Vol 27, No 6 (2019)

Biostratigraphy and lithofacies of the Viséan and Serpukhovian deposits of the southeast of the East European platform
Kulagina E.I., Gorozhanina E.N., Gorozhanin V.M., Filimonova T.V.

This paper presents new data on the biostratigraphy and sedimentology of Upper Viséan and Serpukhovian deposits (Lower Carboniferous) from boreholes in the southeast of the East European Platform around the Sol-Iletsk Swell (Orenburg region). Based on rock lithology, sublatitudinal facies zones are recognized in the studied area. The deposits are represented by open shallow shelf facies, up to 500 m thick, in the area of the Sol-Iletsk Swell and near-side zone of the Preuralian Foredeep. To the south, at the margin of the Northern Pericaspian, their thickness sharply decreases to 36 m, and the succession is composed of carbonate-clay sediments of the relatively deep shelf. Based on foraminifers and conodonts, the Upper Viséan and Serpukhovian are subdivided using the horizons of the stratigraphic scheme of the East European Platform, and foraminiferal zones are recognized. The base of the Serpukhovian in the high-energy shallow-water facies of the open shelf is drawn at the entry of the foraminifers Janischewskina delicata and Endothyranopsis plana; in lower-energy facies, it is placed at the level of the first appearance of Neoarchaediscus postrugosus; in the clay-carbonate facies of the relatively deep shelf it is based on the appearance of the conodont Lochriea ziegleri. The distribution of microfauna from the five boreholes, the characteristics of the foraminiferal zonal assemblages, and the interregional correlation are discussed.

Стратиграфия. 2019;27(6):3-28
The age of the Pre-Callovian Jurassic sequence at the southwest of Tatarstan (central Russia, Tarkhanovskaya Pristan’–Dolinovka reference section) and the status of the Upper Bajocian “Garantiana-beds”, previously described from here
Ippolitov A.P., Gulyaev D.B.

In the present paper we describe and discuss belemnite finds from the basal part of the middle Jurassic sequence at the southwest of the Republic of Tatarstan (Tetyushi district). The belemnites were collected from the outcrops located along a shoreline of the Kuybyshevskoye reservoir (Volga river) between the place Tarkhanovskaya pristan’ and the former village Dolinovka. These belemnites indicate that the basal part of the Jurassic sequence is Early Bathonian (Ishmae Zone) or, less probable, Middle Bathonian in age. Such dating triggers a critical review for the age of the middle Jurassic sequence in the region. In particular, poorly preserved ammonites previously collected from the same outcrops higher in the succession and interpreted as members of the Late Bajocian subfamily Garantianinae, are in fact Late Bathonian Gowericeratinae. Consequently, “Beds with Garantiana” – nominally the most ancient ammonite-based biostratigraphic unit within the whole Jurassic of European Russia, based on this assemblage, is invalid.

Стратиграфия. 2019;27(6):29-40
The problem of the non-marine cretaceous strata correlation in the north-east of Russia: the conditions of florogenesis in the volcanic region
Shczepetov S.V., Neshataeva V.Y.

The most part of the fossil floras from the Cretaceous volcanogenic formations of the North-East of Russia differs significantly in systematic composition from the same-age paleofloras of coastal lowlands. In order to explain the features of their formation, the modern data on the dynamics of vegetation cover on the volcanic plateaus of Central Kamchatka were used. It was shown that in the sites where the paleofloras in geological disposals of the Okhotsk-Chukchi volcanogenic belt were found, there was practically no erosion, but there was the abundance of volcanic material suitable for the formation of disposals. After the massive powerful eruptions, the inland districts of the vast volcanic areas were isolated from the sources of diasporas. Vegetation cover in these areas recovered mainly due to the pool of local species, i.e., maintained as a diasporic sub-climax. The lack of competition from angiosperms contributed to the long-term preservation in such paleofloras the ancient groups of plants and the formation of new taxa on their basis.

Стратиграфия. 2019;27(6):41-54
Palynostratigraphy and genesis of upper cretaceous and Cenozoic deposits in the southern part of the Kulunda depression, Altai region
Lebedeva N.K., Kuzmina O.B., Khazina I.V., Rusanov G.G., Glinskikh L.A.

The results of palynological and micropaleontological study of Upper Cretaceous–Cenozoic strata exposed by boreholes (BH) 23 and 19 of the Aleisk Square (Altai Region) are presented. The obtained data allowed to substantiate the age of deposits, to make assumption about its depositional conditions and to clarify the division of the section into suites. Two palynological assemblages were established in the Cretaceous part of the BH 23 section: the first characterizes the Len’ki Formation and dates by Senomanian–Turonian, the second one is revealed in the Upper-Sym Subformation and dates by the Maastrichtian. The Paleogene Ostrovnoye Formation of continental genesis lies on the Upper Cretaceous sediments. In BH 23 and BH 19, this formation contains spore and pollen spectra of presumably Late Paleocene–Early Eocene and Middle Eocene age respectively. According to palynological data, the Late Miocene age of the sediments at the upper part of BH 23 section and its affiliation to Pavlodar Formation have been substantiated. The structure of palynological assemblages, features of macerate and the absence of foraminifera indicate the continental genesis of the Upper Cretaceous–Paleogene sediments common in the southern part of the Kulunda Depression of the Altai Region.

Стратиграфия. 2019;27(6):55-77
Dinocysts from the mid–upper Eocene Aktumsuk section, Ustyurt, Uzbekistan: biostratigraphy and paleoenvironments
Iakovleva A.I., Shcherbinina E.A., Muzylev N.G., Aleksandrova G.N.

The results of palynological study of the Mid–Upper Eocene sediments of the Aktumsuk key-section (Ustyurt Plateau, Uzbekistan), calibrated with nannoplankton data, are presented. Dinocyst stratigraphical distribution permitted to recognize five Dinoflagellate zones from the Peri-Tethys zonation: Costacysta bucina, Enneadocysta pectiniformis, Rhombodinium draco, Rhombodinium perforatum, and Thalassiphora reticulata. First-order calibration with nannoplankton zones permitted to precise the lowermost occurrences of the key dinocyst species. Based on the dinocyst and nannoplankton data, two important stratigraphic hiatuses, corresponding to the upper Ypresian and Upper Bartonian–Lower Priabonian, were recognized. Analysis of quantitative fluctuations of different groups of palynomorphs through the section indicates paleoenvironmental changes in this part of the Peri-Tethys during the Lutetian–Priabonian: the beginning of significant transgressive phase in the early Lutetian, relative deepening in the Mid Lutetian; after the break in sedimentation at the end of Bartianian–beginning of Priabonian the sedimentation continues again in the open-marine (outer neritic) environment.

Стратиграфия. 2019;27(6):78-102
Palynological profile and depositional environment of the Ishim formation (upper Miocene) in Tobol-Ishim interfluve, Western Siberia
Kuzmina O.B., Khazina I.V., Smirnov P.V., Konstantinov A.O., Agatova A.R.

For the first time some outcrops of the Upper Miocene Ishim Formation on the south of Tyumen Area near Pyatkovo, Masali and Bigila villages are studied by palynological method in detail. A series of mineralogical analyzes of these sediments and radiocarbon analysis of the Quaternary sediments overlying the Ishim Formation are done. Four palynocomplexes (PC) are established in the Ishim Formation: PC1 with Botryococcus; PC2 with Botryococcus, Sigmopollis; PC3 with Alnus, Polypodiaceae, Botryococcus, Sigmopollis; PC4 with Betula, Alnus, Corylus. The layers with PC1, PC2 и PC3 are traced in two outcrops near Masali and Bigila Villages. PC4 is revealed from the sands and aleuropelits of the outcrop near Pyatkovo Village, it is characterized by a significant content of diverse pollen of temperate termophylic broad-leafed taxa and by the presence of rare typical Miocene elements (Таxodiaceae, Nyssa, Tsuga). The PC3 and PC4 are compared with the complexes well known from the Neogene sediments of Western Siberia.

PC5 with Betula, Herbae, Fungi is revealed from the bedded silts overlying the Ishim Formation in Masali outcrop. Previously, these sediments were attributed to the Late Miocene Pavlodar Formation. The composition and the structure of PC5 allowed making an assumption about Quaternary age of the enclosing sediments. Radiocarbon analysis of the organic substance from the silts showed, that these sediments were accumulated in the Late Pleistocene (Sartan Ice Age).

For the first time the information about microphytoplankton (Botryococcus, Pediastrum, Zygnemataceae, Sigmopollis) and other nonpollen palynomorphs, contained in Ishim Formation (Upper Miocene) and in Pleistocene sediments, is given. On palynological data, some stages of development of the Late Miocene Ishim Basin and the type of vegetation surrounding this basin are considered. The depositional environment of Pleistocene sediments (Masali outcrop) is reconstructed.

Стратиграфия. 2019;27(6):103-123

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