Fault-Related Salt Tectonics in the Southern North Sea, The Netherlands

Abstract

This chapter describes the relationship between basement faulting and salt flow in the southern North Sea in general and in the Dutch Central North Sea Graben area specifically. The research was executed within a national program on radioactive waste disposal in The Netherlands and is based on a 2000-km regional two-dimensional seismic survey. Salt structures consist of Upper Permian Zechstein salt. The salt structures are, almost without exception, related to basement faults. This paper concerns the relative location of the basement faults and salt structures, the triggering of salt flow, and the rate of this flow. The Netherlands sector of the continental shelf can be subdivided into a number of salt provinces on the basis of their developmental stage. This subdivision coincides with the structural units. The maturity of the salt structure is proportional to the throw of the basement fault. A relationship exists between basement faulting and increased salt flow, and the interference of fault systems in the basement is reflected in the geometry of the salt structures. The effect of basement faulting on salt flow appears to correspond with the results of previously published physical modeling. The buoyancy force related to the density inversion alone seems insufficient to pierce the overburden. Weakening of the overburden and enhancing the buoyancy forces by differential loading enable the salt to flow and breach the overburden.