Radiation of the middle Devonian conodonts in ne Salair (South of West Siberia)

Skoritsky I.S.¹, Izokh N.G.²

1Novosibirsk State University, Novosibirsk, Russia

lam__@mail.ru

2A.A. Trofimuk Institute of Petroleum Geology and Geophysics sb ras, Novosibirsk, Russia

Izokhng@ipgg.Nsc.Ru

A new stage in development of conodont genera Polygnathus Hinde and Icriodus Branson et Mehl is noted in Middle Devonian. For the first time radiation in their lineages was proposed by K. Weddige and W. Ziegler [3]. In Eifelian from ancestor Polygnathus costatus patulus developed Polygnathus costatus group. Most diversity of this fauna is noted for the costatus-australis zones and then reduces at the upper Eifelian boundary. Similar trend was found for Icriodus. Thus in Eifelian new Icriodus groups were formed - regularicrescens, struvei and werneri [3]. Study of Eifelian conodonts from north-east Salair revealed similarity in their radiation with that known from German sections (Eifelian Mountains).

At NE Salair, vicinity of Gurievsk town, Eifelian Pesteryovo Formation is represented by bedded and reef limestones cropped out in the Malaya Salairka Quarry. From carbonates of Pesteryovo Fm diverse conodont association was obtained [1]. It is dominated by Polygnathus costatus and Icriodus regularicrescens. The Polygnathus costatus group is characterized by coarse ribs on the upper surface of platform. The Icriodus regularicrescens group has narrow platform of I-element ornamented by short denticles. Conodont association includes Polygnathus costatus partitus Klapper, Ziegler et Mashkova, Polygnathus costatus costatus Klapper, Polygnathus costatus oblongus Weddige, Polygnathus pseudofoliatus Wittekindt, Polygnathus angusticostatus Wittekindt, Polygnathus aff. trigonicus Bischoff et Ziegler, Tortodus sp., Icriodus regularicrescens Bultynck and Icriodus sp. 2, characteristic for partitus-costatus-australis zones.

Eifelian-Givetian boundary interval was investigated in sections near Prokopievsk town [2]. Conodont association is different here, represented by Polygnathus linguiformis klapperi Clausen, Leuteritz et Ziegler, Polygnathus pseudofoliatus Wittekindt, Icriodus norfordi Chatterton, Icriodus platyobliquimarginathus Bultynck and Icriodus sp. Genus Polygnathus possess wide flattened platform. Genus Icriodus has wider platform ornamented by large denticles and wide basal cavity.

Conodonts from NE Salair are cosmopolitan species being an evidence of broad relations of the Middle Devonian Salair basin with other paleobasins. Middle Devonian conodonts radiation trends identified in the Eifelian Mountains can be traced in Salair paleobasin as well.

Study has been supported by RFBR grants № 11-05-00737, 11-05-01105, RAS Projects 28. Contribution to the IGCP 596.

References:

1. Izokh, N.G. Biodiversity of Devonian conodonts from the West Siberia //Berichte des Institutes für Erdwissenschaften, Karl-Franzens-Universität Graz. ISSN 1608-8166. IGCP 596 Opening Meeting. Graz, 19-24th September, 2011, Band 16, p. 49-51.

2. Middle-Upper Devonian and Lower Carboniferous Biostratigraphy of Kuznetsk Basin. Field Excursion Guidebook. International Conference “Biostratigraphy, paleogeography and events in Devonian and Lower Carboniferous” (SDS / IGCP 596 joint field meeting) / Eds. N.K. Bakharev, N.G. Izokh, O.T. Obut, J.A. Talent. (Authors: N.K. Bakharev, N.G. Izokh, A.Yu. Yazikov, T.A. Shcherbanenko, S.A. Anastasieva, O.T. Obut, S.V. Saraev, L.G. Peregoedov, V.G. Khromykh, O.A. Rodina, I.G. Timokhina, T.P. Kipriyanova). Novosibirsk, July 20 – August 10, 2011. – Novosibirsk: Publishing House of SB RAS. 2011. 98 p.

3. Weddige, K., Ziegler, W. Evolutionary patterns in Middle Devonian conodont genera Polygnathus and Icriodus // Geologica et Palaeontologica, 1979, V. 13, p. 157-164, 3 text-figs; Marburg.