Comments on facies development and stratigraphy of the Devonian, Barrandian area, Czech Republic
Bulletin of Geosciences, volume 78, issue 4;
pages: 299 - 312;
Received 24 July 2003;
Accepted in revised form 2 October 2003;
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The Devonian of the Barrandian area is characterized mainly from the viewpoint of facies development. Several types of facies changes are shown to occur, some of them within a few dozens of metres, some other within a distance of several kilometres. Even though the basin has been shortened during the Variscan orogeny, the distinct lateral changes in limestone composition are surprising. Micritic limestones pass often more or less abruptly or gradually into predominantly bioclastic limestones. Platy limestones with shale intercalations pass into crinoidal bioclastic limestones. The attempts to explain such rapid facies changes by tectonics, or even by nappe structures, is needless because many examples show that they can be explained by variations in depositional environments and sedimentary mechanisms. The specific and more or less isolated Koněprusy area with its special lithological and stratigraphic development represents a serious problem. However, it can be shown that its isolation is not absolute and many stratigraphic and facies analogues can be found in near and more distant sections. The plausibility of paleogeographical reconstruction of the Devonian basin in central Bohemia is also discussed. It is documented that small relics of Devonian rocks do not allow reliable paleogeographic reconstruction and that the occurrences of Devonian rocks outside the limits of the Barrandian area indicate a presence of large marine basin with a broad gateway to the ocean. Even though shallow-water sedimentation prevailed during the Devonian, there is no indication of the presence of a coast and/or a shoreline. The main facies boundaries in the Barrandian Devonian are oblique to the strikes of Variscan structures. However, the course of the Devonian facies boundaries conforms with the strikes of structures associated with tensional regime in the Barrandian Upper Cambrian. The attached list of significant Devonian localities summarizes 72 sections and outcrops on which the Devonian stratigraphy is based.