Permian Rotliegendes of Northwest Europe Interpreted in Light of Modern Desert Sedimentation Studies

Abstract

The Permian redbeds of northwest Europe, termed the Rotliegendes, are continental clastic sediments laid down under desert and semidesert conditions. Recent drilling in the North Sea, Netherlands, and north Germany has shown that these beds are in a sedimentary basin up to 2,000 km long and 500 km wide. This basin is in the foreland of the Variscan mountains. (Hercynian orogeny) and is of part-orogenic origin and partly fault bounded. Volcanic rocks are present locally, especially in the east. The Rotliegendes strata attain a maximum thickness of approximately 1,500 m. A central shale and halite facies (Haselgebirge facies), corresponding to a salt lake, changes toward the southern basin margin first to anhydritic clay (Ten Boer member) and then to sandstone and conglom rate of the Slochteren member (wadi deposits and eolian sands). Paleowind directions were essentially from east to west. Deflation of the alluvial fans spreading northward from the Variscan mountains resulted in accumulation of up to 200 m of dune sands in the southern North Sea area. The dune sands form the reservoir rock for important accumulations of gas. At present, the proved and probable reserves of Rotliegendes gas in the North Sea, Netherlands, and western Germany are about 2,500 × 109 cu m (85 × 1012 cu ft). The interpretations of Rotliegendes facies are based on a study of modern deserts and their sediments (wadi sediments, dune sands, and the sediments of inland and coastal sabkhas).