pdf № 290, February

DOI: 10.19110/2221-1381-2019-2-3-13

A detailed description of the section of the Middle Jurassic terrigenous deposits exposed on the Yarenga River, Arkhangelsk Region, is provided. The section represents a new locality of fossil remains of Jurassic marine reptiles. Among them, the postcranial elements of the plesiosaur Muraenosaurus dominate. Pliosaur and ichthyosaur finds, each represented by a single bone, also occur in the assemblage. The palynological and micropaleontological data support the Early — Middle Bathonian age of the deposits. The lithological characters of the rocks and the presence of rare foraminifera indicate shallow marine environments. The significance of new discoveries for the fossil record of the Jurassic marine reptiles is briefly discussed.

Keywords: Jurassic, lithology, plesiosaurs, ichthyosaurs, foraminifera, microphytofossils, Sysola Formation, Bathonian, Mezen Syneclise.

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DOI: 10.19110/2221-1381-2019-2-14-21

The physical properties of the polymetamorphic formations of the Marunkeu eclogite-gneiss complex in the Polar Urals were analyzed. The patterns of density distribution and magnetic susceptibility of rocks were revealed. We assessed how primary mineralogical composition of metamorphic rocks and subsequent mineral transformations during polymetamorphism influenced the physical properties of rocks. A qualitative interpretation of materials of magnetic and gravitational surveys was performed. We showed that a wide range of magnetic properties of rocks of the Marunkeu complex were not reflected in a magnetic field, which was associated with the leveling role of polymetamorphism. It was established that a more stable petrophysical characteristic, less dependent on metamorphic transformations of rocks, was their density. It was mainly determined by the composition of the protoliths. Therefore, gravimetric data were crucial for establishing the geology and characteristics of the deep structure of the Marunkeu complex. Based on the interpretation of gravimetric materials, we showed that the formations enriched with high-density rocks (metaperidotites, eclogites and apoeclogitic amphibolites) sank to the north and belong to the lower formation of the Marunkeu complex. It supported an idea of the sublatitudinal structural plan of the Marunkeu complex. This was an additional argument in favor of referring the object under consideration as to early Precambrian formations and interpreting it as a tectonically displaced fragment of the Lower Precambrian crystalline base involved in the structure of rocks of Uralian orogeny.

Keywords: Polar Urals, Marunkeu eclogite-gneiss complex, deep structure, petrophysical characteristic, specific magnetic susceptibility, density inhomogeneities.

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DOI: 10.19110/2221-1381-2019-2-22-28

Products from ammonites are currently in high demand. The author for the first time studied in detail the mineral composition and gemological characteristics of the interior and jewellery ammonites of the Yaroslavl region. Late Jurassic ammonites redeposited in the water-glacial Quaternary sediments. Ammonites are characterized by a nacre layer with bright multi-colored iridescence.

The complex of ammonite studies included the determination of microhardness, specific gravity, luminescence, optical-petrographic analysis, determination of the mineral and chemical composition, electron-probe and electron-microscopic studies. Ammonites consisted mainly of apatite (42—67 wt. %) and calcite (16—48 wt. %). Quartz, glauconite, kaolinite, hydromica, goethite, pyrite and x-ray amorphous phase were present. The following elements-admixture had high content, wt. %: Sr — 0,170 and Ba — 0,028. The contents of radioactive and carcinogenic elements were at the level of background.

The walls and partitions of the ammonite shell completely lost the original aragonite composition and consisted of apatite, calcite with inclusions of goethite and pyrite. The iridescence of the pearlescent layer was associated with lamellar layers of predominantly apatite, which inherited the structure of lamellar layers of aragonite. The color of irisation was determined by the size and orderliness of the plates and did not depend on their mineral composition.

Ammonites of the Yaroslavl region are of commercial interest as interior samples. Fragments of the pearl layer with bright iridescence can be used to make ammolite cabochons.

Keywords: ammonite, aragonite, apatite, irization, ammolite, jewelry materials, Yaroslavl region.

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DOI: 10.19110/2221-1381-2019-2-29-35

The goal of the project was to study shungite-bearing rocks — unique commercial minerals. We need better understanding of the petrophysical parameters of the rocks at mined deposits to meet the changing requirements for the properties of the materials, depending on their application. The results of the study of maksovites, saprobitumolitic rocks (carbon free 35—45 %) from the Maksovo body of the Zazhogino deposit located in the northeastern Fennoscandian Shield, Karelia, were reported. The object of study is confined to the Trans-Onega suite of the Ludicovian superhorizon of the Lower Proterozoic unit. Gabbro-dolerite sills, which contributed to the contact alteration of the maksovites that affected the composition and properties of the rocks at the deposit, were identified. To assess the qualitative characteristics of the structural varieties of maksovite as a non-metalliferous commercial mineral for the building industry, their petrophysical parameters were studied using optical and electron microscopy, chemical (silicate) analysis and X-ray fluorescent spectrometry.

Keywords: saprobitumolites, shungite matter, maksovites, exocontact zone, density, water absorption, porosity, strength.

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DOI: 10.19110/2221-1381-2019-2-36-43

The study is based on the data of vibroseis survey in the urbanized area of Syktyvkar. Areas of above-norm velocity and acceleration vibration values zones intersection were determined. The vibrational impact consequences probability is high in the form of building base settlement up to 2 mm / year in weak and dense soils within such areas. The vibration acceleration maximum rms-root mean square values were recorded: for the component x — 0.254 m/s, y — 0.207 m/s, z — 0.622 m/s; and vibration speed: for the component x — 1.195 ґ 10 m/s, y — 7.54 ґ 10 m/s, z — 1.318 ґ 10 m/s. These values are repeatedly higher than the normative ones. 3 areas with a high vibration damping gradient were contoured on the displacement schemes. As a result, additions were itemized to the Syktyvkar seismic microzoning map from the geoecological city conditions viewpoint in terms of vibroseis load on buildings foundation soils. These conditions create an additional increment to the amplitude of possible earthquakes. We made conclusion about the ecological geological environment state transformation in the contoured zones in restrained urban conditions.

Keywords: vibroseis field, vibroseis survey, geological environment, geoecological conditions, urbanized area.

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DOI: 10.19110/2221-1381-2019-2-44-52

The article discusses the role of cluster analysis in the sciences of classiology, defines clusters using text as well as logical and mathematical formulas. For the first time, the ideas and methods of cluster analysis are discussed side by side with the graph theory. The algorithm is defined for the automatic recognition of multivariate clusters by joining string clusters — clusters with have a common point (a row in the table of point-to-point distances).

Separately, the following special issues are discussed: the choice of critical path, clustergrams, transformation of input data for cluster analysis, and interpretation of plain (two-dimensional) images of multivariate cluster analysis.

Keywords: classiology, classification, cluster analysis, critical path, algorithm, computer program, graph.

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