The base of the Permian System, Cisuralian Series and Asselian Stage is defined 27m above the base of Bed 19, Aidaralash Creek, northern Kazakhstan, where it coincides with the first occurrence of "isolated-nodular" morphotype of Streptognathodus "wabaunsensis" conodont chronocline.
The Aidaralash Creek section is located in the Aktjubinsk (Aqtöbe) region of the Southern Ural Mountains of northern Kazakhstan, approximately 50km east of the city of Aqtöbe.
The strata of Beds 1 through 39 (Gzhelian to Sakmarian) consist of hemipelagic silt and clay, with occasional sand and very coarse sand lenses.
First occurrence of "isolated-nodular" morphotype of the Streptognathodus "wabaunsensis" conodont chronocline, 27m above the base of Bed 19.
Termination of Prouddenites-Uddenites lineage at the top of Bed 19.
Introduction of Svetlanoceras primore and Prostacheoceras principalein Bed 20.
Base of the Sphaeroschwagerina vulgaris-S. fusiformis Zone coincides with the contact of Beds 19.5 and 19.6.
Ultradaixina disappears and Schellwienia becomes scarce at the contact of Beds 19.5 and 19.6. Species of Sphaeroschwagerina first appear at this level.
Conodont FAD of isolated-nodular morphotype of Streptognathodus "wabaunsensis"
The first appearance of "isolated-nodular" morphotype of the Streptognathodus "wabaunsensis" chronocline can be recognized in the basinal shales in Usolka in the lower part of Bed 16 (Chuvashov et al., 1990) and in the cyclic succession of the American mid-continent. It first occurs in the Glenrock Limestone Member of the Red Eagle Limestone (Chernykh and Ritter, 1994). Although not recognized at Aidaralash, the first appearance of Streptognathodus nodulinearis in Kansas and Usolka nearly coincides with the first occurrence of the "isolated-nodular" morphotype, making it a useful accessory indicator of the boundary.
Davydov, V. I., Glenister, B. F., Spinosa, C., Ritter, S. M., Chemykh, V. V., Wardlaw, B. R., and Snyder, W. S., 1998. Proposal of Aidaralash as Global Stratotype Section and Point (GSSP) for base of the Permian System. Episodes 21/1, p. 11 - 18.
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Chuvashov, B. I., Chernykh, V. V., and Mizens, G. A., 1993. Zonal divisions of the boundary deposits of the Carboniferous and Permian in sections of different facies in the south Urals. Permophiles 22, p.11-16.
Chernykh, V. V. and Ritter, S. M., 1994. Preliminary biostratigraphic assessment of conodonts from the proposed Carboniferous-Permian boundary stratotype, Aidaralash Creek, northern Kazakhstan. Permophiles 25, p. 4-6.
Chuvashov, B. I., Dupina, G. V., Mizens, G. A., and Chernykh, V. V., 1990. Report on Upper Carboniferous and lower Permian sections, western slope of the Urals and pre-Urals. Uralian Branch U.S.S.R. Acad. Sci., Swerdlovsk, 368p.