Lake Van Research Articles

Site characterization in the Van settlement (Eastern Turkey) using surface waves and HVSR microtremor methods

The settlements around Lake Van are generally located on young, unconsolidated, saturated, Quaternary aged, current lake and stream sediments. The region is under active tectonism, and many destructive earthquakes have occurred in the area both recently and in historical times. The site effect plays a very crucial role in the prediction of earthquake damage to existing structures and in the planning and design of new structures. The main purpose of this study is to determine the mechanical and physical properties of soils in and around the settlement area of Van and to determine their behaviour under a possible earthquake. Considering these situations, both borehole-based geological data and data obtained from geophysical methods were collected in the Van settlement area.Within the scope of this study, 247 boreholes (the maximum drilled depth approximately 5 km), 185 shallow seismic profiles, 56 multi-channel analysis of surface wave (MASW) profiles, and more than 200 single-station microtremor measurements were collected in the study region, and the soil structure of the study area was evaluated and mapped by analysing the data obtained. In order to investigate the engineering properties of the study area, the parameters such as shear-wave velocity (Vs) at each layer, average Vs down to 30 m depth (Vs30), soil classification, fundamental frequency (period) and the ground motion amplification factor, have been prepared. All of the geological and geophysical data sets obtained in the study area within the scope of this study were mapped with GIS-based database features, and an updatable database was prepared for future works.

Large-volume basaltic hyaloclastite eruption along a propagating land/lake lithosphere fracture at Lake Van (Eastern Anatolia): impact of volcanism on the evolution of Lake Van V

The Incekaya hyaloclastite cone (eastern Anatolia, Turkey), the focal point along a major eruptive fissure, was the main source of an unusually large explosive basaltic eruption. The ca. 80 ka-old eruption began onshore with scoria cones from a 5 km N-S fracture propagating toward Lake Van (surface area of 3755 km2). At the intersection with the fault-bounded lake basin, a ca. 400-m-high subaerial hyaloclastite edifice formed, which can be crudely subdivided into a main lower massive bulk of hydrothermally altered lithic-rich hyaloclastites (CL) topped unconformably by a > 30-m-thick, well-bedded fallout tephra (CU). The CU tephras are correlated with (1) widespread onshore hyaloclastite fallout deposits mostly west-southwest of the cone and (2) a ca. 2-m-thick, ca 80-ka-old bedded hyaloclastite (V-60), part of a 220 m ICDP (International Continental Scientific Drilling Program) core, drilled in Lake Van, 27 km N of Incekaya. The hyaloclastite unit was seismically identified as being the most widespread and well-defined reflector throughout much of western Lake Van. A minimum volume of > 9 km3 fallout hyaloclastite tephra is estimated when the area of the seismic reflector is extrapolated to the coast and 2 km inland. Seismic reflectors also suggest at least two (hyaloclastite?) intralake cones rising up to 388 m above the lake sediment surface 1.5 km NW off Incekaya cone and were possibly erupted along the same fracture. The total volume of hyaloclastites includes (a) subaerial Incekaya cone, (b) the inferred subaqueous continuation of the cone(s), (c) the bedded intralake and onshore deposits, and, tentatively, (d) a widespread (seismically defined) mass flow deposits directly beneath Incekaya reflector of roughly 20 km3 and may represent the deposits of explosively erupted basaltic magma. Sideromelane shards, the main clast type, are dominantly angular, and most show ≪ 50 vol.% vesicles. Less common tachylite clasts are poorly vesicular (< 50 vol.%). Structural transitions and interlayering between tachylite and sideromelane are ubiquitous. Fluidal and pumiceous lapilli are present in the basal massive facies. Bulk rock and glass compositions indicate constant composition of the slightly evolved Al-rich basalt magma. Olivine (Fo78–82) and plagioclase (An70–80) microphenocrysts, many skeletal with growth features, and microlites make up < 1 vol.% and suggest rapid magma ascent. The high explosive energy of the eruption is interpreted to be due to (1) high magma discharge rates and shearing in the eruptive jet and (2) magma-water interaction conditions. Approximate temporal coincidences with the Incekaya eruption include the following: (a) an abrupt cessation in the supply of evolved tephra from the adjacent Suphan Volcano to the lake sediments, which ended abruptly for ca. 60 ky, (b) an extreme fall in lake level by ca. 150 m, and (c) a drastic increase in pore water salinity (Na+ and Cl− (g/L)) and pH.

Endemic Plants of Lake Van Basin

This study was carried out on endemic plants collected from the Lake Van basin between 1994 and 2002. As a result, 98 endemic taxa, 23 of which grow only in the Lake Van basin, were determined. Including the endemic taxa reported before from the region, a list of 259 endemic taxa belonging to 34 families and 117 genera were compiled. Twenty-three of 259 taxa listed, are unique to the Lake Van Basin. There are 249 endemic taxa in the VANF Herbarium. The authors collected 98 of them. The other 151 endemic taxa were determined by other researchers. Ten endemic taxa were recorded from the literature. In addition to the features in the Flora of Turkey, new features and variations of nine endemic taxa identified. Total 612 images and 200 pictures belonging to 98 endemic taxa scanned and transferred to computer. All images were uploaded to the web page, Virtual Herbarium of the Lake Van Basin, which is also a part of VANF Herbarium.

Authigenic replacement of cyanobacterially precipitated calcium carbonate by aluminium‐silicates in giant microbialites of Lake Van (Turkey)

AbstractStudies of modern cyanobacterial mats and biofilms show that they can precipitate minerals as a consequence of metabolic and degradational activities paired with ambient hydrochemical conditions. This study looked at modern microbial mats forming giant, tower‐like, groundwater‐fed, calcareous microbialites in the world's largest, highly alkaline lake; Van Gölü (Lake Van), East Turkey. Results show that microbial systems play a role not only in carbonate precipitation but also in the formation of siliceous mineral phases. Transmitted light microscopy, scanning electron microscopy and spectral observations revealed that, within the extracellular polymeric substances excreted by the mats abundant minute aragonite grains precipitated first in vivo. These minute grains were quickly succeeded and/or supplemented in the dead biomass of the cyanobacterial mat by authigenic Al–Mg–Fe siliceous phases. Silicon dioxide is available in large concentrations in the highly alkaline water of Lake Van. Divalent cations (Ca and Mg) are delivered to the microbialites mostly by groundwater springs. The precipitation of the fine‐grained siliceous phases is probably mediated by bacteria degrading the cyanobacterial biomass and complexing the excessive cations with their extracellular polymeric envelopes. The bacteria serve as nucleation centres for the subsequent precipitation of siliceous mineral phases. Generally, the biphasic (calcareous and siliceous) mineralization – characterizing Lake Van microbialites – is controlled by their interior highly dynamic hydrogeochemical situation. There, the dramatically different alkaline lake water and the Ca–Mg‐charged groundwater mix at various rates. The early diagenetic replacement of the in vivo aragonite by authigenic siliceous phases significantly increases the fossilization potential of the mat‐forming cyanobacteria. Lake Van and its giant microbialite tufa towers act as a model explaining the transformation of early diagenetic mineral phases observed in many modern and ancient carbonate marine deposits, particularly those influenced by diffusion of silica‐enriched and metal‐enriched pore waters from below the water–sediment interface.

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.

Late Quaternary lacustrine storm deposits: sedimentological properties and regional significance (Lake Van Basin-Eastern Turkey)

Coastal environments are exposed to frequent and intense storm events which are one of the most important elements of sedimentation dynamics in nearshore environments. However, lacustrine storm deposits are rare Late Quaternary sediments of the Lake Van Basin, Turkey, which allow to analyse that kind of storm deposits in a closed lacustrine basin. The storm-induced sedimentary structures evaluated in these deposits reflect erosional and depositional storm processes and encompass erosional surfaces, graded bedding, wave-ripple crossbeds, parallel bedding, shell beds and biogenetic escape structures. They are present in both marginal and relatively deeper lacustrine facies. Evaluations of sedimentological and palaeontological features of storm deposits together with modern storm records of the Lake Van indicate intense storm effect on sedimentation.

Lithology of sediment core VAN04, Lake Van, Turkey

Lithology of sediment core VAN04, Lake Van, Turkey

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.

Van Gölü Havzası Fasulye Genotipleri (Phaseolus vulgaris L.) Arasındaki Genetik Çeşitliliğin Fenotipik ve Moleküler Yöntemlerle Belirlenmesi

Van Gölü havzasının değişik yörelerinden toplanmış olan 95 fasulye genotipinin genetik akrabalık ilişkileri hem fenotipik hem de moleküler yöntemlerle incelenmiştir. Fenotipik yöntemde, 71 adet morfolojik özellik incelenmiş ve bunlar arasında yüksek korelasyon gösterenler değerlendirme dışı bırakılarak fasulye genotiplerine ait 61 adet ölçüm veya gözlemden yararlanılmış; moleküler yöntemde ise 28 primerden elde edilen 219 adet polimorfik ISSR belirteci ve 10 primerden elde edilen 76 adet polimorfik RAPD belirteci kullanılmıştır. Fasulye genotipleri arasındaki genetik akrabalık dereceleri, fenotipik ve moleküler veriler kullanılarak elde edilen değişik matrislerden (Öklid ve Jaccard katsayı matrisleri) dendrogram oluşturularak incelenmiştir. Fenotipik olarak incelenen genotiplerin %69,5‘inin Güney Amerika (Andean) ve %30,5‘inin Orta Amerika (Mesoamerican) orijinli olduğu ve genotipler arasında yüksek genetik çeşitliliğin olduğu saptanmıştır. Fenotipik ve moleküler verilerin birlikte incelenmesi sonucunda, Güney Amerika ve Orta Amerika orijinli genotiplerin; bodur ve sırık genotiplerin; beyaz, diğer tek renkli ve çok renkli tohumlara sahip genotiplerin ayrı kümelenmelerde yer aldıkları gözlenmiştir.

Morphology and phylogeny of Apertospathula oktemae n. sp. (Ciliophora, Haptoria, Spathidiida) from Lake Van, Turkey

A new spathidiid ciliate, Apertospathula oktemae n. sp., was isolated from bottom sediments on the eastern shore of Lake Van, Turkey. The living cells are clavate and 45–80 × 17–30 μm in size. This species is characterized by a lasso-shaped circumoral kinety composed of more than 100 dikinetids, 16 meridionally arranged somatic ciliary rows, a three-rowed dorsal brush with 1.5–2.0 μm long bristles, an oblong and curved macronucleus with an ellipsoidal or globular micronucleus, numerous refractive granules in the anterior portion of the cell, and a single posterior contractile vacuole. This new species lives in alkaline brackish water. Apertospathula oktemae differs from congeners by their body shape, number of oral dikinetids, presence of refractive granules, and their habitat. This is the first study to investigate the 18S rRNA gene sequence of a member of the genus Apertospathula. Phylogenetic trees show that Apertospathula oktemae is most closely related to Arcuospathidium sp. There is a discrepancy between the morphological classification system of the spathidiid ciliates and their molecular phylogeny. To overcome this problem, more molecular data, obtained from more taxa from various geographical regions of the world, are needed.

GEOCHEMICAL AND PETROLOGIC EVOLUTION OF OTLAKBAŞI BASALTIC VOLCANISM TO THE EAST OF LAKE VAN

Collision-related Otlakbaşı volcanism to the east of Lake Van occurred by eruptions from extensional fissures. In this study, it is investigated new Ar-Ar age data and major, trace and rare earth elements characteristics of the Otlakbaşı basaltic volcanism. The Ar-Ar age data indicate that this basaltic volcanism erupted in Early Pliocene time in contrast to its previously known as Quaternary age. The volcanic products are basaltic composition and close to alkaline-subalkaline division line. Results of fractional crystallization accompanied by assimilation (AFC) modeling imply that fractional crystallization can be negligible compared to crustal contamination in the evolution processes of the magma chamber and ratio of the crustal contamination to the fractional crystallization (r values) varies from 0.1 to 0.35. Enrichment of large ion lithophile elements (LILE) and light rare earth elements (LREE) relative to high strength field elements (HFSE) and behavior of mobile elements (Ba and Th) reveal that the mantle source region of the Otlakbaşı basaltic volcanism might have been enriched by melts that were derived from subducted sediments. Depletion in Rb and K elements of the fractionated-corrected samples indicate that amphibole and/or phlogopite could be the presence in the mantle source. Results of partial melting model studies show that this basaltic volcanism can be predominantly produced by the melting of the spinel peridotite source. Metasomatized spinel bearing lithospheric mantle may be responsible for the eruption of the Otlakbaşı basaltic volcanism.

Active tectonics of Erçek Lake Basin and lithostratigraphy of basin deposits (Van, Turkey)

The Erçek Lake Basin&#x0D; (ELB) is located in the eastern part of Van Lake and has an area of approximately&#x0D; 100 km2. The eastern section presents gully morphology towards&#x0D; Özalp. Oligo-Miocene and Plio-Quaternary units cover the basement rocks of the&#x0D; study area. Oligo-Miocene units are folded on both the southern and northern&#x0D; parts of ELB. However, in the north of the basin, northward dipping thrust&#x0D; faults generally developed along E-W. In the south, the fold axes differ by a&#x0D; maximum of 30 ° from the E-W to the north. The distribution of the structural&#x0D; elements within the Plio-Quaternary units is rather limited, and these are more&#x0D; prominent in the north of the Erçek Lake. There are a few normal faults in&#x0D; these structural elements. The development of these normal faults occurred as a&#x0D; consequence of the N-S compression in the region and developed in the active&#x0D; tectonic evolution of the region. The Kozluca left lateral strike-slip fault,&#x0D; which also deforms the western margin of Lake Erçek and the intra-lake&#x0D; morphology, is one of the other intra-plate structural elements within the&#x0D; contracted continental crust.

Turk –Mongol Clans That Came to the Van Lake Basin During the Mongol Occupation

XIII. yüzyılın&#x0D; ikinci yarısında meydana gelen Moğol istilası Anadolu’ya çok sayıda Türk ve Moğol&amp;nbsp;kabilesinin gelmesine sebep&#x0D; olmuştur. Moğollar,&amp;nbsp;askeri birliklerini teşkil eden&#x0D; Moğol&amp;nbsp;ve Türk&amp;nbsp;aşiretlerini Anadolu’nun doğu bölgelerine yerleştirdiler. Zira Doğu Anadolu yaylak-kışlak hayat tarzını sürdüren bu aşiretler&#x0D; için uygun özellikleri barındırmaktaydı. İlk kez Celaleddin&amp;nbsp;Harezmşah’ı takip eden&#x0D; Çurmağun&amp;nbsp;Noyan’la birlikte&#x0D; gelen bu topluluklar arasında Uygur, Karluk&amp;nbsp;ve çok sayıda Türkmen&amp;nbsp;topluluğu da vardı.&amp;nbsp; Bu bağlamda Yassıçemen yenilgisinden sonra, çoğunluğu Kanglı&#x0D; ve Kıpçak Türklerinden müteşekkil Harezmli ordusu başıboş bir vaziyette Anadolu’ya dağılmıştı. Selçuklu ve Eyyubi hizmetine alınan bir grup&#x0D; Harezmlilerin Van ve çevresine iskân edildikleri yer adlarından&#x0D; anlaşılmaktadır. Ayrıca Selçuklu&amp;nbsp;fütühatıyla Azerbaycan’a gelen çok&#x0D; sayıda Oğuz boyunun&amp;nbsp;Moğol istilasıyla birlikte Doğu&#x0D; Anadolu’ya ve bilhassa Van Gölü Havzası’na akın ettiği kaynaklarda&#x0D; anlatılmaktadır. &#x0D; &#x0D; Bölgeye esas büyük nüfusun gelişi&#x0D; Hülegü’nün Batı seferi sonucunda olmuştur. Hülegü’nün ordusunda başta Uyrat,&#x0D; Sulduz, Celayir, Tatar, Sünit olmak üzere çok sayıda Moğol boyu vardı. Bu Moğol&#x0D; kabileleri Van Gölü’nün kuzeyindeki Aladağları yaylak olarak kullanıyorlardı.&#x0D; İlhanlı devletinin yıkılışından sonra da bölgede varlıklarını devam&#x0D; ettireceklerdir. Hülegü yöreyi stratejik öneminden dolayı Ahlat merkezli bir&#x0D; eyalet içerisine aldığı gibi bölgeye Türk ve Moğol boylarını da iskan etmiştir.&#x0D; Akkoyunlu&amp;nbsp;ve Kara Koyunlu&amp;nbsp;Türkmenlerinin de Moğol istilasıyla geldikleri&#x0D; düşünülürse Van Gölü Havzası’nın demografik yapısının nasıl teşekkül ettiği&#x0D; daha iyi anlaşılmaktadır.&#x0D; &#x0D; Yukarıda bahsi geçen Türk-Moğol&#x0D; boyları, önce İlhanlı devleti içerisindeki taht mücadeleleri, ardından devletin&#x0D; yıkılmasıyla başlayan hâkimiyet mücadeleleri ve nihayet Kara Koyunlu ve&#x0D; Akkoyunlu mücadeleleri sonucunda başta İran ve Orta Anadolu olmak üzere çevreye&#x0D; göç edeceklerdir.&amp;nbsp;

Generic assignment of Leuciscus kurui Bogutskaya from the upper Tigris drainage, and a replacement name for Alburnus kurui Mangit Yerli (Teleostei: Leuciscidae).

The generic position of Leuciscus kurui Bogutskaya, 1995 is reviewed through a comparison of morphological and molecular characters (COI). The molecular data place L. kurui in Alburnus, close to Alburnus timarensis from the Lake Van basin. Alburnus kurui (Bogutskaya) is distinguished from this species by lacking a ventral keel and possessing both a very low number of gill rakers and midlateral scales. Alburnus selcuklui, from the upper Tigris drainage, cannot be distinguished from the widespread A. sellal and is therefore treated as a synonym of this species. Alburnus kurui Mangit Yerli, 2018 is a junior secondary homonym of A. kurui (Bogutskaya, 1995) and A. carianorum is proposed as its replacement name. Several specimens of Alburnus caeruleus and Alburnus heckeli shared the same haplotypes as some A. sellal and therefore these species cannot always be distinguished by mitochondrial molecular characters. Alburnus caeruleus and A. heckeli are treated as valid species. Other individuals of A. caeruleus have haplotypes very different from A. sellal, and A. heckeli is well distinguished from A. sellal by having more gill rakers. The Lake Van basin as a separate freshwater ecoregion and the treatment of several species of Alburnus in synonymy of A. mento are discussed.

Controls on Cyclic Formation of Quaternary Early Diagenetic Dolomite

AbstractThe origin of sedimentary dolomite and the factors that control its formation within the geological record remain speculative. In most models, dolomite formation is linked to evaporative conditions, high water temperature, increasing Mg/Ca ratio, increasing alkalinity, and high amounts of biomass. Here we challenge these archetypal views, by documenting a case example of Quaternary dolomite which formed in Lake Van at constantly low temperature (&lt;4°C) and without direct control of the latter conditions. Dolomite occurs within highstand sediments related to suborbital climate variability (Dansgaard‐Oeschger cycles). We propose that dolomite precipitation is a product of a microbially influenced process, triggered by ecological stress, resulting from reventilation of the water‐sediment interface. Independently from the validity of this hypothesis, our results call for a reevaluation of the paleoenvironmental conditions often invoked for early diagenetic dolomite‐rich intervals within sedimentary sequences and for caution when interpreting time series of subrecent lacustrine carbonates.

Inhibitory properties of some heavy metals on carbonic anhydrase I and II isozymes activities purified from Van Lake fish (Chalcalburnus Tarichi) gill.

In this study, CA I and II isoenzymes were purified from Van Lake fish gills by using Sepharose-4B-L-tyrosine-sulfanilamide affinity chromatography and to determine the effects of some metals on the enzyme activities. For purified CA I isoenzyme, yield, specific activity, and purification fold were obtained as 42.07%, 4948.12 EU/mg protein, and 116.61 and for CA II isoenzyme, 7%, 1798.56 EU/mg protein, and 42.38 respectively. Activity of CA was determined by measuring "CO2-hydratase activity". Purity control was checked by SDS-PAGE. In vitro inhibitory effect of Cu2+, Ag+, Cd2+, Ni2+ metal ions, and arsenic (V) oxide were also examined for both isozymes activities. Whereas Cu2+, Ag+, Cd2+, and Ni2+ ions showed inhibitory effects on both isozymes, arsenic (V) oxide showed activation effect. IC50 values were calculated by drawing activity %-[I] graphs for metal ions exhibiting inhibitory effects. IC50 values were determined as 3.39, 6.38, 13.52, and 206μM for CA I isozyme and 6.16, 20.29, 46, and 223μM for CA II isozyme respectively.

Investigating the effect of hydroclimatological variables on Urmia Lake water level using wavelet coherence measure

Abstract In this paper, wavelet transform coherence is implemented to examine the impacts of hydroclimatological variables on water level fluctuations in two large saline lakes in the Middle East with a similar geographical location, namely, Urmia Lake in north-west Iran, which has an extremely simple ecological pyramid where water level decrease produces a very sensitive ecosystem, and Van Lake in north-east Turkey. The present study investigates trends in higher order moments of hydrological time series. The aim of this paper is to investigate the complexity of Urmia Lake water level time series which could lead to decrease fluctuations of time series. To this end, the strength and relationships between five hydroclimatological variables, including rainfall, runoff, temperature, relative humidity, as well as evaporation and water level fluctuations in the lakes were determined and discussed in terms of high common power region, phase relationships, and local multi-scale correlations. The results showed that among the hydroclimatological variables, runoff has the most coherencies (0.9–1) with water level fluctuations in the lakes. Although both lakes are located in a similar climatic region, for the recent 15 years, adverse trend in water level fluctuations of Urmia Lake indicates a critical condition for this lake.

Relationships between soil properties, topography and land use in the Van Lake Basin, Turkey

The objective of this study was to determine the relationship between soil properties and different topography and land uses in the Van Lake Basin, Turkey. It has sharp and sheer slopes, and the big differences on altitude generally occur from the mountainous formations. Surface soil samples (0–20 cm) were taken from 40 different points with three different topography (backslope, footslope and terrace) and three different landuses (wheat, clover and pasture). Some of the studied soil properties (soil texture, electrical conductivity [EC], pH, lime content, organic matter content, macro and micro nutrients) changed in response to land use and topography. The clay, boron content, pH and EC values increased from the backslope to the terrace. Soil organic matter and EC values were lower in cultivated wheat and clover fields than in uncultivated pasture. The EC values had significant positive correlations with CaCO 3 , organic matter, K, B, Cu contents at 5% level and with Mg at 1% level statistically. The soil nutrient contents of cultivated wheat and clover fields were generally lower than the uncultivated pasture. The nutrient contents of soils in cultivated fields decreased due to nutrient uptake by crops. Soil texture, EC, pH, lime, organic matter and nutrient contents significantly varied in different topographic positions due to leaching, transporting and accumulation.

Discrimination of Holocene tephra units in Lake Van using mineral magnetic analysis

Detailed magnetic analysis of the four sediment cores from Lake Van, Eastern Turkey dating back to 9.4 cal ka BP were carried out for discriminating and correlating tephras and laminated sediments in four different cores. Six tephra units (T0, T1, T2, T3, T4 and T5) with distinct magnetic properties were identified in the cores. The tephra units are characterized by ferrimagnetic material, with a grain size in the pseudo single domain (PSD) range. There is no significant correlation between magnetic susceptibility peaks of the different tephra units except for the tephra T1 and T2. On the contrary ARM profiles show significant correlations as remanent magnetization indicators. The tephra units T1 and T2, have a higher magnetic susceptibility and a higher intensity of remanent magnetization, and finer grain size than the other tephra units. The results suggest that there is a clear difference between the magnetic properties of the different tephra units and the lake sediments. Our findings show that also differential deposition of volcanic material including magnetic mineral occurs during the transport with distance from the volcanic source.

A new species of Enchytraeus (Enchytraeidae, Oligochaeta) from the profundal of Lake Van, the world's largest soda Lake (Turkey, East Anatolia).

Enchytraeus polatdemiri sp. nov. (Enchytaeidae, Oligochaeta) was discovered in the framework of a sampling campaign of the benthic invertebrate fauna of the hyperalkaline Lake Van in Eastern Anatolia, Turkey, the third-largest closed lake and the largest soda lake on Earth. It was the only oligochaete species found in all samples. DNA sequencing included a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene, and a fragment of the nuclear histone 3 (H3) gene. For comparison, specimens from laboratory cultures of E. albidus Henle, 1837, a widespread and morphologically similar species, were sequenced as well. The new species differs from E. albidus in comparatively small body size, 2 or 3 chaetae per bundle, saddle-shaped clitellum, absence of a copulatory field between the male pores and vasa deferentia usually not extending beyond the clitellum. The individual gene trees of COI and H3, as well as the combined phylogenetic analysis of both trees, recovered Enchytraeus polatdemiri sp. nov. as a monophyletic group within the genus Enchytraeus, closely related to E. albidus, but with an average p-distance for COI of 14.5 %. E. polatdemiri sp. nov. may have evolved from a local population of Enchytraeus albidus, a species well-adapted to changing salinity conditions, or from a common ancestor into an extremophile species that dwells and reproduces in the profundal of a strongly alkaline soda lake.