Reconstructing the evolution of the latest Pennsylvanian–earliest Permian Lake Odernheim based on stable isotope geochemistry and palynofacies: A case study from the Saar-Nahe Basin, Germany

Finely laminated sediments archived the evolution of the latest Pennsylvanian–earliest Permian Lake Odernheim, Saar-Nahe Basin, Germany. A succession of evolutionary stages can be distinguished based on variable carbonate carbon (− 5 to + 2‰) and oxygen (− 7 to + 5‰) isotopic compositions of dolomite. Sedimentary organic matter represents primarily a mixture of detrital vascular plant material ( δ 13C around − 21‰) and lake derived photosynthetic algal matter ( δ 13C around − 27‰). This distinction based on organic carbon isotopes is further supported by palynofacies analyses and Rock-Eval data. An additional contribution from bacterial biomass is likely. Bacterial sulphate reduction, and thus anaerobic remineralization of sedimentary organic matter, is indicated by the presence of sedimentary pyrite. Observed geochemical changes are attributed to temporal variations in the water balance of Lake Odernheim, including times of stronger evaporation as well as times showing substantial input of freshwater.