Sammendrag
Early Permian (Artinskian) bryozoans and associated depositional environment are described from selected outcrops of the evaporitic / carbonate of the Gipshuken Formation, eastern Central Spitsbergen (Svalbard), Arctic Norway.
The up to 280 m thick Gipshuken Fm. is divided into a number of local, informal members featuring massive carbonate breccias and rhythmic interbeds of carbonates, evaporites and marls. The depositional period of this unit (Sakmarian to Artinskian) was characterised by the gradual regression of the sea across Svalbard. As a consequence, intertidal to supratidal lagoons, mudflats and sabkhas developed on the platform carbonates. These extreme environments could support only a low-diversity biota mostly consisting of algae, small foraminiferans and gastropods.
The studied interval comprises the Templet Member which includes a wide range of facies from black shales with high TOC content to carbonate grainstones with high porosities and massive impermeable layers of gypsum. It forms the upper part of the Gipshuken Fm. and overlies a succession of interbedded evaporites and carbonates. Three major transgressive surfaces occur in the lower part of Templet Mb where bryozoans are locally present. The colonies are often diagenetically altered (dolomitized, silicified) and internal structures, important for detailed identification, are often destroyed. But some colonies are better preserved, and species of Dyscritella (Trepostomata) and various fenestrates have been identified. Some fenestrate and trepostome species from the Gipshuken Fm. have previously been published, including Toulapora svalbardense (originally erroneously described as a species of the cryptostome genus Hinaclema). The very low diversity is considered to be a result of extreme environmental changes, especially regarding fluctuations in water depth (and energy) and salinity (evaporation).
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