Phenanthrene biomarkers in the organic matter of Precambrian and Phanerozoic deposits and in the oils of the Siberian Platform

The composition and distribution of phenanthrenes (polyaromatic compounds) have been studied in chloroform extracts from dispersed organic matter (OM) of clayey, siliceous, carbonate, and terrigenous rocks of different ages and facies and from some oils of the Siberian Platform. Phenanthrenes have been analyzed by gas chromatography-mass spectrometry. High contents of 1,7,8-trimethylphenanthrene and 1,1,7,8-tetramethyl-1,2,3,4-tetrahydrophenanthrene are present in the OM of Vendian and Cambrian carbonate-shale deposits and in ancient oils of the Nepa-Botuobiya and Anabar anteclises. The OM of Permian continental deposits and oils of the Vilyui syneclise is dominated by 1-methyl-7-isopropylphenanthrene (retene). A triangular diagram for identification of the types of original OM of rocks and classification of genetically related oils has been constructed based on the assessment of phenanthrene biomarker distribution. Putative pathways of the formation of phenanthrene biomarkers are discussed.     

Features of the Behavior of Ionospheric Parameters В0 and В1 in the High-Latitude Zone

Geomagnetism and Aeronomy - The climatological features and behavior of the parameters B0_Neh_I, B1_Neh_I found from N(h) profiles calculated by the curves from the virtual heights during...     

The Early Callovian genus <Emphasis Type="Italic">Сadochamoussetia</Emphasis> (Ammonoidea,Cardioceratidae) in the lower reaches of the Anabar River,Northern Central Siberia

The species Cadochamoussetia aff. subpatruus (Nik.), Cadochamoussetia surensis (Nik.), and Cadoceras cf. simulans Spath are found for the first time in the lower reaches of the Anabar River. The first two species are characteristic of the Lower Callovian Cadochamoussetia subpatruus Subzone of Central Russia, which is equivalent to the Siberian Cadochamoussetia tschernyschewi Zone. Species of the genus Cadochamoussetia, found for the first time in the Arctic, are described. Shells of Siberian representatives of Cadochamoussetia are distinguished from the typical East European species by their larger umbilicus, which is similar to that of the ancestral genus Cadoceras. It is suggested that the Siberian taxa belong to the oldest representatives of this genus, which appeared in the early Callovian Arctic seas and later migrated to seas of Central Europe and England.     

Crustal deformations related to the formation of new tolbachik volcanoes in 1975–1976, Kamchatka

The paper discusses the results of geodetic investigations performed in the region of the large 1975–1976 Tolbachik fissure eruption in Kamchatka. Using data from repeated triangulation and trigonometric levelings, horizontal and vertical displacements have been detected in an area of 3,500 km². Two zones have been recognized: the tension and uplift zone that is probably due to magma intrusion from depths to the surface along the line of new cones and the extensive compensative subsidence zone located at a distance of 20–50 km from the nearest newly-formed cones. Measurements made with small distance measuring device showed the dynamics of feeding basalt dykes intrusion and made it possible to determine their width (a little greater than 1 m) and magma and gas overpressure (50–250 bar). Data have been obtained on dimensions and growth of cones and on vertical ground deformation in the area of new cones during and after the eruption.     

First Results from VLF Observations during the Transarctica 2019 Polar Expedition

Geomagnetism and Aeronomy - The first results are presented for observations of the VLF emissions (1–15 kHz) conducted at polar latitudes during the expedition Transarctica 2019, which was...     

Problems of Oxfordian and Kimmeridgian stratigraphy in northern Central Siberia (Nordvik Peninsula section)

The Oxfordian–Lower Hauterivian section of the Nordvik Peninsula (northern Central Siberia) is a reference for developing zonal scales for various fossil groups and improving the Boreal zonal standard. In the middle 1950s–late 1980s, it was studied extensively by geologists, stratigraphers, lithologists, and experts on various fossil groups. These studies yielded rich fossil and microfossil collections and a set of parallel zonal scales for various faunal groups. Recently, a new detailed ammonite zonation of the Oxfordian and Kimmeridgian units of this section has been proposed. These results contradict the previous biostratigraphic data on ammonites, foraminifers, and palynomorphs. In the present paper, all the biostratigraphic data on the Oxfordian and Kimmeridgian units of the Nordvik Peninsula (Cape Urdyuk-Khaya) and northern Central Siberia undergo a comprehensive analysis and comparison with those on the Boreal Realm. The ammonite-constrained stratigraphic position of the lower Upper Jurassic in the Cape Urdyuk-Khaya section is interpreted as Upper Oxfordian or Middle Oxfordian. In our view, this difference in the understanding is due to the misidentification of some Oxfordian ammonite forms. The zones based on other fossil groups (foraminifers, dinocysts) which were distinguished in the Upper Oxfordian and Kimmeridgian sections of the Nordvik Peninsula are well traceable circumarctically. Their stratigraphic position in various regions of the Northern Hemisphere is constrained by ammonites and bivalves. However, if we use the last alternative ammonite zonation of this section part, hardly explicable contradictions will appear in interregional foraminiferal and dinocyst correlations.     

Spatial Structure of the Illuminated Area of the Auroral Hiss Based on Ground-Based Observations at Auroral Latitudes

Geomagnetism and Aeronomy - The article presents the results of ground-based observations of very low-frequency (VLF) auroral hiss bursts at the Lovozero (Russia) and Kannuslehto (Finland)...     

Processing high-frequency electromagnetic logs from conducting formations: linearized 2D forward and inverse solutions with regard to eddy currents

High-performance algorithms and software have been designed for fast 2D forward modeling and inversion of high-frequency electromagnetic logs to recover the patterns of electrical conductivity and relative permittivity (dielectric constant) of rocks. Forward modeling implies linear representation, with regard to eddy current, of attenuations and phase shifts of electromagnetic fields propagating in 2D conducting formations. In order to improve the modeling quality, the background model is chosen proceeding from the eddy current pattern in a heterogeneous subsurface. The inverse solution is obtained by pseudoinversion of the sensitivity matrix of relative amplitudes and phases. Joint 2D inversion of phase shifts and attenuations improves the reliability of the inferred spatial conductivity distribution and allows estimating permittivity. The reported numerical experiments on inversion of synthetic and field EM logs prove the possibility of estimating the permittivity of complex terrigenous and carbonate reservoirs with water- and oil-filled porosity.     

The main fault zone of East Sayan

Based on the structural and tectonophysical studies of the East Sayan fault zone (the stress fields determined from the slipping planes; and strain fields from dykes), we were able to describe more definitely the character of this regional fault. The right-lateral strike-slip on the rupture at the main stages of its development is established.     

Effectiveness of using correcting multipliers in calculations of the total electron content according to the IRI2007 model

A comparison of the total electron content (TEC) of the ionosphere calculated using different correcting multipliers in the IRI2007 model with experimental data indicates that this model, which is not empirical with respect to the TEC, does not adequately reflect the quantitative and qualitative features of the TEC behavior. The situation can be improved by using new empirical models of the critical frequency and equivalent thickness of the ionosphere and new methods for determining the TEC.