A strontium and sulfur isotopic study of Permo-Triassic evaporites in the Northern Calcareous Alps, Austria

Pervasively deformed Permian and, to a lesser extent, Triassic evaporites of the Northern Calcareous Alps form a tectonic mélange, collectively known as (Alpine) Haselgebirge. Isotopic compositions of S and Sr and trace-element concentrations of Sr and Ba in Ca-sulfate minerals were investigated in terms of their stratigraphic and paleoenvironmental significance. jority of the samples yielded δ34S values ranging from +9.8 to + 13.8% indicating precipitation from Late Permian seawater with local modifications due to bacterial sulfate reduction (BSR). 87Sr86Sr ratios of these samples range widely from 0.7070 to 0.7098, but most samples show Sr isotope values between 0.7070 and 0.7074, overlapping with the accepted Late Permian seawater values. Comparison of both S and Sr isotopic compositions of individual samples reveals distinct trends of isotopic enrichment and depletion that can be linked to early diagenetic BSR, mixing with continental surface- or groundwaters, and burial diagenesis. Concentrations of Sr tend to be lower and Ba values show a tendency toward values higher than those reported from marine evaporites, implying variable diagenetic alteration. ic evaporites are volumetrically less important in the Haselgebirge than their Permian counterparts and are characterized by marine Upper Scythian to Lower Anisian S and Sr isotope values. In three localities hitherto unknown inclusions of these Triassic evaporites were identified within the Haselgebirge melange.