Volga-Vyatka Region), Russia

Early Kazanian fauna of the Nemda River Basin

Galina P. Nestell1, Merlynd K. Nestell1, Galina V. Kotlyar2, 3,

Olga L. Kossovaya2, 3, Dieter Weyer4

1University of Texas at Arlington, Arlington, USA, gnestell@uta.edu

2Karpinsky All-Russian Geological Research Institute, St. Petersburg, Russia

3Kazan Federal University, Kazan, Russia

4Museum of Natural History, Berlin, Germany

The presence of bioherms or “reefs” in the Kazanian deposits of the Nemda River Basin was first

described by Solodukho in 1954. He divided the Kazanian strata into lower and upper parts based on lithology and faunal content with the bioherms considered to occur in the lower part. The authors investigated sections of Kazanian strata in the Kremeshki, Chimbulat and Popovtsevo quarries. Bioherms were found only in the first two named quarries and are composed of crinoid and bryozoan remains, and also contain gastropods, ammonoids, foraminifers, brachiopods and rare rugose corals. The encompassing deposits are represented by lagoonal lithofacies with shallow water brachiopods, bivalves, abundant foraminifers, conodonts, and rare ammonoids. Foraminifers from the bioherms and encompassing rocks are represented by almost the same species such as Pseudoammodiscus megasphaericus, P. microsphaericus, Hemigordius discoides, Polarisella elabugae, Nodosaria noinskyi, and Geinitzina spandeli, which are typical for the lower part of the Kazanian. Ammonoids are found in the bioherm of the Kremeshki quarry and represented by Sverdrupites amundseni, S. harkeri, Biarmiceras esaulovae, B. kremeshkense, Medlicottia postorbignyana. According to Leonova and Shilovsky, the first two species are known in the Roadian of many regions. Conodonts have been found in the Kremeshki and Chimbulat quarries in the lagoonal lithofacies and include species Sweetina triticum and Kamagnathus khalimbadzhae, which are characteristic for the lower part of the Kazanian of the Volga-Kama area, and the first one occurs in the Jinogondolella nankingensis zone of the Roadian of North America. Brachiopods are present in bioherms and encompassing deposits, but differ by their species composition.

The species Globiella hemisphaerium, Cancrinella ledjensis, Terrakea hemisphaeroidalis,

Odontospirifer subcristatus, Bajtugania netschajevi are found in the bioherms, whereas in the

encompassing deposits the species Cancrinella cancrini, Aulosteges wangenheimi, Cleiothyridina pectinifera, Stenocisma superstens, Odontospirifer subclatratus are present. The main difference of the brachiopod assemblages in the bioherms is in the complete absence of the Licharewiidae (genera Licharewia and Tumarinia), and thin costate spiriferids. Rugose corals are found in the reefal facies of the Kremeshki quarry and are represented by species Paracaninia variabilis known from younger deposits in the Arctic. Only foraminifers have been found in the lower part of the section in the Popovtsevo quarry suggesting a very restricted marine environment. They are represented by species typical for the lower part of the Kazanian of the Volga-Kama Region such as P. megasphaericus, P. microsphaericus, Nodosinelloides netschajewi, Nodosaria hexagona, N. noinskyi, N. farcimeniformis, Pseudonodosaria nodosariaeformis, P. lata, Ichthyolaria longissima, and G. spandeli.

Nestell G.P. et all., 2015 Early Kazanian fauna of the Nemda River Basin (Volga-Vyatka Region), Russia/G.P. Nestell, M.K. Nestell, G.V. Kotlyar, O.L. Kossovaya, D.Weyer//XVIII International Congress on the Carboniferous and Permian. August 11–15, 2015, Kazan, Russia. Abstracts Volume / D.K. Nurgaliev, A.S. Alekseev, G. Della Porta, O.L. Kossovaya, G.V. Kotlyar, S.V. Nikolaeva, V.V. Silantiev, M.N. Urazaeva (Eds.). — Kazan: Kazan University Press, 2015. — 228 p., p-135

Date: 2016-01-14; view: 1202