Strontium isotopes in the Zechstein (Upper Permian) anhydrites of Poland: evidence of varied meteoric contributions to marine brines

Strontium isotope ratios have been determined on 74 anhydrite samples from seven borehole cores in the Polish Zechstein. Five of the borehole cores are located in the basin and isotope results from these samples show a nearly pure marine signal. Results from one borehole core, located near the Zechstein coastline that migrated through time, record a stronger, in consistent influence of continental strontium to a marine base. Intermittent meteoric influence is recorded in anhydrites from other borehole cores close to the carbonate platform that was emergent during the anhydrite deposition. Consistency of isotope values indicates a marine signal and there is a narrow range in consistent values from 87Sr/86Sr near deltasw –215 (0.70702) for the oldest anhydrites and near deltasw –205 (0.70712) for the youngest an hydrites. Comparison with a sea water 87Sr/86Sr curve based on samples in West Texas and a Permian-Triassic boundary value from China shows that the Polish Zechstein in these seven boreholes is latest Permian in age and major deposition represents a short time interval (~2 million years). Strontium isotope ratios reported by other workers indicate some of the younger Zechstein elsewhere indicate even greater continental influence is in agreement with the interpreted sedimentological set ing for those anhydrites.