Role of the olistostromes and olistoliths in tectonostratigraphic evolution of the Silesian Basin in the Outer West Carpathians

The Silesian Series deposited in the proto-Silesian and Silesian basins and preserved within the Silesian Nappe, represents most complete continuous basinal sedimentary succession (Late Jurassic–Early Miocene) within the Outer Carpathians. It contains intercalations of numerous olistostromes that occurred during every stage of flysch basin evolution, from rift and post-rift, through orogenic to postorogenic stage. The olistostromes represent sediments of sub-marine debris-flows and avalanches. They are of different size and composition and were derived from ridges and their slopes bordering proto-Silesian and Silesian Basins. 0However the main source was the tectonically active southern slope and adjacent ridges — the Silesian and Bukowiec ridges. Composition of olistostromes is an important source of knowledge about the geological structure and history of ridges and basin slopes, which now are not preserved. Some large olistoliths and olistoplaques have been incorrectly interpreted as thrust sheets, so detail studies of their true origin allowed correct interpretation of local tectonics.

► Olistostromes occur in different lithostratigraphic levels of the Silesian Series. ► They are connected with every orogenic stages of evolution of the Silesian Basin. ► We describe more important olistostromes and present conditions of their origin. ► Size and composition of olistoliths depended of built of source areas. ► The studies partly allowed reconstructing structure of the basin slopes and ridges.