In the Carnic Alps of Austria and Italy a broad spectrum of distinct paleokarst features of Lower Carboniferous age has been recognized, including an extensive paleorelief at the surface dated mainly by conodonts, collapse breccias, silcrete horizons, fissures and strata-bound ore deposits; in the subsurface are caves with cave sediments and paleo-karst-related cements. The paleokarst is associated with the unconformity that separates the Devonian to Lower Carboniferous limestone sequences from the overlying flysch deposits of the Hochwipfel Formation. In terms of the currently used conodont zonation, this event occurred during theScaliognathus anchoralis-Doliognathus latus zone, which corresponds to the latest Tournaisian or the Tournaisian/Visean boundary in Belgium.

In the Carnic Alps of Austria and Italy a broad spectrum of distinct paleokarst features of Lower Carboniferous age has been recognized, including an extensive paleorelief at the surface dated mainly by conodonts, collapse breccias, silcrete horizons, fissures and strata-bound ore deposits; in the subsurface are caves with cave sediments and paleo-karst-related cements. The paleokarst is associated with the unconformity that separates the Devonian to Lower Carboniferous limestone sequences from the overlying flysch deposits of the Hochwipfel Formation. In terms of the currently used conodont zonation, this event occurred during the zone, which corresponds to the latest Tournaisian or the Tournaisian/Visean boundary in Belgium.Field observations as well as biostratigraphic, microscopic and isotopic data establish a sequence of events which explain the karst features observed within a spatial and temporal framework. A drop in sea-level during the Late Tournaisian resulted in extensive limestone dissolution and karstification at surface and subsurface levels, and in local formation of fissures, caves and breccias. Almost simultaneously, a high-porosity silcrete regolith developed at the surface, exhibiting characteristic microporous and alveolar textures and composite void fillings of a euhedral quartz, chalcedony and mosaic quartz. Spar calcite coating on the cave walls may represent original speleothems, which predate the densely laminated and predominantly fine grained cave sediments. These and radial fibrous calcite in the fissures were generated in a phreatic environment. Finally, a slow rise in sea-level promoted the formation of crystal silt and clastic internal sediment in fissures, leading to the formation of rubble pack breccias and the transgression of the Hochwipfel Formation. Their high content of radiogenic strontium (plus other indications) rather suggest a crystalline rock source than a sea-water or host rock origin.

A 330-metre core drilled through the marine Permian/Triassic boundary in the Carnic Alps of Austria allows closely correlated studies of geochemistry, petrography and palaeontology across the boundary. The isotope shifts and metal concentrations are extended, multiple and complex, and do not resemble those seen at the Cretaceous/Tertiary boundary. Both the carbon isotope shifts and the chemical events (including an indium anomaly) may have causes related to a major regression of the sea.