Marine ingressions into the Middle/Late Permian saline lake of the Southern Permian Basin (Rotliegend, Northern Germany) possibly linked to sea-level highstands in the Arctic rift system

摘要

A huge saline lake existed in the Southern Permian Basin (SPB) of Northwest Europe during Late Wordian to Early Wuchiapingian. More than 2500 m thick continental siliciclastics and evaporites of the Upper Rotliegend II were deposited before the marine Zechstein transgression flooded the basin. Marine deposition took place in the Arctic rift system between East Greenland and the Fennoscandian Shield at that time interval. Sediments of the Foldvik Creek-Group reflect relative sea-level fluctuations. Short-termed pre-Zechstein ingressions from the Boreal realm into the SPB are known by the marine lamellibranch Liebea reichei. However, sedimentological analysis of different saline lake horizons show, that the marine influenced saline lake horizon does not differ lithologically from other saline lake claystone layers in the Rotliegend succession. The Sr-87/Sr-86 ratios of anhydrite (0.7089-0.7100) reflect deposition in a continental setting. In contrast to this, S-isotopic values (more than + 11.7%. CDT) reflect marine pre-Zechstein ingressions into the SPB in the middle Niendorf and Munster Members. S-isotopic values of anhydrite can be used as an indicator for marine influence in the SPB. The pre-Zechstein ingressions superimpose the climatic triggered lake-level fluctuations of the Rotliegend saline lake. Two marine ingressions can be integrated into a set of regularly recurring abnormities in the depositional evolution. These important evolutionary steps, the saline lake formation, the Garlstorf ingression, the P, Ameland and Bahnsen lake level highstands, the Niendorf ingression, and the Zechstein transgression, show a periodicity of more or less 1 Ma. One million year cyclicity is also known from deposits of the Arctic rift system in East Greenland (Wegener Halvo and Ravnefjeld Formations). A correlation of the Upper Rotliegend II-deposits with the succession of East Greenland is proposed, based on the assumption that the marine ingressions as well as the exceptionally intensive saline lake expansions could be linked to sea-level highstands in the Arctic rift system. The result is the first correlation of Upper Rotliegend II-deposits with marine strata.