The Devonian carbonate complexes in the Rhenish Trough of the Variscan Geosyncliue (central Europe) range in age from Eifelian to middle Frasnian and occur at:
(1) The outer shelf (southeast margin of the Old Red Continent) in the western part as a broad shelf- lagoon facies overlying deltalike clastic deposits (Belgium, Aachen, Eifel) and in the eastern part as isolated reef complexes and shelf-margin reefs on local platform rises (Bergisches Land, Sauerland).
(2) Isolated submarine volcanic rises in the internal part of the trough on submarine ophiolites (Lahn- Dill syncline, Elbingerode in the Harz Mountains).
(3) The inner shelf (northwest margin of the Mitteldeutsche Schwelle within the mobile belt) overlying crystalline rocks (borehole Saar 1).
Five types of carbonate complexes can be distinguished in central Europe. The Devonian carbonate complexes reach a maximum thickness of 1,300 m (Balve). The size varies from small patch reefs to reef complexes nearly 100 km2.
Carbonate sedimentation started everywhere with carbonate bank deposits (Schwelm facies). This carbonate platform is the foundation for the true reefs. The well-bedded carbonates of the bank deposits are commonly dark and fine-grained. The potential reef builders, stromatoporoids, tabulate, and rugose corals, do not build wave-resistant structures but form only widespread biostromal structures of low relief in a muddy environment. Eight subfacies of the bank deposits are distinguished.
Figures & Tables
Reefs in Time and Space: Selected Examples from the Recent and Ancient
This collection of papers examines various aspects of reef form and development. Despite their variety of topic and treatment, they have two unifying elements: a fresh look at old themes and historical evolution. Although much has already been written about reefs, these papers provide interesting and important insights to our continuing understanding of them. These papers were originally part of a symposium entitled Reef Complexes in Time and Space, held at the annual SEPM meeting in Calgary, June 1970.