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Foraminifera and Late Cenomanian-Turonian biostratigraphy of the northern palaeobiogeographic district of Western Siberia

Podobina Vera

Geologos

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2013

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Vol. 19, No. 3

201--227

EN

The study of 114 core samples from seven borehole sections of the Van-Eganskaya area in the central part of Western Siberia yielded sufficient data to investigate the Late Cenomanian-Turonian foraminifers, palaeoenvironments, and the Late Cenomanian-Turonian biostratigraphy of this poorly studied area. Two Late Cenomanian foraminifer zones were established, viz. a (lower) Saccammina micra - Ammomarginulina sibirica Zone and an (upper) Trochammina wetteri tumida - Verneuilinoides kansasensis Zone. They reflect changes in the species composition of the foraminifer assemblages and lithology of the host rocks of the Uvatskian Horizon. In the lower part of the upper zone, beds with Gaudryinopsis nanushukensis elongatus are present. The changes in the species composition and lithology of the upper Cenomanian resulted from water-depth variations during the Boreal transgression. Two distinct assemblages and two homonymous zones, viz. the (lower) Gaudryinopsis angustus and the (upper) Pseudoclavulina hastata zones occur in the Turonian clayey cap-rocks of the superimposed Kuznetsovskian Horizon. Comparison of the Late Cenomanian-Turonian assemblages from the West-Siberian and Canadian provinces of the same Arctic palaeobiogeographical realm shows that the West-Siberian species are the same as, and closely related to, Canadian taxa, along with geographical subspecies. This comparison allows a detailed correlation, which results in a precise dating of the foraminifer zones.

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First 230Th/U date of middle Pleistocene peat bog in Siberia (key section Krivosheino, Western Siberia)

Maksimov F. E. F. E., Laukhin S. A., Arslanov K. A., Kuznetsov V. Y., Shilova G. N.

Geochronometria

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2012

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Vol. 39, no. 4

241-251

EN

A ¹⁴C date older than 53900 yrs BP was obtained for the uppermost part of the buried peat bog in Krivosheino section (Middle Pleistocene of Western Siberia). These sediments also yielded ²³⁰Th/U dates of 195 _-9.1 ka using the leachate alone (L/L) and 204 ⁺¹⁷ _-13 ka using total sample dissolution (TSD) models. Peculiarities of 230Th/U dating are discussed. Palynological investigation of the buried peat bog together with underlying and overlaying sediments, and comparison with palynologi-cal data from Baikal and Elgygytgyn lakes revealed that the peat layer in Krivosheino section was formed at the end of Shirta Interglacial (Marine Isotopic-Oxygenous stages MIS-7), when climate conditions at all studied sites were more severe compared to the modern ones.

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The Danian and Selandian calcareous benthic foraminiferal assemblages and biostratigraphy of Western Siberia

Podobina Vera

Geologos

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2011

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Vol. 17, No. 2

97--110

EN

Danian and Selandian successions in western Siberia are rich in calcareous benthic foraminifers. The assemblages with a constant systematic composition that have the widest lateral occurrence are distinguished as foraminiferal zones. The Brotzenella praeacuta Zone was established in the low-carbonate, clayey beds that form the transition from the Gankinskaya Suite to the Talitskaya Suite. These transitional beds are assigned to the Danian. The calcareous benthic foraminifers in this zone occur mainly together with agglutinated forms. The zone is traced along the areas of the largest subsidence of the Mesozoic-Cenozoic basin, principally in depressions. The transition from the Cretaceous to the Palaeogene is represented by a continuous succession, in which the Danian deposits escaped from erosion and were found to contain the B. praeacuta assemblage. In Danian rocks with a shallow-marine facies (near Beryozovo and in the Ust’-Tym depression, Fig. 1), the Bathysiphon nodosarieformis - Glomospira charoides assemblage occurs. It is dominated by primitive forms in addition to more advanced tests (mainly Late Maastrichtian relic species). The overlying Selandian (Middle Palaeocene) foraminiferal assemblages are assigned to the Talitskaya Suite. The Ammoscalaria friabilis assemblage is widely spread and is represented mainly by agglutinated quartz-siliceous forms. Beds with these species are attributed to the Ammoscalaria friabilis Zone, which can be correlated with beds in the East containing Cyclammina coksuvorovae. The Cibicidoides proprius assemblage is known from the lower and middle beds of the Talitskaya Suite in Transuralia, the Omsk Depression and more south-eastern areas; the species of this assemblage are characteristic of the Selandian.

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Bryozoans from the Jurginskaya Formation (Famennian, Upper Devonian) of the Tom-Kolyvansk area (Western Siberia, Russia)

Tolokonnikova Zoya

Geologos

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2010

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Vol. 16, No. 3

139--152

EN

Nine bryozoan species are described from the Jurginskaya Formation (Famennian, Late Devonian) from Western Siberia, Russia, namely: Leptotrypella pojarkovi Orlovski, 1961, Rhombopora subtilis Nekhoroshev, 1977, Klaucena lalolamina Yang, Hu, Xia, 1988, Eofistulotrypa famennensis sp. n., Atactotoechus cellatus sp. n., Nikiforopora jurgensis sp. n., Eridotrypella tyzhnovi sp. n., Mediapora elegans sp. n., and Klaucena gracilis sp. n. The studied assemblage shows palaeogeographical affinity with Kazakhstan, Kirgizia, Transcaucasia, China, and the United States of America.

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The foraminiferal assemblages of the uppermost Kimmeridgian-Volgian succession of Western Siberia and their correlation potential 157 INTRODUCTION During the last few decades, the stratigraphy of the uppermost Jurassic-lowermost Cretaceous (scope, sequen

Podobina V., Gabysheva E., Tatyanin G.

Volumina Jurassica

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2009

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Vol. 7, no. 1

157-172

EN

The present study summarizes the data on the continuous stratigraphic sequence of foraminiferal assemblages from the Volgian deposits of the south-east of Western Siberia. Microfaunal analyses of 650 core samples from 18 boreholes of Volgian deposits were performed. Eighty two foraminiferal species, identified from the samples, were combined into the Volgian assemblages. On the basis of these assemblages, four biostratigraphic units were established in the range of foraminiferal zones and foraminiferal beds with characteristic species. These biostratigraphic units correspond to the upper part of the Kimmeridgian/ lower part of the Volgian, the Middle Volgian (lowermost and uppermost beds), and the Upper Volgian. A detailed biostratigraphic analysis of the Volgian beds was carried out, which enabled a correlation scheme to be developed for major regions of Russia. West-Siberian foraminiferal assemblages were correlated with those of Europe and North America within the Panboreal Superrealm. The species composition of foraminiferal assemblages was analyzed, and correlatable species ere established. This provided an opportunity to correlate coeval strata from Western Siberia, East European (Russian) Platform, northern territories of Siberia and Arctic Islands, Canada, Spitsbergen and England. The possibility was established for correlating Volgian-Tithonian deposits of the Panboreal and Tethys-Panthalassa Superrealms through the Dnieper-Donets Basin where faunas of both southern and Boreal-Arctic types are met.

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Upper Jurassic dinoflagellate cyst biostratigraphy of the Shaim petroleum-bearing region (Western Siberia)

Trubicyna A., Ilyina V.

Volumina Jurassica

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2006

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Vol. 4, no. 1

216-217

EN

The results of palynological analysis of the sediments of the Abalak Formation from five boreholes in the Shaim petroleum-bearing region (northwestern part of Western Siberia) allow determining the Late Jurassic (Oxfordian to Volgian) age of the deposites in question. The study of taxonomic composition and stratigraphic distribution of dinoflagellate cyst as well as spores and pollen grains, acritarchs and prasinophyts have provided the basis for a local biostratigraphic subdivision of these deposits. The geosequence of five dinozones has been defined.

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The problem of establishing the Tithonian Stage in Western Siberia

Podobina V., Gabysheva E., Tatyanin G.

Volumina Jurassica

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2006

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Vol. 4, no. 1

205-206

EN

In 1996 the Volgian Stage was withdrawn from the General Stratigraphic Scale and replaced with the Tithonian Stage by the Resolution of the Interdepartmental Stratigraphical Committee of Russia. However, this did not solve the problem of correlation between the Volgian and Tithonian stages. The problem of identifying and mapping the Tithonian Stage within the Boreal deposits becomes unresolved. On this basis the Volgian Stage was retained in the West Siberian Stratigraphical Scale as the terminal Jurassic Stage, owing to the impossibility of the application of the new standard directly to the Boreal sections. The difficulties in comparison between the Regional Scale and the Standard one arise not only for the ammonite zones, but also in correlating the West Siberian foraminiferal zones. Numerous boreholes penetrating Western Siberia and combined studies on core samples enable tracing the continuous sequence of the Volgian foraminiferal zones and beds. The foraminiferal sequence traced through the Nyarginskian type section in the southeast of Western Siberia may serve as an example. There, in the Upper Kimmeridgian – Lower Volgian deposits, the f-beds with the Pseudolamarkina sp. Assemblage were established. The Middle Volgian Spiroplectammina vicinalis-Dorothia tortuosa F-zone was divided into two subzones: the lower Spiroplectammina vicinalis-Saracenaria pravoslavlevi subzone and the upper Dorothia tortuosa subzone The Upper Volgian deposits enclose the Ammodiscus veteranus-Evolutinella volossatovi F-zone. At the Jurassic/Cretaceous boundary, the taxonomy of benthic Foraminifera is essentially different. The phylogenetic succession of numerous foraminiferal genera during the Volgian Age indicates the integrity of the Volgian Stage. A number of genera are characteristic only for the Volgian. Benthic Foraminifera forming the basis for establishing the Upper Jurassic assemblages, and the Volgian ones in particular, showed a wide distribution in the Late Jurassic marine basins of the Boreal belt: Northern Europe (Russia and Poland), Northeast Asia, Northern America (Northern and Northwest Canada, Northern Alaska), islands of the Arctic Region and shelves of northern seas. This wide distribution of the Volgian Foraminifera resulted from the Late Jurassic transgression. The Boreal and Tethyan foraminiferal assemblages differ essentially each other in their taxonomy, which result in significant difficulties in correlation between the Volgian and Tithonian deposits of Boreal and Tethyan belts, respectively. Besides, the distinctive feature of all provinces of the Boreal belt is the absence of planktonic foraminifers or their insignificant development. The direct correlation of the Volgian assemblages is possible only within the Boreal belt, basing on the taxonomical analysis of foraminiferal assemblages and the presence of the species of correlation value. The correlation of the Volgian-Tithonian deposits of the Boreal and Tethyan belts is feasible only at the level of Lower-Middle Volgian substages and the Tithonian. We suppose that at present it is impossible to find direct counterparts of the Upper Volgian Substage.

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Problems on the Middle Oxfordian biostratigraphy of Western Siberia

Podobina V., Polkovnikova E., Tatyanin G.

Volumina Jurassica

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2006

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Vol. 4, no. 1

206-207

EN

The knowledge of biostratigraphy of the Middle Oxfordian part of the section of the Verkhnevasyuganskiy Subhorizon although quite good is insufficient for solving all the problems of dating, detailed correlation, and identification of sandy beds of the substantial oil-and-gas bearing deposits complex in the new borehole sections. Another cluster of problems includes the detailed subdivision of two Middle Oxfordian ammonite zones (a-zones) of Western Siberia and their correlation with the coeval Plicatilis Zone of the Submediterranean zonal scheme. At present, two a-zones are distinguished in the Middle Oxfordian of Western Siberia: the lower zone with the Cardioceras densiplicatum and the upper zone with Cardioceras tenuiserratum. Two parts are distinguished in the Cardioceras densiplicatum Zone corresponding to the Cardioceras vertebrale and Cardioceras maltonense subzones. The upper zone is not subdivided, and it is based on the appearance of ammonites of the subgenus Cawtoniceras. Foraminifera are of exceptional biostratigraphical importance when the material from cores is considered where ammonoid finds are generally rare. The Middle Oxfordian sedimentary complex of Western Siberia contains foraminiferal assemblages of two f-zones: Ammodiscus thomsi-Tolypammina svetlanae and Trochammina oxfordiana. The former includes several isochronous beds recognized in different areas of the region. In the circum-polar Urals, L. G. Dain distinguished beds with Ammodiscus thomsi, Tolypammina svetlanae. In western areas, V. I. Levina distinguished beds with Ammodiscus cheradospira (=Ammodiscus aff. pseudoinfimus (=Ammodiscus thomsi) and Eomarssonella paraconica. In the southern area, V. F. Kozyreva recognized beds with Ammodiscus ex gr. pseudoinfimus (=Ammodiscus thomsi) and Trochammina oxfordiana. In the central and southern districts, beds with Trochammina oxfordiana and with Glomospirella galinae were established by G. M. Tatyanin. The geographical range of the Ammodiscus thomsi-Tolypammina svetlanae Zone covers: Western Siberia, the Preuralian, Yamal-Tyumen, Kazym-Konda, Froly-Tambey, Pur-Vasyugan facies districts (the Danilovskoye, Abalak, Vasyugan, Maurynya formations). In the Yenisey-Khatanga depression N. V. Sharovskaya distinguished beds with Trochammina oxfordiana, Lenticulina memorabilissima, now this is the Trochammina oxfordiana Zone (its top correspond to the Ammodiscus thomsi - Tolypammina svetlanae Zone). The range of the Trochammina oxfordiana Zone covers: Western Siberia, the Khatanga and Taz-Kheta facies districts, Central Siberia, the Paksa facies district (Sigovoe Formation). The analysis on the available findings of the Middle Oxfordian ammonites in the south-east of Western Siberia may offer a key to reconciling the combined macro- and microfauna finds with the ammonite scale, and refining the lower and upper boundaries of the Middle Oxfordian foraminiferal associations. This could make possible tracing and comparing the changes in the systematic composition of the foraminiferal assemblages within two Middle Oxfordian ammonite zones which include the sections of the oil-and-gas bearing horizons.