Ammonites of the subfamily Collignoniceratinae have been found in the Turonian Stage of Western Siberia. These findings have made it possible to substantiate the Collignoniceras woollgari zone in the Middle Turonian of this region, to recognize the ammonite dispersal features in the Arctic region, and to clarify the paleogeography of the Turonian age. Based on the occurrence frequency of Collignoniceras woollgari regulare in the boreholes in the north of Western Siberia, their penetration into the West Siberian basin through the Arctic region from the Western Interior Sea of North America is most likely. Collignoniceratinae has been identified for the first time in the Upper Turonian of the Yangoda River (west of the Yenisei–Khatanga regional trough).

This paper presents the results of analysis of the morphological and size–quantitative features of similar species of benthic foraminifers, Viveja globigeriniformis (Neckaja, 1948) and Viveja excavatus (Brotzen, 1936), which have a high biostratigraphic and paleogeographic significance within the Boreal–Atlantic and Arctic basins. Based on the analysis, we have confirmed the generic affiliation and validity of the species and established the variation limit of diagnostically important features. We have also determined the stratigraphic distribution of the species in the representative sections of Western Siberia and the Cis-Urals region. It has been revealed that the widest distribution of Viveja excavatus is typical of the Arctic regions of Western Siberia and that of Viveja globigeriniformis for the southern part of Western Siberia and the Cis-Urals region.

The taxonomic affiliation of the species Haplophragmoides (?) emeljanzevi Schleifer, 1966 and Recurvoides paucus Dubrovskaja, 1962 is revised. It is shown that both species should be assigned to the subfamily Recurvoidinae Alekseychik-Mitskevich, 1973, and classified in a new genus Bassoviellum gen. nov. Representatives of the new genus from the Volgian, Ryazanian and Valanginian Stages of the Arctic (Upper Jurassic and Lower Cretaceous) are described. The identification criteria of the species have been clarified.

The presence of ammonites of the subfamily Collignoniceratinae has been established in the Turonian Stage of Western Siberia. These findings allowed us to recognize the Collignoniceras woollgari zone in the Middle Turonian of this region, as well as to recognize the peculiarities of ammonite dispersal in the Arctic and clarify the palaeogeography of the Turonian age. Based on the frequency of occurrence of Collignoniceras woollgari regulare in the boreholes in the north of Western Siberia, their penetration into the West Siberian basin through the Arctic from the Western Interiort Sea of North America is most likely. For the first time Collignoniceratinae were determined in the Upper Turonian of the Yangoda River (west of the Yenisei-Khatanga regional trough).

Bioerosion structures, including holes, pits, and grooves, on the surface of benthic foraminiferal tests from the Upper Cretaceous and Paleogene of Western Siberia are studied. Their morphology is examined, their possible origin and the paleogeographic and stratigraphic distribution in sections representing marine basins of Western Siberia are discussed. The ichnospecies assemblage studied includes Oichnus simplex Bromley, 1981, O. paraboloides Bromley, 1981, O. gradatus Nielsen et Nielsen, 2001, and O. ovalis Bromley, 1993.

Research subject. Boundary Jurassic-Cretaceous sediments of the western part of the Yenisei-Khatanga Regional Trough. Materials and methods. The main correlation tools were seismostratigraphic, logging, and biostratigraphic methods. Litho- and biofacies methods were used to reconstruct the development conditions of the Yanovstan Formation and the NKh group of the Ryazanian Stage reservoirs. Results. The composition of macro- and microfauna complexes was defined, analogues of the ammonite and foraminiferal zones of the Upper Volgian substage and the Ryazanian stage of Siberia were established. The structure of the Upper Jurassic and Ryazanian complexes of the western part of the Yenisei-Khatanga Regional Trough was detailed. Conclusions were made about the formation conditions of the Volgian and Ryazanian deposits. Conclusions. The sediments were found to have been formed in a sea basin with stable salinity and low water energy, in relatively deep-water conditions. Mixed turbidite systems with multipoint supply sources were identified, in which the terrigenous material was supplied from southeast to northwest.

Upper Cretaceous magnetostratigraphy of northern West Siberia has been reconstructed using new paleomagnetic data from five wells in the Kharampur oil-gas-condensate field (1049, 109N, 106P-Yu, 105N, and 2073N). The scientific motivation of this investigation was to construct a composite Upper Cretaceous magnetostratigraphic section of the north of Western Siberia based on integrated paleomagnetic and biostratigraphic data, which represent a part of the Upper Cretaceous magnetic polarity scale of all Western Siberia. The study area is located within the Middle Pur trench in the Pur-Taz interfluve. Natural remanent magnetization in the samples of the Pokur, Dorozhkovo, Okhteurievka, Kuznetsovo, Lower Berezovo, and Upper Berezovo Formations was analyzed by stepwise alternated field (AF) and thermal demagnetization and used to compile the magnetostratigraphic sections of the five wells. Correlations among the well sections form a basis for a composite magnetostratigraphic record of Upper Cretaceous (Cenomanian through Campanian) strata in the area. The composite section comprises two normal polarity zones NK2(sn-st) and NK2cp and correlates with the regional Upper Cretaceous magnetostratigraphic section of southern West Siberia, as well as with the global polarity time scale.

—The post-Cenomanian sedimentary sequence of the East Messo-Yakha oil and gas field in the southern Gydan Peninsula comprises twelve lithological units (beds) correlated to Upper Cretaceous, Paleogene, and Quaternary regional stratigraphic stages and formations. The facies of the sedimentary units are constrained from lithology and microfossils. The stratigraphic division is based on bio-stratigraphy (fauna and spore-pollen assemblages), paleomagnetism, and geochronology (quartz and feldspar grains dated by optically stimulated luminescence). The deposition record is interrupted by six large stratigraphic unconformities. The obtained data provide new insights into the Late Cretaceous, Paleogene, and Quaternary paleogeography of the area.

The structure of the continental upper cretaceous symskaya suite in the territory of the Kulundino-Chulymsky facies region is considered. A preliminary division of it into three cyclites is proposed: kuznetsovsky, lower berezovsky and upper berezovsky-gankinsky

The lithostratigraphic framework of the lower part of the Cretaceous deposits in northeastern Western Siberia is considered. The paleontological characteristics of sandstone beds of the NKh group have been refined, and biostratigraphic dating of the beds has been performed.

As the title implies the article presents the results of many years comprehensive research of the Western Siberian Upper Cretaceous stratigraphy (without Cenomanian). The volume of Upper Cretaceous formation, their biostratigraphic and lithological characteristics are discussed. Based on the analysis of new materials (lithological, biostratigraphic, well geophysics investigation data, magnetostratigraphic, seismostratigraphic), the regional correlation scheme of formations, members and beds has been refined. A new model of correlation schemes, a scheme of facies zoning, and reasonable changes in the nomenclature of the Upper Cretaceous formations are proposed. The Slavgorod and Ipatovo horizons have been replaced by a single Berezovo horizon. Specific properties description of the new suites, established at the first (Okhteurievo, Tagul, Bolshaya Laida, Nizhnaya Agapa), have been done.

A monographic description of representatives of the genus Parrelloides from the Upper Cretaceous of West Siberia (Campanian and Maastrichtian) has been performed. The established species of this genus, including two new ones, P. aquilonius and P. variabilis, are described. The stratigraphic range of the genus has been extended. The generic assignments of P. sibiricus (Neckaja) and P. proprius (Podobina) are revised. The Maastrichtian species P. aquilonius sp. nov. and P. variabilis sp. nov. occurred in the northern part of the West Siberian basin, P. sibiricus (Neckaja) in the central and southern parts, and P. proprius (Podobina) in the southern part.

The results of stratigraphic and facies studies of the Callovian and Upper Jurassic of the Kazym-Konda facies region (West Siberia) are presented. The sequence of subdivisions of the boreal zonal standard is established. The section is composed of rocks with predominantly shallow marine genesis; their composition depended on sedimentation cyclicity and sea level fluctuations. The highest incoming rates of sedimentary material were associated with transgressive episodes in the Callovian, Middle Oxfordian and Middle Volgian. Stratigraphic breaks and periods of deficient sedimentation in the Late Oxfordian, Kimmeridgian, Early Volgian and Late Volgian correspond to regressive episodes in the section.

Представлены результаты исследований надсеноманского комплекса отложений ВосточноМессояхского месторождения (юг Гыданского полуострова). Выделено двенадцать литологических пачек, сопоставленных с региональными стратиграфическими горизонтами и свитами верхнего мела, палеогена и четвертичной системы. Фациальная принадлежность стратонов обоснована результатами анализа их литологических характеристик (литофациального) и комплексов микрофауны (биофациального). Выполнены комплексные стратиграфические исследования: биостратиграфические (микрофаунистические и палинологические), магнитостратиграфические и датировки методом оптически стимулированной люминесценции зерен кварца и полевого шпата (ОСЛ). Установлено шесть крупных стратиграфических несогласий, дана оценка их длительности. Уточнены представления о палеогеографии севера Западной Сибири в позднемеловое, палеогеновое и четвертичное время.

Summary Authors investigated main aspects of tectonics impact on sedimentation process of Western Siberian Upper Cretaceous deposits. Four seismic sequences were delaminated in Upper Cretaceous deposits in which several benches were determined. Periodic regression episodes in Upper Cretaceous depositions were detected. Tectonic faults influence on stratigraphic units geological structure was defined.