Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, eastern Turkey

Quaternary Science Reviews xxx (2014) 1e20

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Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, eastern Turkey €g
atay a, b, *, N. O
retmen a, c, E. Damcı a, c, M. Stockhecke d, e, Ü. Sancar a, b, M.N. Çag a, c € K.K. Eris¸ f, S. Ozeren a _
a Kampusu, 34469 Maslak, Istanbul Technical University, Eastern Mediterranean Centre for Oceanography and Limnology (EMCOL), Ayazag _ Istanbul, Turkey b _ Istanbul Technical University, Faculty of Mines, Geological Engineering Department, Turkey c _ Istanbul Technical University, Eurasia Institute of Earth Sciences, Turkey d Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Surface Waters Research and Management, Switzerland e ETH, Geological Institute, Zurich Universitaetsstrasse 5, 8092 Zurich, Switzerland f
, Turkey Fırat University, Department of Geological Engineering, Elazıg

a r t i c l e i n f o

a b s t r a c t

Article history: Received 5 August 2013 Received in revised form 14 September 2014 Accepted 29 September 2014 Available online xxx

Sedimentary, geochemical and mineralogical analyses of the ICDP cores recovered from the Northern Basin (NB) of Lake Van provide evidence of lake level and climatic changes related to orbital and North Atlantic climate system over the last 90 ka. High lake levels are generally observed during the interglacial and interstadial periods, which are marked by deposition of varved sediments with high total organic carbon (TOC), total inorganic carbon (TIC), low detrital influx (high Ca/F) and high d18O and d13C values of authigenic carbonate. During the glacial and stadial periods of 71e58 ka BP (Marine Isotope Stage 4, MIS4) and end of last glaciationedeglaciation (30e14.5 ka BP; MIS3) relatively low lake levels prevailed, and grey homogeneous to faintly laminated clayey silts were deposited at high sedimentation and low organic productivity rates. Millennial-scale variability of the proxies during 60e30 ka BP (MIS3 is correlated with the Dansgaard eOeschger (DeO)) and Holocene abrupt climate events in the Atlantic. These events are characterized by laminated sediments, with high TOC, TIC, Ca/Fe, d18O and d13C values. The Lake Van NB records correlate well in the region with the climate records from the lakes Zeribar and Urmia in Iran and the Sofular Cave in NW Anatolia, but are in general in anti-phase to those from the Dead Sea Basin (Lake Lisan) in the Levant. The relatively higher d18O values (0 to
0.4‰) for the interglacial and interstadial periods in the Lake Van NB section are due to the higher temperature and seasonality of precipitation and higher evaporation, whereas the lower values (
0.8 to
2‰) during the glacial and stadial periods are caused mainly by relative decrease in both temperature and seasonality of precipitation. The high d18O values (up to 4.2‰) during the Younger Dryas, together with the presence of dolomite and low TOC contents, supports evaporative conditions and low lake level. A gradual decrease in the d18O values from an average of
0.4‰ during the humid early Holocene to an average of
3.5‰ during the more arid late Holocene suggests an increasing contribution of winter precipitation. The changes in the seasonality of precipitation in eastern Anatolia are probably caused by changes in the temperatures of North Atlantic and Mediterranean and in the strength of Siberian High. © 2014 Elsevier Ltd. All rights reserved.

Keywords: Lake Van Northern Basin Multproxy analyses 90 ka climate records Lake level ICDP PaleoVan

1. Introduction

_ * Corresponding author. Istanbul Technical University, Eastern Mediterranean
a Kampusu, 34469 Centre for Oceanography and Limnology (EMCOL), Ayazag _ Maslak, Istanbul, Turkey. Tel.: þ90 (0) 212 2856211; fax: þ90 (0) 212 285 6080.
atay). E-mail address: [email protected] (M.N. Çag

Lake Van is located at an altitude of 1648 m above sea level (masl) on the East Anatolian Plateau in eastern Turkey (Fig. 1a). The lake is surrounded by Quaternary Volcanoes of Nemrut (2948 masl) and Süphan (4058 masl) to the west and north, and the Bitlis metamorphic massif (3500 masl) to the south. The East Anatolian

http://dx.doi.org/10.1016/j.quascirev.2014.09.027 0277-3791/© 2014 Elsevier Ltd. All rights reserved.


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

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atay et al. / Quaternary Science Reviews xxx (2014) 1e20

Fig. 1. (a) Google Earth map of Lake Van on the Eastern Anatolian plateau, showing drainage basin, location of the ICDP Northern Basin (NB) and Ahlat Ridge (AR) drilling sites (stars), Nemrut and Süphan volcanoes, Mus¸ basin, Bitlis massif, Kotum sill, Tatvan basin, Northern ridge (NR) separating the Northern Basin from rest of Lake Van, and the depositional coastal terraces (polygons; TK: Kotum, TA: Adilcevaz, TE: Ercis¸, TME: Muradiye-Erçis road, TKV: Karasu Valley, TB: Beyüzümü, TEG: Engil, Gevas¸). Also shown are the outcrops of Adilcevaz Limestone (AL) and marbles of the Bitlis Massif (Mrb) (from S¸enel and Ercan, 2002). (b) Inset map shows plates, plate boundaries and plate motions in Eastern Mediterranean, and locations of Van, Konya, Urmia and Zeribar lakes, RV Marion Dufresne core 9501, Sofular and Soreq caves, and S¸enyurt meteorological station (SY).

Plateau was uplifted starting around 12 Ma, as a result of collision of €r and Yılmaz, 1981; Arabian plate with the Eurasian plate (S¸engo € r et al., 2003, 2008; Dewey et al., 1986; Keskin, 2003; S¸engo Sumita and Schmincke, 2013a). Lake Van occupies the eastern part of the Van e Mus¸ depression that evolved as a pull-apart basin during the neotectonic regime of Turkey when the North and East Anatolian faults formed and Anatolian Block started its westward €r and Yılmaz, 1981). The depression was motion (Fig. 1b; S¸engo separated into Van and Mus¸ basins by the eruptions of the Nemrut Volcano, and thereafter the Van Basin started accumulating fresh waters at ca 600 ka BP (Yılmaz et al., 1998; Litt et al., 2012a; Sumita and Schmincke, 2013a; Stockhecke et al., 2014b). Lake Van is the fourth largest terminal lake and largest soda lake on earth having a volume of 607 km3, area of 3570 km2 and a maximum depth of ca 450 m (Degens and Kurtmann, 1978). The deepest part of the lake is the Tatvan Basin in the southwest, which has a roughly circular shape with a diameter of ca 25 km (Fig. 1a). The Tatvan Basin is separated from the ~410 m-deep small Ahlat subbasin and 260 m-deep Northern Basin (NB) by the NEE-trending Ahlat (AR) and Northern ridges having elevations of 300e370 m and 75e200 m below the present lake level, respectively (Çukur et al., 2014, this volume). Lake waters have a salinity of 21.4‰ and a pH of 9.81 (Landmann et al., 1996a; Kempe et al., 2002; Reimer et al., 2009). Lake Van is presently a monomictic lake and anoxic below 300 m (Kipfer et al., 1994; Peeters et al., 2000; Reimer et al., 2009; Stockhecke et al., 2012). Van region has a continental climate with cold and wet winters and warm and dry summers. Lake's surface water temperatures range from 21 to 25  C in summer and 2 to 7  C in winter (Kavak and
an, 2012). The annual precipitation is ~400 mm/yr. The Karadog total fresh water input by direct precipitation and river runoff is 4.2 km3/year (Degens and Kurtmann, 1978), which mostly occurs as
lu et al., winter snow and rain and river runoff in spring (Kadıog 1997). The freshwater influx reaches maximum levels in late spring and early summer by snow melting on the surrounding mountains. Lake Van has no outflow: its shallowest possible outflow channel is the Kotum valley in the southwest with a sill elevation of 1737 masl, 90 m above the present lake level (Fig. 1a)

(Schweizer, 1975). Measurements since 1944 have shown that the lake shows inter-annual lake level variations ranging from a minimum of 1646.69 masl in January 1963 to a maximum of _ I., _ 1996, 2008). Kempe et al. (1978) 1650.55 masl in June 1995 (E.I.E. related the recent lake level changes mainly to sun spot cycles with a periodicity of 10e11 years. Presently lake level shows seasonal average variation of 42 cm. Lake Van is situated in a key continental position at the crossroads of North Atlantic, Siberian high pressure and mid-latitude subtropical high pressure systems near the boundary between the continental Eastern Anatolian and continental Mediterranean zones (Türkes¸, 1996; Türkes¸ and Erlat, 2003; Ünal et al., 2003; Akçar and Schlüchter, 2005). The lake is affected mainly by subtropical and polar air masses, with migration of the subtropical jet northwards over Mediterranean Sea in summer and southwards over North Africa in winter. This seasonal migrating pattern results in hot and dry summers and cold and wet winters in the Eastern Mediterranean region in general and in eastern Anatolia in particular (Türkes¸ and Erlat, 2003). The strong sensitivity of the Lake Van to climate change has long been established. Its continuous, wellpreserved varved sedimentary sequence of the late PleistoceneeHolocene (last ~20 ka BP) age shows climatic and related lake level changes (Kempe and Degens, 1978; Lemcke, 1996; Landmann et al., 1996a,b, 2011; Kempe et al., 2002; Wick et al., 2003; Litt et al., 2009, 2014, this volume). Lake levels higher than today have been evidenced by the widespread presence of lake terraces located up to 107 m above the present lake level around Lake Van (Valeton,
lu et al., 2010). According to 1978; Kempe et al., 2002; Kuzucuog
lu et al. (2010), important transgressions with high lake Kuzucuog levels occurred sometime before 105 ka BP (1755 masl), between 100 and 35 ka BP (1730e1735 masl), between 26 and 24.5 ka BP (1700e1705 masl) and between 21 and 20 ka BP (1700e1705 masl). With its annually laminated (varved) sediments and location at the crossroads of the different climate systems in the Near East, Lake Van became the target of International Continental Drilling Program (ICDP) “PaleoVan” Project since 2004 (Litt et al., 2009). Two sites (Ahlat Ridge and Northern Basin) in the western part of Lake Van were drilled in 2010 within the framework of PaleoVan


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

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atay et al. / Quaternary Science Reviews xxx (2014) 1e20

Project (Fig. 1a). The main objective was to recover sedimentary records of several glacialeinterglacial cycles (Litt et al., 2011, 2012a; Litt and Anselmetti, 2014, this volume). The Ahlat Ridge drillholes extend 220 m composite below the lake floor (mcblf) at
365 m and covers the last 600 ka years record confirming the sensitivity of Lake Van to past climate changes (Stockhecke et al., 2014b; Litt and Anselmetti, 2014, this volume). The present study documents the results of multiproxy analyses of 144.5 m-long (composite) cores recovered from four boreholes drilled at
245 m in Northern Basin (NB) site, extending back to 90 ka. Our main objective is to reconstruct the lake level and palaeoclimatic changes over the last 90 ka. The multiproxy analyses involves stable oxygen and carbon isotopes, total organic carbon (TOC), total inorganic carbon (TIC) and m-XRF elemental and XRD mineralogical analyses. The resolution of our multi-proxy data on average ranges from about 300 years for the TOC, TIC and stable isotopes to ~3 years in the case of m-XRF analysis. The age model for the composite section is based on six AMS radiocarbon datings of terrestrial plant remains (this study) and tephrochronology established by Sumita and Schmincke (2013b) and (Stockhecke et al., 2014a, this volume) using 40 Ar/39Ar dating and Landmann et al. (2011) using varve counting. We compare our NB Lake Van multiproxy records with the global and regional records, including NGRIP ice core (NGRIP, 2004); Sofular Cave (nothwestern Turkey) (Fleitmann et al., 2009); Zeribar and Urmia lakes (Iran) (van Zeist and Bottema, 1977; Stevens et al., 2001; Synder et al., 2001; Wasylikowa, 2005; Djamali et al., 2010), and Dead Sea (Lake Lisan) (Israel) (Bartov et al., 2002; Stein et al., 2010; Litt et al., 2012b) records (Fig. 1b). 2. Materials and methods 2.1. Northern Basin ICDP cores A total of four parallel boreholes were drilled and a gravity core was recovered from the Northern Basin (NB) ICDP site (38.705 N/ 42.567 E) at water depth of
245 m in 2010 (Fig. 1a). The holes reached a composite depth of 145.49 mcblf. The composite record includes some gaps due to incomplete core recovery at intervals corresponding to tephra levels. These levels include 61e68 mcblf, 110e113 mcblf, 123e130 mcblf, and 135e141.5 mcblf. The cores were described, photographed, and then sampled using U-channel and discrete sampling in the Marum IODP-ICDP Core Repository in Bremen, Germany. The discrete samples were collected on average at every 10 cm from the lacustrine sedimentary facies (laminated clayey silt and homogenous clayey silt facies), with exclusion of the event deposits (mass flow and tephra units). The U-channel samples were used for m-XRF elemental analysis and the discrete samples for the TOC, TIC, XRD mineralogical and stable isotope analyses. 2.2. Geotek Multi-Sensor Core Logger analysis Magnetic susceptibility and gamma density were measured in the Ahlat field camp at 2 cm resolution according to the standard procedures, using a Geotek Multi-Sensor Core Logger (MSCL) (Weaver and Schultheis, 1990). The MSCL data were smoothed by computing10-point moving averages before plotting against the stratigraphic age. 2.3. m-XRF core scanner elemental analysis The Lake Van NB cores were analysed for multi-element composition at 5 mm resolution using Itrax XRF Core scanner equipped with XRF-EDS, X-Ray radiography and RGB colour camera

3

(Thomson et al., 2006). A fine focus Mo X-ray tube was used as the source. The X-ray generator was operated at 40 kV and 50 mA, and a counting time of 10 s was used for the m-XRF elemental analysis. Semiquantitative elemental concentrations were recorded as counts per second (cps). The m-XRF Ca/Fe values were smoothed by computing 100-point moving averages, and the averaged data were plotted against the stratigraphic age. 2.4. XRD mineralogical analysis Semi-quantitative mineralogical analysis of 49 powdered bulk sediment samples were analysed using a Bruker D8 Advance XRD (X-ray diffraction) instrument equipped with a Lynxeye detector. The samples, selected on the basis of the oxygen isotope analysis, were mounted on concentrically grooved sample holders made of polymethyl methacrylate (PMMA) having 25 mm diameter. Samples were analysed using Cu Ka radiation and operating conditions of 30 kV, 40 mA, D 2Ɵ ¼ 0.00571346 step-size and 0.1 s scanning speed. Mineral identification was made using the search and match programme for the major characteristic mineral reflections, and semi-quantitative estimation of the relative mineral percentages were calculated from the peak heights of the principal reflections of the minerals detected in the samples, using MacDiff programme (V4.2.5) (Petschick, 2000). 2.5. Total organic carbon (TOC) and total inorganic carbon (TIC) analyses TOC and TIC contents of freeze-dried samples were analysed using a Shimadzu TOC/TIC analyser. Total carbon (TC) content of samples was measured by burning the sample at 900  C and measuring the evolved carbon dioxide. TIC was analysed by treating the samples with 85% phosphoric acid, heating the sample to 200  C and measuring the evolved carbon dioxide. The TOC content was calculated as the difference between the TC and TIC contents. The precision of both analyses was better than 2% at 95% confidence level. The TOC and TIC data were smoothed by computing threepoint moving averages, and the averaged data were plotted against the stratigraphic age. 2.6. Stable oxygen and carbon isotope analyses Oxygen and carbon isotope ratios of the bulk carbonate fraction (d18Oc and d13Cc) of 298 lake sediment samples (excluding the event deposits) and four samples of Lower Miocene Adilcevaz Limestone in the western drainage area of Lake Van were measured using an automated carbonate preparation device (KIEL-III) coupled to a gasratio mass spectrometer (Finnigan MAT 252). Powdered bulk samples were reacted with dehydrated phosphoric acid under vacuum at 70  C. The isotope ratio measurement was calibrated based on repeated measurements of NBS-19 and NBS-18. The precision of the method was ±0.1‰ for d18Oc and ±0.06‰ for d13Cc (1s). The d18Oc and d13Cc data were smoothed by computing threepoint moving averages, and both the raw and averaged data were plotted against the stratigraphic age. 2.7. Radiocarbon analysis Accelerator Mass Spectroscopy (AMS) radiocarbon (14C) analyses of six terrestrial plant remains (twigs) were made at Woods Hole NOSAMS facility (Table 1). The 14C ages were calibrated to calendar ages using INTCAL option of CALIB programme V. 6 (Reimer et al., 2004; Stuiver et al., 2005).


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

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Table 1 AMS radiocarbon ages obtained from terrestrial plant fossils in the Northern Basin site. C age ±1s (years)

Hole-section, core depth (m)

Laboratory number

Composite depth (m)

14

A1-H1, 0.98 A5-H2, 0.10 A11-H1, 0.09 C11-H2, 0.7 C12-H1, 0.09 C15-H2, 1.02

OS-89765 OS-89728 OS-89523 OS96476 OS-96763 OS-96498

1.12 13.80 31.12 34.31 35.68 78.38

645 3880 15,300 16,450 17,200 29,900

± ± ± ± ± ±

30 45 45 160 150 920

C age ±1s (years) 14

610 4330 18,580 19,715 20,600 34,250

± ± ± ± ± ±

48 78 69 418 554 1040

3. Results 3.1. Lithology Four lithofacies are discerned in the 145.49 m-long composite stratigraphic section of the NB site, based mainly on visual observations. These are: a) banded and/or laminated silt, b) homogeneous clay-bearing silt, c) tephra, and d) graded (turbiditic) sandesilt (Fig. 2). The first two of the lithofacies were deposited by normal lacustrine sedimentation, whereas the last two by event sedimentation. In addition to their sedimentary structures, the four lithofacies are distinguished by distinct physical properties (magnetic susceptibility and density) and chemical composition (m-XRF major and minor elemental and TOC/TIC contents). Locally, some intervals of the NB section show soft sediment deformation structures formed by sliding and slumping, which are classified under “deformed units”. The laminated clayey silt lithofacies is one of the two normally deposited lacustrine sedimentary facies of Lake Van, and consists commonly of orange-brown and red, and less commonly grey, green and yellow tinted silt with subordinate amounts of clay (i.e., clayey silt) (Fig. 2). The laminae are sub-mm thick and the bands are few cm thick (Figs. 3 and 4). This lithofacies is relatively enriched in TOC (average: 2.64 ± 1.22 wt%, 1s) and TIC (average: 2.85 ± 0.88 wt %, 1s), and consists of clayesilt-organic matter-rich dark and carbonate-rich light lamina forming varves. Sediment trap and core studies shows that the dark coloured laminae is deposited during winter, whereas the light laminae during late spring, summer and autumn when Ca-rich freshwater inflow increased (Lemcke, 1996; Stockhecke et al., 2012). This lithofacies was deposited during warm and wet periods with high lake levels (Stockhecke et al., 2014b). The varved-structure indicates seasonal variation in temperature and precipitation (high seasonality). The distinctiveness of laminations is variable in different intervals of the NB, faint lamination indicating low seasonality. The total thickness of the laminated lithofacies in the NB site is 16.68 m, forming 13.3% of the total composite stratigraphic thickness. This lithofacies has low magnetic susceptibility (<20 SI), K (500e800 cps) and density (1.2e1.63 g/cm3), and low Ti (200e500 cps) and Zr (500e1000 cps), and high Ca (1e1.7  104 cps) contents, all suggesting low siliciclastic detritaland high carbonate-mineral contents. The laminated lithofacies is common in the interval representing last 14.5 ka (Fig. 2). Homogeneous clayey silt lithofacies is the other normal lacustrine sediment type of Lake Van, together with the laminated lithofacies (Fig. 2). It is commonly grey and consists mainly of silt-size particles with variable amounts of clay. In terms of grains size and colour, the homogenous silt lithofacies is similar to the homogenite part of the graded sandesilt lithofacies (see below). However, the two lithofacies are different in sedimentary textures and associations: the homogeneous clayey silt lithofacies is commonly interbedded with the laminated lithofacies, whereas the graded sandesilt lithofacies

Fig. 2. The Northern Basin (NB) composite stratigraphic section and pie plot showing the relative proportion of the different lithofacies and deformed units. Some important stratigraphic units (Nemrut Formation, Ahlat Pumice, Incekaya hyaloclastite) and MIS5/MIS4, MIS4/MIS3 and Pleistocene/Holocene boundaries are also shown on the section. The MIS-stage and Pleistocene/Holocene boundaries are based on correlations of NB multi-proxy records with NGRIP (NGRIP, 2004) and marine oxygen isotope (Lisiecki and Raymo (2005) records (see text for discussion). Note that the lower part of the composite section contains gaps due to problems in core recovery, encountered mainly in the tephra units.

shows size grading in its lower part and is associated with a basal turbiditic graded sand unit (Fig. 4). The homogeneous clayey silt lithofacies contains lower TOC (average: 2.10 ± 0.67 wt%, 1s) and TIC (average: 1.81 ± 0.74 wt%, 1s) contents than the laminated clayey silt lithofacies, and has intermediate magnetic susceptibility (50e150 SI), density (1.3e2.0 g/cm3), Ca (0.7e1 104 cps) and K (600e800 cps) values (Fig. 3), suggesting subequal amounts of siliciclastic- and carbonate-mineral contents. The homogenous clayey silt lithofacies constitutes 5.2% of the NB composite


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

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atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

Fig. 3. Core photograph, X-ray radiography, magnetic susceptibility, gamma density and m-XRF elemental profiles of the NB stratigraphic section between 16.96 and 18.20 mcblf, showing laminated clayey silt, graded sandesilt (turbiditeehomogenite, massflow), homogeneous clayey silt, tephra and deformed sediment lithofacies. The black tephra at 17.68 mcblf and graded coarse tephra at 17.6 mcblf have high magnetic susceptibility, K and Zr values and the basal coarse part of the graded sand silt units have high magnetic susceptibility and density values. Most tephra is redeposited as graded massflow units.

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6 M.N. Çag
atay et al. / Quaternary Science Reviews xxx (2014) 1e20


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

Fig. 4. Core photograph, X-ray radiography, magnetic susceptibility, gamma density and m-XRF elemental profiles of the NB section between 10.45 and 11.18 mcblf, containing a 55 cm-thick graded sandesilt (turbiditeehomogenite) unit (lithofacies). The coarse, graded basal layer has sharp and possibly erosional base and is characterized by high magnetic susceptibility and Zr values that decrease upwards indicating of the fining upward grain size. The homogeneous clayey mud part of the unit has homogeneous physical and chemical properties. Note the presence of a 12 cm-thick similar graded mass flow unit between 10.43 and 10.55 mcblf near the top and homogenous grey clayey mud unit near the base of the section.

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stratigraphic section. It was deposited during low lake levels, under oxic bottom waters, and cold and dry climatic conditions. This lithofacies correlates with banded clayey silt lithofacies of Stockhecke et al. (2014b). Graded sandesilt lithofacies was deposited by mass flow processes (turbidity currents). It is characterized by a sharp, and often erosional basal contact, overlain by a dark brown or grey graded sand in the lower part, a dark grey laminated very fine sandesilt in the middle, and grey homogeneous silt with some clay (homogenite) in the upper part (Figs. 3 and 4) (see also Stockhecke et al., 2014b). It is the most common lithofacies in the NB site, forming 60% of the composite stratigraphic section. The lithofacies is especially frequent in the intervals during 28e15.4 ka (57e23 mcblf) and ~33 ka BP (68.4e71.4 mcblf interval), following the depositon of the Nemrut Formation (Fig. 2). Many of the graded sandesilt units, especially those deposited at ~33 ka BP, are composed mainly of reworked tephra. Their thickness varies from a few cm to about 1.5 m. The graded sandesilt lithofacies consisting of dark-grey tephra material commonly have high density and magnetic susceptibility (ca 200e300 SI) values (Figs. 3 and 4). The uppermost homogeneous mud (homogenite) part of these units has TOC (average: 1.91 ± 0.46 wt%, 1s) and TIC (average: 1.92 ± 0.39 wt%, 1s) contents similar to those of the homogeneous clayey silt lithofacies, but lower than those of the laminated clayey silt lithofacies. Tephra lithofacies commonly consists of sand- and lapilli-size volcanoclastic material having a layer thickness ranging from a few mm to tens of cm in the NB section (Fig. 2). The colour is variable from black, dark grey to brown (Fig. 3). There are two types of tephra: airfall and reworked (re-deposited). The latter was deposited in the form of debris avalanches and turbidite units, and thus classified under graded sandesilt lithofacies. The proportion of the airfall tephra in the composite stratigraphic section is 12.6%. Mainly two types of tephra compositions can be distinguished on the basis of m-XRF elemental analysis: those enriched in Large Ion Lithophile Elements (LILE; e.g., K, Rb, Sr) and High Field Strength Elements (HFSE; e.g., Zr) having peralkaline magma affinity and those enriched in Ca, but relatively depleted in LILE, HFSE, K and Zr, displaying calc-alkaline affinity (Fig. 3). The major tephra layers of mainly airfall type occur within the intervals 5.70e7.85, 21.38e27.5, 31.20e36.30, 59e75, 102e102.5 and 134.5e135 mcblf (Fig. 2). Except for the second youngest and the oldest tephra intervals, all tephra is mainly trachytic in composition, and was extruded from the Nemrut volcano. The major tephra unit is the Nemrut Formation, which is located in the interval between 59 and 75 mcblf (dated between 33.7 and 28.6 ka BP; Sumita and Schmincke, 2013a,b). The second major tephra between 21.38 and 27.5 mcblf shows calc-alkaline affinity, which is most likely produced from the Süphan volcano (Fig. 1a). The lowest tephra (Incekaya hyaloclastite) between 134.5 and 135 mcblf is basaltic in composition with high in Ti and Fe contents, and was extruded as a fissure eruption in the south about 80 ka BP (Notsu et al., 1995; Sumita and Schmincke, 2013a,b; for teprochronological information see Section 3.2, Table 2). The tephra layers commonly contain pumice of different sizes. Because of the lighter density of pumice and its slow deposition from pumice rafts, some tephra units show reverse or density grading. The tephra layers, especially those containing dark grey to black pebble-to sand-size pumice, have the highest magnetic susceptibility values (>300 SI) (Figs. 3 and 4). Such layers are marked also by high gamma density. Deformed units are formed by slumping, sliding, and avalanching, mostly under subaqueous conditions. Some of them show convolute bedding, chaotic internal structure, and locally includes clasts of laminated and homogeneous clayey silt facies and

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Table 2 Chronostratigraphic data used for the age model of the NB site composite stratigraphic section. Dated material

Method and source

Land plant Tephra Tephra Land plant Tephra Tephra Pleis./Holoc. bound. Tephra Tephra Tephra Tephra Tephra Tephra Tephra Tephra Land plant Land plant Land plant Nemrut Form. Land plant Tephra Tephra Tephra Tephra Tephra Tephra Tephra Tephra Tephra Tephra Tephra Ahlat Pumice Tephra Tephra _ Incekaya pumice

AMS 14Ca Correlation, Correlation, AMS14C Varve, V4c Varve, V6c OI&14Cd Correlation, Correlation, Correlation, Correlation, Correlation, Correlation, Correlation, Correlation, AMS14Ca AMS14Ca AMS14Ca 40 Ar/39Are AMS14Ca Correlation, Correlation, Correlation, Correlation, Correlation, Correlation, Correlation, Correlation, Correlation, Correlation, Correlation, 40 Ar/39Are Correlation, Correlation, 40 Ar/39Arf

a b c d e f

b

V1 V2b

V8b,c V10b,c V11b,c V12b,c V13b,c V14a,c V15b,c V16a,c

V32b V33b V34b V35b V36b V37b V39b V40b V41b V42b V43b V53b V57b

Composite depth (mblf)

Age (years BP)

0.00 1.12 1.36 7.83 13.80 17.11 17.65 19.50 20.66 20.79 20.93 20.96 20.96 21.04 21.13 21.35 31.12 34.31 34.68 59.00e75.00 78.38 88.01 89.30 89.44 89.98 91.64 94.60 96.45 96.55 96.71 97.03 97.19 102.25 106.78 120.26 134.50e135.00


60 (2010) 610 ± 48 700 2350 4330 ± 78 7000 8150 11,690 12,960 13,250 13,460 13,490 13,510 13,530 13,580 14,070 18,580 ± 69 19,715 ± 418 20,600 ± 554 28,600e33,700 34,250 ± 1040 42,910 44,200 44,670 46,020 48,810 53,480 56,800 57,140 57,580 58,060 58,380 59,400 ± 10,000 64,360 70,610 80,000

This study. Stockhecke et al. (2014a, this volume). Litt et al. (2009), Landmann et al. (2011). Dansgaard et al. (1993), Gulliksen et al. (1998). Sumita and Schmincke (2013b). Notsu et al. (1995).

pumice in a volcanic matrix (Fig. 3). Liquefaction and water escape structures are common. This lithofacies is especially well represented in the intervals of 60.9e65.53 mcblf, 73.55e75.50 mcblf, 85.40e87.5 mcblf, 91.60e93.15 mcblf, 100.05e103.40 mcblf, 107.50e110 mcblf and 141.4e144.5 mcblf (Fig. 2). Deformed graded sandesilt units are present with greater frequency between 19.4 and 40.6 mcblf (11.5e24 ka BP). Slump and slide deposits consisting mainly of volcanic material have high magnetic susceptibility values (200e300 SI) (Figs. 3 and 4). 3.2. Chronology and age model The chronostratigraphy of the NB composite section is based on: (a) six calibrated AMS datings of terrestrial plant material from the NB section (Table 1); (b) correlation with varve chronology of previously recovered short cores (Litt et al., 2009; Landmann et al., 2011), correlated with the NB section, and (c) correlation with 40 Ar/39Ar ages of tephra layers on land sections and in Ahlat Ridge site ICDP cores (Sumita and Schmincke, 2013b; Stockhecke et al., 2014a, this volume, Stockhecke et al., 2014b) (Table 2). The chronostratigraphic data were used to construct an age versus composite depth model (Fig. 5). Event deposits (mass flow, tephra, and deformed lithofacies) thicker than 0.2 m were excluded from the


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carbonates, pyrite, and Fe-silicates and clay minerals) have relatively high MS values, whereas biogenic (carbonaceous and siliceous) and siliciclastic sediments consisting mainly of diamagnetic minerals (e.g., quartz and calcite, opal) have low and even negative MS values (Stoner et al., 1996). Early diagenesis in anoxic sediments can reduce MS values due to reduction of Fe-oxyhydroxides. In the NB site, high MS values correlate with either tephra levels, intervals rich in detrital input, or mass transport deposits of mainly tephra origin (Fig. 6). Very high MS values (up to 500 SI) are observed during 34e17 ka. Relatively high MS values occur in time intervals of 5.5 ka-present, 44e41 ka, 51e47, 80e65 ka and 87e84 ka. Some peaks and high values, such as those at 2 ka, 6.3 ka, 33e28 ka, 71e70 ka are related to the tephra layers. The high values during 33e28 ka correspond to the Nemrut Formation. An important feature of the gamma density and MS profiles is a change from relatively low values for the early-mid Holocene (9e6 ka BP) to high values for the late Holocene. 3.4. Total organic (TOC) and inorganic carbon (TIC) distributions

Fig. 5. The ageedepth model for the NB composite stratigraphic section obtained using AMS 14C (this study) and 40Ar/39Ar tephra ages (Sumita and Schmincke, 2013a,b; Stockhecke et al., 2014a, this volume) and varve ages of tephra (Litt et al., 2009; Landmann et al., 2011). Ages of marine isotope stage boundaries from Lisiecki and Raymo (2005). See Tables 1 and 2 for details.

ageedepth model. The upper and basal boundaries of the thick tephra layers, such as the Nemrut Formation (V-19 in the AR record; Stockhecke et al., 2014a, this volume), were given the same age obtained for the unit by Sumita and Schmincke (2013a,b). Considering sparse data, gaps in core recovery and the large error margin in the age of Incekaya hyaloclastite, we have drawn a straight line through the data points for the lower part of the stratigraphic section (Fig. 5). According to the age model, the NB composite section extends back to ~90 ka BP. The multi-proxy records (Ca/Fe, d18O, TOC, lithology) of the NB section plotted against the age show good temporal correlation with the global d18O records of ice, ocean, and lake cores (Dansgaard et al., 1993; Gulliksen et al., 1998; Kirby et al., 2002; NGRIP, 2004; Lisiecki and Raymo, 2005) (see Section 4.4). This indicates robustness of our age model. Our age model for the NB section differs somewhat from that of Stockhecke et al. (2014a, this volume), because in the latter “composite depth” and “eventfree composite depth” are used for age modelling.

TOC and TIC distributions along the NB composite stratigraphic section for the last 90 ka and 25 ka are given in Figs. 7a,b and 8a,b. The data resolution is 220 year/sample for the last 30 ka and 370 year/sample for the period 33e90 ka BP. The sampling resolution is particularly low in the intervals 82e90 ka BP, 80e75 ka BP, 33.5e29 and 20e14.5 ka BP, which are mainly due to high proportion of the event deposits and gaps in the core recovery. TOC and TIC contents of lake sediments are mainly a function of primary productivity (photosynthesis) and organic matter preservation during settling and burial. Organic productivity is favoured by warm and humid conditions and high lake levels during the periods of high surface runoff. Such conditions would promote water stratification, anoxic bottom waters, and organic matter preservation. In the NB section, such an interpretation is corroborated by the higher TOC and TIC contents for the interglacial periods such as the Marine Isotope Stage 1 (MIS1) and MIS5 than those for the glacial periods (MIS2 and MIS4) (Fig. 7a,b). The highest TOC values (>4wt %) are found in the intervals 4.9e4 ka, 6e5.5 ka, 7.8e6.4 ka, 51.5e45.5 ka, 72.0e70.5 ka and 80.5e74.5 ka BP. During the glacial periods MIS2 (24e11.5 ka BP) and MIS4 (59e71 ka BP), TOC values are commonly lower than 2.5 wt %. During 59e33 ka BP (the earlier part of MIS3), some intervals with relatively high TOC values (3e5 wt %) are observed. Highest TIC values (>4 wt %) occur during the Pleistocene/Holocene transition, mid-Holocene, and earlier part of MIS3 (51.5e32 ka BP) (Figs. 7b and 8b). TOC and TIC values for the NB section show significant positive correlation with each other for all MISs (r ¼ 0.43e0.85), except for the MIS2 for which no correlation exists between TOC and TIC (r ¼ 0.05). The highest correlation coefficient of 0.85 between TOC and TIC values is found for MIS5a-b. The TOC distribution in the NB section shows close similarity to the NGRIP ice core isotope distribution (NGRIP, 2004; Steffensen et al., 2008; Wolff et al., 2010) over the last 90 ka (Fig. 7a,f); the main exception being the higher variability of the NB data for the Holocene compared to the homogenous distribution of the NGRIP data (Fig. 8a,g).

3.3. Physical properties 3.5. XRD mineral composition MSCL magnetic susceptibility (MS) and gamma density measurements are standard methods used in for stratigraphic correlations between drill holes. Both properties depend on the mineral composition and grain size of the sediments, which are in turn related by the depositional conditions. Detrital sediments and tephra layers containing ferromagnetic (e.g. magnetite, haematite and greigite) and paramagnetic iron minerals (FeeTi oxides, FeeMn

Bulk mineralogical analysis of lake sediments provides information on the relative amounts of detrital and authigenic minerals. The amount of detrital mineral influx in the lake depends on weathering and erosion processes in the watershed, which are themselves controlled by the climate. Detrital (siliciclastic) mineral (e.g., quartz) influx would be higher during cold and dry periods


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Fig. 6. The Multi Sensor Core Logger (MSCL) magnetic susceptibility (a) and gamma density (b) profiles of the Northern Basin composite stratigraphic section, representing 10-point moving average data. The intervals with absence of data correspond to gaps related mainly to tephra layers.

with scarce vegetation than during warm and wet periods with dense vegetation. Authigenic carbonate-mineral composition provides useful information on chemical evolution of lake waters. In particular, aragonite and dolomite formation is favoured over calcite by high salinity and high molar Mg/Ca ratio, which are indicative of evaporative conditions (Mackenzie and Pigott, 1981; nchez and Gonza lez, Burton and, Walter, 1987; De Choudens-Sa 2009). Results of the XRD mineralogical analysis of 49 samples are plotted for the NB section, and together with the d13C ve d18O values, are presented in Fig. 9. Calcite is commonly the most abundant carbonate mineral with its relative abundance varying between 15 and 33% of the total major minerals (Fig. 9e). The mineral has particularly high abundances during 71.5 ka BP, 80 ka BP and 28e18 ka BP, and low relative abundances during 17 ka BP-present and 70e50 ka BP. Aragonite is the second most abundant carbonate mineral. It shows relatively high abundances during 15e4 ka BP (MIS1), 48e33.5 ka BP (MIS3) and 80e58 ka BP (mainly MIS4 and MIS5a), and low abundances during 58e48 ka BP, 33.5e15 ka BP, 33.5e15 ka BP and during the last 4 ka BP (Fig. 9d). Aragonite abundance correlates positively with the d18O and d13C values and negatively with dolomite and quartz abundances along the NB section (Fig. 9aef). These relations suggest the association of aragonite with evaporative phases of the lake. Dolomite is the least abundant mineral with its relative abundance varying between 3 and 54%. Relatively high (>10%) dolomite abundances are found at 4 ka, 11.5 ka, 42.5 ka, 48 ka, 50 ka and 51 ka (Fig. 9c), suggesting high salinity and Mg/Ca conditions during these periods. A minor fraction of the carbonate minerals detected by the XRD analysis is probably of detrital origin, the main possible source of which in the NB site is the Lower Miocene (Burdigalian) Adilcevaz Limestone that outcrop in the northwestern sector of the drainage basin (Fig. 1a). The limestone is highly fossiliferous, and has in part reef carbonate characteristics. The marbles in the Bitlis metamorphic massif in the south, Quaternary travertine deposits in the southeast and scattered small outcrops of PalaeoceneeEocene carbonates in the east and southeast are outside the watershed of the NB. 3.6. m-XRF Ca/Fe distribution The Fe concentration of lake sediments depends mainly on detrital mineral influx from the watershed, whereas the Ca concentration reflects the amount carbonate minerals (calcite,

aragonite and dolomite) precipitated authigenically from the alkaline waters. Therefore, CaeFe ratio shows mainly the authigenic carbonate amount versus detrital-mineral amount, which is in turn controlled by various factors, such as organic productivity, precipitationeevaporation (PeE) water balance, and density of vegetation cover in the watershed. m-XRF Ca/Fe profile along the NB composite stratigraphic section shows relatively high values during the Holocene, BøllingeAllerød (BeO; 15e13 ka BP), late MIS3 (45e33.5 and 28.5e24 ka BP) and MIS5a (75 and 73e70 ka) (Figs. 7e and 8e). During the Holocene, high Ca/Fe occurs during the period 0.5 ka to present, 4.4 ka BP, 5 ka BP, 6 ka, 6.7 ka BP, 7.5e7 ka BP, 9e8 ka BP and 9.8 ka BP (Fig. 8e). The ratio is low during MIS4 and early part of MIS3 (from 70 to 50 ka BP), and the main part of MIS2 from 23 to 14.5 ka BP, suggesting relatively low density of vegetation and high rate of erosion, and/or low carbonate deposition. 3.7. Stable oxygen and carbon isotope distributions In terminal lakes such as Lake Van, the main factors controlling the oxygen isotope composition of waters (d18Ow) and precipitating carbonates (d18Oc) are the water balance (EeP), temperature, seasonality of precipitation, vapour source and mineral composition of the carbonate fraction (Tarutani et al., 1969; Talbot, 1990; Talbot and Kelts, 1990; Li ve Ku, 1997; Cole et al., 1999; Gat et al., 2001; Stevens et al., 2001). The d13C value depends mainly on water balance, organic productivity and d13C value of the carbonate rocks in the watershed. The effects of the various factors on the d18O and d13C values of bulk carbonate in Lake Van sediments are discussed in Section 4.1. The d18O values of the Lower Miocene Adilcevaz Limestone, a possible source of detrital carbonate influx in the NB site, range between
3.5 and
5.3‰ and its d13C values uniformly gather around þ1‰ (Table 3). Even though the Adlicevaz Limestone does € not show any freshwater diagenesis (Ercan Ozcan, pers. Comm.), their d18O values are much lower than those of fully marine carbonates, which commonly range between 0 and þ3‰ (e.g., Wefer and Berger, 1991). The d18Oc and d13Cc values of bulk carbonate of 298 sampes from the NB composite section are plotted in Figs. 7c,d and 8c,d. The resolution of the data for the Holocene (MIS1), MIS2, MIS3 and MIS4 and MIS5a-b are 169, 240, 330, 375 and 512 year/sample, respectively. d18Oc values vary between
6.2 and þ4.2‰ over the last 90 ka, with the average of 1.1‰ and standard deviation (s) of 1.94‰. The d13Cc values change between
3.6 and þ6.8‰ (s ¼ ‰ 2.33). There is


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

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Fig. 7. TOC (a), TIC (b), d13Cc (c), d18Oc (d), and Ca/Fe (e) profiles along the NB composite stratigraphic section of Lake Van representing the last 90 ka. Also shown are the Northern Greenland Ice Project (NGRIP) d18O record (f) (NGRIP, 2004), and Sofular speleothem d18O record (NW Turkey) (g) (Fleitmann et al., 2009). In samples with relatively high dolomite at 4 ka, 11.5 ka, 42.5 ka, 48 ka, 50 ka and 51 ka, dolomite contribution to d18Oc value is 0.5‰, 1.3‰, 2.0‰, 1.1‰, 1.2‰, 0.5 and 0.6‰, respectively. HE: Heinrich event. The discontinuities in the Ca/Fe data represent the coarse tephra intervals where m-XRF analysis could not be performed.

a strong positive correlation between the d18O and d13C values for the last 90 ka as well as for different MISs, with a correlation coefficient (r) ranging between 0.65 and 0.97. The highest correlation is found for MIS4 and the lowest for MIS5. On a detailed time scale, this positive correlation between the d18Oc and d13Cc values is disturbed for the Younger Dryas (YD) and 10e8.5 ka BP periods. The d18Oc and d13Cc values also show significant positive correlations with TIC and TOC values, as observed from the general similarities in trends of their down core profiles (Figs. 7aed, 8aed). The d18Oc values (average ± 1s) for the 90e71 ka (MIS5a-b), 71e57 ka (MIS-

3), 57e30 ka, 30e14 ka BP (MIS2), 11e4 ka BP (early-middle Holocene), and 4 ka-present (late Holocene) periods are 0.01 ± 1.3‰,
0.78 ± 1.7‰,
0.40 ± 1.5‰,
1.97 ± 1.5‰,
0.44 ± 1.9‰ and
3.45 ± 1.8‰. The d18Oc values for the interglacial periods (MIS5a-b, MIS3 and early-middle Holocene) are therefore ~3e3.5 ‰ heavier than those for the late Holocene, 1.5e2 ‰ heavier than those for the MIS2, and ~0.5‰ heavier than those for the 71e57 ka BP (MIS-3). The Holocene d18O values fluctuate between
6.2 and þ1.5‰ (average:
2.40‰), with relatively high values (0 to þ1.5‰) during the early and middle Holocene. Superimposed on these long-term


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Fig. 8. TOC (a), TIC (b), d18Oc (c), d13Cc (d) and Ca/Fe (e) profiles along the NB composite stratigraphic section of Lake Van representing the last 30 ka. Also shown are Northern Greenland Ice Project (NGRIP) isotope record (f) (NGRIP, 2004) and Sofular speleothem (NW Turkey) oxygen (g) carbon (h) isotopes records (Fleitmann et al., 2009). In samples with relatively high dolomite at 4 ka and 11.5 ka, dolomite contribution to d18Oc value is 0.5‰ and 1.3‰, respectively. HE: Heinrich event. The discontinuities in the Ca/Fe data represent the coarse tephra intervals where m-XRF analysis could not be made.


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during which poor correlations exist between the two variables, The d13Cc values for MIS5a-b, 60e30 ka BP and the early Holocene are up to 5‰ greater than those for 70e60 ka BP (MIS4) and 30e14 ka BP (MIS2) periods. 4. Discussion 4.1. Factors affecting the stable isotope composition of bulk carbonate in Lake Van sediments

Fig. 9. Variation in relative proportion of major minerals (cef) and d18O (a) and d13C (b) values in the NB composite stratigraphic section of Lake Van. In samples with relatively high dolomite at 4 ka, 11.5 ka, 42.5 ka, 48 ka, 50 ka and 51 ka, dolomite contribution to d18Oc value is 0.5‰, 1.3‰, 2.0‰, 1.1‰, 1.2‰, 0.5 and 0.6‰, respectively.

changes, other abrupt short-term positive excursions occur during the YD and 60e30 ka BP (MIS3) (Fig. 8d). Downcore trends of the d13Cc values are commonly similar to that of d18Oc (Figs. 7c and 8d), except for the early Holocene and YD, Table 3 Oxygen and carbon isotope ratios of Lower Miocene Adicevaz Limestone from the western drainage basin of Lake Van. Sample No

d18O‰ VPDB

d13C ‰ VPDB

ENM13 ENM 17 ENM 20 ENM 49


3.9
4.7
5.3
3.5

1.2 0.8 0.9 1.0

In the Lake Van NB section, the d18Oc values for the interglacial periods MIS5, MIS3 and early to middle Holocene are ~2‰ higher and d13Cc values 3e4 ‰ higher than those for the later part of Last Glacial and Lateglacial (30e14 ka BP) periods (Figs. 7c,d and 8c,d). The high positive correlation between d18Oc, and d13Cc in the NB record suggests that these variables are controlled mainly by the amount of preciptation (P) and evaporation (E), and specifically the PeE balance in a closed lake (e.g., Talbot and Kelts, 1990; Li ve Ku, 1997; Roberts et al., 2008). The control of PeE balance on d18Oc in Lake Van, is further corroborated by the strong correlation between the aragonite content and d18Oc (see Section 4.2, Fig. 9c,f). However, in the Lake Van NB records, correlation of the high TOC and d18Oc values with high lake levels during interglacial periods suggest that other climate parameters such as moisture source, sea surface temperature (SST), lake water temperature, rainfall amount, continentality and seasonality may also affect lake water d18O (Rozanski et al., 1992; Bar-Matthews et al., 1999; Cole et al., 1999; Gat et al., 2001). The principal source of the moisture for the main winter precipitation in the Lake Van region is the storm tracts originating in the North Atlantic, which is strongly modified in the Eastern Mediterranean (Karaca et al., 2000). For spring precipitation, the Black Sea may also be a vapour source (Djamali et al., 2010; Roberts et al., 2011). Even though Eastern Mediterranean (EM) seawater has been considered to be an important source of vapour for the precipitation in eastern Anatolia (Karaca et al., 2000; Bozkurt and Sen, 2011), the values of d18OG. ruber from the EM and Lake Van d18Oc values show opposite trends, especially during the Last Glacial and Lateglacial periods (44e17 ka), with more tendency to correlate during interglacial periods of MIS5a-b, MIS3 and the early Holocene (Fig. 10a,c). This suggests that factors other than the source effect are important for the trends of Lake Van d18Oc values during the Last Glacial-lateglacial interval. The oscillations of the EM d18OG. ruber values over glacialeinterglacial intervals are attributed to changes in the River Nile input and SST (and insolation) (Almogi-Labin et al., 2009; Fig. 10a,b). The Lake Van NB d18Oc values correlate well with the Mediterranean SST and insolation (Fig. 9b,c). Both parameters conformably show a decreasing trend during 44e24 ka and 10e6 ka and an increasing one during 18e11 ka, suggesting a SST or insolation effect on the precipitation and lake water d18O values. This is supported by recent modelling studies by Bozkurt and Sen (2011) which show that an increases in the EM SSTs causes increased precipitation in eastern Anatolia. In general, temperature controls the isotopic composition of precipitation by condensation and isotope partitioning during phase transitions (i.e., evaporation and condensation) (Cole et al., 1999). Increase in temperature enriches the precipitation in the heavy isotope. The rate of enrichment for the Anatolian stations is between 0.6 and 0.7‰  C
1 (IAEA/WMO, 2014). Thus, a temperature decrease of 5e10  C from the interglacial to the Last Glacial would cause a 3e7 ‰ drop in the d18O values of the precipitation in the Lake Van basin. On the contrary, during interglacial/interstadial periods (e.g., MIS5a, MIS3 and DansgaardeOescher, DeO events),


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Fig. 10. a) d18OG. ruber values in RV Marion Dufresne core 9501, south of Cyprus (Almogi-Labin et al., 2009), b) insolation (65 N July) and SST curves determined by alkenone analysis in Eastern Mediterranean (grey shaded area; compiled by Almogi-Labin et al., 2009), and in Western Mediterranean (line drawing; Martrat et al., 2004) cores, c) d18Oc values (threepoint moving average) of Lake Van NB stratigraphic section. For position of the RV Marion core, see Fig. 1a.

the temperature increase would cause an increase in the d18O value of precipitation input into the lake, and/or evaporative enrichment of the heavy isotope. Another important factor to consider is the elevation effect that causes relative enrichment of 16O in the snow falling on the mountainous catchment areas surrounding Lake Van. Melting of snow cover on the mountains particularly at the glacial/interglacial and stadial to interstadial transitions would provide isotopically light waters to Lake Van (Kwiecien et al., 2014, this volume). Seasonal variations in the amount and isotopic composition of precipitation over glacialeinterglacial cycles are also a possibility in continental regions, such as eastern Anatolian Plateau (e.g., Jouzel et al., 1997; Stevens et al., 2001). In the S¸enyurt ~150 km northwest of Lake Van (Fig. 1a), the modern weighted isotopic mean of precipitation d18O is
9.6‰ VSMOW (1s ¼ 5.65‰) (IAEA/WMO, 2014), with a considerable enrichment of 16O reflecting the preferential rain out of the 18O because of the high seasonality, altitude and continentality of the region. Seasonality of precipitation is therefore an important factor to consider. For example, Stevens et al. (2001) estimate that a reasonable reduction in spring and summer precipitation and increase in winter precipitation at S¸enyurt northwest of Lake Van (Fig. 1b) would result in a negative shift of 3.6‰ in the weighted annual d18O value of precipitation. Thus, such a shift in the seasonality of precipitation would further contribute to the relatively low d18O values observed during the 70e63 ka BP (MIS4) and 33.5e14.5 ka BP (Last Glacial to deglaciation period) and the late Holocene in the NB record. The d13Cc value depends mainly on water balance, organic productivity and d13C value of the carbonate rocks in the watershed. Water balance has similar effect on d13C values as it has on the d18Oc values, with the d13Cc values becoming more positive with increase in the EeP balance (e.g., Talbot and Kelts, 1990; Li ve Ku, 1997). Increase in organic productivity (eutrophication) in a lake results in more positive d13C values of lake waters. This is especially marked for the early Holocene for which the highest TOC (organic productivity) and d13C values and low correlation between the d18O and d13C values are observed (8a,c). Beside the isotopic composition of lake water, the bulk authigenic carbonate d18Oc values of lake sediments is controlled by both the temperature of carbonate precipitation and the carbonate mineral composition. The d18Oc value of precipitating carbonate

mineral is enriched over that of dissolved inorganic carbon, and is inversely related the temperature of precipitation. The rate of decrease in d18Oc for calcite is 0.23‰  C
1 (O'Neil et al., 1969). Inorganic aragonite is enriched in d18O, relative to calcite, by about 0.6‰ (Tarutani et al., 1969); the temperature effect on the d18Oc value of aragonite is similar to that of calcite (Grossman and Ku, 1986). In contrast to the small difference between the oxygen isotope fractionation of calcite and aragonite, there is large fractionation effect for dolomite, relative to calcite, by 3‰ (Land, 1980). Temperature fractionation effect on d13C of calcite is much smaller than that on d18O, with d13C values becoming lighter at 0.035‰  C
1 (Emrich et al., 1970). The temperature dependency for aragonite is the opposite to that of calcite (Grossman and Ku, 1986). The effect of Mg content in calcite on carbon isotope fractionation is an increase at 0.06‰  C
1 (Tarutani et al., 1969). As explained in Section 3.5, the carbonate minerals in the NB section consist mainly of calcite and aragonite with local occurrence of dolomite (Fig. 9cee). Especially the presence of dolomite may complicate the interpretation of the d18Oc values, because of the large isotope fractionation effect for the mineral. For this reason, some workers adjusted d18Oc values by subtracting the contribution of dolomite in proportion of its relative amount (e.g., Roberts et al., 2001). In the NB section, the high dolomite contents correlate with high d18Oc values (Fig. 9a,c), and thus most probably related to high evaporation. There are six samples containing greater than 10% dolomite. Contribution of dolomite to the overall d18Oc value in those samples ranges from 0.5‰ (at ~5 ka BP) to 2.0‰ (at ~42 ka BP). The contribution to the maximum d18Oc value of 4.2‰ marking the Pleistocene/Holocene transition is þ1.3‰ (Fig. 9a,c). The additional factor is the temperature; assuming shifts of
5  C for the YD (Dansgaard et al., 1993) and 10  C for the Last Glacial, the temperature effect on the overall d18O value of precipitation during the YD and the Last Glacial would be þ1.1 and þ2.2‰, respectively. Conversely, during interglacial stages the increase in the average temperature of carbonate precipitation would lower the d18O value of authigenic carbonates. However, the effect of increasing temperature on calcite-water fractionation (decrease), would be much smaller than its effect (increase) on the d18O values of precipitation over glacialeinterglacial cycles in Lake Van region.


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

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The theoretical d18O value of modern carbonate precipitating from Lake Van is 0.93‰ VPDB (Lemcke and Sturm, 1997), and the measured d18Oc value of the most recent carbonate is 0.6‰ VPDB (this study) and 0.78 ‰ VPDB (Lemcke and Sturm, 1997). The small differences between these measured and theoretical values can be explained by local differences in temperature of precipitation and in the relative proportion of different carbonate minerals present in the analysed sediment samples. An additional factor is the possible detrital carbonate influx from the Adilcevaz Limestone (Fig. 1a). Considering the d18O values of
3.5 to
5.3‰ for the Adilcevaz Limestone, such an influx could in general lower the d18Oc values of the bulk carbonate (Table 3). With the available data, it is not possible to make a quantitative evaluation of the detrital carbonate input at the NB record. However, minor detrital carbonate influx from the Adilcevaz Limestone at the NB site cannot be ruled out. Such an influx would have been possible especially during the Last Glacial and Lateglacial periods when high soil erosion rates from the watershed prevailed, as shown by the low Ca/Fe values (Figs. 7e and 8e). In view of the above discussion, we interpret the characteristic high interglacial/interstadial and low glacial/stadial d18Oc and d13Cc values in the Lake Van NB section in terms of orbital-scale variations in the temperature and seasonality of precipitation. During the glacial and stadial periods, low temperatures result in isotopically light snow precipitation, which together with less evaporative conditions causes light isotope values in the lake waters, whereas during the interglacial/interstadial periods, higher temperatures and seasonality of precipitation and more evaporative conditions lead to relatively high isotope values in the lake waters and its precipitating authigenic carbonates. On a millennial-scale, the DeO events, which are characterized by increase in d18Oc and d13Cc values, together with the laminated lithology and high TOC, TIC, and Ca/Fe, are warm and humid periods, whereas stadials (i.e., HEs), with low d18Oc and d13Cc values (and low Ca/Fe, TOC and TIC contents), are cold and dry (Fig. 7aef). The YD, on the other hand, is characterized by high d18Oc values, TIC content, detrital influx (i.e., low Ca/Fe and reduced TOC contents), and occurrence of dolomite, all suggesting cold, dry and evaporative conditions (Figs. 8c,e,a and 9d). We interpret the decreasing trend of d18Oc values in the early Holocene to a gradual increase in the proportion of winter snow precipitation, which appears to have stabilized at an average d18Oc value of
3.5 ± 1.8‰ during the late Holocene. 4.2. Factors affecting carbonate mineral composition in Lake Van sediments Calcite is commonly the most abundant carbonate mineral througout the NB stratigraphic section, followed by aragonite and relatively rare dolomite (Fig. 9bed). Although the saturation Index (SI) values of present-day Lake Van waters for calcite and aragonite are 1.14 and 0.99, respectively (Reimer et al., 2009), aragonite is expected to be the predominant carbonate mineral in Lake Van sediments, because high Mg/Ca in Lake Van water would favour aragonite precipitation over calcite (Mackenzie and Pigott, 1981; nchez and Gonza lez, Burton and, Walter, 1987; De Choudens-Sa 2009; Reimer et al., 2009). However, our XRD analysis of recent Lake Van sediments and sediment trap studies of Stockhecke et al. (2012) shows that calcite is the most abundant mineral precipitating from Lake Van waters. In the sediments, this was explained by pseudomorhic replacement of aragonite by calcite, as shown by Kempe et al. (2002) using scanning electron microscope (SEM) observations. However, the positive correlation between the relative abundance of aragonite and the d18Oc and d13Cc values in the NB stratigraphic section supports a relationship with salinity (EeP balance) and/or temperature, rather than a replacement process.

Increase in the relative amounts of aragonite, together with similar increases in the d18Oc and d13C values, during the warm periods MIS1, MIS4 and BøllingeAllerød (BeA) in the NB record suggest that the amount of aragonite is related to Mg/Ca, temperature, salinity, and thus evaporation of the lake waters (Figs. 7c,d and 9c,e,f). Conversely, the relatively low aragonite abundance observed during the Last Glacialedeglaciation (~30e17 ka BP) is probably related to low salinity and/or low temperature conditions. Similar relations were previously reported in Lake Van by Lemcke and Sturm (1997) and in Nar Lake in central Turkey by Jones et al. (2006) and Jones and Roberts (2008). There is an antithetic relationship between the abundances of aragonite and dolomite in the NB section, which suggests the replacement of aragonite by dolomite (Fig. 9c,d). Present-day alkalinity and salinity of the lake water are 155 mM and 22‰, respectively, and molar Mg/Ca ratio is greater than 40 in surface waters, and increases to 52 at 400 m depth (Reimer et al., 2009). The Lake Van waters are therefore supersaturated with respect to dolomite (saturation index, SIdolomite ¼ 3.85e4.10). However, possibly because of kinetic factors, dolomite is rare in Lake Van; it was previously reported in major amounts only in the 15e16 ka old sediments, which was interpreted as a sign of intense evaporation and complete dessication of the lake (e.g., Landman et al., 1996a, b, 2011; Reimer et al., 2009). In the NB record, dolomite is found in samples having high d18Oc values (>3.0‰), which is in part due to the isotope fractionation effect for dolomite, relative to calcite, of 3‰ (Land, 1980; Fig. 9c). High dolomite amounts occur during YD and MIS5/MIS4 transition and HE5 (45 ka BP) (Figs. 8 and 9). Presence of dolomite in the Lake Van samples strongly suggests high E/P under dry evaporative conditions. For example, in the Coorong lagoon and lakes in southern Australia, micritic dolomite forms during summer when the evaporation is highest and the evolved brines mix with the groundwaters under high molar Mg/Ca (>10) conditions (e.g., Hardie, 1987; Warren, 1990). Presence of such a brine with a salinity of 40‰ (a value nearly twice the salinity of present lake Van water) was found in the pores of the sedimentary interval corresponding to 15e12 ka BP in the NB section (Litt et al., 2012a). 4.3. Lake level changes over the last 90 ka Multiproxy NB records imply climatically controlled significant lake level changes over the last 90 ka in Lake Van. This is also supported by the presence of lowstand deltas and onlap sequences in the subaqueous seismic reflection profiles (Damcı et al., 2012; Çukur et al., 2012, 2014, this volume) and coastal terraces located at different elevations (Schweizer, 1975; Valeton, 1978; Kempe
lu et al., 2010; Fig. 1a). et al., 2002; Kuzucuog A quantitative lake level curve for Lake Van covering some glacialeinterglacial cycles requires transfer functions between the multiproxy parameters and climate variables. In this study, we attempt to reconstruct a relative (qualitative) lake level curve for the last 90 ka in Lake Van (Fig. 11), using the multiproxy data presented in Section 3, together with the results of studies published on the seismic stratigraphy and coastal lake terraces. Concerning the use of lithology in lake level, we correlate the laminated clayey silt lithofacies with high lake levels and the grey homogenous clayey silt lithofacies with low lake levels, as explained in Section 3. 1 (see also Landmann et al., 1996a,b; Stevens et al., 2001; Kempe et al., 2002; Stockhecke et al., 2014b). Furthermore, a change from a distinct to a faint varve structure is interpreted to indicate a change from a deep lake with anoxic bottom waters to a shallow lake with oxic bottom waters. We relate the high TOC and TIC concentrations, as well as high d13Cc and Ca/Fe values, to high lake level during warm and humid


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

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Fig. 11. Relative lake level curve for Lake Van for the last 90e26 ka (a) and 26 ka-present (b). The semiquantitative lake level curve is relative to the modern lake level representing “0 m” (1647 masl), and based on TOC, TIC, and m-XRF elemental analysis (this study) and ages of low stand deltas in seismic sections (Damcı et al., 2012; Çukur et al., 2014, this
lu et al., 2010). See text for discussion. YD: Younger Dryas, BeA: BøllingeAllerød. volume) and coastal lake terraces (Kuzucuog

periods characterized by high surface runoff. Such conditions would promote primary productivity (photosynthesis) and deposit organic- and 13C-rich sediments. High surface runoff from the watershed would supply nutrients and Ca for the primary production and authigenic carbonate deposition, respectively. High lake level would also cause water stratification, anoxic bottom waters and efficient organic matter preservation. During warm and wet periods, the presence of a dense vegetation cover in the watershed would reduce erosion rates, which together with an increase in carbonate precipitation in the lake, would cause high Ca/Fe values. As discussed in Section 4.1, the use of d18Oc data in study of relative lake level changes is complicated because of the involvement of many factors, including temperature and seasonality of precipitation, and authigenic carbonate mineralogy, besides the EeP balance. However, some abrupt increases in d18Oc,, together with dolomite and low TOC concentrations, are interpreted to indicate low lake levels and evaporative conditions. On the basis of the above considerations, the hydrological system in the watershed and the Lake Van level follows a general wet and high-stand interglacial versus dry and low-stand glacial pattern, which is overprinted by short-term variations during stadials and interstadials (Fig. 11; also see Stockhecke et al., 2014a, this volume). During the MIS5b interstadial (~90e82 ka BP), lake level was probably similar or some metres lower than the present day level

during (Fig. 11a), as suggested by laminated lithology and moderate TOC values (Fig. 7a). Markedly laminated clayey silt lithology, high TOC, TIC and Ca/Fe during 82e71 ka BP (MIS5a) suggests higher lake levels than those for the MIS5b stadial. This conclusion is supported by the presence of peat (swamp) deposits under the _ ~80 ka old Incekaya basaltic hyaloclastite unit in the southwest coastal area of the lake (Sumita and Schmincke, 2013a). Such coastal peat deposits usually form close to sea or lake level. However, its present-day elevation at 1777 masl (i.e. 129 m above the present lake level and 40 m above the sill in Kotum) is most likely to be partly due to tectonic uplift (Sumita, personal communication). The period from 71 to 59 ka BP (MIS-4) was a cold and dry period, with low TOC, TIC and Ca/Fe values and high aragonite content (Fig. 7). Relatively low d18Oc values (
0.8 ± 1.7‰) during this period are likely to be due to the relatively increased winter precipitation rather than the positive lake water balance. A low lake level during this period is also supported by the presence of a low stand delta package at
120 m according to the seismic stratigraphic data (Damcı et al., 2012; Çukur et al., 2014, this volume) (Fig. 8a). The Lake Van level was in general lower than the modern lake level during 60e34 ka BP. This regressive period was interrupted by transgressive episodes corresponding to the DeO events (Dansgaard et al., 1993; Vidal et al., 1999; Maslin et al., 2001; Schulz, 2002; Bartov et al., 2003; Hemming, 2004). These events are observed during 57, 53, 46 and 35 ka BP in the Lake Van NB record,


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

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and marked by relatively high d18Oc, Ca/Fe, TOC and TIC values (Fig. 7aef). During the onset of these interstadials, relative lake level rises took place as result of initial melt water input, followed by an evaporative drop, as suggested by the positive d18Oc excursions (Fig. 11a; Kwiecien et al., 2014, this volume). Presence of dolomite suggests that some evaporative regressions of the lake also occurred during 50.5e48.5 ka and 42 ka BP (Fig. 11a). Rapid negative excursions of TOC, TIC, d18Oc and d13Cc values in the NB stratigraphic section at ~34 ka BP suggest a dramatic change of environmental conditions in Lake Van. This change corresponds in time to the formation of 1730e1735 masl-high terraces (i.e., ~85 m above present-day lake level; e.g., Beyüzümü terrace, Fig. 1a)
lu et al., 2010) and an onlapping seismic stratigraphic (Kuzucuog sequence (Çukur et al., 2014, this volume), all indicating a rapid lake level rise to the Kotum sill threshold at 90 m above the present lake level. The rapid transgression was likely the result of melt water delivery with low d18O and d13C values during the DeO event following HE4 (~35 ka BP; Wolff et al., 2010; Blockley et al., 2012). The alternative hypothesis is that the transgression was caused by the deposition of large amount of tephra material (i.e., the Nemrut Formation) ejected during the Nemrut caldera forming eruption (Sumita and Schmincke, 2013a). The presence of two terraces dated at 26e24.5 and 21e20 ka BP reaching 1705 masl in Kotum, Karasu, Ercis¸, Engil and Muradiye
lu et al., 2010); and low Ercis¸ (Fig. 1a; Kempe et al., 2002; Kuzucuog d18Oc values and aragonite contents suggest a positive PeE balance and high lake levels during the end of Last Glacial period (30e15 ka BP). On the other hand, the lithology (predominantly homogeneous grey clayey silt interbedded with subordinate laminated clayey silt lithofacies) of this period suggests mainly low lake levels with some intervening transgressive episodes. We suggest that the low d18Oc values and aragonite content are caused by the predominant winter precipitation and low water temperatures. The two terraces were likely deposited during the interstadial events (Hemming, 2004; Wolff et al., 2010; Blockley et al., 2012). The intervening regression correlates with the timing of HE2 and the next low level (~
200 m) coincides with the timing of HE1 (Fig. 11). The sedimentation rate was particularly high and mass flow events were frequent during 21e15 ka BP. Trace amounts of dolomite and negative correlation between low TOC and intermediate TIC values suggest that low lake levels prevailed during this period (Figs. 8a,b and 10b). Previously, Landmann et al. (1996a,b, 2011), studying deep basin cores, suggested the complete desiccation of Lake Van during 16e15 ka BP. Although there are many lines of evidence for a dramatic regression of the lake during that time, there is no evidence of a complete desiccation neither in the NB (
245 m) (this study) nor the AR (
365 m) (Stockhecke et al., 2014b) records. Strong evidence for lake level drowdown during 16e15 ka also include subaqueous prograding deltas at ca
200 m in the seismic sections in the Northern and Tatvan basins, which date back to 20e17 ka BP (Damcı et al., 2012), or 30e16 ka BP (Çukur et al., 2014, this volume). Considering the ~
200 m sill depth of the Northern ridge, the Northern Basin was probably separated from the rest of Lake Van during this low stand period. Sediments of the BøllingeAllerød period (BeA; 14.7e12.8 ka BP) are grey laminated clayey silt at the NB site. Low resolution of the TOC, TIC and stable isotope data for this interval does not allow us to reach firm conclusions regarding the lake levels. The two samples in this period have relatively low TOC and moderate TIC, d18O and d13C values, with the TOC and TIC values negatively correlated (Fig. 8a,b). We interpret these data in terms of lake levels similar to or little lower than the modern lake level. During the YD cold period (12.8e11.5 ka BP; Dansgaard et al., 1993; Gulliksen et al., 1998; Kirby et al., 2002), faintly laminated clayey silt with some

event deposits were deposited at the NB site. Geochemical and mineralogical proxy records (presence of dolomite and low Ca/Fe) indicate a cold and dry climate, high detrital influx and evaporative regression of the lake level. Reconstructions based on d18Oc, Mg/Ca and Sr/Ca of bulk carbonates, Lemcke and Sturm (1997) modelled the YD lake level to be 45e90 m lower than the modern level, depending on the humidity and temperature assumed in the calculations. During the early Holocene, high TOC, TIC and Ca/Fe values suggest relatively high lake levels with some rapid millennial scale variation having amplitudes of a few tens of metres (Fig. 11b). High lake levels are also indicated by the presence of the early to middle
lu et al., 2010). The Holocene terraces near river mouths (Kuzucuog increased lake levels during this period were mainly caused by initial melt water input, followed by a gradual increase in winter precipitation during the early to the middle Holocene, as suggested by the gradually decreasing d18Oc values. A rapid middle Holocene transgression during 5e4 ka BP, with distinctly laminated lithology and high TOC and Ca/Fe values, was followed by a general regression during 4e1 ka BP. The regressive period is characterized by low d18Oc, TOC and TIC values. We interpret the low d18Oc values during this period to be the result of increased winter precipitation relative to spring, summer and fall precipitation. Based on deep basin core analyses, a lake level curve extending back to 20 ka BP was previously established for Lake Van (Landmann et al., 1996a,b, 2011). These authors' and our lake level curves are similar in showing a major regression during 15e16 ka BP, a rise during the BeA, a drop during the YD, and a rise during the early Holocene stating from 8 ka BP. In detail, however, there are also differences, especially in estimation of the regression during 15e16 ka, as discussed earlier, and in the lake level changes during the late Holocene. For the latter period, our multiproxy data suggest fluctuating lake levels, rather than a uniform lake level suggested by Landmann et al. (2011). 4.4. Climate records: global and regional comparisons The 90 ka-long NB section shows orbital scale climatic and climatically controlled environmental changes over the last 90 ka, including those in salinity, organic productivity, and lake level. The laminated sediments of the interglacial and interstadial periods, with their high TOC, TIC and aragonite contents and Ca/Fe values, show warm and wet conditions with high organic productivity, organic matter preservation and Ca-rich runoff from the drainage basin. On the contrary, except for the interstadial intervals, the Last Glacial and stadial periods were cold and dry, with low organic productivity and organic matter preservation, and high detrital influx from the watershed. The d18Oc values of interglacial sediments are in general higher than those for of Last Glacial and Lateglacial sediments in the Lake Van NB record (Figs. 7d and 8c), suggesting the control of temperature and seasonality of precipitation on the lake water d18O values over glacialeinterglacial cycles (see discussion in Section 4.2). Some short-term, abrupt excursions of d18Oc and Ca/Fe values in the NB record correlate with the stadial and interstadial events observed in the NGRIP ice core d18O record (NGRIP, 2004) (Figs. 7f and 8g). The most marked abrupt excursions are related to the MIS5/MIS4 (~71 ka BP) and MIS4/MIS3 (~58 ka BP), transitions and the HE5, HE1 and YD (Figs. 7d and 8c). Some positive excursions in the d18Oc and Ca/Fe during 60e33 ka BP are related to the warm and humid DeO events, such as the ones observed about 57, 53, 46, 43 and 34 ka BP in the NB record. However, the DeO events in the NB record are not as clearly discernable as in the Ahlat Ridge (AR) records (Stockhecke et al., 2014b), mainly because of the interruptions of the former by the event deposits.


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

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The fact that the Anatolian and Near East climates are affected by the DeO events in the North Atlantic is also corroborated by the stable isotope records of Sofular Cave in western Black Sea coast of €ktürk et al., Turkey (Figs. 1b, 7h and 8h,i; Fleitmann et al., 2009; Go 2011) and Soreq cave in Israel (Bar Matthews et al., 1999). The Sofular record (especially the d13C data) shows first order Greenland interstadials (Figs. 7h and 8i). Both the Sofular and Greenland ice core records correlate well with most NB multiproxy records, except for the high fluctuations during the Holocene at the NB site. The generally good correlation of the NB Lake Van with the Sofular cave and Greenland ice core records support the existence of teleconnections via the storm track originating in the North Atlantic and reaching at least as far east as the eastern Anatolian Plateau, after possible modifications in the Mediterranean (Wigley and Farmer, 1982; Karaca et al., 2000). On a local scale, our Lake Van NB multiproxy records correlate well with the pollen data for the Lake Van Ahlat Ridge site (Litt et al., 2014, this volume). On a regional scale, the NB Lake Van records during the LGM and Lateglacial show good correlation with various climate records from the Lake Zeribar and Lake Urmia, both located in same Irano-Turanian Floral Province as Lake Van (Fig. 1b; Litt et al., 2009). In good agreement with the Lake Van NB records, the Lake Zeribar records show relatively cold and dry conditions and generally low lake levels during the LGM and upper pleniglacial (20e12.8 ka BP). These periods in Lake Zeribar coincide with complete decline of arboreal pollen (van Zeist and Bottema, 1977), high diatom-inferred conductivities (Synder et al., 2001) and complete absence of marsh and shore plants (Wasylikowa, 2005). The period from 40 ka to 25 ka, however, is probably more humid with high lake levels in both Lake Zeribar and Lake Urmia, as suggested by moderately low diatom conductivity values and well developed marsh and aquatic flora in Lake Zeribar (Synder et al., 2001) and pollen and sedimentary data in Lake Urmia (Djamali et al., 2008). However, the Last Glacial transgressions in these Iranian lakes are not well dated. High lake levels during the Last Glacial in Lake Lisan (precursor of the Dead Sea in the Levant) (Kaufman et al., 1992; Bartov et al., 2002, 2003; Stein et al., 2010) and Konya Lake in central Anatolia (Roberts, 1983) (Fig. 1b) correlate probably with the transgressive episodes of 33, 26e24.5, and
lu et al., 2010; this study). The 20e21 ka BP in Lake Van (Kuzucuog highest lake levels in Lake Lisan (precursor of Dead Sea) is observed during 28e20 ka BP, which is followed by a regression until 14 ka BP causing a ~180 m drop in the lake level (Bartov et al., 2002; Stein et al., 2010). These hydrological changes during the end of Last Glacial and Lateglacial in Lake Van and Lake Lisan are therefore similar. The aridity observed during the YD in the NB Lake Van records is also demonstrated in Lake Zeribar by very high d18O values (Stevens et al., 2001) and high lake conductivities (Synder et al., 2001) and in Lake Urmia by the palynological data (Djamali et al., 2008). In the Dead Sea, however, the YD is relatively wet (Stein et al., 2010). The early Holocene macroplant record for Lake Zeribar suggests a warm and wet climate particularly during 8e5 ka BP, with a generally high lake level interrupted by some regressions (Wasylikowa, 2005). This finding in Lake Zeribar is in good agreement with our early Holocene NB Lake Van records that show generally warm and wet conditions with some short dry periods. The early Holocene (10e6.5 ka BP) pollen record of the Dead Sea in the Levant points to a warm and arid climate (Litt et al., 2012b) that is therefore in antiphase to the climate conditions in Lake Van and Lake Zeribar basins. The mid-Holocene Optimum Period (MHOP), with high lake level, occurred during ~6e4 ka BP in Lake Zeribar (Stevens et al., 2001) and Lake Van (Wick et al., 2003), whereas the same period in the Dead Sea area was warm and arid (Litt et al., 2012b). In our Lake Van NB records, however, the MHOP with very high TOC and

17

d18O values occurs during 5e4 ka BP, ~1 ka later than the date suggested by Wick et al. (2003). The discrepancy in the age of the MHOP between Wicks et al.'s (2003) and our records in Lake Van are likely due to the differences in the age models. The MHOP in Lake Van is preceded by an arid period during 6e5 ka BP with relatively low organic productivity and high detrital influx (i.e., low Ca/Fe) (Fig. 8aee). The period after 4 ka BP is relatively arid in the NB Lake Van record, with alternating wet and dry conditions. Relatively dry periods, with low TOC, TIC, d13Cc and d18Oc values, occur during 3.5 ka BP, 2.5 and 0.4 ka BP (Fig. 8aed). The arid late Holocene period in Lake Van correlates with similar hydrological conditions in Lake Zeribar (Synder et al., 2001), and in the Dead Sea (Litt et al., 2012b). The relatively low and fluctuating d18Oc values during the late Holocene are most likely to be due to the centennial-to millennialscale changes in seasonality of precipitation, as discussed in Sections 4.1 and 4.3. Reduced springesummer and increased winter precipitation was previously also suggested to explain the low d18Oc values and reduced organic productivity in the Lake Zeribar sedimentary record (e.g., Stevens et al., 2001). Rapid shifts in the pattern of precipitation and anti-correlation with the Dead Sea system are likely to be related to changes in the temperatures in the North Atlantic and Mediterranean and the strength of the Siberian anticyclone. Important influence of the Siberian High on the precipitation of the Near East and Middle East regions have been known for some time (e.g., La Fontaine et al., 1990; Synder et al., 2001; Türkes¸ and Erlat, 2003; Sen et al., 2011). It is hypothesized that during cold (stadial) periods, the Siberian High probably strengthens and expands south over Anatolia, pushing the moisture-bearing storm tracks from the North Atlantic and Mediterranean to the south of the Anatolian peninsula. This mode therefore causes dry conditions in eastern Anatolia and wet conditions in the Levant. During interglacial and warm (interstadial) periods, however, the Siberian High weakens and retreats north and northeast towards Siberia and central Asia, allowing the moist air masses and precipitation over eastern Anatolia. The strength of Siberian High is believed to be related to the positive and negative phases of the North Sea-Caspian pattern (NCP) of Kutiel and Benaroch (2002) (Jones et al., 2006; Sen et al., 2011). During the Holocene, seasonal changes in precipitation in Anatolia are probably related to changes in temperature (insolation) and teleconnections with the North Atlantic and Indian monsoon systems (e.g., Jones et al., 2006). Increase in temperatures appears to have increased the winter precipitation (related to North Atlantic) relative to the summer precipitation (related Indian monsoon rainfall), and vice versa. 5. Conclusions The 144.5 m long composite stratigraphic section of ICDP cores recovered from the NB of Lake Van covers the last 90 ka BP and consists of four lithofacies: laminated clayey silt, homogeneous clayey silt, tephra, and graded (turbiditic) sandesilt lithofacies. In some levels, these units show soft sediment deformation, and are classified as “deformed units”. Multiproxy core analyses of the stratigraphic section provide evidence of orbital, North Atlantic DeO and Holocene abrupt climate events and lake level changes. The early Holocene, 80e70 ka BP (MIS5a) and to a lesser extent 60e33.5 ka BP (MIS3) were relatively warm and humid periods, characterized with laminated sediments and high organic productivity (TOC) in the NB stratigraphic section. The variability during MIS3 was caused by the DeO events. The sediments deposited during 90e85 ka BP (MIS5b), 70e60 ka BP (MIS4) and 33.5e14.5 ka BP (MIS2) are mainly grey homogeneous clayey silt


atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027

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that have low TOC, TIC and Ca/Fe values, indicating cold and dry climate with high detrital influx and relatively low lake levels. The glacial and stadial periods have relatively lower d18Oc and d13Cc values than those for interglacial and interstadial periods. The low values of the glacial/stadial are the result of low seasonality of precipitation and relative increase in the contribution of the 16Orich winter precipitation rather than overall increase in the PeE balance. On the contrary, during interglacial/interstadial periods, higher temperature and seasonality of precipitation and evaporation result in heavy isotope values in the lake waters. The DeO interstadials during 57, 53, 46, 43 and 34 ka BP are characterized by high d18Oc and d13Cc values and low detrital input (high Ca/Fe), which suggest relatively high evaporation and low erosion rates caused by warm and humid conditions and dense vegetation cover in the drainage basin. During the period between 33.5 and 14.5 ka BP (MIS2) mainly grey homogeneous clayey silt, with low TOC, TIC and Ca/Fe values, was deposited. This sediment composition in general indicates cold and dry climate, low lake level, low vegetation density and high detrital influx. However, some high lake levels are indicated by the presence of þ50 m high coastal terraces, formed during the interstadial intervals. The presence of low stand deltas extending down to ~
200 m below the present lake level, together with multiproxy core data from the NB site, suggest a significant regression between 20 and 15 ka BP. Such a dramatic regression probably isolated the NB from the rest of Lake Van, but did not completely desiccate the lake. Deposition of faintly laminated sediments and multiproxy records indicate an evaporative regression of Lake Van during the YD. This was followed by rapid millennial scale climate and lake level oscillations during the Holocene. High lake levels with some brief regressive intervals prevailed during the early Holocene. The early Holocene transgression is well represented by distinctly laminated sediments with high TOC and TIC contents and coastal terraces rising ~50 m above the present lake level. This transgressive period was followed by a relatively arid and regressive period during 4e1 ka BP. The NB Lake Van climate records are conformable with the NGRIP ice core and the Sofular speleothem records, indicating teleconnections with the North Atlantic system. On a regional scale, the NB Lake Van records correlate with climate records from the Urmia and Zeribar lakes in Iran, but are mainly in anti-phase to the YD and Holocene climate and hydrological conditions in the Dead Sea Basin (Lake Lisan) in the Levant. The relatively low d18O values during glacial and Lateglacial periods and negative d18O excursions during the Holocene are likely to result from decreases in spring and summer precipitation and increased winter (snow) precipitation. The rapid oscillations in the Holocene climate, Lake Van level and seasonality of precipitation are all probably related to changes and feedbacks associated with changing temperatures in the vapour source regions (i.e., North Atlantic and Mediterranean) and in the strength of the Siberian anticyclone. Acknowledgements We thank the PaleoVan team for support during collection and sharing of data. The authors acknowledge funding of the PaleoVan drilling campaign by the International Continental Scientific Drilling Program (ICDP), the Deutsche Forschungsgemeinschaft (DFG), the Swiss National Science Foundation (SNF) and the Scientific and Technological Research _ Council of Turkey (TÜBITAK) (Project No. 108Y279 granted to MNÇ). We acknowledge the support of Umut Baris¸ Ulgen, Zeynep Erdem and Georg Heumann for U-channel and discrete sampling

of NB cores in Bremen, Dursun Acar for m-XRF analysis in EMCOL laboratories, and Burak Yalamaz for figure drafting. Prof. Ercan € Ozcan for providing fresh representative samples of Adilcevaz €hl, Limestone samples for the isotope analysis. We thank Ulla Ro Alex Wuipers, Hans-Joachim Wallrabe-Adams, Vera Lukies and Holger Kuhlmann from the IODP Core Repository Bremen for their support during the sampling parties. €
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atay, M.N., et al., Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, Please cite this article in press as: Çag eastern Turkey, Quaternary Science Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.09.027