G. Drozdzewski, 1983. "Tectonics of the Ruhr District, Illustrated by Reflection Seismic Profiles", Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces, A. W. Bally
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Seismic surveys were made in the context of an intensive exploration and reserve assessment of the coal mines on the northwestern margin of the Ruhr district. Combined with hundreds of 1,500 m (4,921 ft) coreholes, the seismic lines served to clarify structural details in the coal mining district. Results of the program were published in a monograph (Drozdzewski et al, 1980), which provided a detailed analysis of the structures of the area. Both Vibroseismic and explosive sources were used to obtain seismic sections and 3-D seismic sections which were produced by the Prakla-Seismos GMBH processing center in Hannover, and interpreted by teams of geophysicists, mining engineers and geologists.
The Ruhr district is part of the foredeep of the Variscan folded belt of western Europe. Mining operations in an area of 110 by 50 km (68 by 31 mi), provide access to very detailed subsurface structural information.
During the Upper Carboniferous some 6,000 m (19,685 ft) of paralic sediments were deposited. Coals seams first appear during the Namurian C and range into the Westfalian C. While sedimentation persisted in the northern Ruhr district, folding already started to the south of the area. Thus, in this process the southern Ruhr district was shortened by folding and subordinate thrust faulting to about one-half of its original width. Toward the north and west, folding intensity decreases gradually. The foldbelt is segmented by conspicuous transversal and diagonal faults.
During and after the folding regional differential uplift occurred. In the Niederrhein area up to 2,000 m (6,562 ft) of Upper Carboniferous strata were eroded prior to the deposition of the Late Permian Zechstein formation. Overlying the folded and block-faulted Variscan folded belt, a relatively thin veneer of Zechstein marls, clays, anhydrites, dolomites, and most importantly, salt was deposited. The original salt thickness in the Niederrhein area is estimated to be about 250 m (820 ft). Salt solution has modified the original thickness. The overlying Triassic Buntsandstein formation is about 500 m (1,640 ft) thick and consists of poorly consolidated sandstones, which are often acquifers, and clays with some salt toward the top.