Lake Van Region Research Articles

The Role of Upper Mantle Forces in Post‐Subduction Tectonics: Plumelet and Active Rifting in the East Anatolian Plateau

AbstractThe spatiotemporal interaction of large‐ and regional‐scale upper mantle forces can prevail in collisional settings. To better understand the role of these forces on post‐subduction tectonics, we focus on mantle dynamics in the East Anatolian Plateau, a well‐documented segment of the Arabian‐Eurasian continental collision zone. Specifically, we analyze multiple forces in the upper mantle, which have not been considered in previous studies in this region. To this end, we use a state‐of‐the‐art 3D instantaneous geodynamic model to quantify the dynamics of thermally defined upper mantle structures derived from seismic tomography data. Results reveal a prominent SW‐NE‐oriented mantle flow from the Arabian foreland to the Greater Caucasus–a plumelet–through a lithospheric channel under the East Anatolian Plateau. This plumelet induces localized dynamic topography (∼500 m) around the extensional Lake Van province, favoring NE‐directed compression and westward escape of the Anatolian plate. We suggest that the Lake Van region is an active magma‐rich intraplate rift in the Africa‐Arabia‐Anatolian plume‐rift system. The rift zone was probably initiated by Neotethyan subduction‐related forces and has been reactivated and/or sustained by the plumelet‐induced convective support. Our findings are consistent with numerous observations, including the recent low‐ultralow seismic velocities with a SW‐NE splitting anisotropy pattern, geochemical and petrological studies, and local kinematics showing upper mantle‐induced extensional tectonics in the collisional region.

Derivation of a 1-D seismic velocity model for the Lake Van region

Derivation of a 1-D seismic velocity model for the Lake Van region

Identification of magnetic mineralogy and paleo-flow direction of the Miocene-quaternary volcanic products in the north of Lake Van, Eastern Turkey

Abstract One of the major challenges facing geochemistry, petrology, and volcanology researchers is the difficulty in determining the origin and paleo-flow directions of igneous and volcanic rocks. It is not possible to clearly determine origins and paleo-flow directions in areas with numerous volcanic centers. Anisotropy of magnetic susceptibility (AMS) is a valuable method that provides insights into the origins and paleo-flow directions of lavas that are complex to study. The presence of volcanic materials with thicknesses up to 1 km, coming from different sources at varied time intervals in the north of Lake Van, makes this area an ideal setting for implementing AMS in establishing paleo-flow directions. This study presents the magnetic mineralogy and AMS analysis of volcanic rocks from the Miocene to the Quaternary in the Lake Van region. We conducted isothermal remanent magnetization (IRM) and high-temperature susceptibility (HTS) studies to determine the magnetic mineralogy. IRM studies revealed that (titano)magnetite is responsible for the magnetization in most samples, while both (titano)magnetite and hematite are responsible for the rest. Alteration degrees and Curie temperatures of the rock samples were also determined through HTS measurements. There is good agreement between the anticipated directions of lava flow and our findings for nearly all volcanic rocks.

Determination of the shear wave velocity structure of substations by the HVSR inversion method using broadband and strong ground motion earthquake data in the Lake Van region, eastern Türkiye

Determination of the shear wave velocity structure of substations by the HVSR inversion method using broadband and strong ground motion earthquake data in the Lake Van region, eastern Türkiye

Multiple parameter analysis for assessing and forecasting earthquake hazards in the Lake Van region, Turkey

A detailed spatial-temporal analysis of the seismic activity in and around the Lake Van region was performed using several seismotectonic parameters such as b-value, Z-value, relative intensity (RI), pattern informatics (PI), and Coulomb stress changes. Correlations between these parameters were analyzed to estimate and forecast potential seismic hazards in the Lake Van region. Particular attention was paid to the parts of the study region that exhibited smaller b-values, higher Z-values, and high-stress changes at the beginning of 2022 and to the locations of earthquake hotspots determined from the composite earthquake forecast map for 2022–2032, i.e., Muradiye, Çaldıran, Özalp, Erçek, Van city center and Gevaş covering the faults of Çaldıran, Yeniköşk, Erciş, Malazgirt and the fault zones of Saray and Van. To provide more accurate interpretations regarding potential earthquake occurrences in the near future, the seismotectonic parameters analyzed in the scope of this study were compared with the corresponding seismological, geological, geodetical, and geochemical variables reported in the literature. This comparison showed that, firstly, our results are consistent with those reported in previous studies, and, secondly, all these variables should be interpreted in combination to correctly assess strong earthquake hazards. Furthermore, this type of multiple-parameter analysis may be important for the description of seismic, tectonic, and structural characteristics of the nature of the crust. Our findings show that almost all seismotectonic parameters indicative of anomaly regions, i.e., lower b-values, higher Z-values, high-stress distribution, and hotspots, were recorded in the same parts of the study region. Thus, the anomaly regions detected at the beginning of 2019 and between 2022 and 2032 may be considered to be potential zones of future great earthquakes. To summarize, the correlations among these variables may provide accurate information for assessing and forecasting earthquake hazards in this region.

Investigation of site effect of Lake Van region (eastern Turkey) by using strong ground motion records

The site effect plays a very important role in determining the structural damage that may occur in a possible major earthquake. In this study, seventy-nine strong ground-motion records (M > 4.5) from past earthquake events in the Lake Van region, recorded by 14 accelerometer stations located on dissimilar geological units, were analyzed for local soil properties using horizontal-to-vertical spectral ratio (EHVSR) method. In addition, EHVSR results were compared with Standard Spectral Ratio (SSR) results, which is another method used to determine soil amplification. The obtained predominant period, amplification factor, seismic vulnerability index (Kg) and bedrock depth values were examined. The EHVSR results show that the predominant frequencies of the sites and the amplification factor values were estimated as 0.58–5.77 Hz and 1.84–7.5, respectively. The seismic vulnerability index (Kg) values, which are crucial parameter in hazard assessment, change from 1.6 to 30. The bedrock depths range between 11 and 186 m for the study area. From the results of this study it is found that the damage may be high after a possible destructive earthquake in the study area where the predominant period, amplification, Kg values and bedrock depth are high.

Geodynamics of East Anatolia‐Caucasus Domain: Inferences From 3D Thermo‐Mechanical Models, Residual Topography, and Admittance Function Analyses

AbstractWe investigate anomalous topography in the Anatolia‐Caucasus domain of the Arabian‐Eurasian plate convergence zone. To achieve this aim, we use three‐dimensional (3D) geodynamic modeling in addition to analyses of the non‐isostatic components of surface topography based on residual topography and free‐air gravity admittance functions. The numerical experiments are based on two different temperature models obtained from P‐wave tomography data that are sensitive respectively to large and small‐scale variations of upper mantle structures. Our results suggest a long‐wavelength convective support of topography, which is in general agreement with the uncompensated pattern of residual topography and free‐air admittance values, as well as previous modeling studies. At shorter wavelengths, we provide new constraints on the regional dynamic processes related to 3D variations of the upper mantle flow vectors and associated surface deflections. Positive dynamic topography is found over the East Anatolian Plateau (∼400 m to ∼1.2 km) that is consistent with inferred lithospheric thinning processes pertinent to the tectonic evolution of the Tethyan orogenic system. We further show dynamic topography in the plateau (≥500 m) that may account for extensional tectonics in the Lake Van region interpreted from local kinematic and geophysical studies. In conjunction with the observations, negative anomaly patterns are estimated in the western part of the Black Sea (∼−2 km), the eastern Pontides arc (∼−200 m), and the northeast Arabian Plate (∼−1 to −2.3 km). Our model results also suggest a link between large‐scale mantle flow and SW‐NE‐directed general pattern of the SKS‐based anisotropy beneath the region.

Single nucleotide polymorphisms of GDF9 gene/exon 2 region and their associations with milk yield and milk content traits in Karakaş and Norduz sheep breeds

Karakaş and Norduz sheep have been adapted to the Lake Van region of Turkey for many years as being domestic genetic resources and meat, milk, and fleece traits are a reliable economic resource especially preferred by small family businesses around the area. In this study, the data set consisted of milk yield (MY) and milk content components; milk fat (MF), fat-free dry matter (FFDM), dry matter (DM), protein (Pro), lactose (Lac), pH, acidity H (aH), and lactic acid (Lac). Besides, Karakaş (n = 30) and Norduz (n = 26) sheep were chosen to investigate based on the SNP method. Correspondingly, genomic DNA from both breeds exon 2 of the GDF9 gene region was amplified, 815 base pairs (bp) in length, by means of PCR. Therefore, there were three noval SNPs detected in both breeds under investigation. Although SNP1 and 2 with genotypes of GG and AG had statistically significant impacts on both milk production and milk components (p < 0.01), SNP3 with genotypes of TT, TC had no significant effects on the milk characteristics in question.

Coulomb Stress Change and Size-Frequency Distribution for Lake Van Region

Coulomb Stress Change and Size-Frequency Distribution for Lake Van Region

Lake Van (Southeastern Turkey) Experiment: Receiver Function Analyses of Lithospheric Structure from Teleseismic Observations

The P and S wave receiver functions and their joint inversions are used to study the lithosphere beneath the Lake Van region using approximately 600 teleseismic earthquake data (Mw ≥ 5.8) at different azimuths collected from 10 permanent broadband stations operated by Kandilli Observatory and Earthquake Research Institute and Disaster and Emergency Management Authority in the region. The dataset is taken from the European Integrated Data Archive. The simulated annealing method is used for the joint inversion of P-wave and S-wave receiver functions, since the P410s phase cannot be detected reliably in the depth stacks. This may be due to the low olivine content and high basalt content at this depth. The inversion process is therefore performed without travel time residuals. The crustal thickness is observed at nearly 45 km in all the velocity models obtained from the inversion. The relatively low-velocity layer (Vs = 3.4 km/s) at depths of the middle crust may be associated with volcanic centers near Nemrut, in the west of the region. Additionally, another low-velocity layer (Vs = ~ 3.0 km/s) is observed in the upper crust around the Suphan Volcano. Also, Vp/Vs and Poisson’s ratios are calculated for the study area. Their high values (Vp/Vs ≥ 1.85, and σ ≥ 0.285) correspond to the partial melting of the lower crust in the region. According to velocity models obtained from the inversion results, the most important outcome is that the average variance of the Moho discontinuity (~ 45 km) and lithosphere–asthenosphere boundary (~ 90 km) under the seismograph stations can be interpreted as a likely part of the Arabian oceanic plate in relation to the collision zone.

Transregional Perspectives: Characterizing Obsidian Consumption at Early Chalcolithic Ein el-Jarba (N. Israel)

ABSTRACTThis paper details the characterization of 48 obsidian artifacts from Ein el-Jarba, an Early Chalcolithic site of the southern Levantine Wadi Rabah culture (6th millennium cal b.c.). By melding sourcing data from energy-dispersive X-ray fluorescence spectroscopy with the artifacts’ techno-typological specifics, we contrast Ein el-Jarba’s obsidian consumption practices with those of broadly contemporary and earlier communities in the context of the period’s emergent transregional character. The results attest to a major reconfiguration of long-term traditions, with well-known Cappadocian and Lake Van region source materials now supplemented by obsidian from the Caucasus, such material’s most southerly distribution. These diverse resources are believed to have circulated within the same exchange networks, mediated by communities of the Halaf culture to the north. Most of Ein el-Jarba’s obsidian was in the form of pressure blades from a common technical tradition, the implements likely procured ready-made from the well-connected site of Hagoshrim.

Spatial and Temporal Variations of Gutenberg-Richter b-Values Using Classic Method of Moment (CMM) and Seismicity in and Around Van Lake

The aim of this study determined spatial-temporal variations of Gutenberg-Richter b-values using the Classic Method of Moment (CMM) and seismicity in and around Lake Van. We wrote a Matlab program for this method in the Matlab system. The faults for the Van region used as updated in the GIS system given the reference from the different sources by Bayrak and Türker (will be used in the doctoral thesis). Around Lake Van divided into 4 different seismic source regions. For each seismic source region, probabilities ranging from 0 to 1, the annual probability of exceedances and return periods were calculated for the next 25, 50 and 100 years. Van region determined the seismicity b value changes, β-values. We mapped spatial variations of the b-values using the GIS system. As a result, Lake Van region (region 2) occurred 7.1 magnitude an earthquake in the next 100 years with 31 % probability levels. If it occurred in the 50 years with 15 % probability levels, in the 25 years with 7.8 % probability levels. We estimated the low b-values in the Lake Van so, it has been the high seismicity and can be occurred an earthquake as the high magnitude in the next years. This study will be lead to earthquake hazard analysis and seismic hazard studies in and around Lake Van.

Seismites as an indicator for determination of earthquake recurrence interval: A case study from Erciş Fault (Eastern Anatolia-Turkey)

The southern part of the Eastern Anatolian Plateau is a key region for understanding the tectonic activity and related deformation patterns of the Arabian–Eurasian collision zone. The geological record of seismic events collected from lacustrine deposits of Lake Van Basin is a critical requirement for seismic hazard assessment and seismic risk reduction. Our paleoseismic investigations revealed well-preserved seismites at five locations in late Pleistocene lacustrine deposits. The seismites were dated using an optically stimulated luminescence dating method and were arranged according to their ages. Their type, such as convolute, dish-and-pillar, flame, and ball-and-pillow structures, as well as their locations, ages, and stratigraphic distribution enable us to identify the responsible fault and the earthquake recurrence interval. On the basis of these properties, the Erciş Fault has been recognized as the structure responsible for creating the seismites. The time span between the seismites indicates an apparent earthquake recurrence interval of 125–250 years for large earthquakes (M ≥ 5) related to the Erciş Fault. The method applied here enriches our knowledge on the seismic hazards present in the northern Lake Van region.

Investigation of the relation between feline infectious peritonitis and retroviruses in cats

Feline infectious peritonitis (FIP) infection is a highly pathogenic and fatal systemic inflammatory disease in cats. Although FIP infection is associated with the immune system, there are several predisposing factors of the disease. FIP has a high rate of interaction with other infectious agents. The feline immunodeficiency virus (FIV) and Feline Leukemia Virus (FeLV) infections play a predisposing role by reducing immunity against FIP. This study was conducted with the Turkish Van cats, which is a cat breed specific to the Lake Van region of Turkey, between 2014 and 2015. Ascites and organ damage symptoms were identified by pathological analysis in 15 Van cats that were brought to the Van Yüzüncü Yıl University. Polymerase chain reaction (PCR) was used to investigate the presence of FIV and FeLV in the homogenate of brain, lung, liver, kidney, spleen and intestines tissue samples with lesions. As a result of the analysis, FIV was identified in 1 (6.7%) out of 15 cats, and all cat samples were found to be positive in terms of FeLV (100%). In the phylogenetic analysis of positive samples, all FeLVs were observed to be in endogenous-FeLVs. In the FIV phylogenetic analysis, our study strain was found to be in the FIV sub-group B. The fact that FIP positive cats were also FeLV positive at the same time has attracted the attention to the pathogenesis of Endogenous-FeLV in malignant diseases, which has not yet been understood. Particularly, it was concluded that the prevalence of FIP infection can be reduced by paying attention to FIV and FeLV vaccination in multiple-cat sheltering environments in young cats.

Paleogeographic implications of the Permian shallow marine carbonates in the eastern Lake Van region (eastern Turkey): Foraminiferal biostratigraphic and sequence stratigraphic constraints

The study focuses on the Middle Permian recrystallized limestone succession, previously considered as Triassic, at the eastern parts of Lake Van (eastern Turkey) representing the northern margin of Gondwana. The Middle Permian successions in the region are mainly composed of slightly metamorphosed, recrystallized limestones. The shallow‐water depositional settings of the studied units are characterized by the relative dominance of smaller foraminifers and rare occurrence of fusulinids. Middle Permian foraminifers recorded from eastern Anatolia are typically Tethyan assemblages for the Capitanian (Guadalupian) age. Detailed microfacies analysis by textural analysis and faunal assemblages have been undertaken throughout the studied sections. The Capitanian carbonates of the region are mainly characterized by six major microfacies types representing shallow marine environments, ranging from foreshoal environment to shoal and backshoal environments. Within the scope of sequence stratigraphic interpretations, vertical stacking patterns of these microfacies types reflecting different depositional environments reveal the presence of two third‐order depositional sequences, each of which consists of a transgressive systems tract and a highstand systems tract. Within the context of sequence stratigraphy, the microfacies changes point out the relative sea‐level fall towards the upper part of the sections, coinciding with the onset of a regression recorded worldwide in the Capitanian.

Long‐distance interaction in Urartu?: Provenance and composition of copper alloys from Ayanis, Turkey

The paper analyses tin bronze weaponry found at the first‐half‐of‐the‐seventh‐century‐BCE Urartian fortress in the Lake Van region of eastern Turkey. Examples of finely manufactured artefacts provide evidence for the consumption of high‐quality bronzes in a well‐defined elite context. This study tests for the presence or absence of long‐distance procurement of the raw materials used to produce status objects. The results of quantitative elemental and lead isotope abundance ratio analyses show that the bronzes were produced with varying copper tin alloys, and the copper was procured from several possible locations, including Anatolia and Cyprus.

The provenance of Kul Tepe obsidian artifacts: Syunik and the highlands of Armenia as possible seasonal pastureland

Excavations at the site of Kul Tepe in the Jolfa region in north-western Iran have unearthed various archaeological materials from Late Neolithic/Early Chalcolithic to Achaemenid periods (end of 6th millennium to 3rd century BC). During the Chalcolithic and the Bronze Age most lithic tools used in Kul Tepe were made of obsidian. From the first and second excavation seasons, 53 and 32 obsidian samples were selected and analyzed by pXRF. According to the results, the main source of obsidian for the workshops in Kul Tepe was Syunik, but other sources in the Lake Sevan Basin like Ghegam, Bazenk, Choraphor and Gutansar and the Lake Van region (Nemrut Dağ and Meydan Dağ) were utilized also.

The mineralogy and firing behaviour of pottery clays of the Lake Van region, eastern Turkey

AbstractThe present study focused on the mineralogical and chemical characterization and firing behaviour of clays from the Lake Van region and compared them with the same characteristics established for two ancient pot sherds. Four pottery clays collected from Kutki and Kuşluk in the Kesan Valley to the south, from Kavakbaşı to the southwest and from Bardakçı village on the east coast of Lake Van were analysed by X-ray diffraction to identify mineralogical composition (bulk clays and &lt;2 μm fractions after heating at 300–500°C and ethylene glycol solvation). Further analyses were conducted to determine the size distribution, chemical composition and physical properties of test bodies derived from these clays. The in situ weathered schist forming the primary micaceous red clays which are suitable for local pottery production are characterized by large muscovite-sericite-illite and small calcite contents. In contrast, the Bardakçı clays are dominated by large smectite contents and are only used sparingly in mixtures of local pottery production because they undergo firing shrinkage and present drying and firing flaws in the fired bodies. Firing ranges of ~800–900°C were inferred from the mineralogy and colours of the two ancient sherds from Kutki. As a result of mineralogical analysis of fired and unfired test bodies of these pottery clays and pot sherds, two different types of pastes were determined for pottery production in the Lake Van region: metamorphic and volcanic paste, the former characterized by a calcite-poor and mica-sericite-rich matrix and the latter by large smectite and small calcite contents.

Biomarkers in Lake Van sediments reveal dry conditions in eastern Anatolia during 110.000–10.000 years B.P.

AbstractLipid biomarkers were analyzed in Lake Van sediments covering the last 600 ka, with a focus on the period between 110 and 10 ka, when a broad maximum in pore water salinity as a relict from the past suggests dry conditions. The occurrence and distribution of biomarkers indicative for terrestrial plants (long‐chain n‐alkane C29), haptophyte algae (methyl alkenones C37) and halophilic archaea (archaeol) all point toward a dry climate in Lake Van region during this time interval. The hydrogen isotopic composition of C29 n‐alkanes (δDC29) and C37 alkenones (δDC37) is enriched between MIS 4 and MIS 2, which is interpreted as a decrease in the regional ratio of precipitation to evaporation. Similarly, the low abundance of the acyclic glycerol dialkyl glycerol tetraether GDGT‐0 relative to archaeol, quantified by the Archaeol and Caldarchaeol Ecometric (ACE) is assumed to reflect the presence of halophilic euryarchaeota adapted to high salinity water. The climate around Lake Van appears in phase with the Yammouneh basin 800 km southwest and Lake Urmia 250 km southeast of Lake Van over the last two glacial periods. The results highlight the potential of combining ACE, δDC29, and δDC37 for reconstructing salinity changes and regional precipitation to evaporation ratio from lake sediments.

Crustal S-wave structure around the Lake Van region (eastern Turkey) from interstation Rayleigh wave phase velocity analyses

This study focuses on the average crustal and the upper mantle structure throughout the Lake Van region of eastern Turkey. The study aimed to investigate the structure with the fundamental mode interstation Rayleigh wave phase velocities from the local and the regional earthquakes recorded by Kandilli Observatory and Earthquake Research Institute stations. Considering back azimuth differences of each source and station path, six different broadband station pairs and 27 earthquakes were selected to determine the 1-D shear-wave velocity structures throughout the region by using an interstation method (slant stacking technique). The linearized least squares algorithm was used to obtain the 1-D shear-velocity model that best fit the observed phase velocity dispersion curve. The normalized statistical resolution matrix was calculated to measure the reliability of the solution. Inversion results revealed that the solution quality of the upper crust is weak due to the high resolution lengths. The average shear-wave velocities in the lower crust scale down to approximately 3.5 km/s. It was inferred that this low-velocity zone shown in the lower crust may be associated with widespread volcanism. Final 2-D S-wave velocity models obtained from the inversion revealed that the crust-mantle boundary is ~42 km, and shear velocities vary from 3.6 to 4.2 km/s. Furthermore, the upper mantle (~45-70 km) velocities are slower than globally suggested models (e.g., IASP91), and this is possibly related to shallow hot asthenospheric material.