Sedimentary and pedogenic record of seasonal humidity during the Permian-Triassic transition on the SE margin of Central European Basin (Holy Cross Mountains, Poland)

Abstract

The transition from the late Permian to Early Triassic was associated with one of the biggest biotic crises in the entire Phanerozoic which affected life in both marine and continental settings. Unlike in the marine realm, the environmental dynamics in continental palaeoenvironments across the Permian-Triassic interval are still poorly understood. In order to fill this knowledge gap, we studied the Permo-Triassic continental succession from the SE part of the intracontinental Central European Basin (CEB). High-resolution sedimentological logging of over 1700 m of cores, supplemented by micromorphology of palaeosols, palynofacies, and quantitative spore-pollen analyses, allowed reconstructing major steps in palaeoenvironmental evolution, and assessing the magnitude of extrinsic factors responsible for such development. The studied interval is dominated by redbeds deposited in arid, semi-arid, and sub-humid subenvironments in which palaeosol profiles are important elements of facies architecture. Vertical and lateral facies arrangement indicate three major development stages associated with progradation of a large distributary fluvial system towards the centre of the basin. These stages correspond to the main lithostratigraphic units in the studied area. In the first stage, the saline mudflats were replaced by muddy floodplain facies and then by medial and proximal parts of the ephemeral fluvial system of the Podzamcze Formation. The overlying Siodła Formation represents the stage of environmental stabilisation associated with widespread pedogenesis resulting in the formation of thick cumulative palaeosol profiles. The last stage was marked by the influx of coarse-grained fluvial sediments of the Jaworzna Formation and change in soil character towards less evolved types in overbank facies of the Szczukowice Formation. The change in the sedimentary record and soil types reflects the successive humidification in the SE part of the CEB, supported by increasing contribution of the hygrophytic over mostly xerophytic palynomorphs in the upper Permian palynological assemblage. This humidification trend was likely an environmental response to global warming in the late Permian.