The lower permian freshwater carbonates of the Slawkow graben, Southern Poland: Sedimentary facies context and stable isotope study
Abstract During early Permian times the post-Hercynian rift valley known as the Slawkow graben was filled with typical continental molasse deposits including fanglomerates and olistolites, playa flat sediments with evaporites, volcaniclastics and carbonates deposited in small spring-fed basins (oasis environment). Lithofacies variability, lithofacies relationships, sedimentary structures and paleokarst data indicate a highly changeable sedimentary environment controlled by climate, syndepositional faulting, and accompanying volcanism. Differential uplift resulted in a high-relief topography, the basin-margin mountains probably having a relative altitude of up to 1000 m. The stable isotopic composition ( δ 13 C, δ 18 O) of the spring-related carbonates indicate seasonal temperature differences of up to 15°C, a value that is close to the average annual temperature amplitude in the present-day subtropical zone. Other environmental indicators (e.g. red beds, evaporites, braided-stream sediments) corroborate the isotopic interpretation. A longer-term 6–7 year cycle, reflected in δ 18 O-composition of the carbonate, is attributed to rainfall fluctuations.