Thin black dolomites occur within the evaporitic Alpine Haselgebirge Formation (Late Permian) of the central and eastern Northern Calcareous Alps, Austria. They have been compared with the southalpine Bellerophon Formation byTollmann (1964). Samples obtained from the gypsum-anhydrite deposit of Wienern am Grundlsee, Styria, are mostly unfossiliferous mudstones (dolomicrite and dolomicrospar) devoid of sedimentary structures. Only few samples contain a low-diversity ostracode fauna. Electron microprobe and X-ray diffraction analysis indicate well-ordered and near-stoichiometric dolomite (49.9±0.2 mol% CaCO3). The oxygen isotopic composition varies between −3.0 and −5.7‰ PDB. The δ13C ratios fall into two distinct groups: −0.9 to +1.9‰, and −3.5 to −6.8‰ PDB. The carbon isotope data of the first group indicate a predominantly marine origin of the carbonates. The significantly depleted δ13C ratios of the second group are probably due to freshwater influx into the basin and/or sulfate reduction. Sulfur and strontium isotope data from intercalated anhydrite and gypsum preclude an entirely non-marine origin of the brines. The light δ18O ratios are probably due to early diagenetic sulfate reduction and/or dolomite recrystallization during moderate burial. A detailed interpretation of the depositional environment is rendered impossible because of the pervasive alpine tectonics. However, northalpine ‘Bellerophon’ carbonates appear to be restricted to areas of major anhydrite deposition, and are absent in the halitedominated facies.