baltica. However, part of the PA is still attributed to the presence of mafic magmatic rocks. 2- Publication:
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EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.5946L