Environmental and climatic changes during the Pleistocene–Holocene in the Bor Plain, Central Anatolia, Turkey

Palaeogeography, Palaeoclimatology, Palaeoecology 440 (2015) 564–578

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Environmental and climatic changes during the Pleistocene–Holocene in the Bor Plain, Central Anatolia, Turkey Türkan Bayer Altin a,⁎, Meriam El Ouahabi b, Nathalie Fagel b a b

Nigde University, Faculty of Science and Letter, Department of Geography, 51240 Nigde, Turkey University of Liege, Department of Geology, AGEs, Quartier Agora, Allée du 14 Août, B-4000 Liege, Belgium

a r t i c l e

i n f o

Article history: Received 8 June 2015 Accepted 9 September 2015 Available online 18 September 2015 Keywords: Bor (Niğde) Clay minerals Paleoenvironment Paleoclimate Lake deposit Quaternary

a b s t r a c t The Bor Plain lies in a round-shaped flat basin in the southern part of the Central Anatolia. It is located at the southeastern end of the Tuzgölü Fault Zone—which is the NW trending, active normal fault zone and extends between the north of the Tuzgölü (Lake Tuz) at NW and at Kemerhisar (Niğde) SE. According to geomorphologic and geologic studies, this plain was occupied by lake during the Pleistocene. The first high lake level (terrace) and the latest high lake level (terrace) were determined at 1170–1150 m and 1110–1100 m, respectively. Pleistocene and Holocene alluvial and lacustrine deposits are composed of claystone, sandstone, mudstone, limestone and paleosol units. These units contain mostly calcite and clay minerals (palygorskite, smectites, illite and chlorite), and lesser amounts of quartz, phillipsite, cristobalite, feldspar, plagioclase, goethite and, muscovite. The results of this study are compared with the results of sedimentologic and dating obtained from Konya–Ereğli Plain. According to this comparison, 1—the latest high lake terraces were dated 23,000 to 17,000 yr BP. The high lake level was changed, 2—sandy level with carbonate determined in stratigraphy indicates that a dry phase dominated after 17,000 yr BP, and 3—black and brown muds indicate that the shallow freshwater lacustrine phases and sandy levels were formed between 12,500 and 1100 yr BP during late glacial stage. Paleosols, muddy levels and shallow lake deposits were formed in the environment of the Holocene during 6000–5000 yr BP. Carbonate-rich sandstone and mudstone deposits show that this period was interrupted by the second drought in the latest stage. Temperatures have increased due to hot climate conditions and salinization has begun and been still ongoing. © 2015 Elsevier B.V. All rights reserved.

1. Introduction Pleistocene high water-level of the pluvial lakes in the Central Anatolia Region of Turkey has been known for a long time. One of these lakes occupied the Konya Basin located in the west of the Bor Basin (Bor Plain). In this region, the long-term hydrological evolution of closed basins has left various landforms and deposits (Fontugne et al., 1999). Geomorphological mapping (Erol, 1978, 1984, 1991, 1997) and dating of lacustrine deposits permit the reconstruction of the paleo-geography of the Konya Basin at around the time of the Last Glacial maximum. The first study on only Bor Plain was done by Gürel and Lermi (2008). The results of detailed sedimentological and partly geochemical analysis of the various non-marine sedimentary facies were presented in their study. Most of the studies are associated with Konya pluvial lake. The physicochemical and mineralogical properties of paleosols and sediments, and the formation and diagenesis of carbonates under the lacustrine environment in the Konya Basin, were studies by Müller et al (1972), Inoue et al. (1998), Reed et al. (1999) and Kuzucuoğlu et al. (1999). Initial sedimentological studies and 14C dating ⁎ Corresponding author. E-mail address: [email protected] (T. Bayer Altin).

http://dx.doi.org/10.1016/j.palaeo.2015.09.011 0031-0182/© 2015 Elsevier B.V. All rights reserved.

of the shoreline deposits were undertaken by Roberts et al. (1979) and Roberts (1980, 1983) who concluded that the last period of high water levels is dated Last Glacial Maximum (23,000–17,000 14C yr BP) prior to its desiccation in the final part of the Pleistocene. Further 14C dates of similar age were published (Naruse et al., 1997), although the coarsegrained facies were wrongly interpreted by them to be alluvial fan deposits. None of these studies found any evidence of vertical tectonic deformation of Late Quaternary shoreline terraces around the Konya basin (Karabiyikoğlu et al., 1999). Other radiocarbon chronological studies of Late Pleistocene Konya Basin were also conducted by Kuzucuoğlu et al. (1999), Fontugne et al. (1999), Karabiyikoğlu et al. (1999), and Boyer et al. (2006). Bor Basin was subjected by closed lacustrine system during Pleistocene. Lake level changes of closed lacustrine systems are good indicators of climatic changes because of their quick response to the variations of the water input/output terms of the hydrological balance (Eugster and Hardie, 1978). In these closed lakes, evaporation leads to element supersaturation in water and to consequent mineral precipitation (Kuzucuoğlu et al., 1999). The mineralogical composition and sedimentological characteristics of lacustrine deposits in closed, semi-arid, lacustrine depressions reflect climatic changes through lake level and lake chemistry changes (Müller and Wagner, 1978).

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The aim of this study is to present mineralogical properties of the lacustrine deposits and geomorphological evaluation of the Bor Plain from the Pleistocene to Early Holocene. Our purpose is also to highlight the environmental and the climatic changes in the southern part of the Central Anatolia (Turkey). 2. Geologic and geographic settings The Bor Basin is mostly surrounded by mountain ranges rising up to 3000 m from southern and containing limestone rocks (Fig. 1). Thus, these ranges isolate the Central Anatolia from the Mediterranean cyclonic depressions and the cool and humid air from the north. The Taurus Mountains mainly consist of marine carbonates prior to Miocene epoch (Bolkar carbonate platform and other sedimentary rocks) (Dhont et al., 1998). The fresh moraine ridges occupied down to 2000 m elevation along the valleys on the north-looking slopes of the Mt. Bolkar (summit at 3525 m, Medetsiz Hill) (Bayer Altın, 2006). The east part of the Bor plain is a part of the Niğde massif which forms an ophiolitic melange which has undergone deformation and metamorphism together with the underlain formations (Göncüoğlu, 1986). The study area is the south part of the Central Anatolian Volcanic Province (CAVP). CAVP has developed since the Late Miocene over on Oligocene foredeep basin located between the Central Taurus Range and Kırşehir crystalline massif (Innocenti et al., 1982; Pasquare et al., 1988). The origin of the magmatism of this province is dominated by calc-alkaline

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products (Innocenti et al., 1982; Gourgaud et al., 1992; Temel, 1992). Andesite and Basaltic volcanoes of various ages since the Late Miocene are scattered on the Bor Basin, from the north of the area (Mt. Melendiz–Mt. Keçiboyduran) (Dhont et al., 1998). Vents of the Keçiboyduran (2727 m)–Melendiz Mountains (2963 m) are distributed along a fault parallel to the Tuzgölü accident (Türkecan et al., 2004). Tuzgölü Fault system has affected the evolution of these two lower Pliocene volcanoes (Toprak and Göncüoğlu, 1993) (Fig. 2). Tuz Gölü Fault Zone (TGFZ) is a NW–SE trending, dipping towards SW, active, right lateral strike–slip component normal fault zone which extends between north of Tuz Gölü and Kemerhisar (Niğde) and has a length of 200 km (Kürçer and Gökten, 2014a). According to Kürçer and Gökten (2014b), TGFZ is a structure of NE–SW trending extensional tectonic regime that was activated by the early Pliocene. The land characteristics also show the availability of fluvial deposits, travertines, hot springs, fractures and faults. As well as Tuzgölü Fault (TF), the Niğde Fault (NF) has been controlled from the east and south margins of the basin (Fig. 2). This fault is one of the major faults that define the southern margins between Kemerhisar and Bor settlements. Hot springs located in Kemerhisar are resulted by this fault. NF strikes NE– SW and is cut and displaced into several segments by the TF (Toprak and Göncüoğlu, 1993). The prevailing climate is semi-arid in the study area, with a mean annual precipitation of 350 mm and mean temperature of 0 °C in January and 23 °C in July (MGM, 2015), and is made up of about 52% of the plain surrounded by Mt. Melendiz (Demirkesen, 2009). The

Fig. 1. a: Location of the study area and b. 3D view of the study area and its surrounding mountains.

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Fig. 2. Geological map of the study area. This map was compiled from 1/500,000 scaled. Geological map of Turkey (MTA, 2002) and the location of the samples.

main valley is the Küçüköz stream coming from Mt. Melendiz. This stream flows in front of Niğde settlement and discharges into Akkaya pond and then goes through the Bor Plain. In addition, the Bor Plain is also fed by some streams coming from Mt. Melendiz, Mt. Keçiboyduran and Mt. Bolkar from north and south, respectively. 3. Material and methods 3.1. Material L2 is found in the south foot of Mt. Melendiz and located between 37° 55′ 11.4″ North latitude and 34° 32′ 30.08″ East longitudes.

The locality has a mean elevation of 1147 m asl and is found above dark-colored volcanic rock that is basaltic in composition. The samples were taken from two different sites (site a, b) (Fig. 2). The thickness of the lacustrine deposit consisting chiefly of clay in site (a) is about 3 m and the height of another deposit reaches 5 m in site (b). 15 samples taken from site 2a and 13 samples taken from site b, in total 28 samples were taken each every 20 cm up and 40 cm up in this locality, respectively. The deposit consists locally of intercalated beds of clay and gravel coarse. L3 is found on the Altunhisar road and near the quarry. The locality is located between 37° 55′ 07.7″ North latitude and 34° 30′ 53.6″ East longitude. The mean elevation of the locality is 1104 m asl. It is

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suggested that the locality is a paleo-shoreline terrace, probably belonging to Pleistocene. The samples were taken from two different sites (3a, 3b) of the same lacustrine deposit. The thickness of site-a is 5 m and site b is 3 m. 9 samples in site-a and 7 samples in site b were taken in this locality. First core (Drill 1) has been done between Kemerhisar and Seslikaya settlements and 37° 55′ 0.76″ North latitude and 34° 30′ 53.05″ East longitude. The locality has a mean elevation of 1083 m asl and probably corresponds to the shoreline of the paleolake. For lithostratigraphic analyses to reconstruct ancient environmental changes, we obtained undisturbed vertical core

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sections of sediments using drilling equipment at two sites. One of them is shoreline and another is bottom of the lake. 24 lacustrine sediment samples were obtained from about 12 m drilling core (first core). 12 samples were taken from first 1 m of earth's surface. In total 36 samples were obtained. Ten lacustrine sediment samples were obtained from about 9 m drilling core (Drill 2) in the area located between Emen and Seslikaya settlements. This drilling core is located between 37° 48′ 39.5″ North latitude and 34° 27′ 05.4″ East longitude and has a mean elevation of 1078 m asl. The sediments are composed by mudstone and clays, indicating that this area corresponds to a paleolake.

Fig. 3. Geomorphological map of the foot of Mt. Melendiz–Bor settlement.

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3.2. Methods To identify the lateral and vertical distributions of Tclay (Total clay) or clay minerals, two stratigraphic sections in the Bor Plain were examined using drill core. One of them (Drill 1) is located between Kemerhisar and Seslikaya settlements; another (Drill 2) is located between Seslikaya and Emen settlements. The first of these corresponds to edge of the former pluvial lake; another corresponds to bottom of the former pluvial lake. The mineralogical analysis was performed by X-ray diffraction (XRD), with a Bruker D8-Advance diffractometer, using Cu-Kα radiation on powdered bulk sediment and on the b 2 μm fraction. For bulk sediment analysis the relative abundance of minerals was estimated from the height of the main peak multiplied by the correction factors proposed by Cook et al. (1975). For the clay fraction analysis the whole sediment was decarbonated with HCl (0.1 mol/L) and the b 2 μm fraction separated by settling in a water column. Samples were mounted as oriented aggregates on glass slides (Moore and Reynolds, 1997). For each sample three X-ray patterns were recorded: air-dried (N), ethylene-glycol solvated for 24 h (EG), and heated at 500 °C for 4 h (H). The background noise of the X-ray patterns was removed and the line position, intensity peak, and integrated area were calculated with DIFFRACplus EVA software (Bruker). Semiquantitative estimations of the main clay species were obtained on EG runs according to the methods of Biscaye (1965). Scanning Electron Microscope (SEM) techniques were used for the investigation of the samples at METU (Middle East Technical University, Department of Metallurgical and Materials Engineering Laboratory, Ankara, Turkey). On the basis of XRD results obtained from 180 samples, four clay dominated samples were prepared for SEM analyses by adhering the fresh, broken surface of each rock sample onto 350 Å thick Au film of gold coated sample chips, using a Giko ion coater. The detailed geomorphology map using Erol System, which is based on the Neogene and Quaternary erosion cycles of Turkey in relation to the erosional surfaces and their correlated sediments, will be derived from 1:25,000 scaled topography maps. According to this system, denudational evolution of the Anatolian Peninsula and the Taurus Mountains to the south has been a continuous process under the control of neotectonic phases, climatic changes and sea level oscillations since

the Late Oligocene (Erol, 1991). Denudational surfaces of different ages have been studied in relation to their correlated sediments (Erol, 1991; Fairbridge et al., 1997). The age of the landform systems was indicated by Erol (1991) as DI, II, III, and IV and the Pleistocene terraces as ‘S’ levels. 4. Results The results of the study consist of two separate parts: 1—geomorphological results including field observation, using aerial photographs and 1:25,000 scaled topographic and geologic maps, 2—sedimentological results including mineralogical analyses of about 90 samples taken from Locations 2, 3 and Drill cores (1 and 2), and stratigraphy of drilling cores of lacustrine sediments. 4.1. Geomorphological results The deposit is composed by three layers: 1) the main rock substrate, 2) laminated layer, and 3) a boulder layer are found on it and covered by the actual soil. The deposit is characterized by large-scaled coarse gravel lenses, suggesting a flood deposit. As indicated by the fluvial erosional surfaces along the foot of the northeastern slopes of Mt. Bolkar and their continuation towards the east–southeast up to the environs of Bor town (Fig. 3), it is believed that prior to a former closed lake phase in the Bor Basin, a fluvial period started during the Late Pliocene (DIII). Fluvial glacis type terraces (DIV), probably of Early Pleistocene age, are to be observed at about 1170–1200 m, that is, about 60–90 m above the bottom of the Küçüköz valley. Following a former fluvial glacis phase in the basin, the first pluvial lake developed during the Middle Pleistocene. Its maximum level is estimated as 1170 m and the lowest level is 1150 m (Location 2). During this time, in contrast to the lake terraces in the basin, two additional sets of the coeval fluvial terraces were developed in the Küçüköz valley to the east (Fig. 3). These two gravel terraces at about + 40 m and +60 m elevation are obviously of a different nature and they may easily be differentiated from the +60 m to +90 m elevated glacis-type early Pleistocene fluvial terraces. If the lower fluvial gravel terraces of the

Fig. 4. A spillway over the lava threshold towards the bottom of the plain.

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Küçüköz valley towards the south are observed, these gravel terraces disappear and instead the traces of lake coastlines become visible towards the south of the Melendiz lava threshold (Fig. 4). This former lake, which extended along the foot of steep slopes around the Bor Plain, should had received fairly large amounts of glacial and snow meltwater from the summit areas of the Mt. Bolkar and Mt. Melendiz during the Wurm glacial period. In the second phase of the Pleistocene lake, its maximum level is estimated as 1130 m. The lowest level of this terrace is 1100 m (Location 3). During this time, the alluvial fans seem to have been relatively more developed into the pluvial lake along the foot of the Mt. Melendiz. However, these fans are not as obvious as the young fans (probably Holocene) because these fans were covered by pyroclastic materials. Following the second phase lakes, a climatic transition towards the Early Holocene was dominant in the basin. In spite of being surrounded by high mountains, and the presence of several hot springs bringing groundwater into the basin, it had low water level during this stage.

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This may indicate the influence of gradually increased drought towards recent times, but the continuing subsidence in the central part of the basin should also be considered. The geomorphologic proof of this are hot springs formed by Niğde Fault extended towards Kemerhisar settlements. Indeed drilling cores have encountered at least 7–12 m of detritic materials such as clay, sand, mud and gravel which are considered to be of probably Plio-Quaternary. Maximum level of this lake is estimated as 1100 m and the lowest level is 1090 m. At the end of this phase the coastline traces seem to be receded towards the bottom of the basin and several minor dejection cones spread along the foot of the Mt. Melendiz. Therefore, the coastline of 1090–1080 m is proposed as the transition between the Early to Middle Holocene lowest terraces and late Holocene and Bor pluvial lake bottom. The several small alluvial fans back of the mounds were developed on the lowest terraces which are formed on the basaltic lava flows near the Bayat village, as the lake had receded in front of the Kınık, Çıplaktepe, Kayı and Topraktepe mounds (Fig. 5).

Fig. 5. Geomorphological map of the foot of the Mt. Melendiz–Bayat village.

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Table 1 Mean (±1σ) of the semi-quantitative relative abundance (%) and measured d-spacing (Å) reflection intensity for bulk and clay (b2 μ) fraction minerals over the selected sequences. ≤5 correspond to trace minerals. Minerals

Measured intensity of reflection d (Å)

Average relative abundances (%)

±1σ

Calcite Tclay Cristobalite Phillipsite Palygorskite Goethite Muscovite Hornblende Sepiolite Talc Clinoptilolite Quartz k-Feldspar Smectite Plagioclase

3.02 4.44 4.05 5.0 10.62 2.44 9.78 8.32 12.08 9.56 8.88 3.32 3.20 17.82 3.16

36 21 15 12 10 7.5 7 b5 b5 b5 b5 b5 b5 ≤5 b5

10 5 5 5 3 5 2 – – – – – – – –

4.2. Mineralogy In the terraces (Location 2 and 3) and bottom of the plain (Drill 1 and 2), clayey samples reveal that calcite is the main mineral with an average ranging from 29% to 36% (±10). Tclay is the second most abundant mineral ranging from 15 to 20% (±5), followed by the groups of cristobalite, phillipsite, palygorskite, goethite and muscovite (Table 1). Quartz, hornblende, sepiolite, talc, clinoptilolite, K-feldspar and plagioclase are distinct minerals in these sequences. They are sporadically present in all the deposits. Cristobalite (15% ± 5) was also punctually observed in all sections of the locations. The main assemblage changes along the studied sequence. Calcite is the dominant mineral at Location 2a, 3b, Drill 1 and 2. At Drill 1, its value reaches maximum value in the upper 517 cm up to values as high as 74%. Tclay is the dominant mineral at Location 2b and 3a. Its maximum values range between 22% and 33% in these locations. These minerals are followed by cristobalite (Figs. 6, 7). The change of mineralogical dominance suggests transition from glacial to interglacial conditions and confirms dry and warm period. The change of mineralogical

Fig. 6. 2a, b: Lacustrine deposit, 1, 2: vertical changes of percent amounts of mineral content of the pluvial lake deposits.

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Fig. 7. 3a, b) Lacustrine deposit, 1, 2) vertical changes of percent amounts of mineral content of the lake deposits.

dominance suggests transition from glacial to interglacial conditions and confirms dry and warm period. This calcite-rich period may indicate intensified erosion of the carbonate-rich highland areas. The sediments have a predominance of sand, clay sand–mud and paleosol fractions. As indicated in Fig. 8, the lower levels of the sequence were composed of calcrete. This unit is overlain by a well-developed paleosol intercalated with brown and black sand from 11 m to 9 m. High levels contained brown colored sand intercalated with white colored sand and mud. This unit is overlain by black colored mud intercalated with white colored sand and white colored mud up to about 3 m. The uppermost level of this profile contained white colored mud or clay intercalated with brown colored mud and sand. The basement of the profile consists of 4 m thick white colored mud which represents probably the shallow lake sediments. White and brown colored mud occurs at the top of the profile reaching up to 1 m thick and 2 m thick, respectively. The values of calcite and Tclay show opposite variations in all locations. At Drill 1, while calcite increases in the upper 517 cm up to values as high as 74%, Tclay decreases up to 8% in this section (Fig. 8). In addition to Drill 1, at Location 3a, b, value of Tclay is 22% and 25% in 170 cm and 300 cm, respectively, calcite decreases up to 8% in these sections. Values of plagioclase and k-feldspar range from 0% to 43%. However, plagioclase increases in the upper 438 cm up to 75%. In contrast, calcite decreases down to 5–10% in this part (Fig. 9).

As indicated in Fig. 9, in order to understand current clay mineral forming processes in a soil, it is essential that the contribution of inheritance is clearly understood. With regard to transformation of clay minerals, a general example would be: illite ~ vermiculite ~ smectite. This reaction proceeds through a process of depletion and exchange of interlayer K and concomitant decrease of layer charge (Wilson, 1999). Such changes are, however, deceptively simple and have given rise to much debate about the precise mechanisms involved, as will be discussed later. Millot (1964) distinguished ‘degradation’ and ‘aggradation’ as separate forms of the transformation process. The above conversion of illite to montmorillonite involves depletion of elements from illite and is termed degradation, but the reverse reaction (aggradation) involves addition of K and other elements. Millot (1964) considered that degradation was characteristic of weathering rocks and soils, but that aggradation was rare in such environments. Moreover, the presence of talc probably indicates erosion from metamorphic rocks. Illite contents are identified by the peak intensity at ~10 Å on EG at Locations 2b, 3a and 3b (Figs. 10 and 11). The occurrence of kaolinite is determined from a double around 3.5 Å, resulting from the overlapping of the (004) chlorite reflection at 3.54 and (002) kaolinite reflection at 3.57 Å under either N or EG condition. The chlorite/kaolinite peak intensity ratio measured at 3.54 Å and 3.57 Å is then applied to the intensity of the 7 Å (EG) peak to estimate the contribution of kaolinite.

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Fig. 8. Stratigraphy of the drilling core of lacustrine sediments obtained between Bor and Emen settlements (A), Emen and Seslikaya settlements (B). Vertical changes of percent amounts of mineral content of the pluvial lake deposits (b: first 1 m of Drill 1 core, c: Drill 1, d: Drill 2).

The peaks indicate the dominance of primary minerals (illite, chlorite) because of dominance of physical erosion in L2b. Moreover, a part of the chlorite (fresh chlorite) has its 14 Ǻ reflection preserved after heating at 500 °C. In addition, 14 Ǻ peak of chlorite is replaced by a diffraction band between 10 and 14 Ǻ, when it is more or less degraded, such behavior points to a partial vermiculitization of the chlorite (Thorez, 2000). Chlorite, illite, and interstratified mineral 10–14 Ǻ are mainly primary clays in Drill 1. A predominantly detrital rather than authigenic origin is suggested for most of the clays. Shallow-water platform carbonates contain illite and illite–smectite (Jones and Sellwood, 1989). Most intense reflection for sepiolite is 12.10 Å and for talc at 8.39 Å, 8.45 Å, 8.40 Å and 8.41 Å. Deposition of sepiolite indicates the continued evaporation. Although the presence of sepiolite in sediments is generally considered diagnostic of a highly saline and alkaline environment, sepiolite is seldom reported in playa deposits in the western United States (Papke, 1972). Chlorites are also unusual: the 14 Ǻ reflection is variably and sensitively reduced in intensity after heating at 500 °C in Drill 2 (Fig. 12). 4.3. SEM determination Samples from Drill 1 and 2 cores mostly contain calcite (Fig. 13a). The thin calcite crystals were deposited in the first stage of the lake and then eroded (Fig. 13b). Clastics, illite and smectites were grown around calcite crystals. Palygorskite fibers generally formed in the voids by dissolved minerals between grains in the detrital units (Fig. 13c). In the first 3 m of Drill 1 core, clastics have rounded corners (Fig. 13d). They were probably transported by wind. This means that semi-arid climate conditions dominated in the environment. The

angular clastics (Fig. 13e) were identified in the 5 m of Drill 1 core. They were probably transported by glacier and then deposited in the lake. This means that cold-dry climate conditions were dominated in the stage in which this level was formed. The plant spore (6 m of Drill 1 core) (Fig. 13f), a root of plant (3 m of Drill 2 core) (Fig. 13g), illite (3 m and 6 m of Drill 2 core) (Fig. 13h, i) was coated with thin calcite crystals. For this reason, it can be said that continental and evaporitic climate were dominate in this level of the cores. 5. Discussion 5.1. Paleoenvironmental changes Mineralogical abundances suggest that the paleolake occupying the Bor Plain was very sensitive to dynamic climate oscillations and associated environmental changes from Pleistocene to Holocene. The mineralogical composition and sedimentological characteristics of lacustrine deposits in closed, semi-arid, lacustrine depressions reflect climatic changes through lake level and lake chemistry changes (Müller and Wagner, 1978). Environmental changes are marked by inverse relationship between calcite and clay minerals. In all locations, the values of calcite and Tclay show opposite variations of all the samples. As already discussed in former studies (e.g. Karakaş and Kadir, 1998; Kuzucuoğlu et al., 1999, 2011; Haberzettl et al., 2007; Zolitschka et al., 2009), these changes correspond to the transition from glacial to interglacial conditions (Nuttin et al., 2013). Calcite and low Mg-calcite precipitation is usually attributed to periods of high water level and low rates of evaporation, whereas high Mg-calcite, protodolomite and perhaps dolomite

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Fig. 9. Vertical changes of percent amounts selected minerals of Drill 1 core.

precipitation occur during periods of low water level and high evaporation (Landmann et al., 1996). An increase in Tclay indicates a high degree in chemical weathering and high erosion of clay and soil material, associated with rather humid climate, whereas low Tclay suggests a predominance of physical weathering, stable soils and/or low erosion

rates due to a drier climate (Ülgen et al., 2012). Moreover, lake deposits have mainly inherited primary minerals like illite and chlorite, the most weathered clay are mixed-layers in the study area. Calcite is deposited in freshwater and cool conditions (Kuzucuoğlu et al., 2011). Thus, calcite precipitation is usually attributed to periods of high water level and low

Fig. 10. Samples of L2 X-ray diffraction derived from the three classical runs; in natural conditions (N), after ethylene-glycol solvation (EG) and after 500 °C heating (H).

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Fig. 11. Samples of L3 X-ray diffraction derived from the three classical runs; in natural conditions (N), after ethylene-glycol solvation (EG) and after 500 °C heating (H).

rates of evaporation (Kuzucuoğlu et al., 1999). Calcite in sediments of the lake terraces is related primarily to the contribution of glaciofluvial detritus eroded from carbonate rocks in the surrounding source area and derived from limestone in alluvial fans located at the foot of the Mt. Bolkar in the south part of the study area. In dry periods, following the precipitation of carbonate units under wet conditions, mud cracks and dissolution voids formed in Konya Plain (Karakaş and Kadir, 1998). According to Kuzucuoğlu et al. (1999), the origin of carbonates (detritic, primary precipitation, diagenetic precipitation) is determined by use of mineralogic (texture, habitus) criteria. The quantitative analysis of the mineral content of carbonated sediments allows us to produce additional information in evidence of parallel or nonparallel time variations of the proportions of the sediment components. First 1 m of the drill core, values of calcite and Tclay are very close, suggesting occurrence of moderate climate in Late Holocene. Values of both of them are very low in lower part of Drill 1, which reflects climatic

condition of Early and Middle Holocene, while plagioclase increases maximum level of 52%. Value of calcite is 40% whereas value of Tclay is 12%. This corresponds to arid climate of Early Holocene. In the middle part of the core, similar values of calcite and Tclay were associated with transition from arid to moderate conditions. This moderate period is interrupted by a short-term arid period. In this level, calcite increases up to 67% while Tclay decreases up to 9%. In Drill 1 core including all Holocene samples, values of calcite and Tclay are close. In the middle part, value of calcite increases up to 4% while Tclay decreases up to 8%. This change corresponds to the transition from humid to arid climatic conditions. Moreover, upward increasing calcite contents and decreasing Tclay contents in the drill cores reflect climatic changes from cooler and dry Early Holocene to warmer and wetter present-day conditions. Changes in water temperature and evaporation stress impact variously the solubility of the calcium carbonates species (Kelts and Hsu, 1978; Kuzucuoğlu et al., 2011). According to Ülgen et al. (2012), the humid

Fig. 12. Samples of Drill 1, first 1 m of Drill 1 and Drill 2 X-ray diffraction derived from the three classical runs; in natural conditions (N), after ethylene-glycol solvation (EG) and after 500 °C heating (H).

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periods are reflected by high values in Tclay and low values in Ca/Ti, C/N and aragonite/calcite, and arid period is indicated by reversed proxy values in İznik lake located in the NW of Turkey. Chlorite and illite are the main clay minerals. Conversely, illite and chlorite exhibit a relative increase during glacial periods (Yuretich et al., 1998). A rise in temperature, evaporation and restriction of lake water has been recorded by the following mineral succession: first calcite, followed by Tclay, followed by smectites. When a decrease in temperature, evaporation and restriction occur, this succession is reversed. The formation of cristobalite is likely related to volcanic rock erosion in the study area, brought to the lake after weathering since basaltic lavas are present at the foot of volcanic mountains surrounding the plain. In all locations, generally values of cristobalite increase in the level where values of calcite and Tclay close. This suggests the occurrence of a dominant temperate climate in these levels. Mizota et al. (1987) concluded that cristobalite in soils formed by weathering of volcanic ash in temperate and tropical regions, was of primary igneous origin. It has been known that cristobalite is commonly found associated with vitric tuff owing to alteration of silicic volcanic glass (Iijima and Tada, 1981), or directly as fine matter in volcanic ash (Baxter et al., 1999). Cristobalite is also reported as a ground mass and cavity filling in tholeiitic basalts, andesite, rhyolite (Hunter, 1998) and volcanic hydrothermal deposits (Sant et al., 2003). Menking (1997) concluded that sediments characteristic of glacial periods contain abundant quartz and feldspar in the clay-size fraction because of the abrasive action of valley glaciers that produce vast amounts of rock flour. In our study, lesser amounts of feldspar, quartz and plagioclase were observed throughout the depth of each core. This pattern confirms that these detrital minerals must be derived from glacial period (less evaporation and high precipitation). The lowest kaolinite and quartz values are recorded during the most arid phases in the Konya Basin (Kuzucuoğlu et al., 1999). Minor amounts of quartz may have been the result of some short-lived eolian input and/or been derived from contemporaneous volcanic ash from nearby volcanic activity (Karakaya et al., 2004). While values of plagioclase and feldspar increase above 50%, values of calcite decrease up to 5%. This implies that these minerals formed during glacial period. According to Nuttin et al. (2013), during the glacial period, the slightly higher abundance of quartz, feldspar and clay groups might result from an increase of gelifraction processes and/or higher eolian supplies in the periglacial environment. As a result of these above interpretations, it can be said that from time to time the cold climate (chemical weathering, low evaporation) was dominant and sometime dry climate (physical weathering, high evaporation) was dominant in the Bor Plain. 6. Paleoclimatic conditions and implications The Bor Basin which is an inner and narrower basin, formed through down-faulting, was occupied by the Pleistocene pluvial lake. The first extensive pluvial lake had developed and its water advanced during the Lower Pleistocene. Lake-level fluctuations significantly played role in the development of sedimentation cycles such as sandflat– paleosols–marshy–carbonate cycles. The results on the Bor Plain mentioned above have been compared with the studies on the Quaternary fills of the Konya Basin (Kuzucuoğlu et al., 1999; Robert et al., 1999; Gürel and Lermi, 2008). Fig. 14 was reconstructed to show the correlation between these two neighboring regions. According to this figure, in the semi-arid Bor Basin, long term hydrological evolution has left various landforms such as coastline, alluvial fan, alluvial and lacustrine terraces reflecting the regional climatic evolution. The results from the different areas on fluvial, lacustrine, paleosols, marshy sediments of Late Pleistocene and Holocene ages are presented by this study. The characterization of the sediments indicates that the lowest part of the Bor Plain stratigraphy contains sandstone, paleosol and mudstone

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layers. These are dated ca. 28,000 to 25,000 yr BP (Robert et al., 1999). The phases of periglacial ‘last main high lake stage’ have been identified and date ca. 22,000 to 17,000 yr BP (Fontugne et al., 1999; Robert et al., 1999; Naruse et al., 1997; Gürel and Lermi, 2008). After 17,000 yr BP, no lacustrine phase reached a level as high as the periglacial lake level (Gürel and Lermi, 2008). The paleogeographic proof of this is an intense melting of the Mt. Bolkar glacial mass (Altın and Bayer Altın, 2005); these resulted in the increase in flow rate of rivers flowing into the basin that caused the increase in lake levels. Levels with paleosols and sandstone in stratigraphy confirm the occurrence of drought periods in the area after 17,000 yr BP. In the case of the Konya basin, there is evidence for a phase of widespread aeolian deflation during the period after the main lake regression (i.e. ca. 17,000 to 12,000 14C BP) as indicated by sand dune activity OSL-dated to this time (Kuzucuoğlu et al., 1998). During the late glacial, shallow fresh water lacustrine phases and paleosols are identified from 12,500 to 11,000 yr BP (Kuzucuoğlu et al., 1997). The Late Glacial to Holocene transition corresponds to sandy level with carbonate, thus suggesting a period of drought. The Holocene environmental evolution shows a period of paleosols–marshy shallow lake sedimentation from 6000 to 5500 yr BP (Boyer et al., 2006). In the Holocene, notable decrease occurred in lake levels and also ice melting totally seized during this period due to intense evaporation of lakes. This period is interrupted by a second drought period, which corresponds to carbonate-rich sandstone and mudstone deposits in the area. In this period, aeolian dunes were formed in Konya Plain (Kuzucuoğlu et al., 1998). The second drought period broke off in the Late Holocene by the renewal of marshes, shallow lake (calcareous silts or limestone) sediments and paleosols (Karabiyikoğlu et al., 1999). During this period, due to temperature increases and closed basin structure, salinization started taking place and the process still continuous (Inoue et al., 1998). Our data suggest that the Bor Plain was under a cold and wet climate in the glacial epochs and under a dry and hot climate in the Last Interglacial epoch and the Early Holocene. Mean annual precipitation over the plain is b350 mm per annum. In summary, both geomorphological and geological investigation show that the sedimentary sections and lake terraces in the Bor Basin represent deep lake environment during Pleistocene and shallow lake environment which is sensitive to minor fluctuation in lake level during the Holocene period.

7. Conclusion The Quaternary history of the Bor Basin had a rather complex evolution. Generally, four advances and four recession periods are determined during the Pleistocene in the basin. Moreover, these periods were interrupted by short-term temperate climate. During the Lower Pleistocene the first extensive pluvial lake had developed and its water had advanced. The lake water started to rise in the early pluvial, responsible for the accumulation of transgressive terrace sediments between 1170 m and 1150 m (SY1). After Lower Pleistocene pluvial phase, three pluvial phases (SY2, SA1 and SA2) developed. The lowest coastline systems (SA2) corresponding to Upper Pleistocene are found between 1130–1110 m. After this phase, the end of the Pleistocene–Early Holocene, the lake extremely recessed. The connection between Konya pluvial lake and Bor pluvial lake had been cut during this period and Bor pluvial lake has changed into an independent lake. The mineralogical data suggest that Bor Basin was very sensitive to climatic oscillations and associated environmental changes from the Pleistocene to Holocene periods. The sequential deposition of carbonates in the lake sediments illustrates trends in the water salinity. In the case of increasing evaporation, peaks of calcite followed peaks in Tclay. Calcrete–sands–mud–paleosols–carbonate cycles are the result of the lake level fluctuations caused by periodic changes in climate

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Fig. 14. Lithologic and chronostratigraphic relationship of the Konya Plain (Robert et al., 1999), Bor–Ereğli Plain (Gürel and Lermi, 2008) and Bor Plain sediments.

and proposed depositional model is presented for the alluvial, shallow lake and, marshy facies. On the other hand, in the Bor Basin, as in other pluvial lakes of the Anatolian plateau (Kuzucuoğlu et al., 1999), there is no strict correspondence between cold–dry and warm–humid periods, as usually indicated during glacial and interglacial periods. For example occurrence of carbonate–mudflat–sandflat deposited in dry and wet environment implied that dry and intermediate climatic conditions were formed in both Pleistocene and Holocene periods. The carbonate deposition in the lake sediments accumulated in the bottom of the plain indicates a decrease in shallow-lake water-level that resulted due to rise of the Bor Basin during the Holocene. Both geomorphological and geological investigation shows that the sedimentary sections and lake terraces in the Bor Basin represent deep lake environment during Pleistocene and

shallow lake environment which is sensitive to minor fluctuation in lake level during the Holocene period. Acknowledgments This research was funded by the TÜBİTAK-BİDEB, 2219 (The Scientific and Technological Research Council of Turkey, Post-doctorate Program). We are much indebted to technician Joel Otten for XRD analyses and technical support in the laboratory (Department of Geology, Liege University, Belgium) and technician Cengiz Tan for SEM microphotography (Department of Metallurgical and Materials Engineering, Middle East Technical University, Ankara, Turkey). We also sincerely thank Assoc. Prof. Ali Gürel (Department of Geology, Niğde University) for accompanying field trips and recommendations.

Fig. 13. SEM photos from D2 and D1 drill samples representing lacustrine deposit. a) Calcite crystals (Cal), b) cement with thin calcite crystals, c) palygorskite (P) fibers forming bridge-like structure with detritic formation of illite (il), d) clastics (Cls) with rounded corners, e) angular clastics, f) plant-spore coated with calcite crystals, g) roots of plant, h) illite between calcite crystals, and i) illite.

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