Search

Актуальность. В настоящее время изучение надсеноманских отложений, в том числе и сложенных кремнистыми породами отложений нижнеберёзовской подсвиты коньяк-сантонского возраста, из разряда теоретического интереса перешло в разряд практически важных исследований. Это связано с тем, что промышленная газоносность подтверждена на шести участках (Ван-Еганский - пласт НБ1, Вынгапуровский - НБ4, Медвежий НБ3-НБ4, Ново-Часельский - НБ3, Комсомольский НБ1, Харампурский НБ1). Выделяется четыре пласта нижнеберёзовской подсвиты (горизонт НБ), однако критериев определения границ этих пластов пока не выявлено. В настоящей работе дано обоснование литолого-минералогических и промысловогеофизических критериев стратиграфического расчленения разреза нижнеберёзовской подсвиты. Объектом исследования является берёзовская свита, отложения которой на севере Западной Сибири содержат значительные ресурсы газа, рассматриваемые как резерв «продления жизни» месторождений при выработке высокопродуктивных отложений сеномана. Цель: повышение эффективности геологоразведочных работ по выявлению залежей газа в кремнистых породах сенона за счёт уточнения стратиграфического строения пород берёзовской свиты. Методы. Расчленение разрезов проводилось по скважинам, пробуренным в последние годы, со сплошным отбором керна и с расширенным комплексом геофизических исследований скважин (ГИС), включающим электрические, радиоактивные, акустические, ядерно-магнитные методы. Минеральный состав определялся путём изучения керна методами рентгеноструктурного анализа (более 300 образцов), инфракрасной спектроскопии (220 образцов). Состав химических элементов в породах устанавливался методами рентгенофлуоресцентного анализа (более 300 образцов) и масс-спектрометрии с индуктивно-связанной плазмой (70 образцов). Результаты. Показано, что граница между пластами НБ2 и НБ3 не имеет однозначных критериев по ГИС. На Медвежьем месторождении эта граница определяется по скачкообразному изменению показаний ядерно-магнитного и акустического каротажей, на Вынгапуровском же месторождении таких скачкообразных изменений на кривых этих методов не отмечается. Показано, что граница между пластами НБ2 и НБ3 имеет чёткую характеристику по минеральному составу пород и определяется резким снижением доли цеолитов (клиноптилолита) при переходе от НБ2 к НБ3. Вместе со снижением содержания клиноптилолита на границе между пластами НБ2 и НБ3 происходит и резкое изменение в химическом составе пород, в частности, отмечается резкое снижение доли стронция. Такая тенденция к снижению доли клиноптилолита и стронция в породах может быть объяснена затуханием вулканической деятельности на юго-востоке Западной Сибири. Relevance. At present, the study of Suprasenomanian deposits, including deposits of the Lower Berezovskaya subformation of CognacSantonian age, composed of siliceous rocks, has moved from the category of theoretical interest to the category of practically important research. This is due to the fact that industrial gas content was confirmed at six sites (Van-Egansky - NB1 formation, Vyngapurovsky - NB4, Medvezhy - NB3-NB4, Novo-Chaselsky - NB3, Komsomolsky - NB1, Kharampursky - NB1). There are four layers of the Lower Berezovskaya subformation (the NB horizon), however, criteria for determining the boundaries of these layers have not yet been identified. In this paper, the substantiation of lithological-mineralogical and commercial-geophysical criteria for stratigraphic dissection of the section of the Nizhneberez subformation is given. The object of the study is the Berezovskaya formation, which deposits in the north of Western Siberia contain significant gas resources, considered as a reserve for «prolonging the life» of deposits during the development of highly productive Cenomanian deposits. The aim: improving the efficiency of geological exploration to identify gas deposits in siliceous rocks of xenon by clarifying the stratigraphic structure of the rocks of the Berezovskaya formation. Methods. The dissection of the sections was carried out on wells drilled in recent years, with continuous core sampling and with an expanded complex of geophysical studies of wells (GIS), including electrical, radioactive, acoustic, nuclear magnetic methods. The mineral composition was determined by studying the core by X-ray diffraction analysis (more than 300 samples), infrared spectroscopy (220 samples). The composition of chemical elements in rocks was determined by X-ray fluorescence analysis (more than 300 samples) and inductively coupled plasma mass spectrometry (70 samples). Results. It is shown that the boundary between the NB2 and NB3 layers does not have unambiguous GIS criteria. At the Medvezhye field, this boundary is determined by the abrupt change in the readings of the nuclear magnetic and acoustic logs, at the Vyngapurovskoe field such abrupt changes in the curves of these methods are not noted. The paper shows that the boundary between the B3 and B2 layers has a clear characteristic of the mineral composition of rocks and is determined by a sharp decrease in the proportion of zeolites (clinoptilolite) during the transition from NB3 to NB2. Along with a decrease in the content of clinoptilolite at the boundary between the B3 and B2 layers, there is also a sharp change in the chemical composition of rocks, in particular, a sharp decrease in the proportion of strontium is noted. This tendency to decrease the proportion of clinoptilolite and strontium in rocks can be explained by the attenuation of volcanic activity in the south-east of Western Siberia.

The analysis of small mammal and freshwater mollusk remains from the fluvial deposits of VI terrace of Dniester R. in Levada section (Moldova, Transnistria) revealed the main characteristic of species composition and evolutionary level of these remains and permitted their placement in the stratigraphic scale of Middle Pleistocene faunas of Eastern Europe. The Levada fauna corresponds to the same stage as the fauna from the fluvial deposits of VI terrace of Dniester in stratotype of Tiraspolian faunistic complex in Kolkotova Balka section. These faunas existed between the Early Tiraspolian faunas which correlate to the second part of MIS 19 and with MIS 18, and the Late Tiraspolian (MIS 16 and MIS 15). Mimomys savini, Lagurus transiens, Microtus (Terricola) arvalidens, Lasiopodomys (Stenocranius) gregaloides are the species most characteristic of these faunas. The Levada fauna reflects interglacial climate conditions. The faunas of this evolutionary level existed during the second part of the Iliinskian Interglacial of the Russian Plain and during the Cromer Interglacial 2 of West Europe. The freshwater mollusks from Levada section (Viviparus tiraspolitanus Pavl., V. subcrasus Lung., Lithoglyphus naticoides C. Pf. and others) reflects a warm climate close to that of the Mediterranean.

The Hongguleleng Formation, the highest and most important Devonian marine carbonate horizon in western Junggar, contains an endemic shallow-water Icriodus–Polygnathus conodont fauna with rare palmatolepids and other genera. The conodont faunas from the Bulongguoer and the Wulankeshun sections are similar, with high abundance (about 40%) of endemic taxa (13 taxa), indicating isolation of the Junggar Basin during early Famennian. Non-endemic species in the faunas suggest that the Lower Member of the Hongguleleng Formation is assignable to the Pa. rhomboidea Zone to the Pa. marginifera marginifera Zone of early Famennian, not including the Frasnian–Famennian boundary. The Upper Member may be of late Famennian–early Tournaisian in age on the basis of our preliminary faunal analysis.

We have studied terrigenous-carbonate rocks in the area near the Sayan mountains in the Irkutsk Region (Russia), specifically at the Shaman Cliff, being the stratotype area of rocks that belong to the Moty group. The cliff’s lower part is composed of sandstones, which fragments gradually decrease in size upward the cross-section. The middle and upper parts are composed of sandy dolomites and dolomites, respectively. In terms of material characteristics, the terrigenous rocks correspond to arkoses. According to the genetic typification, the arkoses are composed of destructed primary igneous rocks. The terrigenous-carbonate rocks contain a carbonate component that gradually increases in the upper part of the cross-section. In the Shaman Cliff cross-section, we distinguish 32 lithological units and eight lithologicalgenetic types of deposits. Paleogeodynamic conditions are reconstructed for the formation of the sedimentation basin. Our study of the Shaman formation reveals specific features of the lithological facies, which suggest that these rocks accumulated in a coastal environment affected by tides. In the study area, clastic materials were mainly removed from an orogen that formed due to the Vendian accretion-collision events in the southern folded frame of the Siberian platform. Dolomites composing the upper part of the cliff are attributed to the Irkutsk formation of the Moty group. Their lithological features give evidence of shallow-marine conditions of their formation, without any supply of clastic material, which contributed to mass dispersal of the Cambrian biota described in [Marusin et al., 2021]. It is our first initiative to draw a boundary between the Shaman and Irkutsk formations of the Moty Group along the base of the carbonate eluvial breccia unit that marks the stratigraphic break. In the cross-section, this boundary represents the border between the Upper Vendian and Lower Cambrian.Our conclusions are generally consistent with the ideas of most researchers about the Late Vendian evolution of the southern margin of the Siberian platform. The results of our study can be used in further investigation of this area and provide a basis for correlating the studied strata with the same-age reference cross-sections of other regions in Siberia.

The paper continues a complex study of the Santonian–Campanian boundary of the Aksu-Dere and Kudrino-2 sections (Bakhchisarai region, Southwestern Crimea), the sedimentological and biostratigraphic data on which are provided in paper 1. This work presents the paleomagnetic, rock magnetic, and geochemical data on C and O stable isotopes. The 87Sr/86Sr values of limestones increase upward the section: from 0.70741 to 0.70752 in Aksu-Dere and from 0.70750 to 0.70755 in Kudrino-2. On the basis of the results, the outcrops are correlated and the Kudrino–Aksu-Dere composite section is compilled, in which we identified paleontological, paleomagnetic, and isotopic markers necessary for the identification of the Santonian–Campanian boundary. The biostratigraphic boundaries are calibrated against the geomagnetic reversal 34n–33r and the SCBE isotopic event; thus, the base of the Campanian Stage should be determined by the base of the Chron 33r. In the volume of the geological record of the Santonian–Campanian boundary, saturation in guide fossil forms, and complex study, the composite section matches the candidates for a Global Boundary Stratotype Section and Point of the Campanian in North Texas and Southern England. This allows us to propose it as one of the candidates of the stratotype or an auxiliary section of the lower boundary of the Campanian Stage.

New complex data have been obtained for two sections of the Santonian–Campanian boundary of Southwestern Crimea. Article 1 presents detailed geological descriptions of sections, lithological, mineralogical, and paleoichnological materials, and the results of determining macro- (crinoids, ammonoids, belemnites) and micropaleontological (dinocysts, nannoplankton, benthic and planktonic foraminifers) remains. On the basis of the results of research, sea level fluctuations, variations in the activity of allogenic input (including pyroclastic material), and other features of sedimentation have been reconstructed. All macro- and micropaleontological data confirm the late Santonian–early Campanian age of the rocks; for each of the micropaleontological groups, biostratigraphic units have been established and a detailed division of the sections has been carried out.

We report the Narmada Seaway began in India during the largest global sea-level transgression and Oceanic Anoxic Event 2 (OAE2) δ13C excursion during the late Cenomanian to early Turonian. The transgression progressed eastward during the Turonian-Coniacian and reached Jhilmili by the end of the Maastrichtian. During this time the Narmada and Godavari Seaways may have joined via the Narmada-Tapti rift and formed a Trans-India Seaway. The history of this major seaway is entombed in a fossil-rich marine transgression of the tectonically active Narmada rift zone. We examined this transgression in the western Narmada Basin, Gujarat, to improve age control based on planktic foraminifera and ostracods and evaluate paleoenvironmental changes based on the Cenomanian-Turonian OAE2 δ13C excursion, δ18O records, and mercury concentrations in sediments as index for volcanic eruptions. Results reveal the onset of the OAE2 δ13C excursion began in the western Narmada Basin during the late Cenomanian coeval with the sea-level transgression and first influx of planktic and benthic foraminifera in the Nimar Sandstone that overlies Archean rocks. The OAE2 δ13C excursion peak was recorded in oyster biostromes followed by fluctuating values of the δ13C plateau in the overlying Limestone with oysters beds, and gradual decrease to background values by the early Turonian. We tested the age of the transgression and δ13C excursion based on planktic foraminifera and ostracod biostratigraphy and successfully compared the results with the Pueblo, Colorado, Global Section and Stratotype Point (GSSP), and the eastern Sinai Wadi El Ghaib section of Egypt.

The Olenekian-Anisian Boundary (OAB) interval is an important time in Earth history, reflecting the last phase of marine ecosystem recovery in the aftermath of the end-Permian mass extinction. Despite this, the Global Stratotype Section and Point (GSSP) for the base of the Anisian remains undefined. The first appearance of the conodont Chiosella timorensis has been proposed as a potential index for the boundary; however, the discovery of this conodont with ammonoids traditionally considered to be Spathian has generated doubts about its suitability. The taxonomy and relationships of early Anisian conodonts, including species of Chiosella, remain understudied, which leads to difficulties in correlation. New species of Neogondolella (N. gradinarui) and Magnigondolella (M. n. sp. D) have been recognized from the leading GSSP candidate section for the OAB at Desli Caira, and from an additional OAB section at Guandao. Furthermore, several species previously identified in Canada and the USA can be recognized from these sections, improving correlation between Tethys and North America. One of these species may serve as a suitable alternative proxy for the OAB; for instance, N. curva appears just below the first Anisian ammonoids in Desli Caira, and just above the first appearance of C. timorensis in both Desli Caira and Guandao. Continued work on sections other than the candidate sections, and on the taxonomy of species outside of those traditionally proposed as indices, is required.

The U–Pb dating of zircons from two samples taken in the stratotype sections of the Middle Permian Gizhiga Formation in the Omolon Massif has been carried out for the first time. Weighted average ages of 266 ± 2 and 265 ± 3 Ma taking the error into account are consistent with the Capitanian age calculated previously by paleontological determination. The observed detrital zircon population has made it possible to identify a few source areas in the Omolon Basin. Pre-Permian zircons are related to erosion of basement deposits of the Omolon Massif and the Middle Paleozoic volcanic rocks of the Kedon Group, while the Permian zircon population is due to the tuff supply from the Okhotsk-Taigonos volcanic arc.

Foraminiferal revision of the Holkerian Stratotype of Britain at Barker Scar, Holker Hall, south Cumbria, UK, allows the subdivision of the section into the Cf4¿, Cf5¿ and Cf5ß subzones (the latter being further subdivided into lower Cf5ß1 and upper Cf5ß2 intervals). The base of Cf5¿ subzone at the base of bed C and base of Cf5ß subzone from the middle part of bed C, occur at 14 m and 10.5 m, respectively, below the traditional basal boundary of the Holkerian at bed K. The lower boundaries of these foraminiferal subzones occur within the main interval affected by dolomitization in the section, which poses problems in defining precisely the bases for these subzones. Nevertheless, in spite of the dolomitization, a more or less continuous foraminiferal record allows a solid correlation of the base of the Cf5ß with the preserved succession in the Livian Substage (defined in Belgium, but also used in France), and it is assumed that the base of this substage should correspond to the base of the Cf5¿ subzone. The base of the Cf5¿ subzone can be correlated with the base of the Russian Tulian Substage, since it contains many taxa in common with the Holkerian. However, further investigation is needed to establish other levels of correlation (e. g., base of the Cf5ß subzone) higher up in the Holkerian substage. All of these problems suggest that the Holkerian, as it is currently recognised, and the Barker Scar stratotype section, in particular, should be reconsidered, and a new para-stratotype section, ideally devoid of dolomitization, should be located and investigated, in order to corroborate the occurrence of the Cf5¿ and Cf5ß foraminiferal subzones compared to those recognised in the Barker Scar Stratotype. These modifications would allow identification of an apparent synchronous faunal event forming the basis of a future subdivision of the Viséan., We would like to thank D. Vachard and C. N. Waters for their constructive comments. 457 PC is grateful to the financial support by the project CGL2016-78738 of the Spanish 458 Ministry of Research and Innovation. MWH was funded by NERC (grant 459 NE/P00170X/1). Vassil Karloukovski, Tereza Kamenikova, David Mindham and 460 Courtney Sprain helped collect the samples. Holker Hall Estate, and Natural England 461 allowed access and permits to collect samples from Barker Scar.

The Permian–Triassic mass extinction included a potentially catastrophic decline of biodiversity, but ecosystem change across this event remains poorly characterized. Here we reconstruct sedimentary factories and ecosystem change across the Permian–Triassic Critical Interval (P–TrCI) in the Xiakou area (South China). Six microfacies (MF) were classified. The succession begins with a eukaryote-controlled carbonate factory (MF-1) that passes upward into an organomineralization-dominated carbonate factory (MF-2–3). Organic-rich marls atop these units reflect carbonate factory collapse (MF-4). Organomineralization-driven carbonate formation restarts prior to the Permian–Triassic boundary (MF-5) and subsequently develops into a mixed carbonate factory where organomineralization and biomineralization are almost equally important (MF-6). MF-1 reflects oxygenated shallow water environments. In contrast, MF-2–6 were all deposited in somewhat deeper environments, some of which episodically exhibited elevated salinities, oxygen depletion, and, possibly, euxinic conditions. Our results demonstrate that distinct changes in carbonate production styles, biodiversity, and environmental conditions are not synchronous at Xiakou. Furthermore, the Xiakou record is strikingly different to that of other localities, even from the same area (e.g., the Global Stratotype Section and Point section at Meishan). Together, these findings highlight the enormous complexity of the P–TrCI and calls simplified views of the Permian–Triassic mass extinction into question.

The Upper Neoproterozoic–Lower Cambrian section in the Olekma River basin is divided (from bottom to top) into the Dikimdia, Seralakh, Porokhtakh, and Pestrotsvetnaya formations, which are mainly composed of dolostones with a subordinate amount of sandstone, silty shales, gypsum, anhydrite, and native sulfur. The isotope data available allow one to substantially correct the stratigraphic units of the Olekma section, which is probably the most completed section on the Siberian Platform, including the transitional strata from the Vendian (Ediacaran) to the Cambrian. The Dikimdia Formation dolostones have typical Late Ediacaran values of 87Sr/86Sr = 0.70837–0.70843 and abnormally high δ13С values (up to 5.1‰), which gives reason to correlate this formation with the Ust’-Yudoma Formation (the stratotype area), the Dengying Formation in South China (548–550 Ma), the Uluntuy Formation of the Baikal Group, and the terminal Ediacaran sections in some other areas. The 87Sr/86Sr ratio decreases upward and reaches a minimum (0.70803–0.70818) near the Porokhtakh–Pestrotsvetnaya boundary. The lowermost part of the Porokhtakh Formation contains a negative carbon isotope excursion (δ13С = –4.4‰) marking the base of the Nemakit-Daldynian Stage, whereas ~8 m below the base of the Pestrotsvetnaya Formation the positive “pre-Tommotian” excursion (δ13С = 4.1‰) is located. There is a sharp decrease in Fe and Mn contents from ~3800 and ~300 ppm to ~2000 and ~130 ppm, respectively, in dolostones at the Ediacaran–Cambrian transition boundary which corresponds to the Seralakh–Porokhtakh boundary. High δ18О values (26.0 ± 1.2‰) do not provide reasons to associate the carbon isotope excursions, the 87Sr/86Sr trend, and variations of Fe and Mn contents with diagenetic alterations.

Although the main stratigraphic frame of the Neogene in North Belgium is well established still several issues remain. This is in particular the case at the boundaries of lithostratigraphic units and where lateral facies have developed. Not only are more biostratigraphic data needed but also the commonly used geophysical well logging needs a better information on the precise influence of the variable mineralogy in the sediments. In particular glauconite, muscovite and clay mineralogy need a detailed analysis. Such an analysis is carried out on the Antwerp Member of the Berchem Formation, the Diest Formation, the Kasterlee Formation and the Mol Formation with particular emphasis on the boundary intervals between these units. Clay minerals, glauconite, feldspars and muscovite are analyzed. Interstratified glauconite/smectite appears to be common in the low abundant dispersed clay fraction of sand rich in glauconite pellets. Marine units generally consist of detrital smectite-rich assemblages while kaolinite becomes more abundant in units under more continental influence. The presence of Fe-rich vermiculite in a clayey top facies of the Diest Formation indicates the influx of soil material containing weathered glauconite. It is common to find that the basal sediments of a new unit contain the mineralogical heritage of the underlying unit. The clay mineral content has helped to differentiate between units, to locate the boundaries between units and to understand the reworking that occurred at the base of new stratigraphic units. The mineralogical information can also be used to interpret the natural radioactivity and resistivity signals in the borehole logs.

This paper aims to evaluate potential biostratigraphic markers for the Visean–Serpukhovian boundary in sections of Europe and Asia, to help identify the base of the global Serpukhovian Stage, which is a high priority task for Carboniferous biostratigraphy. Sections in the Serpukhovian stratotype area in the Moscow Basin contain a gap at the base of the Tarusian Regional Substage (basal in the classical Serpukhovian), so the traditional boundary defined in these sections cannot be precisely correlated with other successions worldwide. The IUGS Task Group to establish a GSSP close to the traditional Visean–Serpukhovian boundary focused on the search for a new boundary marker, primarily on the first appearance datum (FAD) of the conodont Lochriea ziegleri in the lineage Lochriea nodosa to Lochriea ziegleri, considering it to be a suitable biostratigraphic event. The FOD (first occurrence datum) of L. ziegleri has been recognized in many successions worldwide, although only in a few sections the supposed evolutionary lineage of L. ziegleri was inferred. There are serious impediments to the FAD of L. ziegleri being universally accepted as the boundary marker. This paper presents a review of the FOD levels of L. ziegleri documented so far from multiple sections along with other correlatable markers (foraminifers and ammonoids) that can serve as additional points of reference in sections where a conodont record is poor or absent. The reviewed sections are Naqing Section (South China), Verkhnyaya Kardailovka and Kugarchi sections (South Urals, Russia), Mariinsky Log and Ladeinaya Mountain Sections (western slope of the Middle Urals, Russia), Novogurovsky Section (Moscow Basin, Russia), Vegas de Sotres Section (Cantabrian Mountains, Spain), Lugasnaghta Section (County Leitrim, Ireland), Wenne River Bank Section (Germany), and Milivojevica Kamenjar Section (Družetic, NW Serbia). We also included a compilation of data from sections of North England and southern Scotland. In this paper, we will mainly focus on newly described sections, while the discussion of most previously described sections was summarized by Nikolaeva et al. (2001, 2002, 2005, 2009b) and other publications, so they are only briefly mentioned in this review. It should be added that there is no such a thing as a perfect GSSP section, as each section has certain disadvantages, either lithological, paleontological, or both, so it is important to hear and discuss all the different opinions to develop the optimum strategy for future research. In addition, we analyze published records from several sites in North England and southern Scotland. We discuss the first appearances of the ammonoid genera Cravenoceras, Edmooroceras, Lyrogoniatites, Dombarites, and Platygoniatites, the foraminifers Neoarchaediscus postrugosus, Hemidiscopsis muradymica, H. hemisphaerica, species of Janischewskina and Monotaxinoides, Eostaffella pseudostruvei group, Eostaffellina decurta, and Endothyranopsis plana. We publish here for the first time the useful accounts of foraminifers and conodonts from the Mariinsky Log Section and Ladeinaya Mountain Section (Middle Urals, Russia), and re-figure several important type specimens from Europe and the Urals.

The paper deals with the Early Permian (mostly early Kungurian) biotas of the Cis-Urals (Perm region, Russia). Taxonomic composition of the early Kungurian biota of the stratotype area (close vicinity of the City of Kungur) includes algae Algites philippoviensis Naugolnykh, A. shurtanensis Naugolnykh, tracheophytes (higher plants), i.e., equisetophytes Paracalamites spp., conifers Shaidurodendron columnaris Naugolnykh, Walchia appressa Zalessky, vojnovskyaleans Rufloria derzavinii (Neuburg) S. Meyen etc.; invertebrates: coelenterates of uncertain affinity, bivalves Permophorus costatus (Brown), Permophorus sp., Netschajewia sp. cf. N. tschernyshowi (Licharew), gastropods Goniasma angulata (Stuckenberg), terebratulid brachiopods Dielasma sp. cf. D. moelleri Tschernyschew, arthropods (limulids Paleolimulus kunguricus Naugolnykh); vertebrates: chondrichthyan and actinistian fishes. Paleogeographically, the studied area belonged to the near-shore zone of a large lagoon basin disposed along the western-southern part of the Paleo-Urals during the Kungurian time. The main events in evolution of this basin reflect the final phases of the Artinskian sea basin with normal salinity, the transition to an early Kungurian (Philippovian) lagoon, then the appearance of intercalations of evaporate conditions and episodic incursion of marine faunas, and finally a gradual transition to semi-terrestrial environments with the cyanophyte communities in early Ufimian (Solikamskian, early Roadian) time. Climatic conditions in this area changed from semi-humid to semi-arid. A new genus and species of algae Dichothallus divaricatus Naugolnykh n. gen. n. sp. is described on the basis of material originated from the stratotype of the Philippovian Horizon of the Kungurian stage, Lower Permian.

The Ordovician saw major diversification in marine life abruptly terminated by the Late Ordovician mass extinction (LOME). Around 85% of species were eliminated in two pulses 1 m.y. apart. The first pulse, in the basal Hirnantian, has been linked to cooling and Gondwanan glaciation. The second pulse, later in the Hirnantian, is attributed to warming and anoxia. Previously reported mercury (Hg) spikes in Nevada (USA), South China, and Poland implicate an unknown large igneous province (LIP) in the crisis, but the timing of Hg loading has led to different interpretations of the LIP-extinction scenario in which volcanism causes cooling, warming, or both. We report close correspondence between Hg, Mo, and U anomalies, declines in enrichment factors of productivity proxies, and the two LOME pulses at the Ordovician-Silurian boundary stratotype (Dob’s Linn, Scotland). These support an extinction scenario in which volcanogenic greenhouse gases caused warming around the Katian-Hirnantian boundary that led to expansion of a preexisting deepwater oxygen minimum zone, productivity collapse, and the first LOME pulse. Renewed volcanism in the Hirnantian stimulated further warming and anoxia and the second LOME pulse. Rather than being the odd-one-out of the “Big Five” extinctions with origins in cooling, the LOME is similar to the others in being caused by volcanism, warming, and anoxia.

This paper deals with new finds from the Upper Paleozoic Santa Elena Formation that crops out to the east of Uspallata, western Argentina. Current studies reveal the existence in these rocks of a faunal assemblage characterized by the bivalve Myonia aparicioi sp. nov, fossil guide of a new biozone. This fauna is regarded as the youngest of the Pennsylvanian, age confirmed by its relationships with other Late Carboniferous faunas and flora. During the past several years, the relationships between the Late Carboniferous and early Permian faunas contained in this formation had been obscured by strong faulting. However, this uncertainty was answered by the discovery of a structurally uncomplicated section in which the Myonia aparicioi and the early Permian Costatumulus amosi faunas are separated by some tens of meters. These finds reveal the actual relationships between these important key fossils and allow a more precise definition of the Carboniferous–Permian boundary. This locality is recommended for establishing the stratotype and section of this systemic boundary in western Argentina. The existence of an earliest Permian glacial phase is confirmed by the association of these rocks with the brachiopod Costatumulus amosi. The new faunal assemblage occurs in various localities to the east of Uspallata city; the material is very poorly preserved, and the identification of the specimens is based mainly on shape. However, because of its biostratigraphic interest, three new bivalve species are described: Promytilus rochacamposi sp. nov., Permophorus? yrigoyeni sp. nov, and Myonia aparicioi sp. nov. Six further species are also included with nomina aperta because of insufficient material or doubtful generic assignment; these are: Aphanaia? sp., Leptodesma (Leiopteria) sp., Schizodus sp., Vacunella? sp., Myonia? sp., and Streblopteria sp. Specimens previously thought to be “eurydesmatids” probably belong to a new genus.

A new species of the genus Leptoropha (Kotlassiidae, Seymouriamorpha), L. minima sp. nov, is described based on isolated teeth discovered in the Upper Urzhumian beds of the boundary stratotype of the Severodvinian Stage (Republic of Tatarstan, Russia). A sample from the type locality (Monastyrskii Ovrag-D) enabled the tracing of the modification of maxillar and mandibular tooth shape in individuals with skull lengths of 30–60 mm, from the tricuspid pattern to complex polycuspid fan-shaped crowns with a large (up to 14) number of complementary cusps that definitively formed the marginal portions of the protocingulum in the anteriormost jaw teeth. In addition to the type locality, individual teeth attributed to L. minima were identified from the Upper Urzhumian of the Southern Cis-Ural Region (Orenburg Region, Yashkino locality) and the lowermost Severodvinian beds of the Vyatka River basin (Kirov Region, Povoiska locality); findings of teeth of similar morphology at the Sundyr-1 locality (Mari El Republic, Russia) extend the stratigraphic distribution of Leptorophinae to the Upper Severodvinian (Lower Putyatinian) and indicate the presence of the group in the last fauna of the Dinocephalian Tetrapod Superassemblage of Eastern Europe, the Sundyr’ Tetrapod Assemblage.

We present a new marine chronostratigraphy from a high-accumulation rate Arctic Ocean core at the intersection of the Lomonosov Ridge and the Siberian margin, spanning the last ∼30 kyr. The chronology was derived using a combination of bulk 14C dating and stratigraphic correlation to Greenland ice-core records. This was achieved by applying an appositely developed Markov chain Monte Carlo algorithm for Bayesian probabilistic alignment of proxy records. The algorithm simulates depositionally realistic alignments that are consistent with the available radiocarbon age estimates and allows deriving uncertainty bands associated with the inferred alignment. Current composite chronologies from this region are reasonably consistent with our age model during the Holocene and the latter part of deglaciation. However, prior to ∼14 kyr BP they yield too old age estimates with offsets that linearly increase up to ∼40 kyr near the onset of Marine Isotope Stage (MIS) 2. Our results challenge the robustness of previous regional chronostratigraphies and provide a new stratotype for correlation of sediment cores from this sector of the Lomonosov Ridge and East Siberian slope. In particular, they call for a re-interpretation of events in recent sea-ice proxy reconstructions (Xiao et al., 2015) inaccurately attributed to MIS-3 and the Last Glacial Maximum.

Introduction: Currently the issue of identifying stratigraphic units in sedimentary deposits of the Neogene Period in the territory of the Baikal Rift Zone is not completely resolved. To settle this issue we need to compare the results of palynological research of the sediments of the late Cenozoic of the Eastern Sayan and the southern coast of the Baikal Lake and systematize them within the chronological line of the Paleogene and the Neogene. Methodology: All samples were processed in accordance with Grinchuk’s separation method, which includes: treatment with 10% hydrochloric acid (HCl), alkali (NaOH), fluoric acid (HF), and heavy liquid (KJ+CdJ+H 2O). After enrichment the macerate can be seen under a microscope with х400-х600 magnification. The affiliation of spores and pollen to sections, genera, and species was determined by the attributes of the morphological structure of exine, intine, aperture apparatus, pores, and the presence of furrows. Results and discussion: The described palynological material of the deposits of lacustrine-alluvial formation of the southern coast of Baikal and sedimentary formations concealed under the basalts of the Tissa series in the territory of the Eastern Sayan was compared to the data from the stratotype sections of the neighbouring regions. This allowed us to substantiate the correspondence of the obtained data with the stratigraphic boundaries of the regional scheme of the Neogene. During the Eocene angiosperms prevailed in the general composition of pollen. The last stage of the Oligocene is characterized by the domination of gymnosperms, In the lower Miocene the pollen of gymnosperms prevailed as well, but in contrast to the Oligocene, the amount of angiosperm pollen increased. The wide variety of either angiosperm and gymnosperm pollen is typical for the middle Miocene. During the Pliocene the pollen of gymnosperms prevailed. Conclusion: The detailed analysis of the composition of palynocomplexes allowed us for the first time to identify the presence of the Paleogene system deposits in this territory and to organize the spore-pollen complexes of the Neogene in chronological order. On the basis of the palynological research in the Baikal Rift Zone the chronological boundaries of the Tissa series were defined within the context of the Miocene and the lower Pliocene. The age limits of stages and suites of lacustrine-alluvial formation of the southern coast of Baikal within the boundaries of the upper Eocene and the lower Pliocene were also defined.

A burrow previously assigned to the ichnotaxon Palaeophycus insignis is redescribed, and a new ichnotaxon Olongichnus solodukhoi n. igen. n. isp is erected for this flattened, slightly curved, multi-oriented, smooth burrow that has a thick lining with internal and external very fine-grained mucuous layers. It shows subrectangular to oblong form in cross section. O. solodukhoi is collected from the lowermost part of the Member D (Seryi Kamen Member, Pechishchi Beds) of the late Kazanian (middle Permian) stratotype section (East European Platform). It occurs in yellowish grey dolostone formed within open shallow-marine environments. O. solodukhoi records combined feeding and dwelling behaviours of a suspension-feeding organism. It could be produced by burrowing organisms with a simple flattened morphology, such as flatworms or polychaetes; however, we favour elongate and ultra-elongate bivalves as the potential tracemakers of the reported burrows.

The Tre Maroua site in SE France was recently selected by the Berriasian Working Group (BWG) of the International Subcommission on Cretaceous Stratigraphy (ISCS) as the candidate locality for the reference section of the Berriasian Global Boundary Stratotype Point (GSSP). However, on the basis of our preliminary investigation at this site and also from field observations over a larger area, this candidate section is paleogeographically located on a deep-water slope riddled with successive erosional surfaces, stratigraphic hiatuses and breccias. It does not meet at least four of the five "geological requirements for a GSSP". Accordingly, in our opinion, its candidacy must be definitely precluded.

The abstract is available here: https://uscholar.univie.ac.at/o:1633214

At present, the Global Stratotype Section and Point (GSSP) for the base of the Bartonian remains the only GSSP of the Paleogene System to be defined by the Inter- national Subcommission on Paleogene Stratigraphy (ISPS) and the International Commission on Stratigraphy (ICS). Here, we present the results of an integrated, high-resolution study of calcareous plankton and benthic foraminifera biostratigra- phy and a detailed magneto-, chemo-, and cyclostratigraphic analyses carried out through the upper Lutetian to the upper Priabonian pelagic sediments of the Bot- taccione Gorge section near Gubbio, central Italy, to check its stratigraphic com- pleteness and constrain in time the optimal interval for defining and positioning the GSSP for the base of the Bartonian Stage. The high-resolution and solid integrated stratigraphic framework established at Bottaccione confirmed the completeness of the section, which meets the ICS recommendations for a potential designation as a GSSP for the base of the Bartonian Stage. Thus, the Bottaccione section was com- pared with the parastratotype section of the Bartonian in its type area, Alum Bay, UK. On this basis, two reliable criteria for defining and positioning the Bartonian GSSP at Bottaccione are provided: (1) the base of magnetic polarity chronozone C18r as the primary correlation criterion and (2) the base of the calcareous nannofossil Dictyococcites bisectus, which defines the CNE14/CNE15 zonal boundary as a second- ary correlation criterion.

The growth of interest in the Anthropocene has coincided with the rise of geoheritage research and these ideas seem to be mutually enriching. However, very few previous investigations were devoted to the Anthropocene geoheritage. The conceptual treatment of the geoheritage classification demonstrates that the majority of geoheritage types and forms are relevant to the Anthropocene. From types, the most relevant are the stratigraphical, economical and geomorphological types, which include, for instance, such unique objects as the Anthropocene global stratotype candidate sections, exploited ore deposits and man-made landforms, respectively. Ex-situ forms (such as museum collections) and many in-situ forms (such as quarries and roadcuts) result from the geological-scale activity of humans. The practical importance of the strong Anthropocene–geoheritage relationship is linked to communication of Anthropocene-related knowledge and better research coordination. Importantly, geosites and geopaks themselves manifest human influence on the global geological environment, that is, their establishment among the Anthropocene-related forces.

The Eifelian lithostratigraphic succession of southern Belgium is here revised based on new field investigations and reconsideration of biostratigraphic data. The Couvin Formation is divided into four members: the Villers-la-Tour Member recorded the onset of stromatoporoid biostromes, the Petigny Member is a dark fine-grained limestone that recorded the Choteč event, the Cul d’Efer Member is dominated by stromatoporoid-coral biostromes. These first three members were previously united in the Foulerie Member and correspond to the transgressive and highstand system tracts of the Middle Devonian 3rd-order sequence MD1. The argillaceous and bioclastic successive units of the Abîme Member recorded the sequence MD2. Laterally, this sequence is only composed of siliciclastic deposits of the Vieux Moulin, Station and Cimetière members of the Jemelle Formation. The highstand system tract is the newly introduced carbonate Vierves Member. Large bioherms, newly described as the Wancennes Formation, recorded the first two sequences MD1 and MD2. A major sequence boundary caps the Couvin Formation and is overlaid by the transgressive and diachronous Chavées Member of the Jemelle Formation with a depositional gap increasing eastwards. The highstand system tract of sequence MD3 is recorded in the bioherms of the Tienne Sainte-Anne Member (upper part of the Jemelle Formation), also capped by a sequence boundary. These bioherms probably acted as highs around which the sandy deposits of the Lomme Formation accumulated as lowstand system tract of sequence MD4. The Hanonet Formation and its crinoidal Wellin Member form the transgressive system tracts of sequence MD4 that terminates in the bioclastic and biohermal Trois-Fontaines Formation (Givetian). The Kačák event is identified in the transgressive system tract of this sequence. The geographic distribution of facies and of reefs in particular led to the recognition of at least six sedimentation areas corresponding most probably to synsedimentary faulted blocks here defined as the Eau Blanche, Viroin, Lesse, Ourthe, Condroz and Sambre blocks. These sedimentation areas structured the Namur-Dinant Basin and recorded distinct depositional history and were probably active during the Devonian and Carboniferous interval.