Annotation of the results obtained in 2022
In 2022, the scientific program of the project included: 1. Analysis of the distribution of the Akchagyl transgression in the Caspian region based on the synthesis of data on 80 sections of Late Pliocene and Early Pleistocene brackish-water deposits (Piacenzian and Gelasian). The transgression was preceded by a restructuring of the structural-sedimentary plan of the region at the end of the Miocene and Early Pliocene. The restructuring was expressed in a decrease in the role of longitudinal tectonic zonality of the Caucasian-Caspian segment of the Paratethys and surrounding territories and an increase in the role of transverse zonality. The latter manifested itself in the tectonic uplift of the Greater Caucasus, its northern foothills, the Lesser Caucasus and the Armenian Highlands, and in the lowering of the western parts of the basins of the South and Middle Caspian. The impact of factors responsible for the manifestation of longitudinal and transverse zonality controlled the complex shape of the Akchagyl brackish-water basin. The time of the transgression is estimated at ~3.2–1.8 Ma, although temporal estimates of the boundaries require more details. The maximum level of the Akchagyl transgression did not exceed 40–50 m above the current level of the World Ocean. The connection of the Akchagylian basin with the World Ocean, or with the seas associated with it, existed only at the end of the Pliocene and was short-lived. A high probability of connection between the Akchagyl basin and the Arctic Ocean through the northern tributaries of the Kama river and the Pechora depression is shown. No geological data confirms the basin's connection with the southern seas. Based on the current position of the top of the Akchagylian marine deposits in different parts of the basin, the magnitude and rate of the post-Akchagylian Quaternary vertical movements were estimated, varying from 2.5 km in the axial zone of the Caucasus Range to 1.75 km in the western part of the Lesser Caucasus. 2. Study of the late Pliocene Gilbert type delta in the west of the Erzurum depression in NE Turkey. It has been shown that delta deposits mark the confluence of a river coming from the west into Erzurum lake basin of the late Pliocene. The deposits of the delta are dated to the late Pliocene on the basis of the found remains of small mammals and mollusks, and the results of palynological and magneto-stratigraphic analysis. Probably, in the late Pliocene, the Paleo-Araxes valley spread further to the west, and the described delta arose in the place where the sources of the Paleo-Aras flowed into the basin of the Erzurum depression. In the early Pleistocene, the delta deposits were overlain by coarse alluvium after the Erzurum Basin was tectonically isolated from the Araxs river system. At the end of the Early or the beginning of the Middle Pleistocene, the sources of the Paleo-Araxes were intercepted by the upper reaches of the Euphrates River., which drains the depression nowadays. 3. The Recent stage of the development of the Sevan Depression of the Armenian Highlands was reconstructed on the basis of a comprehensive analysis of magneto- and biostratigraphic data, as well as radioisotope dating data. The paleogeography of the Sevan and Shirak depressions in the Pliocene-Quaternary time is reviewed. It is shown that the Sevan Depression originated no later than Pliocene, in parallel with the growth of the Lesser Caucasus and the uplift of the Armenian Highlands. The magnitude of the depression during this period amounted to 550‒650 m. Based on the stratigraphy and lithology of the lake deposits of the Sevan Depression, it was concluded that the Akchagylian transgression at the Pliocene-Pleistocene transition did not penetrate into the Sevan depression, but reached the Shirak Depression located to the west, which was due to either the greater isolation of the Sevan Depression, or its earlier involvement in the regional uplift compared to the Shirak Depression. 4. Field work in the North Caucasus. A field study of reference sections of Akchagylian and its stratigraphic analogues (Late Pliocene-Pleistocene) was carried out in the valley of the Kuban River and its left tributaries (Belaya, Pshekha, Abin, Adagum) and on the Taman Peninsula. A geological and geomorphological study was carried out in the Pshekh-Adler transverse fault zone on the border of the low-mountainous North-Western and high-mountainous Western Caucasus. Important achievements included the bio-magnetostratigraphic characterization of the Belorechensk molasse Formation, which was for the first time reliably dated to the Late Pliocene-Early Pleistocene. For the first time, a biostratigraphic characterization of the Kuyalnik brackish water deposits and their continental counterparts was obtained. 5. Field work in Eastern Turkey. This work was aimed at the study of the reference sections of lacustrine and volcanogsedimentary deposits of the Plio-Pleistocene in the sedimentary basins of the region: Erzurum basin (Pashaurdu section), Horasan basin (sedimentary sequence near the village of Pekechik), Khinis basin (Khynys section), Agri basin (sections in vicinity of the city of Agri). Among the most important achievements of this year, one can note the identification of new, Early Pleistocene, levels in the Pekechik sections, microtheriological, malacological, palynological and paleocarpological sampling of several levels of the composite section. The study of the volcanosedimentary sequence near the city of Hinis showed the marine origin of the Miocene lagoon-lacustrine deposits underlying the Plio-Pleistocene volcanogenic-sedimentary sequence of the Hamurpet and Yollustu formations. 6. Analytical works on the palynology of the Miocene and Plio-Pleistocene sections of Eastern Turkey. Palynological data were obtained in three Miocene and Plio-Pleistocene sections located in Eastern Turkey. Data from the Aşkale (Erzurum depression) and Hinis (Hinis depression) sections characterize the vegetation of the Early-Middle Miocene and provide evidence for the ingression of marine Mediterranean transgressions into Eastern Anatolia based on the presence of marine dinocysts in the spectra. A summary palynological diagram was built for the thick (more than 200 meters) lacustrine-alluvial sedimentary sequence near the village of Pekecik (Horasan depression, upper reaches of the Araxes River). Phytocenoses of the lower, middle, and upper parts of the combined section were restored. Palynospectra of the late Pliocene characterize the vegetation of mixed forests with woody elements of warm-temperate and subtropical types. The spectra of the mid-Early Pleistocene are characterized by a reduction in the diversity of woody vegetation. Palynoassociations of the second half of the Early Pleistocene indicate the dominance of steppe and semi-desert vegetation in the Early Pleistocene and the wide distribution of open steppe landscapes.

 

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Annotation of the results obtained in 2023
In 2023, within the framework of the project "Pliocene-Early Pleistocene restructuring of the structural plan of the Arabian-Caucasian region and its impact on paleogeographic conditions, biota dynamics and the settlement environment of ancient man", work was carried out in the field of neotectonics and paleoseismology, complex lithography and biostratigraphy of the studied areas. The catastrophic East Anatolian earthquake on February 6, 2023 and a series of subsequent seismic events made it possible to study in the field in March-June 2023 and obtain unique geotectonic data. This earthquake of the 7.8 magnitude was the first and strongest in the region in at least 500 years. It is associated with the East Anatolian Fault Zone (EAFZ), as well as with the terminal northern fragments of the Dead Sea Transform (DST). The earthquake activated a segment of the East Anatolian zone of active left-lateral strike slip fault (EAFZ) of the northeastern strike with a length of 361 km. According to the resulting seismic fractures, left-lateral displacements occurred over 318 km. Their maximum amplitude of 8.5 m was observed north of the epicenter. To the northeast of this area, a left-lateral displacement of several meters is sustained for a significant length of the activated segment and is accompanied by an elevation of the southeastern wing by up to 1.5 m. To the southwest of the area of maximum displacements, the shift decreases faster than in the northeast of the activated part of the EAFZ, and the vertical component of the displacements is variable, although the southeastern wing is more often raised. In the extreme southwest, the shift is replaced by discharges, gaping cracks and other manifestations of transverse stretching, which are accompanied by landslides and are largely secondary seismic dislocations. Left-lateral displacements also occurred at the northern ends of the western and eastern branches of the Dead Sea Transform (DST) adjacent to the EAFZ from the south. Despite the fact that the energy distribution of numerous aftershocks along the EAFZ is generally proportional to the distribution of the magnitude of seismogenic displacements, movement along the EAFZ occurred during and immediately after the main shock. In the northern part of the DST, a significant decrease in the amount of energy released by strong earthquakes has been established over the past centuries. We suppose that the tectonic stresses accumulated in the northern part of the DST have become an important geodynamic source of the East Anatolian earthquake. An important result of the project was the generalization of extensive materials on the Pliocene-Quaternary molasses of the Western Caucasus. A comprehensive study of a series of reference sections of the Belorechensk Formation on the left bank of the Belaya River and sections along the Pshekha River, above its confluence with the Belaya River, showed that the Belorechensk Fm is the first and most thick part of the the coarse molasses of the region, formed as a result of an increase in river slopes and erosion energy due to orogenic activation of the Western Caucasus (Trikhunkov et al., 2024, in print). Bio- and magnetostratigraphic data make it possible to date it in the range of 3.5 – 3.0 Ma and divide it into three units: lower, middle and Upper Belorechensk sub-formations, corresponding to three erosive-accumulative cycles of molasses accumulation. The lower (N2/2 bc1) and middle (N2/2 – QE bc2) sub-formations are transitional from the lower to the upper molasses. They are represented by subcontinental mainly sandy-clay with carbonate cementation deposits of the basin contolled by the base level of the Kuyalnitsky brackish water basin. These deposits also include alluvial-deltaic pebbles and sands of the Caucasian rivers and date back to in the range from 3.5 to 3.0 million years and from 2.9 to 1.6 Ma, respectively. The Upper Belorechensk sub-formation (QE bs3) is represented by pebbly alluvial deposits typical of the upper Molasse without carbonate cementation. It was formed at the stage of large river wide valley origination under conditions of a strong erosional increase against the background of the active uplift of the Western Caucasus in later Early Pleistocene (Apsheronian/Gurian). When studying the deposits of the lower subformation in the area of Belorechensk, a unique and diverse mammalian fauna of the Early Villafranchian (Late Pliocene) was discovered for the first time in the North Caucasus. The composition and the evolutionary level of vertebrate fauna make it possible to correlate it with the early Villafranchian, early Villanyian, and MN16a zone of the European biochronological scale, and with the so called warm period of the mid-Late Pliocene in the range of 3.3-3.0 Ma. An important achievement of the project was the systematization of materials on the recently discovered Late Pliocene Plevaka reference section on the Taman Peninsula. Late Pliocene alluvial-estuarine deposits are deposited on industrial sands of the upper ore strata of the Late Cimmerian-Early Kuyalnik and reach a thickness of about 10 m. The lower beds of the strata contain abundant remains of freshwater mollusks and bones of small vertebrates, including the remains of fish, amphibians, reptiles and small mammals. The molluskan association from the lower horizons of the strata is dominated by shells of large and thick-walled bivalves of the family Unionidae of the Pliocene "Levantine" appearance. Fish remains predominate among small vertebrates. In addition to freshwater forms, coastal or migratory species (sea carp, Caspian-Black Sea herring, sturgeon, salmon) are also identified here. This type of fish association indicates conditions of variable salinity and a very close sea. The archaic rizhodont voles Mimomys hajnackensis predominate among small mammals. The small mammal fauna makes it possible to date the host deposits to the Late Pliocene, Piacenzian, the first half of the Kuyalnik regional stage of the Black Sea basin, the mammalian Uryv faunal complex of mammals of the biochronological scheme of Eastern Europe|, and the time interval 3.5-3 Ma. The overlying clay member yielded abundant shells of Dreissena mussels, as well representatives of the genus Pseudocatillus and Hydrobiidae. All these forms are indicators of brackish water conditions. The shells of freshwater mollusks (Viviparus and Unionidae) were also found here. This complex shows that the upper part of the section was formed under conditions of sea level rise and seawater penetration into river forming a brackish estuary or liman. The palynological data on the estuarine deposits of the upper part of the section indicate its formation in the conditions of steppe mixed-grass landscapes. A low percentage of tree pollen may indicate a significant distance of forests from the studied territory. The discovery of a previously unknown rich locality of fauna and flora of the Late Pliocene for the first time allows us to characterize this period in detail and refine the stratigraphic scheme of the Taman-Kerch region.

 

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