Kura Basin Research Articles

Distinguishing climate and tectonic signals in the stratigraphy of the Kura Basin, the southeastern foreland of the Greater Caucasus

Assessing the relative contributions of tectonics and climate in orogenic systems and the stratigraphy preserved within their fringing basins has guided research for decades. Determining the role of these contributions is non-trivial and is difficult due to variations in both magnitude and period over which fluctuations in tectonics and climate occur, typically >105 – 7 years and <105 years, respectively. The Greater Caucasus is a young orogen that offers a unique opportunity to assess these critical roles through analysis of exposures of the foreland stratigraphy. Here, we synthesize available measured stratigraphic sections from within the Kura Fold-Thrust Belt and adjoining regions, creating multiple paleogeographic reconstructions for key regional chronostratigraphic stages, and then assessing the Kura Basin’s response time throughout these stages. We use basin response time as a proxy for whether tectonics or climate fluctuations could be preserved within the Kura Fold-Thrust Belt stratigraphy and, thus, what changes in depositional environments during those periods are more likely to reflect. In general, estimates of basin response times indicate that tectonic signals could be preserved throughout the Kura Basin during the deposition of the Productive Series. Climatic signals would likely be preserved during the deposition of the Akchagyl stage, although tectonics signals cannot be ruled out. During the Apsheronian stage, both tectonic and climate signals can be preserved. These results highlight that a foreland basin system can fluctuate between being able to record mixtures of tectonic and climatic signals during both different geologic stages and within the same stage across a foreland.

Lithofacies, changes in mineral composition and reservoir properties of the Maykopian sediments in the Yevlakh-Aghjabedi Depression

Yevlakh-Aghjabadi depression is a well explored oil province located in the Middle Kura basin between Greater and Lesser Caucasus.The study investigates the lithofacial, mineralogical, and collector properties of the Maykopian sedimentary series within the Yevlakh-Aghjabadi depression, focusing on the Oligocene to Early Miocene epoch. Maykop deposits are widely distributed in the foothill regions of the Lesser Caucasus, both at the surface as natural outcrops and in the geological structure of deeper formations. In this article, in addition to core samples, the results of fieldworks have also been widely discussed. The conducted research indicates favorable paleogeographic conditions for oil and gas presence in these depressions. The sedimentary sequence, up to 2200 meters thick, is divided into Lower and Upper Maykopian subgroups, showing fluctuating thickness distribution. The primary source of clastic materials for the Maykopian suit is the Lesser Caucasus Mountain range. The lithological composition consists of clay, sandstones, and conglomerates, influenced by paleogeographic changes and paleochannels. Collector properties vary, with Lower Maykopian sediments exhibiting better characteristics, especially in the south-western part of the basin. The mineralogical composition dominated by fine-grained feldspars, impacts reservoir quality. Maykopian suits in the oil and gas regions of Ganja and Muradkhanli, which encompass the southernwestern and northern-eastern flanks of the Yevlakh-Aghjabedibasin, as well as conducting extensive research on reservoir properties, will enable the proper direction of future exploration activities. For this purpose, the overall condition of the Maykopian suits and the distribution of lithofacies have been analyzed, and the characteristics of hydrocarbon reservoirs have been determined. Keywords: lithology; lithofacies; Maykopian; sandy and clayey sediments; argillaceous sandstones; porosity; permeability.

An information-analytical overview of mud volcanoes in the lower Kura basin (Azerbaijan)

This article provides an overview of mud volcanoes (MV) of the Lower Kura region (Azerbaijan). The Lower Kura Depression (LKD) occupies the southeastern part of the Kura-Araks lowlands. Tectonically the LKD is considered to be the eastern edge belonging to the west board of the South Caspian Basin (SCB). The large thickness of sedimentary deposits, reaching 25 km, and the high rate of sedimentation are consequences of the activity of the Paleovolga and Paleokura. Mud volcanic structures in the region are widespread and associated mainly with longitudinal fault dislocations of large amplitude. This paper provides an assessment of numerous research data from studies of mud volcanic products of the Lower Kura Basin. Using the PETROMOD software package, mud volcanoes, and the main factors of their formation were analyzed and physical models were built. The identified differences in the chemical composition of gases and water, kerogen types of organic matter contained in rock emissions, make it possible to improve the understanding of sediments located in deep zones, poorly studied or not yet opened. The conducted research and analysis once again prove that the use of new methods for studying mud volcanism, giving preference to comprehensive analysis, is an important requirement of oil and gas geology.

The Monumental Kurgans in Bronze Age in River Kura Basin

The article contains with the archaeological excavations of the Deller Jayir kurgans at 322.700 km of the SCPX (South Caucasus Pipeline Expansion Project) pipeline corridor. These kurgans are located in the territory of Deller Jayir village of Shamkir district of Azerbaijan Republic. About 10 kurgans were recorded in the kurgan field located on a relatively high hill on the right bank of the river, about 100-150 m away from the Jayir River, only 2 of them fell into the pipeline corridor, excavated and explored.
 The surface of the Deller Jayir kurgans consists of stone formations with a clearly visible circular shape and a relatively concave center. They are located close to each other at a distance of 5-6 m. Preliminary analysis of the structures and burial rites in the Deller Jayir kurgans and the forms of the few pottery fragments found in these kurgans show that these kurgans date the transition stage from Middle Bronze Age to the Late Bronze Age, to be precisely, to the 15th-14th centuries BC.

Geological and biotic context of the Plio-Pleistocene evolution of the Caucasus-Caspian Region (Akchagylian transgression)

We discuss geological and biotic aspects of the extensive Akchagylian transgression that occurred in the Caspian region of Eurasia near the Plio-Pleistocene transition, in Piacenzian and Gelasian. It is shown that the onset of the Akchagylian marine sedimentation in Western Turkmenistan (ca. 3.2 Ma) preceded that in the Kura Basin (ca. 3.0 Ma). The position of the upper boundary of the Akchagylian remains uncertain (ca. 2.1 or 1.8 Ma). The analyzed biotic content of the Akchagylian includes molluscs, microfossils (pollen, dinocysts, foraminifers), and mammals. It is noted that specific forms of the Akchagylian aquatic biota co-occur with microfossils that clearly indicate a connection with the World Ocean or related seas. The palynology of the Akchagylian time signals a directed cooling in the Pliocene and Early Pleistocene with several warm and humid epochs. The Akchagylian transgression was preceded by a change of a structural-sedimentary pattern of the region. In the latest Miocene and Early Pliocene, a pre-existed longitudinal tectonic zonation of the Caucasian-Caspian segment of the Paratethys gradually changed into clearly transverse tectonic zonation. The latter was manifested in the tectonic uplift of the Greater Caucasus, its northern piedmonts and the Lesser Caucasus, and in the subsidence of the western parts of the South and Middle Caspian basins. The interplay of longitudinal and transverse tectonic features shaped the configuration of the Akchagylian brackish-water basin and controlled thickness of its deposits. It was the transverse zonation that dominated in the thickness pattern. The increasing role of the transverse zonation in the post-Akchagylian time is manifested in the magnitudes and rates of the Quaternary tectonic uplift. These parameters were calculated based on current heights of the top of the Akchagylian marine deposits in different parts of the basin. The highest magnitudes of uplift are found in the Eastern Caucasus (up to 1980 m on the NE slope and about 2500 m in the axial part) and in the west of the Lesser Caucasus in eastern Turkey (up to 1750 m). The maximum level of the Akchagylian transgression is estimated at 40–50 m above the present level of the World Ocean. We show a low probability of connection of the Akchagylian basin with the Mediterranean Sea or the Persian Gulf, and a high probability of its connection with the Arctic Ocean through the northern tributaries of the Kama River and the Pechora Basin in the NE of East European Plain.

Stratigraphy of the Cenozoic succession in eastern Azerbaijan: Implications for petroleum systems and paleogeography in the Caspian basin

The Cenozoic succession in the Lower Kura Basin includes largely uniform, often carbonate-free mudstones. Because age dating of these sediments has proved difficult, the stratigraphy of the Cenozoic succession and the distribution of organic-rich strata are poorly known. A better understanding of the Cenozoic succession is not only important for petroleum-systems-analysis, but also for the understanding of the Cenozoic evolution of the Caucasus region. Therefore, bulk geochemical data (carbonate, TOC, sulphur, Rock-Eval) of 885 samples and biostratigraphic data were collected along seven outcrop profiles. This enabled the establishment of a continuous stratigraphic record from the Middle Eocene to the Late Miocene (Pontian). The study results show that potential source rocks are present in three stratigraphic units: the Middle Koun (Middle Eocene), Maikop Group (Oligo-Miocene) and Diatom Formation (Upper Miocene). The Middle Koun is about 100 m thick near the Caspian Sea and contains highly oil-prone sediments (2–24 wt% TOC; HI 300–577 mgHC/gTOC), which may generate 1.5 tHC/m2. The Maikop Group contains on average 1.8 wt% TOC, but is often gas-prone. Highly oil prone layers (2–5 wt% TOC; HI 300–450 mgHC/gTOC) are rare. Nevertheless, the Upper Maikop Formation may generate ∼2 tHC/m2. The Diatom Formation contains paper shales with high TOC contents (3–22 wt%) and HI values (350–770 mgHC/gTOC). The paper shale unit is more than 60 m thick near the Caspian Sea and can generate 3.8 tHC/m2. Previously it was thought that the Maikop Group had the highest petroleum potential, whilst Upper Miocene and Middle Eocene source intervals were overlooked. The Middle Eocene to Lower Oligocene succession in the Kura Basin is largely carbonate-free. In contrast, coeval successions elsewhere in the Caucasus region contain sediments with varying, but often high carbonate contents. Differences in carbonate content imply greater water depth during deposition in the Kura Basin.

Tectono-thermal evolution of central Transcaucasia: Thermal modelling, seismic interpretation, and low-temperature thermochronology of the eastern Adjara-Trialeti and western Kura sedimentary basins (Georgia)

Structural interference along the boundaries of adjacent tectonic domains generates complex subsidence and exhumation patterns. In this paper we study a key segment of the convergence zone between the interfering south-verging Greater Caucasus and north-verging Lesser Caucasus retro-wedge. The study area comprises the along-strike transition between the Paleogene Adjara-Trialeti back-arc basin and the Oligocene-Neogene Kura foreland basin of eastern Georgia. During the Neogene, despite their difference in age and subsidence mechanisms, both basins have been progressively inverted to various extent within the overall context of the Arabia-Eurasia continental collision. Thermal modelling of borehole data from the Adjara-Trialeti basin allowed to reconstruct two phases of rapid subsidence, late Paleocene-Early Eocene and Middle-Late Eocene, respectively correlated to flexural loading by the Lesser Caucasus retro-wedge and continental rifting. Integration of thermal modelling, apatite fission-track statistical inverse modelling, and seismic interpretation detected a third subsidence phase in the Early Miocene, possibly related to strike-slip tectonics. Thermal maturity data dictate that 1.0–1.3 km of the Adjara-Trialeti sedimentary succession has been eroded since the onset of structural inversion in the mid-Miocene. The burial history of the western Kura Basin outlines intermittent and asymmetrical episodes of flexural subsidence from the Oligocene to the Late Miocene, due to competing loading by the Lesser Caucasus, the Adjara-Trialeti fold-and-thrust belt and the Greater Caucasus. Finally, during latest Miocene times southward propagation of deformation from the Greater Caucasus induced an additional tectonic loading (1.3–1.8 km) due to the emplacement of thin-skinned thrust sheets, mostly eroded during the Plio-Quaternary.

Neolithization processes in the Middle Kura basin

Research into the Neolithization of the Southern Caucasus has entered a new stage in the 2000s, with a remarkable increase in international archaeological investigations employing cutting-edge feld techniques and related laboratory studies. Current research indicates that full-fledged Neolithic societies emerged in the Southern Caucasus in the early sixth millennium BC, most likely through interaction with Neolithic societies of Southwest Asia. Neolithization took place in the southern Caucasus at the beginning of the sixth millennium BC, most likely as part of the expansion of the Neolithic socioeconomy from the Middle East, where the food production economy had been established at least a few thousand years earlier. However, local adaptation and indigenous cultural development are also likely to have played important roles in this process, by which distinct Neolithic ways of life emerged in the southern Caucasus. Tis article reports on 46 radiocarbon dates obtained from the two recently excavated Early Pot-tery Neolithic sites of Göytepe and Hacı Elamxanlı Tepe, the oldest farming villages known to date in West Azerbaijan. Comparing the dates from other related sites demonstrates that several settlements representing the earliest Pottery Neolithic emerged almost simultaneously at the beginning of the sixth millennium B.C.E. in the northern and southern foothills of the Lesser Caucasus Mountains.

Five-fold expansion of the Caspian Sea in the late Pliocene: New and revised magnetostratigraphic and 40Ar/39Ar age constraints on the Akchagylian Stage

The Global climate reorganisation in the late Pliocene linked to enhancement of the Atlantic Ocean Thermohaline Circulation (AOTC), instigated a transition to glacial-interglacial cyclicity in the Quaternary. Enhancement of the AOTC amplified atmospheric precipitation over the Eurasian interior strengthening Northern Hemisphere Glaciation. Increased rainfall on the vast Russian Plain drained into the endorheic Caspian Sea, which makes the Caspian geological record highly potential for tracing atmospheric precipitation changes. Two major palaeohydrological events in the Caspian Sea, the Akchagylian transgression and the Akchagylian marine incursion, led to a five-fold enlargement of the Caspian Sea surface area and transformed the basin palaeoecology, enabling active interregional faunal dispersals. The Akchagylian Stage still lacks an unequivocal age model with two age constraints – the “long Akchagylian” (3.6–1.8 Ma) and the “short Akchagylian” (2.7–2.1 Ma) standing on magnetostratigraphic studies of geological records in Turkmenistan and the Kura Basin, respectively. The age discrepancies also exist within the Kura Basin, where the fossil mammal-bearing Kvabebi locality with Akchagylian marine fauna was magnetostratigraphically dated at 3.2 Ma. In this paper, we try to resolve the age contradictions for the Akchagylian Stage. We revisit the Kvabebi (Georgia) and Kushkuna (Azerbaijan) sections of the western Kura Basin and provide new magnetostratigraphic and 40 Ar/ 39 Ar age constraints on these marginal Akchagylian deposits. Moreover, we revise the magnetostratigraphy of 25 geological records from Turkmenistan and the Kura Basin and propose a new unified age model for the Akchagylian Stage: 1. Intrabasinal Akchagylian freshwater-mesohaline transgression at 2.95 ± 0.02 Ma; 2. Akchagylian marine incursion through establishment of a Caspian-Arctic connection (2.75–2.45 Ma); 3. Akchagylian–Apsheronian boundary highlighting a Caspian-Black Sea connection at 2.13 Ma. The sudden expansion of the Caspian Sea at 2.95 ± 0.02 Ma potentially correlates to the interglacial intensification of the AOTC between 2.95 and 2.82 Ma. The new ages constrain a much shorter (2.95–2.1 Ma) Akchagylian than in previously mentioned regional geological time scales (3.6–1.8 Ma) and strongly appeal to reconsider the ages of numerous archaeological and mammalian sites in the Caspian region. • Akchagylian transgression at ~2.95 Ma led to a five-fold expansion of the Caspian Sea. • The Caspian Sea level rose due to the switch to a positive water budget. • The Caspian Sea rise correlates with enhanced Atlantic Ocean Thermohaline Circulation. • Interregional correlation of the Akchagylian transgression to the upper Gauss chron. • New integrated age model places Akchagylian between 2.95 Ma and 2.13 Ma.

The Pattern and Kinematics of Deep Deformation of 2012 Ahar-Varzaghan Earthquake Doublet (MW 6.4 and 6.2), a New Seismotectonic Interpretation

The 11th August 2012 Ahar-Varzaghan earthquake doublet Mw 6.4 and 6.2 occurred near the city of Ahar, northwest Iran, in a region where there was no major mapped fault or any well-documented historical seismicity. To investigate the active tectonics and the state of pre and post-seismic stress distribution of the source region, we applied a combination of Coulomb stress change, b-value mapping, and the Fry method. Inferred Coulomb stress field reveals the E–W-striking (dextral) fault responsible for the first event and the NNE–SSW-striking (sinistral reverse) fault for the second event. The high slip stress-released regions in the obtained b-value map and the dominant anisotropies of aftershocks on regional stress-parallel cross-sections achieved by the Fry method, together with the distribution of aftershocks mechanisms, merely highlight the particular wedge-shaped structures namely the rhombic structures. The clockwise block rotation about the vertical axis under the right-lateral regional shear between the Kura basin to the north and the Central Iranian Block to the south and NW-oriented coeval shortening leads to the formation of rhombic structures. The results of this study improve our understanding of the kinematics of active deformation in NW Iran and have important implications for seismic hazard assessment of the region and potential future failure areas.

PETROLEUM SYSTEMS IN THE RIONI AND KURA BASINS OF GEORGIA

The Neogene Rioni and Kura foreland basins in Georgia are located between the converging Greater and Lesser Caucasus fold‐and‐thrust belts. The Rioni Basin continues westward into the Black Sea whereas the Kura Basin extends eastward into Azerbaijan and the Caspian Sea. “Pre‐” and “post‐salt” petroleum systems are distinguished in the Rioni Basin separated by an Upper Jurassic evaporite succession of regional extent. The pre‐salt petroleum system in the northern Rioni Basin is still poorly understood. Bathonian shales have generated oil which has been recorded in Middle Jurassic sandstones. However, as the origin of the oil in Upper Jurassic sandstones (e.g. at the Okumi oil discovery) is still problematic, the pre‐salt petroleum system remains poorly constrained. Gas‐rich, high volatile bituminous coals of Bathonian age may represent a CBM play.The post‐salt petroleum system in the Rioni Basin is charged by two prolific source rock units: the Middle Eocene Kuma Formation and the Oligo‐Miocene Maikop Group. The petroleum potential of the Kuma Formation, which is about 40 m thick, is classified as good to very good. The Oligocene part of the Maikop Group is several hundred metres thick and contains source rocks with up to 5 wt.% TOC in its lower part. Additional source rocks are present in Cretaceous and lower Paleogene levels. Oil is produced from fractured Upper Cretaceous carbonates in anticlinal structures below the Neogene unconformity and from Mio‐Pliocene siliciclastics in fault‐related anticlines. Trap formation and hydrocarbon accumulation is interpreted to have occurred since Maeotian time. Proven oil reserves are very low (∼2 million tons) and suggest low charge efficiency.Several stratigraphic horizons containing potential source rocks are present in the Kura Basin of eastern Georgia. Although oil‐source correlations have yielded unsatisfactory results, the Maikop Group is the most likely source rock, despite its relatively poor petroleum potential which is at best “fair” in the Tbilisi area in the west of the basin. Additional potential source rocks include Middle and Upper Eocene shales. Fractured Middle Eocene volcaniclastic rocks are the best producing reservoirs for hydrocarbons, but oil accumulations are also found in fractured Upper Cretaceous carbonates and in Lower and Upper Eocene, Oligocene and Neogene siliciclastics. Biomarker data suggest a Cenozoic (or Upper Cretaceous) source rock containing abundant terrigenous organic matter. Anticlines and positive flower structures related to compressional tectonics in front of the Greater and Lesser Caucasus fold‐and‐thrust belts form the main trap types. Samgori‐Patardzeuli‐Ninotsminda in the Tbilisi region is by far the largest oil field in Georgia and accounts for nearly 90% of the cumulative production of the country (28.5 million tons). The field was probably charged from a kitchen area located to the north. Strike‐slip faults played a major role as migration pathways. Despite of the presence of many oil seeps, proven reserves in the Georgian part of the Kura Basin are very low (2.4 million tons). This may reflects the presence of traps with poor seal integrity.

Validating far-field deformation styles from the Adjara-Trialeti fold-and-thrust belt to the Greater Caucasus (Georgia) through multi-proxy thermal maturity datasets

Thermal history reconstructions can help to better characterise the geological history of areas that experienced a polyphase tectonic evolution. The integration of published stratigraphic/structural data with new and pre-existing data on thermal maturity (clay mineralogy, Raman spectroscopy, vitrinite reflectance, and pyrolysis) of both surface and subsurface sedimentary successions of a wide region of Georgia including -north to south- the southern Greater Caucasus, the western Kura Basin, and the Adjara-Trialeti fold-and-thrust belt (FTB) provides cogent constraints on its late Mesozoic-Cenozoic tectono-sedimentary evolution.Overall, thermal maturity spans from the low diagenesis (60–80 °C) in the Upper Miocene section of the Kura Basin to anchizone-epizone (about 400 °C) in the central Greater Caucasus axial zone. In more detail, different maturity trends and thermal histories point to the existence of two domains formed by positive tectonic inversion: (i) the Adjara-Trialeti FTB from an Eocene rift basin and (ii) the Greater Caucasus from a Mesozoic rift basin. Multiple thermal indicators, along with stratigraphic/structural evidence, show that the Paleocene section of the Adjara-Trialeti basin fill reached the upper oil window (ca. 115 °C) during maximum sedimentary burial and that the whole basin was then exhumed starting from the late Middle Miocene. A positive correlation between thermal maturity and stratigraphic age points to a limited thermal effect of tectonic loading. In the southern Greater Caucasus, thermal maturity increases progressively with stratigraphic age, from ca. 100 °C (Upper Eocene) to 400 °C (Lower Jurassic), in broad agreement with the reconstructed thickness of the basin-fill succession, thus indicating that most of the thermal maturity was again induced by sedimentary burial.As to the flexural western Kura Basin, its Maikopian (Oligocene-Early Miocene) section reached the oil window (up to ca. 110 °C) whereas the Middle-Late Miocene one is immature. The Kakheti ridge -a highly tectonised portion of the Kura Basin- reached immature to early mature conditions.

Seismotectonic evidence for subduction beneath the Eastern Greater Caucasus

SUMMARY We generated high-resolution 3-D seismic velocity models as well as a relocated earthquake catalogue across the eastern Greater Caucasus and Kura basins. This work was done using data from the recently upgraded Republic Seismological Survey Center's (RSSC) seismic network. We generated our tomographic images of crustal velocity structure in Azerbaijan using double-difference inversions (i.e. tomoDD and hypoDD). Earthquake catalogues from the RSSC between 2011 and 2016 were used; these catalogues include absolute arrival times of 103 288 P- and 120 952 S-wave traveltime picks for 7574 events recorded at 35 stations in Azerbaijan. Beginning with a layered, 1-D velocity model that was estimated using VELEST, we inverted simultaneously for relative location, Vp and Vs on a 3-D grid with dimensions 670 × 445 × 45 km, with a uniform grid spacing of 55 × 55 × 5 km for all of Azerbaijan. We observe that the relocated hypocentres cluster into two depth ranges, at the surface and at depth, that appear to correspond to major fault zones and the top of a subducting plate. Additionally, we note intermediate depth seismicity (∼50–60 km) beneath the Kura Basin, and a northward deepening of earthquake depths. Seismic velocities vary significantly throughout the study region; we observe very slow velocities throughout the Kura Basin between 5 and 15 km, and elevated velocities at 20–35 km. The wholesale velocity structure and seismic structure of Kura Basin strongly mirrors that of the Caspian Sea, which suggests that the geodynamics of the Caspian continue westwards into Azerbaijan. The key results of this study suggest that the northward subduction observed in the Caspian Sea continues beneath the Eastern Greater Caucasus, as well as provides evidence for active faulting along the southern margin of the mountain range.

The Сyclostratigraphy of the Konkian Deposits of Eastern Georgia (Eastern Paratethys, Kura Basin)

The middle Miocene (mainly the Konkian) shallow marine sediments of Eastern Georgia (Eastern Paratethys, Kura basin) have been studied for the first time with cyclostratigraphy methods. Time series analysis (Lomb-Scargle and REDFIT periodograms, Gaussian filter) revealed a statistically significant signal with a 2.4–2.7-m wavelength, which most likely corresponds to the precession cycle. It was established that the sedimentation rate of the studied sediments varied from 8.75 to 13.75 cm/kyr in dependence on different sedimentation environments. It is assumed that the studied Eastern Georgia Konkian deposits (Sartaganian and Veselyankian beds) accumulated during at least 475–600 kyr. The Sartaganian Beds can be correlated with interval of the highest sea-level rise at the TB 2.5 cycle.

Depositional Environments in the Eastern Paratethys during the Final Middle Miocene Transgression (Kura Basin, Eastern Georgia)

The mineral composition and depositional environments of the Konkian in eastern Georgia (Kura trough, eastern Paratethys) corresponding to the Kosovian (13.65–12.829 Ma) in the Central Paratethys and the final Middle Miocene marine transgression in Paratethys are considered. Jurassic and Cretaceous volcanic rocks of the Lesser Caucasus (Adzhar–Trialet and Artvin–Bolnisi zones) were identified as the main provenances for the terrigenous material. Eight lithofacies types distinguished for the studied rocks characterize depositional environments with significant wave or submarine-fluvial influence. The change of depositional environment was controlled by the phases of transgression, as well as by the progradation and lateral migration of the prodelta. The development of depositional environment corresponds to the Konkian stratigraphic beds and reflects the main stages of the final Middle Miocene transgression in the Eastern Paratethys.

Astronomical tuning of the Eastern Georgia Konkian (Kura basin)

The shallow-marine sediments of the Middle Miocene (mainly the Konkian) of the Eastern Georgia (Eastern Paratethys, Kura basin) were investigated by cyclostratigraphy methods. Time series analysis (Lomb-Scargle and REDFIT periodograms, Gaussian filters) revealed statistically significant signal with 2,4–2,7 m wavelength corresponding most likely to the precession cycle. Based on statistical processes, a sedimentation rate of the studied sediments from 8,75 to 13,75 cm/kyr for different depositional setting was detected. We suggest that the studied Eastern Georgia Konkian sediments (Sartaganian and Veselyankian beds) accumulated during of at least 475–600 kyr. The Sartaganian (beds with most diverse marine fauna of the Konkian) can be correlated with interval of highest sea-level rise of TB 2,5 cycle.

Первые результаты оценки глубины поверхности Мохо методом обменных Ps-волн для Азербайджанской части Большого Кавказа

The methodology of the converted waves, or as it is commonly called, the "Receiver function" method, is well known and is widely used throughout the world to study the deep structure of the Earth up to 800 km. The method is based on the registration and interpretation of converted Ps waves. These studies were carried out as part of the International Seismotomo-graphic Laboratory using a software package developed at the University of Missouri (USA). One of the best regions for studying the early stages of mountain building is the Greater Caucasus, where most of the volcanism and mountain building appears to be 5 million years. Of particular interest is the immersion zone of the Kura Basin beneath the Greater Caucasus, the so-called subduction zone, which has not been sufficiently studied to date. To this end, we began our studies of the depth of the Moho border with this region. Thus, for the first time on the basis of the analysis of the wave characteristics of distant earthquakes recorded at seismic and telemetric stations of the RSSC, within the framework of the international project "Transect", the depths of the Moho border for the Azerbaijan part of the Greater Caucasus were refined by the method of exchange reflected Ps waves ("Receiver function"). Seismo-grams of the selected earthquakes were processed using the Seismic Analysis Code (SAC) software package under the MacOs operating system. The study examined seismological data recorded by a network of telemetry stations (N=20) for 2009-2019. In total, 2428 earth-quakes recorded at an epicenter distance of 35 to 90 degrees were analyzed. At the first stage, frequency filtering was carried out in order to eliminate oscillations that were too high, containing the effects of random scattering on inhomogeneities, and too low frequencies that re-duce the resolution. The working range of the periods ranged from two to 10 seconds. Next, two-dimensional and three-dimensional rotation of the axes was carried out. The summation of all traces was carried out with time shifts relative to some reference epicentral distance, which is assumed to be 60 degrees. On the summarized Q-tracks of the receiving functions, the Moho boundary with a delay time of 4.0 sec is clearly distinguished. Thus, a map of iso-lines of the depths of the Moho surface was constructed and depths were determined for the territory of the Guba-Gusar region 48-50 km, the Zagatala-Balakan region 46-47 km, the Shamakhi-Ismayilli region 48-52 km. As it was said earlier, the first definitions of the depth of the surface of Moho in Azerbaijan were made based on the data from the state earthquake and the gravitational model of the Earth's crust. R.M. Gadzhiev in 1965 and E.Sh. Shikhalibeyli in 1996 built such models. The data obtained are consistent with the available data, but discrepancies have been received. Compared with the map constructed according to the GSZ-KMPV and gravimetric data by R.M. Gadzhiev (1965), the difference in the thickness of the earth's crust was from one to 15 km. Compared with the map constructed according to the FGP and gravimetric data by E.Sh Shikhalibeyli (1996), the difference in the thickness of the earth's crust varied from one to 10 km.

Mesozoic–Cenozoic Structure of the Black Sea–Caucasus–Caspian Region and Its Relationships with the Upper Mantle Structure

Abstract—Mesozoic‒Cenozoic tectonic zoning and its evolution are characterized by analysis of geological data on the Black Sea–Caucasus–Caspian region. The following tectonic zones were located in succession to the north of the Mesotethys Ocean in the Early Jurassic: the mobile zone on the Hercynian basement; the Moesian–Black Sea–Trans-Caucasus minor plate with the Precambrian–Baikalian basement, which experienced the Hercynian tectonic and magmatic reworking in the Lesser Caucasus; the relatively deep-water Crimean–Caucasus–South Caspian Trough on the continental crust that thinned in the process of its extension; and the southern margin of the Scythian Plate with a thin sedimentary cover. In the Caucasus, the southern and northern slopes of the deep-water axial trough have been identified, where thick shelf deposits accumulated. Subduction began in the northern margin of the Mesotethys in the Bajocian and island-arc volcanism occurred in the Somkheti–Karabakh zone and Eastern Pontides, the Trans-Caucasus part of the Moesian–Black Sea–Trans-Caucasus Plate, and the southern slope of the Crimean–Caucasus–South Caspian Trough. The volcanism in the Somkheti‒Karabakh zone and the Eastern Pontides lasted into the Cretaceous. The area of island-arc volcanism was inherited by the Eocene collisional volcanic belt. The Crimean part of the Crimean–Caucasus–South Caspian Trough and its northern slope in the Caucasus underwent Cimmerian deformation and shelf facies accumulated there after deformation up to the Miocene, while relatively deep-water sedimentation occurred in the Caucasus–South Caspian part of the Crimean–Caucasus–South Caspian Trough. The Western and Eastern Black Sea basins of extension originated in the Cretaceous on the continental crust of the Moesian–Black Sea–Trans-Caucasus Plate, which thinned in the basins as they were filled by Late Cretaceous, Paleogene, and Miocene marine deposits. In the Pliocene–Quaternary, total undifferentiated subsidence and sedimentation occurred in the Black Sea, and subsidence of the South Caspian, Azov‒Kuban, and Terek‒Derbent basins accelerated. Several phases of Middle and Late Miocene fault–fold deformation formed local uplifts in the mountainous parts of the region. The total uplift of mountain systems occurred in the Pliocene–Quaternary. The formed crustal structures and the velocity inhomogeneities in the upper mantle were compared, which showed that many inhomogeneities were obliterated by sublithosphere flows that spread out of the Ethiopian–Afar superplume. In mantle volumes, where the flow intensity weakened, relics of subducted slabs remained. They are slabs of the Neotethys in the Zagros and the Mesothethys in the Lower Kura Basin, and slabs of the Scythian Plate lithosphere underthrust under the Central Caucasus and more weakly under Steppe Crimea during the Hercynian subduction.

Amplitude, frequency and drivers of Caspian Sea lake‐level variations during the Early Pleistocene and their impact on a protected wave‐dominated coastline

AbstractThe Caspian Sea, the largest isolated lake in the world, witnessed drastic lake‐level variations during the Quaternary. This restricted basin appears very sensitive to lake‐level variations, due to important variations in regional evaporation, precipitation and runoff. The amplitude, frequency and drivers of these lake‐level changes are still poorly documented and understood. Studying geological records of the Caspian Sea might be the key to better comprehend the complexity of these oscillations. The Hajigabul section documents sediment deposited on the northern margin of the Kura Basin, a former embayment of the Caspian Sea. The 2035 m thick, well‐exposed section was previously dated by magneto‐biostratigraphic techniques and provides an excellent record of Early Pleistocene environmental, lake‐level and climate changes. Within this succession, the 1050 m thick Apsheronian regional stage, between ca 2·1 Ma and 0·85 Ma, represents a particular time interval with 20 regressive sequences documented by sedimentary and palaeontological changes. Sequences are regressing from offshore to coastal, lagoonal or terrestrial settings and are bounded by abrupt flooding events. Sediment reveals a low energy, wave‐dominated, reflective beach system. Wave baselines delimiting each facies association appear to be located at shallower bathymetries compared to the open ocean. Water depth estimations of the wave baselines allow reconstruction of a lake‐level curve, recording oscillations of ca 40 m amplitude. Cyclostratigraphic analyses display lake‐level frequency close to 41 kyr, pointing to allogenic forcing, dominated by obliquity cycles and suggesting a direct or indirect link with high‐latitude climates and environments. This study provides a detailed lake‐level curve for the Early Pleistocene Caspian Sea and constitutes a first step towards a better comprehension of the magnitude, occurrence and forcing mechanisms of Caspian Sea lake‐level changes. Facies models developed in this study regarding sedimentary architectures of palaeocoastlines affected by repeated lake‐level fluctuations may form good analogues for other (semi‐)isolated basins worldwide.

Magneto-biostratigraphic age constraints on the palaeoenvironmental evolution of the South Caspian basin during the Early-Middle Pleistocene (Kura basin, Azerbaijan)

The sedimentary record of the Caspian Basin is an exceptional archive for the palaeoenvironmental, palaeoclimatic and biodiversity changes of continental Eurasia. During the Pliocene-Pleistocene, the Caspian Basin was mostly isolated but experienced large lake level fluctuations and short episodes of connection with the open ocean as well as the Black Sea Basin. A series of turnover events shaped a faunal record that forms the backbone of the Caspian geological time scale. The precise ages of these events are still highly debated, mostly due to the lack of well-dated sections. Here, we provide an integrated magneto-biostratigraphic age model for two sections from the Kura Basin – Goychay and Hajigabul. Our results reveal several major intervals with elevated salinity, associated with mesohaline faunas, and propose the following age constraints: 1) The Productive Series-Akchagylian boundary is marked by a marine transgression from the open ocean that occurred around the Gauss-Matuyama reversal (∼2.7–2.6 Ma); 2) The Akchagylian-Apsheronian transition is characterized by a regression event and introduction of a new, “Pontocaspian” mollusc assemblage, dated within the Reunion subchron (∼2.13 Ma). The ostracod assemblages of the two sections do not show a major faunal turnover here; 3) The early Bakunian transgression occurs after the upper Apsheronian lowstand (0.85–0.83 Ma). We conclude that major transitions in the age-indicative mollusc groups sometimes occur at different time intervals (i.e. diachronic) and are highly depended on the local depositional environments. A high-resolution interdisciplinary approach on sections outside the Kura Basin is required to better understand the potential diachroneity of these turnover events in the entire Caspian Basin.