The aim of this study was to reconstruct the location mechanism of a Triassic sandstone wedge within folded Palaeozoic rocks. A vertically oriented Buntsandstein succession (Lower Triassic) from Józefka Quarry (Holy Cross Mountains, central Poland), steeply wedged within folded Devonian carbonates, is recognised as an effect of normal faulting within a releasing stepover. The sandstone succession, corresponding to the Zagnańsk Formation in the local lithostratigraphic scheme, is represented by two complexes, interpreted as deposits of a sand-dominated alluvial plain (older complex), and coarse-grained sands and gravels of a braided river system (younger complex). The sandstone complex was primarily formed as the lowermost part of the several kilometres thick Mesozoic cover of the Holy Cross Mountains Fold Belt (HCFB), later eroded as a result of the Late Cretaceous/Paleogene uplift of the area. Tectonic analysis of the present-day position of the deformed sandstone succession shows that it is fault-bounded by a system of strike-slip and normal faults, which we interpret as a releasing stepover. Accordingly, the formation of the stepover in the central part of the late Palaeozoic HCFB is evidence of a significant role of strike-slip faulting within this tectonic unit during Late Cretaceous/Paleogene times. The faulting was probably triggered by reactivation of the terminal Palaeozoic strike-slip fault pattern along the western border of the Teisseyre–Tornquist Zone.
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Contemporary Conchostraca [clam shrimps] live in temporary and permanent freshwater ponds and pools. They have wide geographic distribution. Their fossils are abundant in the Buntsandstein and very important markers for chronostratigraphic correlation between marine and continental sections. The conchostracan assemblage found in the lowermost Buntsandstein at Zachełmie quarry: Falsisca postera, Falsisca eotriassica, Palaeolimnadia cf. cishycranica, Euestheria ex gr. gutta, Euestheria gutta oertlii indicates the uppermost Permian age of at least the most of Jaworznia Formation [A1 petrographical complex], cropping out at the Zachełmie quarry in the Holy Cross Mountains, Poland.
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