Abstract: Structural Development of the Main Graben Border Fault, Danish Central Graben, North Sea

Ole Graversen

The large scale outcrop pattern of the North Sea Central Graben outlines a double dogleg pattern. The general graben trend is NNW-SSE with two main legs trending N-S and WNW-ESE.

The main boundary fault zone separates the graben floor from the Ringkobing-Fyn High to the east. The fault zone is developed as a complex pattern of intermediate fault blocks between the base Zechstein graben floor (foot wall) and the Ringkobing-Fyn High (foot wall). During the Mesozoic extension and subsidence the graben border fault has cut back into the Ringkobing-Fyn High with variable amounts. The indentation varies from around 1/2 km to more than 1-1/2 km. The graben border fault can thus be divided into a number of fault segments based on the changing orientation and steepness of the fault plane and the variable indentation into the Ringkobing-Fyn High. Within individual fault segments, the intermediate fault blocks may be developed as synthetic tabular fault blocks or they ma show a more complex ramp system development.

The position of the fault segments along the graben border fault correlates with transverse structural anomaly zones mapped at the base Zechstein graben floor to the west. Together the graben floor anomalies and the border

fault segments outline a set of WSW-ENE trending transverse segments cutting across the graben. The transverse anomaly zones parallels the general extension direction.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994