Reefal environments and sedimentary processes of the Anisian Karchowice Beds in Upper Silesia, southern Poland

The Anisian shallow-marine Karchowice Beds of the Upper Silesia represent reefal habitats and circum-reefal environments, where biological-mechanical interactions determine sedimentary processes and facies pattern. The purpose of this study was recognition of the interaction between biological and mechanical controls of carbonate deposition. Such interdependence resulted in considerable lateral variability of thickness and lithological features, observed at a distance of 25 km. The western part of the basin is dominated by proximal facies (reefal facies), whereas the eastern one represents distal facies (fore-reef). Sedimentary succession in the western area is twice as thick than the eastern one. It resulted from different rate of subsidence owing to block tectonics, controlled by reactivated ancestral Silesian-Moravian Fault. Small-scale synsedimentary faults confirm syndepositional tectonic activity in the region. Palaeogeographical position caused that the Upper Silesia was strongly affected by monsoon climate, generating storms. These storms contributed to episodic deposition, prevailing during the sedimentation of Karchowice Beds. However, most of time was represented by prolonged non-deposition periods, recorded as interstratal hiatuses, but also by forming of firmgrounds, micritization and coating of bioclasts or substrate recolonisation by organisms.