Geoelectric heterogeneities of the Kerch iron ore basin

The three-dimensional geoelectric model of the Earth’s crust and upper mantle of the Kerch Peninsula has been built for the first time based on the results of experimental observations of the Earth’s low-frequency electromagnetic field, carried out in 2007—2013 by the Institutes of the National Academy of Sciences of Ukraine. Its physical and geological interpretation and detailing of the near-surface part were carried out according to the data of the audiomagnetotelluric sounding method to study the deep structure of the Kerch iron ore basin. To the east of the Korsak-Feodosiya fault along the southern part of the Indolo-Kuban trough (in the north of the South Kerch and almost under the entire North Kerch zones), a low-resistance anomaly (ρ=1 Ohm∙m) was found at depths from 2.5 km to 12 km about 20 km wide. Its eastern part is located in the consolidated Earth’s crust and is galvanically connected with surface sedimentary strata, while the western part is completely in sedimentary deposits. The anomaly covers the territory of the Kerch iron ore basin and occurrences of mud volcanism. The characteristics of the upper part of the layered section of the Kerch Peninsula in the interval of the first hundreds of meters were obtained from the results of one-dimensional inversion of the audiomagnetotelluric sounding data (frequency range 8—4000 Hz). It is shown that the first 15 m of the section, corresponding to Quaternary deposits, have resistivity values up to 1 Ohm∙m. Below, in the Neogene sediments, the electrical resistance increases to values of 5 Ohm∙m and more. Both horizontally and vertically, the distribution of resistivity values has a variable character, manifesting as a thin-layered structure with low resistivity values. Possibly, such areas have a direct connection with the channel for transporting hummock material and gases. A connection is assumed between the low-resistivity thin-layered near-surface areas, a deep anomaly of electrical conductivity in the upper part of the Earth’s crust, and the likely high electrical conductivity of rocks at the depths of the upper mantle with iron ore deposits, as well as the manifestation of mud volcanism. The heterogeneity of the crustal and mantle highly conductive layers may indicate a high permeability of the contact zones for deep fluids.

Paleomagnetism and magnetostratigraphy of Tarkhanian sediments of the Eastern Paratethus (Skelya section, Kerch peninsula, Crimea)

<p>A detailed paleomagnetic study of Tarkhanian sediments of Skelya section was carried out with the goal to obtained magnetostratigraphy data. The Skelya section is located on the Azov sea side of Kerch peninsula, Crimea (45<sup>o</sup>42′N, 36<sup>o</sup>53′E). The Tarkhanian sediments of Skelya section are represented mainly of clays and have a total thickness of ~ 100 m. According to GTS (2012), the Tarkhanian stage of Miocene is related to the lower part of the Langhian of the General Stratigraphic Scale. Standard paleomagnetic measurements have been carried out to investigate magnetic parameters: natural remenent magnetization, magnetic susceptibility, saturation remanent magnetization, anhysteretic   remanent magnetization varied through out the section. The remanent coercitivity force, determined from backfield demagnetization measurements, range between ~34 and 67 mT.   The composition of the ferromagnetic fraction was examined using temperature dependences of saturation remanent magnetic moment. The thermomagnetic analysis showed that the blocking temperatures are  about 320<sup> o</sup>C and 410-470<sup> o</sup>C and  greigite and titanomagnetite  are the main carriers of NRM in the section.  The biplot of  IRM<sub>-100 mT</sub> / SIRM versus  ARM<sub>40mT </sub>/SARM showed that the ratios fall down into the field around the titanomagnetite and greigite areas. The pseudo-single domain  state of titanomagnetite and greigite was determined from their Mrs/Ms and Bcr/Bc ratios by Day-plot. Paleomagnetic studies have shown that the interval of the Kuvinian beds in its upper part is composed of sediments of reversal polarity magnetization. The rocks of the Terskian and Argunian beds are characterized by intervals of normal and reversed polarity magnetization. This work was supported by Russian Science Foundation, project № 19-77-10075.</p>

The southern birch mouse Sicista loriger (Dipodoidea) in the Crimea: distribution, habitats, seasonal ac-tivity, and abundance

The southern birch mouse is a rare and non-abundant species of small mammals of the fauna of the Crimean Peninsula. Its geographic range has gradually reduced during the 20th century. Initially, the southern birch mouse occupied almost the entire territory of the steppe and foothills of the Crimea. As the area of virgin and unploughed lands decreased, the species disappeared from the most part of the peninsula. Whereas the species had been recorded in 11 administrative districts in the middle of the twentieth century, now it is known only in three districts, in two of which it is extremely rare. Currently the southern birch mouse exists in two isolated populations—a western (Tarkhankut) and an eastern (Kerch)—separated by 200 km of anthropogenic landscapes. Census of small mammals has been carried out on trap-lines for the past 40 years. In a total of 667100 traps-nights, 144 birch mice were collected. Additionally, remains of 56 birch mouse specimens were found in 16862 pellets of the long-eared owl. The birch mouse population in the Tarkhankut Peninsula is small (12 specimens were trapped and 39 specimens were identified in pellets), and its range is largely restricted. The species’ population in the Kerch Peninsula is larger (132 birch mice were trapped and 17 specimens were identified in pellets of birds of prey) and its range occupies the entire area of the Kerch Peninsula. Data of long-term epidemiological surveys showed that the ratio of trapped birch mice in the whole of the Crimea is 0.21 %, whereas their ratio in the steppe zone is 0.29 % at a relative abundance of 0.03 specimens per 100 trap-nights. Birch mice are active from mid-April to mid-November. The peak of activity occurs in April, when 49.9 % of animals were trapped. Among natural enemies, the red fox (Vulpes vulpes) can pose a real threat to birch mice, as well as the long-eared owl (Asio otus) to local micropopulations, especially during the breeding season. In our opinion, despite the generally low abundance of birch mice in the Crimea and the fragmentation of its geographic range, extinction does not threatens this species in the peninsula (especially its Kerch population) under the current management system. Conservation of the southern birch mice populations in the Crimea requires a detailed study of the species’ ecology, especially of limiting factors.

GENETIC MODEL OF MUD VOLCANISM OF THE KERCH PENINSULA (SCIENTIFIC AND APPLIED ASPECTS)

The work is devoted to the results of many years of research and observations of mud volcanoes on the Kerch Peninsula. It aims to reveal the most important factors and aspects related to their origin, activity and impact on the geological history of the region. About 50 fossil and modern mud volcanoes have been defined on the Kerch Peninsula and the adjacent part of the water area. Their activity is consistent with the phases of activation of the alpine tectogenesis of the Crimean-Caucasian segment and is intermittent and impulsive. In the geological history of the peninsula, four main bursts of mud volcanic activity are clearly recorded: in the Upper Maikop, Chokrak-Karagan, Sarmatian and Cimmerian. Its greatest activity is manifested in the late Miocene and early Pliocene. Favorable factors for the development of mud volcanoes within the peninsula are the presence of a thick layer of plastic clays enriched in water and gas fluids, the widespread development of brachyanticlinal folds in the Neogene structural surface and a network of deep faults and fractures. The activity of mud volcanoes is associated with the formation of specific compensation structures – depressed synclines, which have become widespread on the Kerch Peninsula. The latter, depending on the paleogeographic conditions (sea, land) and the structural position of volcanoes in the anticlines, have acquired different specifics of structure and filling. Some depressed synclines are associated with iron ore deposits, which differ from typical iron ores of the mulde type by significant capacity, structural and textural features and material composition. Components of hydrothermal and exogenous origin have been defined in the products of mud volcanism: mud gases, mud waters, mud breccias, which indicates the genetic connection of this phenomenon with deep and near-surface processes. In addition, liquid, solid and gaseous hydrocarbons are often detected in volcanic eruptions. The latter are a criterion for searching for oil and gas at depth. Mud volcanoes of the Kerch Peninsula are a unique testing ground for monitoring the processes of modern mineral formation, the dynamics of deep processes and seismic activity in the region.

History and Modern Status of the Black-eared Wheatear, Oenanthe hispanica (L.) (Passeriformes, Muscicapidae), in Ukraine

Th e history of research of the Black-eared Wheatear Oenanthe hispanica (L.) in Ukraine in XIX–XXI centuries is presented. Th e Black-eared Wheatear is now a rare breeding bird in the coastal area of the Crimean peninsula, and a very rare vagrant species on the other territory of Ukraine. Four breeding regions of the Black-eared Wheatear are found in the Crimean peninsula: seacoast between Sudak and Th eodosia cities; neighbourhood of Sevastopol City; Tarkhankut peninsula; Kerch peninsula. Th e fi rst two breeding regions have been known since the middle of XIX century. In the breeding regions, the breeding areas of the Black-eared Wheatear are not constant: the birds almost never nest in a place for a number of years. Oenanthe hispanica breeds in Crimea in the same biotopes as its sibling species, the Pied Wheatear, Oenanthe pleschanka, which is essentially more abundant there. Th e breeding of single Black-eared Wheatears with the numerous Pied Wheatears increases their interspecies hybridization, which is rather common on the Crimean peninsula. Th ree out of fi ve individuals of Oenanthe hispanica collected in Crimea and stored in various museums turned out to be hybrids with Oenanthe pleschanka. Th e Black-eared and Pied Wheatears have hybridized in the Crimean peninsula for a long time: the hybrids have been recorded in XX and in XXI centuries. Th e hybrids do not occur in a specifi c breeding region, and can be found in any of those.

RELECTIVE SIGNS OF DEGRADATION IN POSTAGROGENIC SOILS OF ANTI-AGRICULTURAL AREAS OF EAST CRIMEA

The results of a study of the physicochemical parameters of fallow soils in the ancient Bosporos chora (Kerch Peninsula) are presented in the article. The most long-lasting indicators of agropedogenesis are associated with the water resistance of aggregates and the composition of organic matter, as was found.

Research of the Crimean Peninsula wind power resources based on hourly data from ERA5 reanalysis

The climatic assessment of the wind resources of the Crimean Peninsula is carried out using the hourly ERA5 data for the 40-year period 1980-2019. It is established that average wind speed in central Crimea is 2–6 m/s. It is lower than on the western coast (4–8 m/s) and on the territory of the Kerch Peninsula (5–9 m/s). It is found that the Kerch Peninsula is the most favorable area for wind generation. The frequency of wind speed for rated output of wind turbines in that region is 15–17% at 10 m and 37–38% at 100 m. The frequency of ineffective wind conditions for wind generation, when the wind speed is insufficient to start a wind turbine, does not exceed 17-22% at 10 m and 11-12% at 100 m. In central Crimea and the Southern Coast of Crimea, the frequency of ineffective wind conditions at a height of 10 m exceeds 40% per year. Also, as a result of the analysis of the diurnal variation, it is found that at 10 m, in June the wind speed in the daytime is higher by average 21% and in December by 6%. The diurnal variation is not noticeably pronounced at a height of 10 m. The revealed seasonal features of the change in wind speed at heights of 10 and 100 m characterize its increase by 31–35% in the winter season compared to the summer. Some local specificity of the Crimea relief, especially mountain ranges, is not taken into account in the work, which is due to insufficient spatial resolution of the reanalysis.

Borate accumulations related to onshore mud volcanism: Case study from the Kerch Peninsula, the Caucasus collision zone

<p>Mud volcanism (MV) is an efficient dewatering mechanism common to collisional settings which provides transport of major and trace elements from deep sedimentary reservoirs to the surface. Boron is the chief geochemical fingerprinting tracer of MV activity. Numerous MVs of the Kerch Peninsula emit water and mud with extreme boron enrichment. Boron content correlates with the burial depth of the source Oligo-Miocene mudrocks yielding the highest boron contents in illite-dominated mud (up to 1500 ppm B) in the Bulganak MV, which represent the deepest endmember (up to 3.5 km) in the Kerch Peninsula. Smectite-dominated mud from shallow depths (1-1.5 km) at small MVs are poorer in both illite and boron (up to 250 ppm). B-enrichment of the parent shale and diagenetically-driven smectite illitization and dewatering are considered as the main prerequisites for boron enrichment in MVs.</p><p>MV waters are mainly related to diagenetically altered basinal water diluted by <sup>18</sup>O- and B-enriched dehydration water released during smectite illitization. The range of boron contents in the Kerch MV waters is as large as 14 to 1640 ppm (470 ppm on average), and the B<sub>MV</sub>/B<sub>SW</sub> ratios are from 3.0 to 354. Waters of small MVs show lower B enrichment (14-73 ppm; B<sub>MV</sub>/B<sub>SW</sub> = 3.0-15.8). The majority of Cl-HCO<sub>3</sub>/Na and HCO<sub>3</sub>-Cl/Na highly evolved saline MV waters sampled in large MVs are also enriched in <sup>18</sup>O (δ<sup>18</sup>O = +9.8 to +14.5 ‰ VSMOW) and D (δD = -30 to -4 ‰ VSMOW) isotopes being also rich in boron (average 650 ppm). Waters of small MVs are poorer in <sup>18</sup>О (δ<sup>18</sup>O = +3.6 to + 6.1 ‰) and B (average 130 ppm). The fluid generation temperatures inferred to be Т<sub>Mg/Li</sub> = 34 to 117°С. In the hot season, MV waters reach a salinity of 40-70 g/L TDS and precipitate halite, Na and Na-Ca borates. At the Bulganak MV field, there is a unique accumulation of MV-related borates, which contain predominant tincalconite and ulexite, minor borax and traces of probertite. The broad occurrence of ulexite in the Kerch MVs is due to the B (460– 630 ppm) and Ca (>30 ppm) ranges of NaCl-dominated brines, which are known to be optimal for ulexite crystallization in modern playas and salars. MV-related borate deposits can form at the following essential conditions: venting of B-rich MV waters; environment akin to playa lake; long dry and hot seasons; evaporation and ensuing increased boron concentration in shallow close MV pools; pH of MV water between 8.5 and 9.5; low permeability of clayey mud cover. <em>The study was supported by the Russian Science Foundation, grant 17-17-01056.</em></p>