Variations of Th/U values in Vendian clayey rocks of north-east East-European Platform and Middle and Southern Urals as reflection redox status of sedimentary basins

Earlier, we considered the features of the redox changes in the near-bottom layer of water in the sedimentation basins that existed during the Late Riphean and Vendian in the eastern and northeastern (in modern coordinates) margins of the Baltic. It is concluded that fairly pronounced variations in the values of a number of redox environment indicators in the Upper Riphean deposits suggested that accumulation of sediments in some regions occurred in dysoksis or close to anoxic conditions. Opposite in the Vendian oxidation conditions predominated in the near-bottom waters. In the present publication, these representations are verified by data on variations in Vendian clay rocks of the of the Th/U values. Analytic data obtained by ICP-MS in IGG UB RAS (Ekaterinburg) were used to analyze the features of the change in this parameter. A total of ≈380 samples of shales and mudstones were analyzed. The average Th content in these samples is 12.0 ± 5.4 ppm, in average post-Achaean Australian shale (PAAS) and upper continental crust (UCC) are 14.6 and 10.5 ppm, respectively. For U, the same parameters are 2.1 ± 1.1, 3.1 and 2.7 ppm. The value of Th/Uav for the Vendian shales of the east, northeast and north of the East European platform is equal to 5.8 ± 2.0 (in PAAS and UCC - 4.7 and 3.9 respectively). In the clay rocks of the Vendian of the Southeast White Sea, Th/Uav varies from below upward along the cross section from 5.8 ± 3.4 to 6.9 ± 2.3 without any definite regularity. The Vendian shales and mudstone of the southern part of the Vychegda trough have the Th/Uav value from 3.5 ± 1.1 to ≈5.0 ± 1.7. Dark-colored low carbonaceous shales of the Buton Formation of the Lower Vendian Serebryanka Group (the Middle Urals), which we considered earlier as deposits formed in a basin with distinctly oxygen-free sedimentation conditions, have the Th/Uav 5.9 ± 1.2, and, most likely, do not refer to sediments of stagnant environments. The new data on the distribution of Th/U values in the clayey rocks of the Valdai, Serebryanka, Sylvitsa, Asha, Kairovo and Shkapovo groups correspond to the idea of the accumulation of these sedimentary formations under conditions of dominance of oxidation environments in very shallow sedimentary basins, some of which may not were actually marine. They emphasize the complex/non-linear nature of oxygenation of the ocean, which began at the end of the Late Riphean and continued in the Vendian, with the inversion of “oxygen environments” in some large sedimentary basins or parts of them in the Early Vendian, to the Vendian and Cambrian boundary, and actually in the Cambrian. Obviously, not only global, but also local factors had a significant impact on this process

Late Ediacaran Redox Stability and Metazoan Evolution

The Neoproterozoic arrival of animals fundamentally changed Earth's biological and geochemical trajectory. Since the early description of Ediacaran and Cambrian animal fossils, a vigorous debate has emerged about the drivers underpinning their seemingly rapid radiation. Some argue for predation and ecology as central to diversification, whereas others point to a changing chemical environment as the trigger. In both cases, questions of timing and feedbacks remain unresolved. Through these debates, the last fifty years of work has largely converged on the concept that a change in atmospheric oxygen levels, perhaps manifested indirectly as an oxygenation of the deep ocean, was causally linked to the initial diversification of large animals. What has largely been absent, but is provided in this study, is a multi-proxy stratigraphic test of this hypothesis. Here, we describe a coupled geochemical and paleontological investigation of Neoproterozoic sedimentary rocks from northern Russia. In detail, we provide iron speciation data, carbon and sulfur isotope compositions, and major element abundances from a predominantly siliciclastic succession (spanning>1000 m) sampled by the Kel'tminskaya-1 drillcore. Our interpretation of these data is consistent with the hypothesis that the $pO_2$ threshold required for diversification of animals with high metabolic oxygen demands was crossed prior to or during the Ediacaran Period. Redox stabilization of shallow marine environments was, however, also critical and only occurred about 560 million years ago (Ma), when large motile bilaterians first enter the regional stratigraphic record. In contrast, neither fossils nor geochemistry lend support to the hypothesis that ecological interactions altered the course of evolution in the absence of environmental change. Together, the geochemical and paleontological records suggest a coordinated transition from low oxygen oceans sometime before the Marinoan (~635 Ma) ice age, through better oxygenated but still redox-unstable shelves of the early Ediacaran Period, to the fully and persistently oxygenated marine environments characteristic of later Ediacaran successions that preserve the first bilaterian macrofossils and trace fossils.Earth and Planetary SciencesOrganismic and Evolutionary Biolog

Upper Vendian in the east, northeast and north of East European Platform: Depositional processes and bio­tic evolution

Subject. Analysis of lithogeochemical proxies in the Upper Vendian mudstones reveals little if any variation in depositional environment for the Redkinian, Belomorian and Kotlinian regional stages in the east, northeast and north of East European Platform. The coeval macrobiota, in contrast, demonstrates significant macroevolutionary and macroecological transformations. Thus, the Avalon-type ecological association consisting of frondomorphs and vendobionts evolved in low-energy inner shelf during the Redkinian, the Belomorian Stage is characterised by diversification of frondomorphs, migration of vendobionts into relatively high-energy depositional settings (shoreface and prodelta), and emergence of tribrachiomorphs and bilateralomorphs, where as the Kotlinian Stage is marked by a sharp decline in taxonomic diversity of soft-bodied organisms (the Kotlinian Crisis). We don’t know to what degree, if at all, depositional parameters as palaeogeodynamics, palaeoclimate, sediment composition, volcanic activity influenced the Ediacaran biota, but these agents were not responsible for the above mentioned biotic transformations. Materials and methods. We suggest that intrinsic factors such as ecological interactions could be the primary trigger of the Kotlinian crisis. This conclusion has been reached based on the study of composition of major rock-forming oxides, rare- and trace elements in fine-grained aluminosiliciclastic rocks (argillites, shales and silt-rich mudstones). Geological samples were collected in outcrops of the Asha Group of South Urals and Sylvitsa Group of Central Urals, as well as from the drill core of the Keltma-1 (Vychegda Trough) and Tuchkino-1000 (Southeast White Sea area) boreholes. We also used the data on chemical composition of mudstones from the Staraya Russa and Vasil’evsky Ostrov formations form the southern slope of the Baltic Shield. Results. With this information in hand we could assess, with varying degree of confidence, such parameters as a degree of recycling of the material supplied into the late Vendian Mezen Basin; sediment provenance; composition of the substrate that microbial mats and soft-bodied organisms lived on in different parts of the basin; and palaeogeodynamic environment at the time when different groups of soft-bodies organisms were emerging

СИНРИФТОВЫЕ ПЕСЧАНИКИ: ОСОБЕННОСТИ ВАЛОВОГО ХИМИЧЕСКОГО СОСТАВА И ПОЛОЖЕНИЕ НА ДИСКРИМИНАНТНЫХ ПАЛЕОГЕОДИНАМИЧЕСКИХ ДИАГРАММАХ

From the early 1980s, the data on the bulk chemical composition of sandstones and mudstones are actively involved for interpretation of the paleogeodynamic settings for sedimentary sequences. Discriminant diagrams such as K2O/Na2O–SiO2/Al2O3 [Maynard et al., 1982], (Fe2O3*+MgO)–K2O/Na2O and others [Bhatia, 1983], SiO2–K2O/Na2O [Roser, Korsch, 1986], (K2O+Na2O)–SiO2/20–(TiO2+Fe2O3+MgO) [Kroonenberg, 1994] etc., are now widely used in regional investigations to classify terrigenous rocks from several paleogeodynamic settings (passive and active continental margins, oceanic and continental volcanic arcs etc.) with a certain ‘percentage of consistency’. The first diagrams DF1–DF2 for syn-rift compositions were published in the early 2010s [Verma, Armstrong-Altrin, 2013]. This article analyzes the bulk chemical compositions of syn-rift sandstones from intracratonic rifts and rifts formed during the break-up of the Columbia and Gondwana supercontinents, rifts within volcanic arcs and related to the collapse of collision orogens (for example, Permian sandstones of the Malužiná formation, Western Carpathians, Slovakia). Our database includes the Neoproterozoic Uinta Mountain Group (USA), the Cretaceous Omdurman formation of the Khartoum Basin (Sudan), the siliciclastic deposits of the Kalahari Basin (East African rift zone), the sandstones of the Vindhyan Supergroup (India), the Neoproterozoic Ui Group of the Uchur-Maya region (Southeast Siberia), the Meso-Neoproterozoic Banxi Group (Southern China), the Mesoproterozoic Belt-Purcell Supergroup (USA), the Oronto and Bayfield Groups of the Midcontinent (USA), as well as the sandstones of the Upper Precambrian Ai and Mashak formations, and the metasedimentary rocks of the Arsha Group (Southern Urals). The article examines: (1) the position of the syn-rift sandstone compositions (fields) on the log(SiO2/Al2O3)–log(Na2O/K2O) classification diagram and the F1–F2 diagram, which gives the possible composition of the catchment areas rocks; (2) the position of the syn-rift sandstone compositions, as well as the average values of various indicator ratios and discriminant functions, in the K2O/Na2O–SiO2/Al2O3, F3–F4, SiO2–K2O/Na2O and DF1–DF2 diagrams. The analysis of the results shows that the fields of the syn-rift sandstones are characterized by a wide dispersion of log(SiO2/Al2O3) (0.4…3.5) and log(Na2O/K2O) values (~0.2…6.0 and more). A number of the values do not fit into the typical areas on the classification diagram of F.J. Pettijohn et al., which suggests that the syn-rift sandstones vary considerably in composition that is controlled by a significant number of factors. The diagram of J. Maynard et al. is not suitable for assigning certain sandstone associations to the ‘syn-rift sandstones’ category. In the diagrams of M. Bhatia and K. Crook, as well as those of B. Roser and R. Korsch, the fields and mean points of the syn-rift sandstones are mainly located in the area of passive continental margins; thus, these diagrams can not be used to classify the syn-rift sandstone associations. Contrariwise, on the high-silica DF1–DF2 diagram [Verma, Armstrong-Altrin, 2013], ~80 % of the objects from our database are localized in the field of syn-rift compositions and show a good correlation with the ‘percentage of consistency’ evaluated by the authors for the samples from similar settings (79–85 %). Thus, according to the data presented in the article, the DF1–DF2 diagram is the most rational and acceptable discriminant diagram for assigning certain sandstone associations to the ‘syn-rift infilling’ category.Для интерпретации палеогеодинамических обстановок формирования терригенных толщ с начала 1980-х годов активно привлекаются данные о валовом химическом составе песчаников и глинистых образований. Опубликован ряд дискриминантных диаграмм, широко вошедших в практику региональных исследований (например, K2O/Na2O–SiO2/Al2O3 [Maynard et al., 1982], (Fe2O3*+MgO)–K2O/Na2O и другие [Bhatia, 1983], SiO2–K2O/Na2O [Roser, Korsch, 1986], (K2O+Na2O)–SiO2/20–(TiO2+Fe2O3+MgO) [Kroonenberg, 1994] и др. Они дают возможность с той или иной «долей соответствия» отнести терригенные породы к образованиям нескольких палеогеодинамических обстановок: пассивных и активных континентальных окраин, океанических и континентальных вулканических дуг. В 2000-х годах предложены диаграммы DF1–DF2 [Verma, Armstrong-Altrin, 2013], на которых впервые появилась область составов, свойственных рифтогенным обстановкам. В статье проанализированы материалы по валовому химическому составу песчаников ряда интракратонных рифтов, рифтов, сформированных при распаде суперконтинентов Коламбия и Гондвана, а также рифтов, приуроченных к вулканическим дугам и связанных с коллапсом коллизионных орогенов (например, пермские песчаники формации Malužiná, Западные Карпаты). К их числу относятся псаммиты неопротерозойской серии Uinta Mountain (США), песчаники меловой формации Omdurman Хартумского бассейна (Судан), силикокластические образования бассейна Калахари (Восточно-Африканская рифтовая зона), отложения надсерии Vindhyan (Индия), уйской серии неопротерозоя Учуро-Майского региона (Юго-Восточная Сибирь), мезонеопротерозойской серии Banxi (Южный Китай), мезопротерозойской надсерии Белт-Перселл (США), серий Oronto и Bayfield рифтовой области Мидконтинента (США), а также псаммиты айской и машакской свит и метаосадочные образования аршинской серии верхнего докембрия Южного Урала. Рассмотрено: 1) положение полей составов песчаников на классификационной диаграмме log(SiO2/Al2O3)–log(Na2O/K2O) и диаграмме F1–F2, дающей представление о возможном составе комплексов пород – источников обломочного материала; 2) положение полей составов песчаников, а также средних значений ряда индикаторных отношений и дискриминантных функций, на диаграммах K2O/Na2O–SiO2/Al2O3, F3–F4, SiO2–K2O/Na2O и DF1–DF2. Анализ полученных результатов позволяет видеть следующее: 1) поля синрифтовых песчаников характеризуются широким разбросом значений log(SiO2/Al2O3) (0.4…3.5) и log(Na2O/K2O) (~0.2…6.0 и более). Ряд из них вообще не укладываются в типовые области классификационной диаграммы Ф.Дж. Петтиджона с соавторами. Это дает основание считать, что состав синрифтовых песчаников может быть весьма различным, так как контролируется значительным числом факторов. Диаграмма Дж. Мейнарда с соавторами не пригодна для отнесения тех или иных песчаниковых ассоциаций к категории синрифтовых псаммитов. На диаграммах М. Бхатиа и К. Крука, а также Б. Розера и Р. Корша и поля, и средние точки составов синрифтовых песчаников в основном расположены в области пассивных континентальных окраин, что делает невозможным их использование для отнесения тех или иных песчаниковых ассоциаций к категории «синрифтовых песчаников». Напротив, на высококремнистой диаграмме DF1–DF2 С. Верма и Дж. Армстронга-Алтрина ~80 % объектов из нашего банка данных локализованы в области составов, свойственных именно рифтогенным обстановкам. Это хорошо соотносится и с авторской оценкой «процента соответствия» для образцов из подобных обстановок (79–85 %). Таким образом, приведенные в статье данные показывают, что наиболее приемлемой дискриминантной диаграммой для отнесения тех или иных песчаниковых ассоциаций к категории «синрифтовых» в настоящее время является диаграмма С. Верма и Дж. Армстронга-Алтрина

Stringent response of Escherichia coli: revisiting the bibliome using literature mining

Understanding the mechanisms responsible for cellular responses depends on the systematic collection and analysis of information on the main biological concepts involved. Indeed, the identification of biologically relevant concepts in free text, namely genes, tRNAs, mRNAs, gene products and small molecules, is crucial to capture the structure and functioning of different responses. Results In this work, we review literature reports on the study of the stringent response in Escherichia coli. Rather than undertaking the development of a highly specialised literature mining approach, we investigate the suitability of concept recognition and statistical analysis of concept occurrence as means to highlight the concepts that are most likely to be biologically engaged during this response. The co-occurrence analysis of core concepts in this stringent response, i.e. the (p)ppGpp nucleotides with gene products was also inspected and suggest that besides the enzymes RelA and SpoT that control the basal levels of (p)ppGpp nucleotides, many other proteins have a key role in this response. Functional enrichment analysis revealed that basic cellular processes such as metabolism, transcriptional and translational regulation are central, but other stress-associated responses might be elicited during the stringent response. In addition, the identification of less annotated concepts revealed that some (p)ppGpp-induced functional activities are still overlooked in most reviews. Conclusions In this paper we applied a literature mining approach that offers a more comprehensive analysis of the stringent response in E. coli. The compilation of relevant biological entities to this stress response and the assessment of their functional roles provided a more systematic understanding of this cellular response. Overlooked regulatory entities, such as transcriptional regulators, were found to play a role in this stress response. Moreover, the involvement of other stress-associated concepts demonstrates the complexity of this cellular response

Redox bottom-water conditions in Neoproterozoic basins on eastern and north-eastern periphery of East-European Platform

The redox bottom-water conditions in the sedimentary basins, which existed during the Late Riphean-Vendian on the east and north-east (in modern coordinates) margins of the Baltic, are investigated. It is concluded that in the context of local, fairly pronounced variations of the bottom-water redox indicators in the Late Riphean (primarily coefficient of stagnation, Mo/Mn, and to a lesser extent - V/(V + Ni)), suggesting that the accumulation of sediments in some areas which we have considered occurred on environment including disoxic or close to anoxic conditions. During the Vendian and appear at the end of the Late Riphean in the bottom waters of almost all sedimentary basins dominated oxidative conditions. The most well substantiated this conclusion for the relatively well-dated Upper Riphean-Vendian interval of the western slope of the Southern Urals, less justified it to other parts of the territory under review. New data in one way or another underscore the complex, non-linear/shift-gradual ocean oxygenation in the Late Riphean and Vendian with inversion “oxygen environments” in some of the major sedimentary basins or their parts in the Early Vendian, on the border of Vendian-Cambrian and in Cambrian itself. It seems, however, that a significant impact on this process acted not only global, but also local factors

Lithogeochemistry of fine-grained Vendian clastic rocks of the Nepa dome, Siberian Platform

It is conducted lithogeochemical investigation of Vendian fine-grained clastic sediments composed Talakh, Parshinsk (Nepa horizon) and Byuk suites (Tyre horizon) of some wells core material in Nepa dome of Nepa-Botuoba anteclise, Siberian Platform. Pelites of all three suites are characterized by variations in the composition from the sandstones to clays, with an increase in clay component up to the section, and have a common geochemical specifics. With moderately alkaline composition they belong to the class of high-K rocks, indicating similar environment of pelite formation due to bring in a shallow marine basin of Vendian passive continental margin the material of chemical weathering platform crusts in conditions of humid climate. Very likely, the source of sediments was the rocks crustal basement of the Siberian platform with possible participation Riphean sediments

SYN-RIFT SANDSTONЕS: THE FEATURES OF BULK CHEMICAL COMPOSITIONS, AND POSITIONS ON PALEOGEODYNAMIC DISCRIMINANT DIAGRAMS

From the early 1980s, the data on the bulk chemical composition of sandstones and mudstones are actively involved for interpretation of the paleogeodynamic settings for sedimentary sequences. Discriminant diagrams such as K2O/Na2O–SiO2/Al2O3 [Maynard et al., 1982], (Fe2O3*+MgO)–K2O/Na2O and others [Bhatia, 1983], SiO2–K2O/Na2O [Roser, Korsch, 1986], (K2O+Na2O)–SiO2/20–(TiO2+Fe2O3+MgO) [Kroonenberg, 1994] etc., are now widely used in regional investigations to classify terrigenous rocks from several paleogeodynamic settings (passive and active continental margins, oceanic and continental volcanic arcs etc.) with a certain ‘percentage of consistency’. The first diagrams DF1–DF2 for syn-rift compositions were published in the early 2010s [Verma, Armstrong-Altrin, 2013]. This article analyzes the bulk chemical compositions of syn-rift sandstones from intracratonic rifts and rifts formed during the break-up of the Columbia and Gondwana supercontinents, rifts within volcanic arcs and related to the collapse of collision orogens (for example, Permian sandstones of the Malužiná formation, Western Carpathians, Slovakia). Our database includes the Neoproterozoic Uinta Mountain Group (USA), the Cretaceous Omdurman formation of the Khartoum Basin (Sudan), the siliciclastic deposits of the Kalahari Basin (East African rift zone), the sandstones of the Vindhyan Supergroup (India), the Neoproterozoic Ui Group of the Uchur-Maya region (Southeast Siberia), the Meso-Neoproterozoic Banxi Group (Southern China), the Mesoproterozoic Belt-Purcell Supergroup (USA), the Oronto and Bayfield Groups of the Midcontinent (USA), as well as the sandstones of the Upper Precambrian Ai and Mashak formations, and the metasedimentary rocks of the Arsha Group (Southern Urals). The article examines: (1) the position of the syn-rift sandstone compositions (fields) on the log(SiO2/Al2O3)–log(Na2O/K2O) classification diagram and the F1–F2 diagram, which gives the possible composition of the catchment areas rocks; (2) the position of the syn-rift sandstone compositions, as well as the average values of various indicator ratios and discriminant functions, in the K2O/Na2O–SiO2/Al2O3, F3–F4, SiO2–K2O/Na2O and DF1–DF2 diagrams. The analysis of the results shows that the fields of the syn-rift sandstones are characterized by a wide dispersion of log(SiO2/Al2O3) (0.4…3.5) and log(Na2O/K2O) values (~0.2…6.0 and more). A number of the values do not fit into the typical areas on the classification diagram of F.J. Pettijohn et al., which suggests that the syn-rift sandstones vary considerably in composition that is controlled by a significant number of factors. The diagram of J. Maynard et al. is not suitable for assigning certain sandstone associations to the ‘syn-rift sandstones’ category. In the diagrams of M. Bhatia and K. Crook, as well as those of B. Roser and R. Korsch, the fields and mean points of the syn-rift sandstones are mainly located in the area of passive continental margins; thus, these diagrams can not be used to classify the syn-rift sandstone associations. Contrariwise, on the high-silica DF1–DF2 diagram [Verma, Armstrong-Altrin, 2013], ~80 % of the objects from our database are localized in the field of syn-rift compositions and show a good correlation with the ‘percentage of consistency’ evaluated by the authors for the samples from similar settings (79–85 %). Thus, according to the data presented in the article, the DF1–DF2 diagram is the most rational and acceptable discriminant diagram for assigning certain sandstone associations to the ‘syn-rift infilling’ category

Chemical composition of sandstones and paleogeodynamic reconstructions

The article analyzes the adequacy of compliance on paleogeodynamic nature of Upper Precambrian sedimentary associations - Bashkir meganticlinorium, Kama-Belaya aulacogene and Uchur-Maya region, received by geological methods and by using discriminant diagrams ?. Meynard et al., B.R. Roser and R. Korsch, and S.P. Verma and ?.S. Armstrong-Altrin. It is shown that among them there are notable differences