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Continental influence on the marine Zechstein Sea: constraints from Strontium isotope compositions of Late Permian evaporites from the northernmost Thuringian Basin (Germany)

The up to 2000 m thick Zechstein succession was deposited in an epicontinental sea during the Late Permian. These deposits are virtually fossil-free and do not contain radiometrically datable volcanic layers. Thus, chemostratigraphy is currently the best method to assign absolute ages to these sediments.

We present 87Sr/86Sr data of the Zechstein succession at the northern rim of the Thuringian Basin. We sampled 26 gypsum and anhydrite samples from drill cores situated at “Alter Stolberg” (Niedersachsen, Germany). The drill cores include the Werra, Staßfurt, and Leine Formations. Our data allow a chemostratigraphic age assignment of these formations at 257-254 Ma. Moreover, we observe frequent outliers towards higher 87Sr/86Sr ratios, which could be interpreted as the contribution of meteoric water to the brine, in-situ Rb decay, or post-depositional hydrothermal or diagenetic overprint. The combination of the 87Sr/86Sr data with mineral composition data of the samples suggests a contribution of meteoric water, probably river water, to the Zechstein Sea as the main reason for the observed outliers. Modelling the amounts of sea water and meteoric water in the brine indicates that 83‒99% of meteoric water would be necessary to explain the highest 87Sr/86Sr ratios observed in the Werra Formation.

Details

Author
Alexandra Käßner1, Marion Tichomirowa1
Institutionen
1Institut für Mineralogie, TU Bergakademie Freiberg, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/5ksj-qw02