Permian Evaporites in North Sea Basin

Thick evaporite beds are present in the Permian beneath the North Sea, and can be correlated with the known successions in Germany and in England. The evaporites are more widespread in the upper division (Zechstein) than in the lower (Rotliegendes). This paper concerns chiefly the Zechstein of the English side of the basin, in which four main evaporite cycles are present. Zechstein salt movement began near the end of the Early Triassic when the overburden was only about 2,000 ft (610 m) thick, and continued throughout the Mesozoic and Tertiary. Movement was earlier in the west than in the east. Salt plugs are associated particularly with the margins of a large NNW-SSE trough which became fully developed during the Jurassic. Important structural features and thickness changes in the Mesozoic and Tertiary rocks were caused by the salt movement, and are almost entirely compensated by salt at depth. As a result, the base of the Permian is nearly parallel, on a regional scale, with the base of the Quaternary though separated from it by about 10,000 ft (3,000 m) of moderately complicated strata.