Geotectonic evolution of the northern Tethyan margins in the Tithonian - sedimentological and biostratigraphical implications (Silesian Basin, Western Outer Carpathians)

During the Late Jurassic the geotectonic reorganization of the extensive shelves on the southern margins of the Eastern European Platform was influenced by rifting in the Carpathian Basin which resulted in formation of the marginal Tethyan seas. The origin of the Silesian Basin was correlated with the first stage of the rifting (Golonka et al. 2000). The process of opening and deepening of the basin was completed at the end of the Jurassic when Neocimmerian movements were intensified and a regression on the Tethyan shelf had reached its peak. At that time, in the Western Outer Carpathians, breccias and olistostromes including mainly carbonate boulders, olistoliths and klippen were formed. In the Silesian Basin the supply of these redeposited materials culminated in Late Tithonian. The marly layers with olistolithes are known from the Cieszyn Silesian. The deposits occur at the top of nonflysch marly deposits, which belong to the oldest units of the Cieszyn Beds of the Polish and the Czech Outer Carpathians. In the Czech Carpathians these deposits correspond to the Ropice horizon (Eliáš & Eliášova 1984), which apart from the Štramberk reef and allodapic Cieszyn Limestones contains also calcareous sandstones and claystones including boulders of metamorphic and magmatic rocks (Eliáš & Eliášova 1984). These deposits yielded foraminifers which were also subject to removal and transportation. These include numerous calcareous (involutinids, placentulininds) and single agglutinated (lituolids) foraminifers which have been reported in rocks containing the olistolithes, but mainly in the overlying marls. Late Tithonian microfossils include also fragments of crinoids, bryozoans, and corals. These layers including calcareous material coming from destruction of the reef complex and carbonate platform can be assigned to a lithohorizon, deposited during geotectonic rebuilding of the northern Tethyan margins.