Abstract

In Czechoslovakia, the Devonian is distributed mainly in two areas: the Barrandian basin (Central Bohemia) and Moravia.

The Devonian of the Barrandian basin is a classic area of the so-called Bohemian or Hercynian development (the Bohemian province) which, particularly in the Lower Devonian, differs so markedly from the classic Rhenish development that a special division into Lochkovian, Pragian and Zlichovian stages has been established for this period. It is characterized by a complete marine succession, a conformable gradual transition from the Silurian (Silurian faunal types, including graptolites, persist into the lower Middle Devonian. The combination of two main, richly differentiated facies types is represented here: organodetrital, or reef, limestones which originated in a shallow-sea environment with considerable water circulation, and dense limestones which were deposited in a more tranquil, deeper water, environment. The character of the fauna is controlled by the facies type. The sedimentation ends with the Givetian flysch facies and the folding dates from the early Variscan orogenic phase.

The Devonian in Moravia represents the southern projection of the European Variscan geosyncline. Transgression from the north to the south occurred across the ancient (Proterozoic) basement from the Early Devonian to the Frasnian. In the Lower Devonian, psammitic-pelitic deposits bearing fauna of the Rhenish type predominate, the Bohemian forms increasing in number from the Upper Emsian. After the upper Middle Devonian, carbonate sedimentation, with a rather cosmopolitan West European-type fauna, took place. Three main facies types have been differentiated: the eugeosynclinal type with a dominance of rather deep-sea shaly facies, initial volcanism and the most complete sequence of strata; the geanticlinal type with a later (Givetian) transgression and a prevalence of shallow-water carbonate facies; and the transitional type that makes the correlation of the two preceding antithetic types possible. The Upper Devonian is everywhere complete and at a number of places the conformable contact with the Carboniferous is demonstrable. The Devonian complexes were intensely folded and locally metamorphosed during the Variscan orogeny.

Minor Devonian occurrences, particularly in the West Sudetic region and the West Carpathians, are also briefly discussed.