North Timan Research Articles

Geologic and Geochemical Features of the Upper Devonian Coals of the North Timan (the Sula River Coal Field)

Abstract —The composition of the oldest coals of the Timan–northern Urals region has been studied comprehensively, and their hydrocarbon and microcomponent characteristics are given. The relationship between different types of coals and Late Devonian plant communities of the North Timan is revealed. It is also determined that some samples contain microspores, megaspores, and plant remains belonging mainly to the lycopod Helenia. The most probable source of jet coals is identified as the wood of the progymnosperm Callixylon. The values of vitrinite reflectance and Tmax and the data on the distribution of polycyclic biomarkers and methylphenanthrenes indicate the low maturation of the coal organic matter. The coal bitumen investigated here is characterized by the dominance of steranes and diaster-13(17)-enes of compositions C28 and C29. The following diterpanes are identified: beyerane, 16α(H)-kaurane, 16β(H)-kaurane, and 16α(H)-atisane. At the same time, phyllocladane is absent.

Compositional Peculiarities of the Upper Devonian Coaly Rocks (The Sula River Section, North Timan)

Compositional Peculiarities of the Upper Devonian Coaly Rocks (The Sula River Section, North Timan)

Composition Peculiarities of the Upper Devonian Coaly Rocks (The Sula River Section, North Timan)

A detailed coal-petrographic and mineralogical-geochemical study of humic coals and coaly rocks in the Sargaev deposits of the Upper Devonian of the Northern Timan (Sula River), which is an example of the burial of the most ancient coal-forming plants, has been carried out. The following types of organic rocks are identified in the section: “jet-like” coal, liptobiolitic silty-clayey coal, and silty-clayey-coaly mixtolites. The studied coals and coaly rocks are composed of humic organic components, represented by vitrinite and liptinite macerals, the inertinite group is of subordinate importance. Vitrinite macerals include gelinite, collotelinite, and telinite (xylenite), liptinite macerals include sporinite, cutinite, liptodetrinite, bituminite, alginite, and a resinous substance, and inertinite macerals include inertodetrinite, semifusinite, fusinite, and funginite. The level of organic matter maturity according to the vitrinite reflectance RV = 0.45–0.55%, corresponds to the transition from proto- to meso-catagenesis (gradations PC3–MС1). The mineral component of mixtolites and high-ash coals consists of kaolinite, chlorite/smectite (with a predominance of the chlorite component) and quartz.

Russian regional Carboniferous stratigraphy

Abstract Several existing schemes for Carboniferous stratigraphy officially adopted in regions of the Russian Federation are summarized and discussed. These regions with different geological histories and distinct depositional settings include the Moscow Basin, the Urals, North Timan, Siberia, the Kuznetsk Basin and the Mongol–Okhotsk, Verkhoyansk–Okhotsk and Kolyma–Omolon regions. Broad correlations based on macro- and microfossils are possible between the regions, while all regional schemes are correlated to the official Russian General Stratigraphic Scheme for the Carboniferous, using zonations based on orthostratigraphic fossils. The Russian General Stratigraphic Scheme is correlated to the International Stratigraphic Scale using ammonoids, conodonts, foraminifers and palynomorphs.

Investigation of scandium in bauxite residues of different origin

This paper focuses on the scandium speciation in bauxite residues of different origin. Insights into mineral-chemical similarities and differences of these materials will be presented and links to their natural geological background discussed. The presented research should provide fundamental knowledge for the future development of efficient and viable technologies for Sc-recovery from bauxite residues derived from different bauxites and accumulating at different localities. In total, five bauxite residues were investigated which originated from Greece, Germany, Hungary and Russia (North Ural & North Timan) using a combination of different analytical tools. Those included: laser ablation inductively coupled plasma mass spectrometry, X-ray absorption near edge structure (XANES) spectroscopy, μ-Raman spectroscopy as well as scanning electron microscopy and electron microprobe analyses. X-ray fluorescence and inductively coupled plasma mass spectrometry were used to determine the overall chemical composition. The investigated samples were found to exhibit a relatively homogenous distribution of Sc between the larger mineral particles and the fine-grained matrix except for Al-phases like diaspore, boehmite and gibbsite. These phases were found to be particularly low in Sc. The only sample where Sc mass fractions in Al-phases exceeded 50 mg/kg was the Russian sample from North Ural. Fe-phases such as goethite, hematite and chamosite (for Russian samples) were more enriched in Sc than the Al-phases. In fact, in Greek samples goethite showed a higher capacity to incorporate or adsorb Sc than hematite. Accessory minerals like zircon, rutile/anatase and ilmenite were found to incorporate higher mass fractions of Sc (>150 mg/kg), however, those minerals are only present in small amounts and do not represent major host phases for Sc. In Russian samples from North Ural an additional Ca–Mg rich phase was found to contain significant mass fractions of Sc (>500 mg/kg). μ-XANES spectroscopy was able to show that Sc in bauxite residue occurs adsorbed onto mineral surfaces as well as incorporated into the crystal lattice of certain Fe-phases. According to our observations the bauxite type, i.e. karstic or lateritic, the atmospheric conditions during bauxitization, i.e. oxidizing or reducing, and consequently the dominant Sc-bearing species in the primary bauxite influence the occurrence of Sc in bauxite residues. In karstic bauxites, underlying carbonate rocks can work as a pH-barrier and stabilize Sc. This prevents the Sc from being mobilized and removed during bauxitization. Hence, karstic bauxites are more prone to show a Sc enrichment than lateritic bauxites. Reducing conditions during bauxitization support the incorporation of Sc into clay minerals such as chamosite, which can dissolve and reprecipitate during Bayer processing causing Sc to be redistributed and primarily adsorb onto mineral surfaces in the bauxite residue. Oxidizing conditions support the incorporation of Sc into the crystal lattice of Fe-oxides and hydroxides, which are not affected in the Bayer process. The genetic history of the bauxite is therefore the major influential factor for the Sc occurrence in bauxite residues.

Low temperature magnetic properties of basalts containing near ~TM30 titanomagnetite

The paper is devoted to studying the mineral composition and magnetic properties, mainly at the cryogenic temperatures, of the Middle–Late Devonian basalts from North Timan. The magnetic minerals in these basalts are dominated by intermediate-composition titanomagnetites (TM25–TM30) which demonstrate unusual magnetic properties in a wide temperature range. At room temperature, a low coercive force coexists with relatively high Mrs/Ms ratios. At cryogenic temperatures, the dependences of magnetic susceptibility on the temperature and frequency of the applied field are characteristic of this titanomagnetite composition, whereas the remanent saturation magnetization acquired at 2 K is destroyed at significantly lower temperatures compared to the synthetic analogs. The obtained results again highlight the necessity of studying the low-temperature properties of titanomagnetite samples with a controlled composition and grain size.

Верхнедевонский комплекс отложений дельтовой равнины на Северном Тимане

Верхнедевонский комплекс отложений дельтовой равнины на Северном Тимане

Late Devonian plant communities of North Russia

The article summarizes researches on the Late Devonian vegetation based on rich palaeobotanical collections from different localities of northern Russia (North Timan). The composition and the structure of the land plant communities are described. Changes in the vegetation are reported during the Frasnian and Famennian. The most diverse palaeovegetation included 29 taxa and occurred in the late Frasnian (Ust'besmozhitsa Formation). It was followed by a floral decrease (6 taxa) in the latest Frasnian (Kamenka Formation). The taxonomic composition of the Famennian vegetation (12 taxa) was much poorer than that of the Frasnian. Differences between the archaeopteridean assemblages of the studied region and the coeval assemblages of the surrounding areas (Russia, Ukraine and Belarus) are discussed. In North Timan, the highest archaeopterid diversity occurred in the Frasnian whereas, in the Donetsk Region of the Ukraine, it occurred in the Famennian.

First U-Pb data on age of granitoids in the basement of the Pechora basin

The Pechora basin, a large regional tectonic struc� ture in the Pechora region, is located between the Timan and Ural mountains (Fig. 1). Its section is com� posed of Upper Cambrian sedimentary-metamorphic and igneous rocks of the basement (Timanides) uni� versally overlain by a platformal cover represented by Ordovician-Cenozoic sedimentary and volcanic rocks. The basement comprises the Izhma, Pechora, and Bol'shezemel'skaya zones. The last two constitute the Bol'shezemel'skaya megablock, and the Izhma zone together with the Timan and Kanin Peninsula form the Timan megablock. According to geophysical and drilling data, the megablocks distinctly differ from each other in the composition and type of magmatism (7). The boundary between them corresponds to the zone of the NWextending Pripechora and Ilych- Chikshino deepseated faults. The thickness of the platformal cover varies from 4-7 km in central areas of the Pechora basin to 1-4 km in arches and uplifts. In this connection, information on the structure and geo� dynamic development of the basement beneath the basin is derived from the core of over 200 boreholes drilled with different purposes up to a depth of 5 km (7). Granitoids have been recovered by 26 boreholes throughout the entire region being more abundant in the Izhma and Pripechora-Ilych-Chikshino zones. Until the end of the 20th century, the age of granitoids was known from the limited K-Ar data (1, 13), most of which correspond to the period of 600-500 Ma. They provided grounds for assuming that granitoids are Vendian-Cambrian in age. Subsequently, geo� chronological dates were obtained by Pb-Pb (Pb evaporation) measurements in single zircon crystals from granites and diorites recovered from several drill� holes (13). These measurements yielded uniform ages in the interval of 567-551 Ma corresponding in the recent stratigraphic scale to the boundary of the Lower and Upper Vendian (12). The dating of zircons from igneous rocks using the radiogenic Pb isotopes is based on the assumption that the 207 Pb/ 206 Pb ratios (ages) remain unchanged after the formation of zircons and host rocks, although this is frequently not the case. The subsequent Rb-Sr investigations of granitoids from the Izhma and Pripechora-IlychChikshino zones (4) recovered by the same boreholes, where zir� con was analyzed, revealed that the Rb-Sr ages are confined to the period of 608-595 Ma, i.e., to the Riphean-Vendian boundary interval (12). These data are quite consistent with the ages obtained for grani� toid massifs in the North Timan structure of the Timan megablock. Their Rb-Sr ages fall into the interval of 597-587 Ma (2), while the Pb-Pb (Pb evaporation) method yielded zircon ages of 621 ± 3.5 Ma (3). Here�

U-Pb dating and provenance of detrital zircons from the Upper Precambrian deposits of North Timan

Timan comprises the southwest edge of the Pechora Plate. The plate basement is composed of variably metamorphosed sedimentary, mainly terrigenous, and igneous rocks of the Late Precambrian age that are generally overlain by Ordovician-Cenozoic platform cover. Poor exposition and discontinuous dis� tribution of the Upper Precambrian outcrops of dominantly fossilfree sedimentary rocks cause considerable disagreements in stratigraphic correlation. This applies equally to North Timan, which represents an uplifted block of basement, in which sedimentary-metamorphic rocks form the Barminskaya Group (~5000 m thick), previously dated as Early Riphean to Vendian. Earlier Rb-Sr and Sm-Nd isotope dating of schist and crosscutting gabbro-dolerite and dolerite establish ed the timing of greenschist facies metamorphism at 700 Ma. Thus, Late Riphean age of the Barminskaya Group has been suggested. Results of local U-Pb dating of detrital zircon from silty sandstones of the Malochernoretskaya Formation, which constitutes the middle part of the outcropping section of the Barminskaya Group, confirm this conclusion. Age data for 95 zircon grains cover the range of 1035-2883 Ma with age peaks at 1150, 1350, 1550, 1780, and 1885 Ma. The mini� mum age of zircons, considered as the lower age constraint on sediment deposition, provides grounds to date the Barminskaya Group as Late Riphean and indicates eroded rock complexes of the Fennoscandian Shield as the possible provenance areas.

U-Pb age of detrital zircons from the Upper Precambrian terrigenous section of North Timan

In terms of neotectonics, the Timan Range and Kanin Peninsula represent a spacious mountainous structure 1150 km long and 80–160 km wide extend� ing in the northwesterly direction from Mount Poly� udov Kamen to Cape Kanin Nos in the Kanin Penin� sula. It consists of isolated en echelon arranged horst� like uplifts with Upper Precambrian rocks cropping out in their arch parts. In the southwest the Timan Range borders the Pechora Plate that surrounds the Karelian part of the East European Platform in the northeast. The boundary between the Pechora Plate and Mezen megablock of the East European Platform

Sea level changes and rapid crustal movements in cratonic areas in the Late Paleozoic

In the Phanerozoic, the sea depth in epeiric sedimentary basins showed considerable variations, often accompanied by regression. In periods of regression and erosion, the subaerially exposed shelf and the adjacent parts of the marine basins gave rise to numerous nonstructural (stratigraphic) hydrocarbon traps. Sea depth variations with a magnitude of up to 100–200 m and 1–3 myr long (third-order cycles) are usually attributed to the eustatic fluctuations of the sea level. To estimate their possible range, a model is proposed which describes the water depth variations as a function of eustatic fluctuations in tectonically subsiding carbonate platforms. We take into account the crustal isostatic response to the changing water load and the finite time necessary for soil and karst formation in the exposed shelf or its upper part. This model allowed analyzing data on the reference sections of the North Timan shallow-water sediments. According to the analysis, the third-order sea level changes in the Middle Carboniferous, Late Carboniferous, and Early Permian did not exceed several tens of meters. During the same period, shorter fluctuations (∼100 kyr) occurred owing to the waxing and waning of large Gondwanan ice sheets. In the first half of the Bashkirian Age (Early Pennsylvanian), regression took place in the East European and North American cratons and then shallow-water sedimentation resumed. This regression is usually attributed to a considerable sea level fall. In some other areas, slow shallow-water sedimentation continued throughout the Bashkirian. This suggests that the Bashkirian regression was due to the crustal uplifts. Short-term uplifts can be explained by ascending convective currents beneath the asthenosphere. In southern North America, they brought an active fluid into the lithosphere. This caused rapid eclogitization-related crustal subsidence in the Arkoma and Anadarko basins as well as intense lithospheric weakening and shortening in the Ouachita Fold Belt.

New data of typomorphic features of diamonds from placers in North Timan

The morphological and spectral-optical properties of diamond crystals from placers in North Timan rivers have been studied with IR-spectroscopy and cathode luminescence methods. As a result, correlation between external characteristics of diamonds (size and degree of mechanical damage) and number of optically active centers has been revealed. The habit and the type of distribution of structural defects in diamond crystals studied are comparable with those in diamonds from the Archangelsk Region and North Timan’s placers. Based on the obtained data, origin issues and possible primary sources of diamonds from North Timan’s placers are discussed.

Late Silurian–Early Devonian tessellated heterostracanOniscolepisPander, 1856 from the East Baltic and North Timan

Late Silurian–Early Devonian tessellated heterostracan<i>Oniscolepis</i>Pander, 1856 from the East Baltic and North Timan

The mid-Carboniferous rugose coral recovery

Abstract The taxonomic diversity of the rugose corals following the mid-Carboniferous ‘lesser mass extinction event’ (Alekseev 1989) may be subdivided into two intervals. The survival interval includes long-ranging survivors, short-ranging survivors ( Dibunophyllum, Palaeosmilia, Diphyphyllum ), survivors with post-crisis ontogenetic changes ( Caninia, Bothrophyllum ), newly-appeared taxa with hypothetical ancestors ( Profischerina, Protodurhamina ) and those of cryptogenic origin ( Lytvophyllum ). The lower limit of the survival interval coincides with the Eumorphoceras/Homoceras Zone and can be identified in the Donetz Basin, Gornaya Bashkiria, Novaya Zemlja, North Timan, Cantabrian Mountains (Rodriguez et al. 1986) and the Western Interior of the USA (Sando 1989). The recovery interval is established by the appearance of the immigrant genus Petalaxis and by increasing specific diversity in pre-existing lineages. Its lower limit corresponds to the Pseudostaffella praegorsky—Profusulinella staffelliformis boundary, the lower boundary of the Westphalian A in the Cantabrian Mountains and the lower boundary of the Atokan Series in the Western Interior of the USA. The radiation interval was marked by the appearance of astreoid colonies in the Petalaxis—Ivanovia lineage at the Fusulinella calaniae—F. vozhgalensis—F. kamensis lower boundary.