GRAVERSEN, OLE, University of Copenhagen, Copenhagen, Denmark. Present address: Maersk Olie og Gas, a.s., Copenhagen, Denmark

ABSTRACT: Basement Tectonics Governing the Development of Salt Structures in the Salt Dome Province, Danish Central Graben, North Sea.

The Salt Dome Province of the Danish Central Graben is situated at the northern margin of the southern Zechstein basin in NW Europe. During the Mesozoic and the Tertiary the Zechstein salt developed into salt pillows, salt ridges and piercement domes in addition to lateral intrusion into sills and uplift structures. The producing oil and gas reservoirs are located in Upper Cretaceous chalk in domes sitting above the salt structures.

The structural outline and main Mesozoic development of the graben area is governed by NNW-SSE to N-S trending basement faults at the pre-Zechstein level. In addition to the faults outlining the main graben trend, NNE-SSW trending fault zones have subdivided the graben floor into transverse segments cutting across the graben area.

Large salt domes at base Zechstein level and pointed piercement domes intruding into various levels of the overlying Mesozoic-Tertiary sequence are developed simultaneously. The salt domes at base Zechstein level are restricted to fault blocks outlined by graben parallel faults within the transverse segments. The salt piercement structures, however, developed at the intersection between the graben parallel faults and the crosscutting transverse faults.

During the graben subsidence, the main factor leading to the different salt structure types is governed by the interference of the graben parallel faults and the transverse faults cutting across the graben.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.