Eastern Black Sea Basin Research Articles

Late Triassic to Middle Jurassic magmatism in the Eastern Pontides (NE Türkiye): Evidence for divergent double subduction of Paleo-Tethys lithosphere

The Meso-Cenozoic geodynamic evolution of northern Türkiye remains a subject of debate primarily due to a lack of systematic geological, geochemical, geochronological, and geophysical investigations. This paper presents comprehensive geochronological and geochemical data on the Late Triassic andesite porphyry, andesite breccia and quartz diorite porphyry, and the Middle Jurassic diabase, and amphibole-poor and amphibole-rich andesite porphyry from Çevrepınar Igneous Complex (Gümüşhane) in the southern part of the Eastern Pontides Orogenic Belt (EPOB), a well-preserved continental arc in the Alpine-Himalayan orogen. Zircon U–Pb geochronology indicates crystallization ages of ∼208–202 Ma (Rhaetian) for the Late Triassic rocks and ∼175–172 Ma (Aalenian) for the Middle Jurassic rocks. Whole-rock geochemical and Sr-Nd-Pb isotopic data, and zircon εHf(t) data indicate that both the Late Triassic and the Middle Jurassic rocks originated by low-degree melting of a spinel lherzolite lithospheric mantle source modified by subduction-related fluids and/or melts. Based on the new and published data, we suggest that the Late Triassic to Middle Jurassic arc magmatism in EPOB occurred as a result of southward subduction of the Paleo-Tethys oceanic lithosphere beneath the northern margin of Gondwana-Land. Late Triassic to Jurassic arc magmatism and basin evolution occurred synchronously in the northern and southern peripheries of the present-day Eastern Black Sea Basin, indicating divergent double subduction of the Paleo-Tethys oceanic lithosphere beneath the northern margin of Gondwana and southern margin of Laurasia during the Early Mesozoic.

Statistical analysis of flood risk perception: a case study for Eastern Black Sea Basin, Turkey

It is very essential in terms of flood risk management to consider social expectations such as risk perception, flood awareness, preparedness, and socio-economic dynamics together with engineering designs. Understanding the way people perceive flood risk can enhance our capability of improving existing flood risk management methods, thus helps us creating disaster resilient societies. In this study, results of a questionnaire which was used for a previous study and had been administered to participants from Eastern Black Sea Region of Turkey were further investigated using statistical methods. The main aim was to understand how demographic factors such as age, gender and education level affect people’s flood risk perception. It was also desired to see that whether they were aware of the parties responsible for taking mitigation measures, or whether they know about possible flood mitigation measures or not. Using the same data with the previous study, but in addition using SPSS software to do statistical analysis, questionnaire results were investigated using convenient statistical tests for each parameter, analysis results were interpreted, and conclusions were drawn. Same tests were conducted using weight coefficients adopted using a certain methodology which is explained in the paper, in order to make a better investigation. Also, results were compared with the results of the previous study. It was seen that there were some consistencies and contradictions between the results of the previous study and this study’s results.

Investigation of climate change impacts on daily streamflow extremes in Eastern Black Sea Basin, Turkey

This study was undertaken to evaluate how future uncertain climate-related hydrological responses and low and highflow frequencies affect local hydrology up to the 2100, depending on different Global Circulation Models (GCM) and different Concentration Scenarios (CS). To this end, daily total precipitation and daily mean temperature data were used for RCP4.5 and RCP8.5 CSs by employing GCMs (GFDL-ESM2M, HadGEM2-ES and MPI-ESM-MR). In the study, the years 1971–2000 were chosen as the baseline period. Future streamflow predictions were modeled by machine learning. The models were calibrated with baseline period data and future streamflow values were predicted by using the best Streamflow Prediction Model during the 2055s (2041–2070) and 2085s (2071–2100) periods. Flow Duration Curves from the streamflow predictions were obtained and by using them, discharges corresponding to 95% probability of exceedance for lowflow and 5% probability of exceedance for highflow were calculated. According to the findings, it is predicted that there will be decrease of approximately 21% in lowflow discharges and approximately 30% in highflow discharges. This prediction has suggested water resources managers to implement mitigation measures to climate change in Eastern Black Sea Basin and most probably in Türkiye, especially in the context of continuity of aquatic life and sustainable water supply. It is expected that the paper will take a very important place in estimating and evaluating the expected changes in basin hydrology in the coming years, especially in the highflows and lowflows, which are the key concepts in hydroelectric power generation and in flood management.

Trends and amount changes of temperature and precipitation under future projections in high–low groups and intra-period for the Eastern Black Sea, the Wettest Basin in Türkiye

This study investigates the possible effects of climate change on temperature and precipitation variables in the Eastern Black Sea Basin, Türkiye’s wettest and flood-prone region. The outputs of three GCMs under historical, RCP4.5, and RCP8.5 scenarios were downscaled to regional scale using the multivariate adaptive regression splines method. The future monthly temperature and precipitation for 12 stations in the basin were projected for three periods: the 2030s (2021–2050), 2060s (2051–2080), and 2090s (2081–2100). In addition to relative changes, high and low groups and intra-period trends were analyzed for the first time using innovative methods. For the pessimistic scenario, an increase of 3.5 °C in the interior and 3.0 °C in the coastal areas of the basin is projected. For the optimistic scenario, these values are expected to be 2.5 and 2.0 °C, respectively. A decrease in precipitation is projected for the interior region, and a significant increase is expected for the eastern and coastal areas of the basin, especially in spring. This result indicates that floods will occur frequently coastal areas of the basin in the coming periods. Also, although the monotonic trends of temperatures during periods are higher than precipitation in interior regions, these regions may have more uncertainty as their trends are in different directions of low and high groups of different scenarios and GCMs and contribute to all trends, especially precipitation.

Analysing the Effects of Atmospheric Teleconnections on Streamflow Regime in the Eastern Black Sea Basin in Türkiye

Analysing the variations in hydrological cycle components is essential for water resources planning and management. In this study, the relationship between the streamflow data belonging to five discharge gauging stations in the Eastern Black Sea Basin in Türkiye and the Arctic Oscillation (AO), East Atlantic-Western Russia (EAWR), North Atlantic Oscillation (NAO) and North Sea Caspian Pattern (NCP) was investigated. For this purpose, Spearman’s correlation test, ensemble empirical mode decomposition (EEMD) and relative importance analysis were used. Accordingly, Spearman’s correlation coefficients were calculated between raw streamflow data, decomposed streamflow data via EEMD and atmospheric teleconnections. Then, the relative importance analysis was applied to determine the atmospheric teleconnections’ influences on streamflow data. The findings showed that the relationship between raw streamflow data and atmospheric teleconnections is generally more significant and negative in the winter and spring. Furthermore, it was observed that the linkage between the decomposed streamflow data and atmospheric teleconnections could differentiate. Although no significant correlation between atmospheric teleconnections and raw streamflow data was detected in some months, significant correlations were detected between atmospheric teleconnections and decomposed streamflow data. This reveals the importance of examining the relationship between atmospheric teleconnections and streamflow data for different periods. The relative importance analysis revealed that the influence of atmospheric teleconnections on streamflow data could change from station to station and from component to component. This study showed that investigating the effects of atmospheric teleconnections on streamflow data for different components and periods is important.

Microplastic pollution in stream sediments discharging from Türkiye's eastern Black sea basin

Rivers are the principal route for terrestrial microplastics to reach the marine environment. The Black Sea exhibits a notable representation because it has a drainage zone almost six times the surface area and is semi-closed, meaning that microplastics tend to gather there. To mitigate MP pollution, it is necessary to identify the contamination sources and then raise public awareness. Thus, the current study focused on the MP presence in the sediment of streams running into the SE Black Sea. 594 MPs were observed in sediment samples from 16 stations along the 350 km coastline. The abundance of MP was higher, particularly in streams that pass through locations with high tourism and industrial activity levels. Detected MPs ranged between 0.1 and 5 mm, while the overall density was smaller than 1 mm. Fragments and fiber MPs were regularly detected, although the presence of films was rarely recorded. The polymer structures that were most commonly observed in the analyzed pollutants were PET and PE. The current study uncovered MP contamination in stream sediments originating from Türkiye's Eastern Black Sea basin and might be a baseline work for future inland water studies.

Innovative Polygonal Trend Analysis (IPTA) in detecting the seasonal trend behavior of statistically downscaled precipitation for the Eastern Black Sea Basin of Turkey

ABSTRACT This study compares projected and past seasonal precipitation trends in the Eastern Black Sea Basin, Turkey. Historical data from twelve stations representing the basin during 1981–2010 was used, while statistically downscaled data from two representative concentration pathway scenarios (RCP4.5 and RCP8.5) outputs of the GFDL-ESM2M general circulation model were utilized for 2021–2050. To determine the seasonal trend behaviors of precipitation variables and transitions between consecutive months, the Innovative Polygon Trend Analysis (IPTA) was implemented. Furthermore, the star concept was employed to illustrate the changing sizes between consecutive periods. Both scenarios showed considerable summer and autumn declines at almost all locations, with low seasonal precipitation variability. These scenarios indicated January to be the important month for trend shift, except for Rize, Pazar, and Hopa stations. The formation of several polygons, polygons intersecting, and polygons not forming on the global regression line show that the hydro-climatic cycle might be chaotic.

Seismic characterisation of multiple BSRs in the Eastern Black Sea Basin

Long offset seismic reflection data reveal the presence of four Bottom Simulating Reflectors (BSR0-3) within folded sediments of the Tuapse Trough, along the NE margin of the Eastern Black Sea Basin (EBSB). Multiple BSRs are observed in other sites worldwide, however, their origin and formation mechanisms are still debated. Here, we investigate the formation mechanisms of the EBSB multiple BSRs based on their seismic character and on their physical properties derived from reflected and refracted arrival seismic velocities. Seismic reflection data are downward continued to enhance refracted arrivals. A 2D travel-time velocity model of the sub-seabed, using combined travel-times from non-downward-continued reflected and downward-continued refracted signals, shows variations in the physical properties at the BSRs and nearby sediments. The P-wave velocity (VP) increase of 1.55–1.72 km/s between the seafloor and BSR0 (258 mbsf) reflects normal compaction trends in sediments, whereas the VP of 1.75–1.83 km/s between BSR0 and BSR1 (360 mbsf) is higher than that expected for sediments at that depth. Beneath BSR1, a VP decrease from 1.83 km/s to 1.61 km/s occurs within a 70-80 m-thick layer including BSR2 (395 mbsf) and extending to BSR3 (438 mbsf). Beneath BSR3, VP increases. Based on an analytical model linking seismic velocity to physical properties, these VP trends can be explained by a gas hydrate saturation from 0 to 2% between the seafloor and BSR0, reaching 4 ± 2% just above BSR1. A free gas saturation of up to 20–25% is estimated within the low-velocity zone between BSR1 and BSR3. BSR1 likely represents the present-day base of the gas hydrate stability zone (BGHSZ), which aligns with the theoretical BGHSZ assuming a geothermal gradient of 26–30 °C/km. Based on seismic polarities and results from travel-time analysis and rock physics modelling, we suggest that hydrate dissociation and recycling processes may explain the negative polarity of BSR2 and BSR3, which are still visible due to the presence of relict gas, and inferred higher gas hydrate saturations close to the present-day base of the stability zone at BSR1. Also, structural and stratigraphic controls seem to have favoured focused free gas flow and hydrate formation at the top of an anticlinal structure, thus likely controlling multiple BSR generation in the EBSB.

Drought analysis using innovative trend analysis and machine learning models for Eastern Black Sea Basin

Drought analysis using innovative trend analysis and machine learning models for Eastern Black Sea Basin

A Preliminary Research on the Trichoptera Fauna of the Kura-Aras River Basin and Eastern Black Sea Streams

The aim of this study is to determine the Trichoptera species distributed in the Kura-Aras river basin and Eastern Black sea coastal rivers within the borders of Turkey. For this purpose, samples were taken from a total of 51 stations, each individual was separated according to its morphological characteristics and species identification was completed. A total of 44 Trichoptera species were recorded as a result of the samplings made from two different river basins with flow within the borders of Turkey. Although Trichoptera species distributed in the Eastern Black Sea basin have been identified before, this study was conducted for the first time for the Kura-Aras river basin. Species identified from the Kura-Aras river system are new records for the basin.

History of the geological development of the Ukrainian sector of the Black Sea from the middle Early Cretaceous to the beginning of the Late Miocene

Regional seismic investigations have made it possible to obtain new knowledge on the geological history of the Ukrainian sector of the Black Sea during rifting from Albian to Cenomanian, post-rift subsidence (Turonian¾Maastrichtian and Paleocene¾Middle Eocene), tectonic compression at the end of the middle Eocene and post-rift subsidence interrupted by a series of short-lived, compressional events (late Eocene ¾ the beginning of the Early Miocene). Rifting occurred simultaneously in the entire area of study and formed three long rift basins, each of which consisted of a system of (half)grabens, separated from each other and their margins by faults with amplitudes of up to3 km. The intensity of Cretaceous rifting was significantly less than would be required to produce continental lithosphere break-up and oceanic crust formation, or through-going «oceanisation» of continental lithosphere. Sedimentation during the pre-Late Eocene post-rift phase took place in relatively shallow marine conditions. Eocene compression caused a strong deformation of the sedimentary cover, partial and complete inversion of rift faults and the formation of three largely separate sea basins, between which a large landmass arose. The primary area of deposition of sedimentary sequences was significantly reduced due to strong deformations caused by compressional phases in the Late Miocene. That which is now the deep Black Sea was a relatively shallow basin until the beginning or even the end of the Pleistocene. Only thereafter did the water depth increase rapidly to more than 2 km. Research results indicate that modern tectonic reconstructions of the Western Black Sea and Eastern Black Sea basins, which are based on assumptions about the formation of the (sub)oceanic crust in these basins and/or different times of their formation, look unreliable. It also follows that any view of back-arc basins as small oceanic basins is not universally applicable.

Russian sturgeon in the eastern Black Sea basin, Georgia

Russian sturgeon in the eastern Black Sea basin, Georgia

Discussion of “Innovative approaches to the trend assessment of streamflows in the Eastern Black Sea basin,Turkey”

The research paper by Akçay et al. applied innovative polygon trend analysis (IPTA) to derive trend length/volume and trend slope between two consecutive months for rainfall/streamflow in the eastern Black Sea basin, Turkey. Although the trend length/volume equation is correct, the trend slope equation is fundamentally incorrect. A brief discussion is presented to apprise the research community of the correct trend slope equation.

Reply to Discussion of “Innovative approaches to the trend assessment of streamflows in the Eastern Black Sea basin, Turkey”

The discussion paper prepared by Barma and Amai (2022) reported that the trend slope calculations made by Akçay et al. (2022) were incorrect. A response to the discussion on this topic is offered.

Hydrocarbon reservoir depth identification in the eastern black sea basin: Implications from euler deconvolution and gravity tensor invariants

The Black Sea Basin (BSB) consisting of Eastern Black Sea (EBS) and Western Black Sea (WBS) basins which separated by the Mid Black Sea High (MBSH) is formed by the collision of Eurasia and Arabian-African Plates. Petroleum and gas hydrate contents of the BSB have been discussed by using different geological and geophysical research. In this study, the gravity gradient tensor and invariant data based on the Bouguer gravity anomaly of the EBS basin were evaluated to define the hydrocarbon reservoirs. Afterwards, Euler deconvolution technique is applied to the invariant to reveal the depth of subsurface bodies. Furthermore, the significant invariant anomalies are compared with known oil seepage and petroleum wells. The depth values of oil trace closest to the known Sürmene and Hopa drill holes were computed as 4809 m, and 4455 m according to the structural index values of SI = 2.

Coupling machine learning with signal process techniques and particle swarm optimization for forecasting flood routing calculations in the Eastern Black Sea Basin, Türkiye.

With the effect of global warming, the frequency of floods, one of the most important natural disasters, increases, and this increases the damage it causes to people and the environment. Flood routing models play an important role in predicting floods so that all necessary precautions are taken before floods reach the region, loss of life and property in the region is prevented, and agricultural lands are protected. This research aims to compare the performance of hybrid machine learning models such as least-squares support vector machine technique hybridized with particle swarm optimization, empirical mode decomposition, variational mode decomposition, and discrete wavelet transform processes for flood routing estimation models in Ordu, Eastern Black Sea Basin, Türkiye. In addition, it is aimed to examine the effect of data division in flood forecasting. Accordingly, 70%, 80%, and 90% of the data were used for training, respectively. For this purpose, the flood data of 2009 and 2013 in Ordu were used. The performance of the established models was evaluated with the help of statistical indicators such as mean bias error, mean absolute percentage error, determination coefficient, Nash-Sutcliffe efficiency, Taylor Diagrams, and boxplot. As a result of the study, the particle swarm optimization least-squares support vector machine technique was chosen as the most successful model in predicting flood routing results. In addition, the optimum data partition ratio was found to be Train:70:Test:30 in the flood routing calculation. The findings are essential regarding flood management and taking necessary precautions before the flood occurs.

КРЕЙДОВИЙ РИФТОГЕНЕЗ У ГЕОЛОГІЧНІЙ ІСТОРІЇ УКРАЇНСЬКОГО СЕКТОРУ ЧОРНОГО МОРЯ

Within the Ukrainian sector of the Black Sea, the Albian-Cenomanian rift faults formed three large rift basins, which consisted of a system of grabens and half-grabens. One of the sublatitude rift basins occupied the modern Karkinit Trough, Krylov-Zmiiny Uplift, Gubkin Ridge and the Sulina Depression on the Odesa Shelf. The second sublatitude basin occupied the modern Tetyaev High, Sorokin Trough, Marine Continuation of the Crimean Folds and, apparently, the Crimean Mountains. The third rift basin extended from the northwest to the southeast and encompassed the Euxinian Graben, Andrusov Ridge, Eastern Black Sea Basin, and Shatskiy High. The greatest depth of the base of the rift sequence is observed in the central part of the Western Black Sea Basin, where it is 15.5–16.5 km. In the Eastern Black Sea basin, the maximum depth is 12.5–13.5 km. The shallowest depths of the base of the rift sequence are characteristic of the Kalamit Swell and the Marine Continuation of the Crimean Folds. During the Cenozoic phases of compression, almost all rift (half)grabens underwent intense folding and vertical movements from several hundreds of meters to 4–5 km. At the same time, most of the rift faults underwent partial or complete inversion.

Investigation of Impact of Vapor Pressure on Hybrid Streamflow Prediction Modeling

In this study, daily streamflow prediction models have been developed for Aksu Stream, in the Eastern Black Sea Basin of Turkey. To reach at this aim, hybrid artificial intelligence models have been developed, by using a new parameter, vapor pressure. Vapor pressure efficiency has been investigated for hybrid streamflow prediction models. Streamflow prediction models have been developed by using Artificial Neural Network (ANN), Multivariate Adaptive Regression Splines (MARS), and their hybrid models. Hybridization of streamflow prediction models has been made with Wavelet Transform (WT). 10 yearly daily hydrological (discharge (m3/s)), meteorological (precipitation (mm), vapor pressure (hPA)) data, and seasonality coefficient have been used as input data of streamflow prediction models. In the selection of the best streamflow prediction model, 14 different day-delayed input combinations have been established by using 10 yearly data. As a result of the study, the highest flow forecast performance model has been determined as Wavelet Artificial Neural Network (WANN) in the study area. In the WANN model, the vapor pressure parameter was found to reduce the error by about 18.5% and improve the forecast performance. This study has concluded that, vapor pressure may be used in the future studies as a new parameter for streamflow prediction models.

Flora and Fauna Conservation in Machakhela National Park Georgia

Biodiversity conservation is the protection and management of biodiversity to obtain resources for sustainable development. The diverse topography and climate has provided conditions to develop a remarkably wide array of landscapes and plant formations. They include two features of plants and plant associations that date back millions of years: the Colchic refugium in the eastern Black Sea basin and the Hyrcanic region on the southern Caspian Sea coast. These “refugia”/refugial forests harbour many locally endemic plants - species that are found nowhere else. They include relict and endemic oaks (such as Quercus imeretina, Q. hartwissiana), Medvedev’s birch (Betula medwedewii), Ungern’s and Smirow’s rhododendrons (Rhododendron ungernii, R. smirnowii) in the Colchic. Machakhela National Park is located 30 km away from Batumi in the foothills of the Lesser Caucasus. Close to the Turkish border, Machakhela expands the protection of the unique ecosystems of the Colchic forests – rich tropical and sub-tropical habitats (temperate rain forests with peat bogs) which contain unrivaled biodiversity, and are rich in relics of the tertiary period: Colchic bot box, chestnut, nut, hazel-nut, and bot trees abound. Trails are being developed and since this park has only been recently established, you can still be one of the first to witness its wet beauty. At the same time these unique forests can mostly be classified as temperate rainforests, due to the same principal reasons as for other temperate rainforest regions: relevant slopes of barriermountains located along coastlines that trap a large portion of the humidity from sea air masses. Montane barriers also contribute to a warm and humid climate that has been present since the late Tertiary and is the primary reason that the Caucasus has acted as a shelter for humid- and warm-requiring (hygro-thermophilous) relicts during the ice age.

Rainfall Intensity-Duration-Frequency Analysis in Turkey, with the Emphasis of Eastern Black Sea Basin

In this study, regional intensity-duration-frequency (IDF) curves for Turkey were developed using the available maximum rainfall intensity values for various durations (D=5, 15 and 30 minutes, and 1, 3, 6, 12 and 24 hours). Multi-nonlinear regression analysis was carried out by using nine kinds of IDF formulas, which were taken by using various IDF formulae in the literature and newly generated formulae. In order to test the reliability of the functions, two criteria were used: the determination coefficient and the mean relative error. IDF analysis in the Eastern Black Sea Basin of Turkey, which is the most raing basin, is also emphasized and studied in detail. It has been concluded that the reliability of the results is high enough and that this paper will motivate and open new horizons to detailed studies on IDF analysis.