• Silurian deposits in the investigated area range in age:: from the Wenlockian across Devonianboundary. They represent the graptolite-shaly facies with siltstones in the upper part of the section. These deposits pass continuously into the Lower Devonian represented by claystones and siltstones intercalated commonly with layers and lenses of limestones enclosing an abundant marine fauna. The siltstones become upwards more and more sandy and comprise commonly layers of fine-grained quartz sandstones; they are often mottled and display commonly mud cracks. This is a typical Oldred fades; it is attributed to the Siegenian to Emsian. Thus, the marine sedimentation persisted in the investigated area continuously all through the Silurian and Lower Devonian. The earliest regression is marked in the Lower Siegenian deposits, while the

•terrestrial oldred-type sedimentation became prevalent in the Upper Siegenian.