Acritarchs of the Mesozoic of Ukraine

Shevchuk, O.; Ivanchenko, Kateryna

doi:10.26565/2410-7360-2021-55-08

Cited by 3 publications

(2 citation statements)

References 8 publications

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“…The neutral zinc vacancy VZn x corresponds to the capture of two holes by oxygen ions surrounding the vacancy and is a center with spin s = 1, the properties of which depend on the interaction of the magnetic moments of localized unpaired electrons on two neighboring O 1ions. Thus, intrinsic point defects with spin s = 1/2 (Zni + , Оi + , VZn 1-, and Vo 1+ ), as well as centers with spin s = 1 (triplet state) of type Оi x , VZn x , and Vo x are paramagnetic [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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Temperature dependence of the EPR signal in ZnO

Хмеленко

Lyashkov²,

Kolbunov³

et al. 2022

JPhysElectron

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Ceramics based on zinc oxide doped with lithium was fabricated. It is shown that an increase in the lithium content in an amount up to 0.1% leads to a decrease in electrical conductivity, and then in the range up to 3% to its increase. The real and imaginary parts of the permittivity decrease with increasing lithium concentration over the entire range of measured frequencies (50 kHz - 3 MHz). Similarly, the signal of the EPR line with g-factor ~1.96 decreases. An analysis of the temperature dependence of the EPR signal intensity with a g factor of ~1.96 gives an activation energy of 0.06 eV, which practically coincides with the depth of shallow donors in ZnO. This makes it possible to identify the EPR signal with g-factor ~1.96 with oxygen vacancies.

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Section: Introductionmentioning

confidence: 99%

“…In the paper [7], devoted to the study of EPR of ZnО powder heat-treated under reducing and oxidizing conditions, it is reported on the observation of three lines with g1=1.955 (Vo 1+ ), g2=1.958 (Vo+Oi 2-) and g3 = 1.987 (Оi 1-).…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of the EPR signal in ZnO

Хмеленко

Lyashkov²,

Kolbunov³

et al. 2022

JPhysElectron

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Jurassic system stratigraphy at the Kamianka village. Part 1. The Kozhulinska formation

Matveev,

Pakki,

Shevchuk

et al. 2023

Visnyk of V.N. Karazin Kharkiv National University, Series Geology. Geography. Ecology

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Introduction. Despite the active research of Jurassic system deposits of Donbas during the last two centuries the issue of their stratigraphy principles is still debatable. The authors` analysis of the available scientific material revealed a conflict between the normatively established requirement to rely on lithostratigraphy during the sediment research, and the fact that the existing common system relies on biostratigraphy. This contradiction could be solved by the study of lithostratigraphic units of the Donetsk Jurassic deposits. Therefore, the purpose of the article was to research the Kozhulinska formation, establish its composition and describe its main features. The Lower Jurassic deposits from the outcrops near the village of Kamyanka (Izyum district) were studied, since the studyable stratotypes of most of the Jurassic strata, which are well exposed in the studied area, are available in this area. Material and methods. The scientific search was based on the analysis of literature, results of previous drilling and mapping works, as well as own field, laboratory and analytical studies. Clay samples were taken from different stratigraphic levels of the formation and from different lithological varieties. Laboratory research was carried out in two directions: using an electron microscope and a spectrometer to detect the material composition of clays. A palynological analysis of these deposits was also carried out, namely, stratified deposits with the help of microphytofossils, including, for the first time, according to the orthostratigraphic group – dinocysts. Results and discussion. The results showed that the Kozhulinska formation was mainly represented by shaly clays (gray, dark gray, sometimes blue-gray) that contained relatively thin layers of sandstones. The main mass of clays consisted of hydromicas, with an insignificant content of montmorillonite, and an even smaller amount of kaolin. The layers of quartz sandstones cemented with clay material were separately traced along the strike. Paleontological remains in the clays of Kozhulinska formation were rare. Palynological groups are mainly represented by pollen and spores, as well as remains of dinophytes, green algae and acritarchs. According to paleoalgological analysis, the sediments of the Kozhulinska formation are dated for the first time. Stratigraphy. Kozhulinska formation is represented by a fairly uniform layer of montmorillonite clays of hydromica composition. The clays are mainly siltstone, but there are, especially in the lower part, washed clean varieties. It is impossible to divide the formation into sub formation based on lithological features. According to biostratigraphic data, deposits are divided into Plinsbachian, Toarian and Aalenian. Paleogeography. At the end of the Early Jurassic and the beginning of the Middle Jurassic era, the territory of the Kamianska area was a low-lying part of the seabed that was drained during low tides. The land that surrounded it was also low-lying and almost did not supply detrital material, however, there is a regular removal of plant detritus. The source of the terrigenous material was the sedimentary complexes of the Donetsk Ridge. Features of the chemical composition of the world are a significant amount of iron (siderite, ocher, chamosite) and the absence of calcium and magnesium carbonates. At the end of the early Aalene, this unstable basin finally regresses, which leads to the accumulation of a powerful subaerial pack of sandstones, which weigh and border the cores of anticlines - elevated areas of the bottom or small islands.

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Jurassic system stratigraphy at the Kamianka village. Part 2. The Cherkas’ka formation

Matveev,

Shevchuk,

Kolosova

et al. 2024

Visnyk of V.N. Karazin Kharkiv National University, Series Geology. Geography. Ecology

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Introduction. The paper is devoted to the study of the Cherkaska formation of the Jurassic system of the North-Western outskirts of the Donbas and is a continuation of a series of publications highlighting the stratigraphy of Jurassic in key areas near the town of Izyum and the village of Kamyanka. Material and methods. The scientific search was based on the analysis of literature, results of previous drilling and mapping works, as well as own field, laboratory and analytical studies. Chemical and X-ray structural analyzes of clays, mineralogical analysis of sands were carried out. Micropaleontological analysis and generalized data on the distribution of fossil remains were carried out. The palynological analysis of these deposits was also carried out, including, for the first time, according to the orthostratigraphic group – dinocysts. Results and discussion. The stratotype of the Cherkaska Formation was not specified. These were probably outcrops of ferruginous sandstones in the area of the village of Cherkaske, Slavic district, Donetsk region. Unfortunately, the deposits of this formation are exposed very fragmentarily, which makes it impossible to indicate a single typical section. As a number of such sections, it is possible to indicate Topalska balka - a clay stratum, and Pidluzhnyi farm - the upper stratum, stratigraphically important Vitcheliian layers were noted only in the village of Sukha Kamianka. Lithology. In this section of the paper, we present the detailed lithological composition of the deposits of the Cherkaska Formation from the three studied outcrops. Paleontological remains. Based on the findings of macrofauna in the sandstones, the dated levels of Witchellia rossica and Stephanoceras humphriesianum can be distinguished, which correspond to the two upper zones of the Lower Bajocian of the International Stratigraphic Scale. Upon the appearance of dinocysts of Pareodinia sp. and a small percentage of Clasopollis pollen (remains of gymnosperms) for the first time dated clays of the Cherkaska sub-formation. Stratigraphy. Within the studied territory, the Cherkaska formation is clearly divided into two parts: the lower one, composed of clays, and the upper one, composed of sandstones, which makes it possible to divide it into sub-formation. Witchellia limestone may be present if the upper sub-formation is eroded. Paleogeography. At the beginning of the Cherkaskyi period, the territory was a flat lowland covered by an extremely shallow sea basin. In the Late Cherkaskyi period, the supply of detrital material increases significantly, but the depth of the basin also increases, the salinity becomes normal, and a normal marine fauna appears. In some places, on the slopes of paleo-elevations, accumulation does not occur, which leads to the formation of deposits of a facies similar to Ammonitico rosso - limestones from Witchellia. Conclusions. The Cherkaska formation represents an important stage in the geological history of the development of northwestern Donbas. The formation marks the beginning of the Middle-Late Jurassic transgression, the beginning of the formation of normal marine sediments, and the activation of differentiated tectonic movements of local structures.

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Acritarchs of the Mesozoic of Ukraine

Cited by 3 publications

References 8 publications

Temperature dependence of the EPR signal in ZnO

Temperature dependence of the EPR signal in ZnO

Jurassic system stratigraphy at the Kamianka village. Part 1. The Kozhulinska formation

Jurassic system stratigraphy at the Kamianka village. Part 2. The Cherkas’ka formation

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