Geology across borders – Towards a consistent interpretation of the subsurface in the Central North Sea covering the Dutch, German and Danish offshore areas.

Geology does not follow national borders and for many areas of application, it is essential to know the characteristics of the subsurface on both sides of the border. In the area of the North Sea, however, consistent interpretation of the subsurface across borders are rare, as most studies carried out here by the Geological Survey Organizations (GSOs) in charge have remained confined to their national territories. As a consequence, the interpretations are often not aligned to each other, and in recent years, it has become more and more obvious by a variety of 3D-modeling projects that there exists in part considerable discrepancies e.g. in depth, distribution and thickness of certain stratigraphic intervals along the borders. Within the framework of the GeoERA research project ”3D Geomodeling for Europe”, the GSOs of the Netherlands, Germany and Denmark addressed these issues and integrated existing national (and regional) geomodels into a harmonized, consistent interpretation of the subsurface in their North Sea offshore border region. The results of the project presented here include: (a) A harmonized cross-border velocity model covering main parts of the Danish, German and Dutch North Sea. (b) A geometrically and stratigraphically consistent geological model of the Central Graben area across the Dutch-German-Danish border. (c) A consistent fault model of a segment of the Coffee Soil Fault. (d) Lithostratigraphic correlation schemes in the area of the Central Graben. The results achieved improve the spatial understanding of the subsurface structures of the project area and serve as a guide for future cross-border studies.