Early Permian Bryozoans of the Ilych River (Northern Urals)

Bryozoans are both abundant and diverse in the Lower Permian deposits of the Northern Urals. Their Asselian, Sakmarian, Artinskian, and Kungurian species have been characterized in many papers. However, revision of many taxa remains necessary. This paper presents the first review of the local bryozoans fauna from the carbonate build-up located in the middle stream of the Ilych River (the right tributary of the Pechora River). The importance of this section is explained by the necessity of establishing the age of the deposits represented there and the absence of any bryozoan record in its previous studies. The Ilych section is exhibited as two outcrops 500 meters upstream the mouth of the Ydjyd An'ju River at the reach Micha Lasta. The deposits are dated on the basis of fusulinaceans as Middle-Late Asselian in the first outcrop, and they are dated as Sakmarian in the second outcrop. Massive light grey limestones contain fragments of bryozoan colonies, rare fusulinaceans, brachiopods, crinoids, green algae, tubiphytes, gastropods, and small foraminifers. Our study resulted in recognizing 4 bryozoan species: Rhabdomeson sp., Rhombotrypella composita, Streblascopora cf. vulgaris, and Parapolypora pravocellata, as well as one new species, namely, Pseudorhabdomeson permium sp. nov. Thin-branched colonies of bryozoans dominate. Reticulate funnel forms are also found. Despite of the high abundance of bryozoans in the section, their fauna is taxonomically monotonous. Locations of bryozoans and relatively large sizes of their fragments are evidences of the "in situ" burial and growth in the shallow-water marine basin withinactive hydrodynamics. Data on other fossils confirm the existence of such a basin and indicate its depth as first tens of meters. At the generic level, bryozoans from the Ilych section demonstrate broad palaeogeographic affinities with faunas from the other regions of Eurasia, North America, Australia, and the Arctic. At the species level, the studied bryozoans had an area, which embraced the Northern Uralian Basin and the Western Arctic. Available data on bryozoans allows to define the age of deposits from the Ilych section as Sakmarian. Further study of bryozoans and fusulinaceans from this carbonate build-up will show a more precise age.

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