Geologicheskii Vestnik

The article describes the Asha molasse of Timanian orogen in the section of Kukrauk stream in the western wing of the Alatau anticlinorium (Southern Urals). Deposits of the Basa, Kukkarauk and Zigan Formations of Asha series of the Upper Vendian are the part of the folded complex of Timanides, the rocks of which, similar to typical molasse, are heterogeneous in material and particle size composition. These deposits are well represented in the coastal cliff s and along the channel of the Kukrauk stream for 11 km and have a thickness of more than 1.5 km. However, the Kukrauk deposits of the creek are not suffi ciently exposed and more complete outcrops of the Zigan Formation are present in roadside excavations along the new part of the Sterlitamak – Beloretsk road on the watershed of the river. Zigan and stream Kukrauk. Several layers of tuff are present there in the mudstones of the Zigan Formation, which is of considerable interest for paleogeographic reconstructions in the region at the boundary of the Vendian and Paleozoic. The new SHRIMP dating of 713.6±6.1 Ma was acquired for zircon from granite pebbles of conglomerates of the Kukkarauk Formation in the section along the Agarda creek, the right tributary of the Inzer river. This dating indicates that in the Late Vendian time, erosion occurred to the rocks close in composition and age to granites of the Mazara massif (710–740 Ma) and the Barangulovo gabbro-granite complex (725±5 Ma), located in the northern part of the Uraltau zone in the Southern Urals, to the east of the Late Vendian sedimentary basin. The outcrops of the Basa, Kukkarauk and Zigan Formations along the Kukrauk stream and on the watershed of Zigan and Kukrauk along the new section of the Sterlitamak – Beloretsk road were proposed as reference objects for paleotectonic and paleogeographic reconstructions of folded complexes.

molasse, Vendian, Orogen, Asha Series, Formation, Basa, Kukkarauk, Zigan, Southern Urals

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