SEISMIC INTERPRETATION OF THE DEEP SUB-SURFACE OF THE NORTHWESTERN GERMAN NORTH SEA

Within the framework of the GPDN project (www.geopotenzial-nordsee.de) a detailed seismic mapping project has been carried out in the northwestern offshore part of the German North Sea sector, the so called „Duck`s Beak”. Until now no detailed geological interpretation is published for this area. Former studies of the deeper underground by Baldschuhn et al. (2001) cover only the central part of the German North Sea.

The interpretation of new 2D and 3D seismic surveys in the „Duck`s Beak”, in combination with stratigraphic and geophysical well data, allows a detailed mapping of seismic horizons and a characterization of their lithological and stratigraphical expressions. We interpret the same seismic horizons, with a few exceptions, previously interpreted in the Geotectonic Atlas of Northwest Germany (Baldschuhn et al., 2001). In addition to this the prominent Rotliegend horizons Ro2 and Ro1 will be analysed.

Based on the mapped horizons structural elements can be delineated, isopach maps are calculated which provide important information for further sedimentological or structural studies. The Mid Miocene unconformity (MMU) reflects the base of a dominant downlapping sequence in the North Sea Basin and reaches from 200 ms to 1540 ms (TWT). Our seismic interpretation reveals a generally NW dipping surface. The downlap sequence above the MMU comprises sediments of the Late Cenoizoic Eridanos Delta. The base of the Paleocene reaches from approximately 880 ms to 2840 ms (TWT). The maximal vertical time thickness from the base of the Paleocene to the MMU is about 1400 ms (TWT). The base of the Paleocene is pierced by several salt diapirs. Above this unit, the Mid Miocene unconformity is generally uplifted by halokinetic movements but only pierced by diapirs in a few cases. The structural geometry of the Neogene in the northwestern German offshore is characterised by crestal graben structures above elongated diapirs and salt intruded fault zones.

Baldschuhn, R., et al. (2001). Geotektonischer Atlas von Nordwestdeutschland und dem deutschen Nordsee-Sektor - Strukturen, Strukturentwicklung, Paläogeographie. Geologisches Jahrbuch, A 153: 3-95.