Stratigraphic Scheme Research Articles

The Problem of Stratigraphical Time Grouping of Earth Science Data

An essential aspect of earth science data is the age they represent. The age, in most cases, is not a simple time stamp measured in years, but often specified as a stratigraphic interval or unit. Numerous schemes exist for age attribution in geological data, referring to various methods of e.g. biostratigraphy, chronostratigraphy, sequence-stratigraphy, magnetostratigraphy. Furthermore, opinions about the relationships between the stratigraphical units differ from author to author and are in a steady historical flux. New stratigraphic units become established and old ones are abandoned. This is a challenge for databases that rely on fixed standards. However, all stratigraphic schemes can be conceptualized as a system of unique names related by opinions and expressed in publications. A database (http://rnames.luomus.fi) linking the names of stratigraphic units with referenced (published) opinions would allow for the development of dynamic models for time grouping based on explicit algorithms. We will present and discuss our database approach to tackle this problem.

STRATIGRAPHY AND THE GEO-FORMATIONAL CORRELATION OF THE GRANULITE COMPLEXES OF THE UKRAINIAN SHIELD. Part 1

Granulite complexes are most common formations in the Precambrian basement of the Ukrainian shield. Their original basis is made up of stratigenic granulite-gneiss complexes belonging to the monofacial type of regional metamorphism. They almost everywhere experienced subsequent metamorphic and ultrametamorphic transformations under both granulitic and amphibolite facies. But at the same time, the complexes quite clearly retained their distinctoriginal geological and formational features. The data of structural-stratigraphic studies indicate the most ancient, early Archean age of granulite-gneiss complexes. However, on the basis of isotopic dating, some of their parts are distinguished as younger stratigraphic units Substantiated stratigraphic subdivision, correlation and dating of the original granulite-gneiss complexes of the Ukrainian Shield are of essential importance not only for understanding of its geological structure and evolution, but also for the entire basement of the East-European Platform. On the Ukrainian shield, these formations are most fully represented and best studied, both in geological and isotopic geochronometric terms, compared with similar complexes of the Platform. The description of the key (reference) section for the Ukrainian Shield, the Pobuzhsky section, compiled during long-term structural-stratigraphic and geological-formational research is given in this paper. The discrepancies between this section and the official stratigraphic scheme and the isotope data obtained for it are considered, the most probable stratigraphic age of the complex is justified. Stratigraphy of granulito-gneiss complexes of other regions of the Ukrainian Shield, their geological-formational and age correlation are the subject of the next paper.

Upper Miocene molluscs of Monti Livornesi (Tuscany, Italy): Biotic changes across environmental gradients

The upper Miocene mollusc assemblages of Monti Livornesi, used as a means to study the nature of Mediterranean benthic communities at the edge of the Messinian salinity crisis, are framed in a high-resolution stratigraphic scheme and quantitatively approached by the study of historical museum collections and modern samples. Instead of a single assemblage from either Tortonian or Messinian age, as previously thought, this fauna comes from three consecutive shallowing-upward depositional sequences bounded by regional unconformities, the Luppiano (upper Tortonian-lowermost Messinian), Rosignano and Raquese units (early Messinian). Facies analysis, taphonomy and quantitative paleoecology show that the Luppiano assemblage is characterised by aragonitic species from a eutrophic brackish-water shallow marine muddy bottom, the Rosignano assemblage by calcitic species from an oligotrophic coarse-grained seafloor close to a coral reef and the Raquese assemblage from an open-marine muddy bottom. Published comparisons between Miocene and Pliocene faunal lists should be considered only crude estimates of faunal change until more is known about the distribution of species along paleoenvironmental gradients. The analysis of Miocene and Pliocene abundance data allows us to frame the Monti Livornesi molluscs along carbonate-siliciclastic and water depth gradients and to reach a better understanding of the effects of salinity crisis on the Mediterranean biota.

THE REGIONAL STRATIGRAPHIC SCHEME OF MESO-CENOZOIC DEPOSITS OF TRANSCARPATHIAN DEEP BASEMENT

In this article, the first comprehensive stratigraphic scheme of Meso-Cenozoic deposits of Transcarpathian Deep Basement is presented. These deposits spread out in the strip between Pieniny Zone of Carpathians and Pannonian Deep. There are three types of thick rock sections from Triassic to Miocene (Eggenburgian). The scheme is based on new tectonical zoning of Transcarpathian Deep Basement. In first time, there are distinguished the structuralfacial units – Uzhgorod-Solotvino and Pripannonian zones (one includes Berehove and Vyshkiv subzones). The distribution, lithofacial composition, paleontological characteristics, thicknesses, stratigraphic relations of all stratones are described in details. The age of deposits is specified and defined according by analisis of macro- and microfaunistic data (mollusks, foraminifers, tintinnids, nannoplankton, and radiolarians). The biostratigraphic scale is developed. The correlation with International Stratigraphic time Scale (2016), with adjacent territories of Slovakia and Hungary, and with Pieniny Zone of Ukrainian Carpathians is done. The sedimentation model illustrated the geohistorical aspects of forming the deposits of Transcarpathian Deep Basement during the Meso-Cenozoic is added.

The Cambrian molluscs of Australia: overview of taxonomy, biostratigraphy and paleobiogeography

Cambrian malacofauna of Australia is among the most taxonomically diverse among time equivalents. By a number of valid mollusc species Australian Cambrian competes with Siberian and Chinese formations. Up to date, 80 valid species and 12 forms in open nomenclature, apparently representing new undescribed taxa, have been recorded from the Lower–Middle Cambrian successions of Australia. In addition, 6 species names can be considered as junior synonyms. Distribution ranges of mollusc species plotted over the modern stratigraphic scheme reveal four major molluscan evolutionary assemblages in the interval of Tommotian–Undillan stages. In paleogeographic aspect, the Cambrian malacofauna of Australia has 29 species in common with Siberian Platform, Kazakhstan, Altai-Sayan, Transbaikalia, Mongolia, South and North China, Morocco, Antarctic, Europe (Denmark, Germany), Greenland, North America, and New Zealand, providing important correlation links between these regional stratigraphic schemes.

Cambrian Mollusks of Australia: Taxonomy, Biostratigraphy, and Paleobiogeography

The Cambrian malacofauna of Australia is taxonomically among the most diverse of synchronous faunas. In the number of described mollusk species, it rivals the Siberian and Chinese faunas. To date, 80 valid species and 12 species in open nomenclature, apparently representing new undescribed taxa, have been recorded from the Lower–Middle Cambrian successions of Australia. In addition, six species names can be considered as junior synonyms. The ranges of distribution of mollusk species plotted over the modern stratigraphic scheme reveal four major molluskan evolutionary assemblages in the Tommotian–Undillan interval. In a paleogeographical context, the Cambrian malacofauna of Australia has 29 species in common with the Siberian Platform, Kazakhstan, Altai-Sayan, Transbaikalia, Mongolia, North and South China, Morocco, Antarctica, Europe (Denmark, Germany), Greenland, North America, and New Zealand, providing important correlation links between these regional stratigraphic schemes.

The Precambrian in the Sub-Polar Urals : the chronostratigraphic aspect.

New geochronological data on the Lower and Upper Proterozoic complexes of the Sub-Polar Urals are presented, where the outcropping Precambrian section in the Lyapin anticlinorium is the stratotype for the entire Timan-Northern Urals region. The author’s version of the stratigraphic scheme for Pre-Palaeozoic formations in the study area is proposed. It is shown that unlike the Bashkir anticlinorium in the Southern Urals, with a complete section of the Upper Proterozoic, our region has no Lower and Middle Riphean deposits. Taking into account the new data on the isotope age of zircons from the Precambrian formations from the various parts of the Timan-Northern Urals region, it is argued that that during the entire Early Riphean and most or all of the Middle Riphean the northeastern margin of the Baltic was outside the zone of marine sedimentation. That is, chronologically, the Timan continental margin was laid down near the boundary of the Middle and Upper Riphean.

Revision of the late Middle Pleistocene stratigraphy and palaeoclimate in Poland

The aim of this paper is a critical verification of the late Middle Pleistocene stratigraphy in Poland in connection with stratigraphical schemes in the neighbouring countries. Although a terrestrial record of the Middle Pleistocene is almost complete in western and southern Europe, it is full of gaps in central and eastern Europe. Eight key sites in Poland and one in Belarus were selected to compile environmental and palaeoclimate data for a revised stratigraphy from the termination of MIS 12 to MIS 6, and the chronology was based on correlation with oxygen isotope stratigraphy and OSL ages. The late Middle Pleistocene record starts with the Holsteinian lake sequences, some of which have been initiated already at the end of MIS 12, persisted through MIS 11 and terminated in mid-MIS 10. In the examined sites, MIS 11 is represented also by deposits of meandering rivers in a temperate climate. In contrast, there is no evidence for deposition in most of MIS 10 and in MIS 9. A warmer and presumably wet episode at the beginning of MIS 8 lead to local erosion, followed by development of small lakes. Modest ice sheet advance into central Europe occurred in the second part of MIS 8, as reflected by a till, glaciofluvial and glaciolacustrine deposits and presumably, also by permafrost and ice wedges in western Belarus. MIS 7 seems to have been generally warm and wet when small lakes and meandering rivers could develop. Such mild conditions were interrupted with cool and probably drier episodes when braided rivers and limited pedogenesis occurred. Saalian ice sheet cover of central Europe in MIS 6 was widespread, but even more importantly, in this stage periglacial environments were dominant, as shown by continuous permafrost, intensive aeolian activity and development of ice wedges and involutions. Braided rivers developed during short wetter intervals.

Biostratigraphy of the late Early Pleistocene (Eopleistocene) of the Southern Fore-Urals region (Russia)

A summary of published and unpublished data on the stratigraphy of the late Early Pleistocene (Eopleistocene) of the Southern Urals region is presented in this paper. The summary follows previous reviews about the characteristics of the Pleistocene deposits of the easternmost part of Europe. The improvement and unification of the regional Quaternary stratigraphic scheme is the main aim of these investigations. In this paper we describe deposits of different origin, which constitute the regional stratigraphic units (Tyulyan, Raevka, Udryak, Khlebodarovka, Dombarovka, Blagovar and Oktyabrsky Horizons), are characterized. During the late Early Pleistocene (Eopleistocene), the Southern Fore-Urals region was characterized by continental climate conditions and by four phases of incisions of the hydrographic network that were related to regional uplift, as well as to the lowering of the base level and the subsequent regression of the Late Akchagylian Sea. Fossil molluscs, ostracods, mammals and pollen are used for the reconstruction of the palaeoenvironmental conditions and the biostratigraphical positions of the main localities. During Raevka, Khlebodarovka and Blagovar times, the climate was cool, and forest-steppe landscapes with prevalent open spaces existed. The climate during the Tyulyan, Udryak, and Dombarovka and Oktyabrsky times was warm, and during these periods, the areas of deciduous and coniferous forests expanded in the forest-steppes. The molluscan fauna of the Early Eopleistocene was a transitional fauna from the Pliocene to the Quaternary because the wet and warm climate, which was favourable to the Pliocene mollusc species, continued in the Southern Fore-Urals during the Early Eopleistocene. The mammalian assemblages are the basis for the biostratigraphical subdivision. The deposits are biostratigraphically correlated to the Lower Eopleistocene on the basis of the appearance of the first unrooted voles Allophaiomys and Prolagurus together with late species of the Mimomys genus. At the end of the Eopleistocene, the unrooted voles Terricola and Lagurina were numerous, the first Microtus appeared, late species of Mimomys were not numerous, and Archidiskodon trogontherii appeared in the mammal faunas of the region. The small mammals of the Tyulyan and Udryak times represent the Odessa faunal assemblage. The mammal fauna of the Oktyabrsky time corresponds to the Tiraspol faunal assemblage. The units are correlated with the Upper Villafranchian – Galerian stages interval in the Western European stratigraphical timescale.

Stratigraphy and tectonic setting of the Barriga Negra Formation in Uruguay: an update

Abstract The aim of this work is to propose a new stratigraphic scheme of the Barriga Negra Formation, in order to solve the controversies in one of the most discussed units of Uruguay. Here, we introduce a new map (unmodified since 1984) and amend the stratigraphic profile for the Barriga Negra Formation, establishing the correct sequence, order and thickness, dividing it in four members (Volcaniclastic, Arkosic Conglomerate, Calcareous Conglomerate and Petromictic Conglomerate Member). We describe by first time the presence of basal volcanic and volcanoclastic rocks that implies a tectonic active environment. Volcaniclastic rock dating yield an U-Pb concordia age of 633 ± 3.4 Ma. Moreover, we show that this unit has no stratigraphic continuity with other units that previously were used to constrain its stratigraphic position, age and paleoenvironment. We confirm unequivocally that the unit is as a continental conglomeratic sequence deposited in arid and active tectonic conditions, and not transitional passive margin deposits as some works claim. ­Finally, we revisit the metamorphism, deformation, stratigraphy, structural relationships of this unit and identify new basement units. As consequence of this new evidence, we reexamine its correlation with other regional units. This work is also a key to understand the chaotic stratigraphic proposals of Uruguay..

СОЧЕТАНИЕ ГОРИЗОНТАЛЬНОЙ И ВЕРТИКАЛЬНОЙ ИНВЕРСИИ ЦИКЛИТОВ В ОСАДОЧНЫХ БАССЕЙНАХ: ПРОБЛЕМЫ И РЕШЕНИЯ

The model of horizontal inversion of sedimentary cycles proposed by the author is supplemented by the provision on vertical inversion arising in large regional transgressions and regressions. The combination of these types of transformation of sedimentary cycles allows to explain the violation of the natural alternation of sand and clay strata at the level of regional horizons, adopted in the official stratigraphic schemes. It allows occurrence of sandy horizons on sandy, and clay – on clay within transition zones. The possibility of revision on this basis of the volume, stratigraphic position and correlation of some suites and horizons on the stratigraphic chart of the Jurassic of Western Siberia is shown.

Graptolite biostratigraphy and dating of the Ordovician–Silurian shale succession of the SW slope of the East European Craton

This paper deals with the graptolite biostratigraphy and age determination of the Ordovician and Silurian lithological successions of the Baltic, Podlasie and Lublin basins that existed during the early Palaeozoic on the SW slope of the East European Craton. The biostratigraphic research described was conducted on core material coming from old boreholes and cores from several new wells. Graptolite zones were identified and the chronostratigraphic succession was constrained, with the depths to the stratigraphic units, especially those considered prospective for petroleum, being determined in the individual borehole sections. Old local stratigraphic schemes of the Silurian used for many years in the Polish geological literature are correlated with the standard schemes. The most complete succession of graptolite zones, both in the Ordovician and the Silurian, is observed in the Baltic region. The number of stratigraphic gaps increases towards the east and southeast of the regions. The stratigraphic range of the Sasino Shale Formation decreases in this direction; in the Podlasie and Lublin regions, it comprises only the Katian Stage. The stratigraphic range of the Jantar Formation in the western part of the area spans not only the Rhuddanian but also part or the whole of the Aeronian. In the Podlasie and especially the Lublin regions, sedimentation of the Jantar Formation began in the latest Rhuddanian–Aeronian. A large stratigraphic gap, spanning part or the whole of the Llandovery and increasing eastwards, was documented in the Podlasie-Lublin region. The biostratigraphic research allowed a more precise constraint on the temporal and spatial extent of erosion of Pridoli deposits and the beginning of coarse-grained, siliciclastic sedimentation (Kociewie Formation) in the Baltic Basin.

Zoya Il'inichna Glezer – life and scientific achievements

Zoya Ilyinichna Glezer is the largest Russian micropaleontologist, a specialist in siliceous microfossils — Cenozoic diatoms and silicoflagellates. Since the 1960s, she systematically studied Paleogene siliceous microfossils from various regions of the country and therefore was an indispensable participant in the development of unified stratigraphic schemes for Paleogene siliceous plankton of various regions of the USSR. She made a great contribution to the creation of the newest Paleogene schemes in the south of European Russia and Western Siberia, to the correlations of the Paleogene deposits of the Kara Sea.

AN OVERVIEW OF PROBLEMS OF REGIONAL SUBDIVISIONS OF THE SOUTHERN UKRAINE PALEOGENE

Results of the analysis of regional subdivisions (horizon, regional stage) of Stratigraphic Schemes of the Southern Ukraine Paleogene starting from the 80s of the last century and ending with modern projects of the Regional Scales are presented. Validity of regional horizons of the Unified Stratigraphic Scheme of Paleogene deposits the Ukraine is confirmed.They are the Belokamenskian and Kachian regional horizons of the Paleocene, of the Bakhchisaraian, Simferopolian, Novopavlovkian, Kumian and the Almian regional horizons of the Eocene, the Planorbellian, Molochnaian, Serogosian, Askanian and Gornostaevkian regional horizons and the Kerleutian regional superhorizon in the Oligocene. Modification of stratigraphic volume of valid regional subdivisions is proved namely the Bakhchisaraian and Simferopolian regional horizons of the Eocene in the Stratigraphic Scheme of Paleogene deposits of the southern regions of Ukraine (1993); the Bakhchisaraian, Simferopolian and Novopavlovkian regional stages of the Eocene and the Molochnaian and Kerleutian regional stages of the Oligocene in the Regiostage Scale of the Tethys province in Ukraine (after Andreyeva-Grigorovich, Maslun, 2014). Errors in stratigraphic basis of Serial Legends to geological map of 1:200 000 scale of the Southern Ukraine are shown.

Biostratigraphy of the Early Pleistocene (Palaeopleistocene) deposits of the Southern Fore-Urals, Russia

A summary of published and unpublished data on the stratigraphy of the Early Pleistocene (Palaeopleistocene) of the Southern Urals region is presented in this paper. The summary follows previous reviews about the characteristics of the Pleistocene deposits of the easternmost part of Europe. The improvement and unification of the Regional Quaternary stratigraphical scheme was the main aim of these investigations. Deposits of different origin, which constitute the regional stratigraphical units (Zilim-Vasilyevo, Akkulaevo and Voevodskoe), are characterized. Malacological data form the base for the biostratigraphical subdivision. At the beginning of the Early Pleistocene, an ingression of the Akchagyl Sea (modern Caspian Sea area) began in the Zilim-Vasilyevo time, which developed as much as possible during Akkulaevo time, and then shortly re-emerged after regression into the territory of the Southern Fore-Urals during Voevodskoe time. During the Early Pleistocene (Palaeopleistocene), the Southern Fore-Urals region was characterized by continental climate conditions, which were influences by the wideapreaded brackish-water gulf of the Akchagyl Sea. Fossil molluscs, ostracods, mammals and pollen are used for the reconstruction of the palaeoenvironmental conditions and the biostratigraphical position of the main localities. The units have been correlated with the Gelasian stage of the Western European stratigraphical timescale.

GEORGES CUVIER — AN OUTSTANDING SCIENTIST-NATURALIST (TO THE 250TH ANNIVERSARY OF BIRTHDAY)

Georges Cuvier belongs to the most largest naturalists of the end of 18th – the first half of 19th century. He published more than 300 scientific works, which considered different problems — from the design of comparative-anatomical fundament for the development of the creatures system, to the questions of natural science. Cuvier suggested his own sight of the progress in organic world, which gave to the geologists the scientific method on geochronology. His theory of catastrophes, which provided the change of the subsequent systems of flora and fauna on the Earth, had a huge influence on the further development of science. The result of its use was the appearance of the stratigraphic scale in the first half of 19th century. The most important reform of the zoological systematics is connected with the Kuvier’s works. On the base of comparative- anatomical method, he justified for the first time the study ot the four main forms of the organization of the creatures, or the plans of the animal kingdom’s structure. The stratigraphic scheme of Paris basin, suggested by Kuvier, became the example pattern for the differentiation of the similar deposits in other regions of Western Europe. A brief biographic data has been provided.

The geological and structural evolution of the long-lived Miocene-Pleistocene La Hoyada Volcanic Complex in the geodynamic framework of the Central Andes, Argentina

The long-lived La Hoyada Volcanic Complex (LHVC) is located in the east of Cordillera de San Buenaventura in Argentina. This region is important for understanding of the geodynamic evolution of the Southern Puna, since it is located in its southern edge, where the transition between normal and low-angle subduction occurs. The aim of this work is to contribute to the knowledge of the volcanism of the Southern Puna through the analysis of the stratigraphy and geological evolution of LHVC. Fieldwork and image analysis have led to a new lithostratigraphic scheme, that identifies lithosomes and unconformity-bounded stratigraphic units defining the stratigraphic architecture of the LHVC. New 40Ar/39Ar ages further constrain the geological evolution of this complex. The resulting stratigraphic scheme combines the lithostratigraphic units into lithosomes and synthemic units, with the identification of at least six superimposed eruptive centers and their products during the LHVC evolution. A new stratigraphic framework for the eastern Cordillera de San Buenaventura, composed by four supersynthems separated by unconformities that reflect periods of quiescence of the volcanic activity, catastrophic destructive events and changes in the magmatic plumbing system, is proposed: 1) San Buenaventura supersynthem (ca. 9–7 Ma), including mainly explosive rhyolitic volcanism; 2) Lower La Hoyada supersynthem (ca. 7–<4.63 Ma), comprising andesitic-dacitic lava flows and domes characterized by a pervasive compressive tectonic deformation; 3) Upper La Hoyada supersynthem (4.63–1.37 Ma), mainly represented by arc-related, calc-alkaline, andesitic-dacitic effusive products and subordinated pyroclastic and epiclastic deposits; and 4) Purulla supersynthem (<1.37 Ma), which comprises volcanic products with bimodal composition related to a Pleistocene extensional volcanotectonic fault system. The application of unconformity-based stratigraphic units provides a powerful tool for understanding the volcanic evolution of eroded long-lived volcanic complexes, with an effective reconstruction of the temporal and spatial relationships among constructive and destructive phases of the volcano history, correlated with the regional volcanic, magmatic and tectonic evolution of the southern Puna.

Unique basite-metabasite structures of the Pobuzhsky ore mining region, their geological significance and ore-bearing prospects (by geophysical and geological data)

The structure and prospects for ore content of three basite-metabasite massifs of the Pobuzhsky ore mining district — Bandurovsky, Troyan and Tarasovsky are considered using the example of the Tarasovska structure of the Middle Bug River of the Ukrainian Shield (USh). The assumption suggested by geologists back in 1990 about the geological and metallogenic uniqueness of these massifs is confirmed by the analysis of both regional geophysical surveys and materials of detailed geophysical works performed within the Tarasovska structure (basite-metabasite massif) in 2017 in connection with the geological-search works. It is shown that all three massifs are located within the epicentral regions of the largest gravity anomalies of the USh — Golovanevska and Bandurovska (68 and 49 mGal, respectively) — and they correspond to local maxima D g a with intensity up to 3—7 mGal against these anomalies. The most ancient enderbite-gneisses of the Yatransky and Khoshchevato-Zavalievsky blocks hosted the considered basite-metabasite massifs. The shape of the arrays is oval-concentric, that is why most geologists viewed them as brachisynclinal folds. According to the data of magnetometric and gravimetric surveys at a scale of 1 : 10,000 and small drilling volumes, the Tarasovska structure 3 ´ 5,5 km in size represents itself as a massif of apo-gabbroids — bipyroxene and amphibole-pyroxene crystal shales (in some places of norites and gabbros) of a clear oval shape surrounded by arcuate bands of skarnoids, garnet-bearing aluminous gneisses and calciphyres, bipyroxene and hypersthene crystal shales, among which for the first time manganese-containing gondites were encountered in the USh. Despite the presence of sedimentary cover overlapping the Tarasovska structure (Sarmatian and Quarterian deposits) of about 25—40 m thick, the massifs of apo-gabroids are distinguished on the background of the surrounding diurnal relief by distinct uplands with amplitude from several up to 10 m that supports the strength of these formations even on the background of enclosing granitoids. Geophysical, structural, petrological and geochemical data support the intrusive nature of the apogabbroids and the contact-metasomatic origin of their banding, rather than the brachisynclinal fold of metamorphosed sedimentary-volcanogenic rocks. The absence or very in-significant content of graphite gneisses in the framing structures of the Tarasovsky massif distinguishes these bands of gneisses, crystal shales and calciphyres from the sections of the Kosharo-Aleksandrovska and Khoshchevato-Zavalievsky suite of the Bug series with specific wide distribution of gneisses of graphite and biotite-graphite composition. The contact-metasomatic nature of the gneiss-crystal-shale-calciferous formations of the Tarasovo structure, as well as the possible metasomatic nature of the graphite and some other gneisses of the Middle Bug River, according to some researchers, raises the issue of the necessity of discussing and in-depth analysis of stratigraphic schemes of the Early Precambrian of the USh. The further direction of geological prospecting within the Tarasovska structure for apatite and titanium ores is discussed, and the most promising areas for the drilling of wells are also considered.

NEW PRINCIPLES IN CREATION OF STRATIGRAPHIC SCHEME OF THE PRECAMBRIAN OF THE UKRAINIAN SHIELD

The article deals with current “Сorrelation chronostratigraphic scheme of еarly Precambrian formations of the Ukrainian Shield” should be divided into two parts: the “Correlation stratigraphic scheme of the Lower-Precambrian formations” and “The scheme by age dividing of non-stratified Lower-Precambrian formations”. They have to be separately approved by two relevant subsections of the Lower Precambrian section NSC of Ukraine. Also, the role of intrusive and ultrametamorphic formations in determining of the stratum position in the stratigraphic scheme should be taken into account.

Lower Bathonian Belemnites and Biostratigraphy of the Central and Southern Parts of the East European Platform: Part 2. Cylindroteuthididae and Belemnotheutididae

Belemnites from the lower Bathonian deposits of the Russian Plate are revised and discussed on the basis of study of the two reference sections—Pletnyovka and Sokur quarries. This is the second part of the investigation dealing with representatives of the family Cylindroteuthididae, and “rostrum-less” belemnites of the family Belemnotheutididae, while members of the family Megateuthididae were discussed in detail in the first part (Ippolitov, 2018). The cylindroteuthidids are found only in the Sokur Quarry and comprise four species all assigned to the genus Pachyteuthis, including a new species, Pachyteuthis mittai sp. nov. For Belemnotheutididae, the presence of a single species Acanthoteuthis foliorostris sp. nov. is recorded, which is the first confirmed record of the genus Acanthoteuthis in the pre-Callovian strata. The study of morphological changes within Cylindroteuthididae across the succession allowed two biohorizons to be recognized and the existing belemnite-based scheme for the lower Bathonian of the Volga Region and its correlation with sections in the Pechora River basin to be updated. As the result of the revision, a complex zonal and infrazonal belemnite-based stratigraphic scheme of the lower Bathonian of the Volga Region is introduced. The presence of an endemic genus deriving from Arctic-Boreal immigrants in the lower Bathonian of the Middle Russian Sea allows the belemnite fauna of this age to be interpreted as the first isolated episode of differentiation of the Boreal-Atlantic Province in belemnites. The study of the development of the cephalopod fauna in the early Bathonian of the Russian Plate indicates a biphase formation of the meridional strait connecting the Middle Russian Sea with the Arctic basins and also supports the hypothesis of a short-term opening of a sublatitudinal Pripyat Strait during the maximum highstand.