Fluid pathways within shallow-generated damage zones of strike-slip faults – evidence of map-scale faulting in a continental environment, SW Permo-Mesozoic cover of the Late Palaeozoic Holy Cross Mountains Fold Belt, Poland

The damage zones of exhumed strike-slip faults dissecting Jurassic carbonates in the south-western part of the Late Palaeozoic Holy Cross Mountains Fold Belt reveal second-order faults and fractures infilled with syntectonic calcite. The subsequent development of a structural pattern of microscopic fault-related structures and calcite infillings reflects the activity of strike-slip faults that began in the Late Cretaceous (Late Maastrichtian) and lasted until the early Miocene (Langhian). The fabric of the syntectonic veins provides insights into the evolution of the permeable fault-related structures that were the main pathways for fluid flow during fault activity. Microstructural study of calcite veins coupled with stable isotope and fluid inclusion data indicates that calcite precipitated primarily in a rock-buffered system related to strike-slip fault movement, and secondarily in a partly open system related to the local activity of the releasing Chmielnik stepover or the uplift of the area. The presence of meteoric fluids descending from the surface into damage zones suggest that the strike-slip faulting might have taken place in a nonmarine, continental environment

Evidence of Late Cretaceous/Cenozoic strike-slip faulting within the late Palaeozoic Holy Cross Mts. Fold Belt, Poland: Józefka releasing stepover

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