The Early Kimmeridgian succession at Kodrąb (Radomsko elevation, central Poland) and its palaeogeographical and palaeotectonic implications

Abstract

The Early Kimmeridgian succession in the Rogaszyn Quarry at Kodrąb (Radomsko elevation) represents mostly shallow-water carbonate platform deposits that, over wide areas of central Poland were controlled by the activity of the tectonic zone being the prolongation of the Holy Cross lineament. The ammonites collected enable precise recognition of ammonite zones – the Platynota and the Hypselocyclum zones, some subzones and horizons. The precise dating enables detailed correlation of the particular units of the succession with those recognized at the eastern and northern borders of the Wieluń Upland and the NW margin of the Holy Cross Mts. The deposits at Kodrąb from the top of the Planula Zone, through the Platynota Zone, up to the lower part of the Hypselocyclum Zone, reveal markedly smaller thicknesses equaling ~15–20% of those of coeval deposits from the adjoining areas. The differences in sedimentary evolution at Kodrąb during the Early Kimmeridgian resulted mostly from local synsedimentary tectonic movements of fault blocks. Beginning from the late Hypselocyclum Chron, these differences markedly diminished, which resulted from the uniform subsidence of a wider area, and disappearance of the shallow-water deposits of the carbonate platforms, being replaced by deeper-water deposits of the Burzenin Formation.