COBISS: 1.01 HYDROGEOLOGY AND HYDROCHEMISTRY OF MARBLE AQUIFER WITH POINT RECHARGE FROM TWO DEEP SINKHOLES, MENDERES MASSIVE, WESTERN TURKEY HIDROGEOLOGIJA IN HIDROKEMIJA MARMORNEGA VODONOSNIKA S PONORNIM TOČKOVNIM NAPAJANJEM (MASIV MENDERES, ZAHODNA TURČIJA) Celalettin §iM§EK'*, Birol KAYA2, Ahmet ALKAN2, Fatih BÜYÜKTOP^U2, Necdet TÜRK3 & Yal^in ARISOY2 Abstract UDC 552.4:551.435.8(560-15) 556.114:552.4(560-15) Celalettin §im§ek, Birol Kaya, Ahmet Alkan, Fatih Büyük-topfu, Necdet Türk & Yalftn Arisoy: Hydrology and hydro-chemistry of marble aquifer with point recharge from two deep sinkholes, Menderes Massive, western Turkey Menderes Massive is a NE-SW-trending metamorphic terrain in western Anatolia. The massive is composed of regionally metamorphosed rocks of mica-schist and marble. The Bozdag Mountain is the main horst system in Kucuk Menderes river basin. It is composed of several N-S oriented small horsts and grabens and contains important karst features, such as poljes and sinkholes. Ayvacik and Subatan Poljes are typical closed depressions draining into Ayvacik and Subatan sinkholes (ponors). Both are developed along the N-S directed fault system. The main objective of this study is to determine the karsti-fication and hydrogeochemical features of water circulating in marble terrain and controlled by deep sinkholes in the Bozdag Mountain. Detailed speleological studies demonstrated that the degree of karstification of marble rock depends on the regional tectonic structure, the mineralogy of marble and the water recharge rate into the sinkholes. Tritium isotope and tracer tests indicate very fast flow and connection between Subatan surface water and a spring in lower elevations with high Ca and Mg ion concentration at the south of the study area. Keywords: Marble rock, karstification, sinkholes, Bozdag Mountain, Menderes Massive, Western Turkey. Izvleček UDK 552.4:551.435.8(560-15) 556.114:552.4(560-15) Celalettin §im§ek, Birol Kaya, Ahmet Alkan, Fatih Büyük-topfu, Necdet Türk & Yalftn Arisoy: Hidrogeologija in hidrokemija marmornega vodonosnika sponornim točkovnim napajanjem (Masiv Meredes, zahodna Turčija) Masiv Menderes je območje metamorfnih kamnin v zahodni Anatoliji, Turčija. Razteza se v smeri SV-JZ in je sestavljeno predvsem iz regionalno metamorfiziranih sljudnih skrilavcev in marmorjev. Goro Bozdag sestavlja sistem manjših grud in tektonskih jarkov, orientiranih v smeri sever-jug. Masiv je delno zakrasel, s tipičnimi kraškimi oblikami, med katere spadata tudi polji Ayvacik in Subatan, ki se drenirata skozi istoimenske ponore. Obe polji sta razviti v prelomni coni orientirani v smeri sever-jug. Glavni namen opisane raziskave je določiti stopnjo zakraselosti območja in hidrokemične lastnosti vode, ki teče skozi marmornati masiv. Podrobne speleološke raziskave so pokazale, da je zakraselost močno pogojena z regionalno geološko strukturo, mineraloško sestavo marmorja in velikostjo dotokov v ponore. Izotopske analize tritija in sledenje podzemnih voda kažejo na hiter tok in povezavo med poljem Suba-tan in visoko mineraliziranimi izviri na jugu obravnavanega območja. Ključne besede: Marmor, zakrasevanje, ponor, gora Bozdag, masiv Menderes, zahodna Turčija. '* Department of Drilling, Torbali Technical Vocational School of Higher Education, Dokuz Eylul University,35860 Torbali-Izmir, Turkey, Corresponding author, e-mail: celalettin@deu.edu.tr 2 Department of Civil Engineering, Dokuz Eylul University, 35160 Buca-Izmir, Turkey 3 Department of Geological Engineering, Dokuz Eylul University, 35160 Buca-Izmir, Turkey Received/Prejeto: 13.12.2013 ACTA CARSOLOGICA 44/2, 205-214, POSTOJNA 2015 CELALETTIN $IM$EK, BIROL KAYA, AHMET ALKAN, FATIH BÜYÜKTOPQU, NECDET TÜRK & YALQIN ARISOY INTRODUCTION In Turkey, carbonate formations are predominantly encountered in the Aegean region and along the Mediterranean coastline within the Taurus Mountain range. Generally in the Aegean region and particularly around Izmir, the karstic formations are classified as alloch-thonous limestone in flysh units and massive marble rock in the Menderes Massive (Fig. 1). The massive carbonate rocks are generally characterized by their well-defined stratigraphy and large spatial extent, whereas alloch-thonous limestone formations are typically distinguished with their deformed geology and limited spatial extent (Erdogan & Gungor 1992; Simsek et al. 2008). Carbonate formations are generally marbles found as metamorphic rocks within the Paleozoic Menderes Massive. The thickness of marble layers are variable but could reach up to 300 m (Erdogan & Gungor 1992). Marble mainly consists of dolomite minerals and is tec-tonically highly fractured (Yavuz et al. 2011). Karstic features such as sinkholes and caves are developed within the marble rock unit. The marble also host a number of large springs with discharges exceeding 200 L/s. Karstic water is used as drinking water resource in Odemis town and its vicinity in the south of Izmir Province (Fig. 1). This study is intended to characterize the karstification and hydrogeochemical features of karst groundwater occurring in the marble units of the Bozdag Mountain of the Menderes Massive in Izmir Province. Fig. 1: Location map of the study area. 206 ACTA CARSOLOGICA 44/2- 2015 HYDROGEOLOGY AND HYDRO CHEMISTRY OF MARBLE AQUIFER WITH POINT RECHARGE FROM TWO DEEP .. DESCRIPTION OF THE STUDY AREA The study area is located within the boundaries of Izmir Province in western Turkey. It is situated approximately 150 km south of the city of Izmir (Fig. 1). Bozdag Mountain is the highest mountain in the region that is famous for its ski center in western Turkey. Paleozoic aged marble rocks are found in the upper parts of the Bozdag Mountain. There are several small plains in the Bozdag Mountain region which are mostly used for agriculture. The mountainous fields are not suitable for settlement because of their high altitudes. The town of Odemis is the main population center in the area located in the southern outskirts of the Bozdag Mountain. The marble aquifer in the study area is a potential water resource for supplying the water demand of this town. GEOLOGICAL SETTING The study area is located in the Alpine-Himalayan oro-genic belt, and is a part of tectonically active zone with numerous fault lines (Sozbilir 2002). The major tectonic lines observed in the study area are the E-W directed graben faults with lengths ranging up to 100 km, which are cut by N-S directed secondary faults (Inci 1991; Su-zen et al. 2006). Major E-S running graben system is the Kucuk Menderes Plain surrounded by Bozdag Mountain to the north, which is the main horst system in the area. The N-S running secondary fault system controls the karst features developed in the Ayvacik and Subatan poljes (Fig. 2). Fig. 2: Geological and sampling location map of the study area (Simsek et al. 2010). ACTA CARSOLOGICA 44/2 - 2015 207 CELALETTIN $IM$EK, BIROL KAYA, AHMET ALKAN, FATIH BÜYÜKTOPQU, NECDET TÜRK & YALQIN ARISOY Fig. 3: Geological block diagram of the study area (Simsek et al. 2010). Paleozoic aged Menderes metamorphic rocks form the basement of the study area and outcrop in many parts of the Bozdag Mountain (Simsek et al. 2010; Kaya et al. 2012) in western Turkey (Fig. 2). The Menderes metamorphic rocks consist of mica, calc-schist and massive marble in their upper level (Hetzel et al. 1998). Marble rock in the Menderes Massive is divided into three parts as low, middle and upper levels. The lower level of marble unit is represented by bedded marble layers that include thin lenses of mica schist. The middle part of the marble layer contains 50-60 m thick marble lenses sequenced with calc-schist. The upper part of the marble unit is characterized by emery bearing marbles that are widely observed in western of the Kucuk Menderes Basin (Er-dogan & Gungor 1992; Gungor & Erdogan 2002; Yavuz et al. 2011). In the study area, the NS-SW trending upper part of the marble in the massive was observed with grey color and a total of thickness of 100 m as shown in Fig. 2. The Quaternary alluvial deposits overlie the Menderes Massive rocks in N-S running graben system. HYDROGEOLOGICAL SETTING The study area has the typical Central Aegean climate characterized by hot and dry summers, and cold and rainy winters. In addition, Ayvacik and Subatan poljes also receive snow in the winter (Fig. 3). These poljes are closed depressions collecting surface waters from the nearby terrain that later drain into the Ayvacik and Subatan sinkholes. The surface areas of Subatan and Ayvacik Poljes are 2.8 km2 and 12.24 km2, respectively. The flow rate measurements in the area were made during the wet season of 2010. The flow rate of Ayvacik stream that drains the Ayvacik Polje in February was 21 L/s. The flow rate then decreased in March (2.8 L/s) and April (1.2 L/s). The Subatan polje is drained by two streams in the north and south of the plain, which confluence near Subatan sinkhole (Fig. 3). The total flow of these streams was 366 L/s, 196 L/s, and 94 L/s in February, March, and April, respectively. During the summer months, both Ay-vacik and Subatan surface waters are dry, but limited flow was observed in the base of sinkholes. Camyayla (SP5 and SP8), Pitrak (SP6) and Su <;ikti (SP7) are the main springs located on the south and west of the study area (Fig. 2). The hydrogeology of the study area is governed by two major aquifer systems (Fig. 2). The first one is the unconfined alluvial aquifer that provides the majority of groundwater for irrigation in the Ayvacik and Subatan plains. The alluvial aquifer is mainly composed of sedimentary sand and gravel deposit that reach up to 90 m in thickness. The second aquifer, on the other hand, is the marble aquifer controlled N-S oriented fault lines (Figs. 2 and 3). MATERIALS AND METHODS Two-stage investigation has been carried out in this study: (i) field and speleological study and, (ii) hydro-chemical, isotope and tracer analysis. The field and speleological studies were carried out to determine the groundwater flow mechanism in the marble unit. The groundwater sampling and tracer analyses were performed to determine the water characteristic and marble hydrogeology. The water samples collected from eight 206 ACTA CARSOLOGICA 44/2- 2015 HYDROGEOLOGY AND HYDRO CHEMISTRY OF MARBLE AQUIFER WITH POINT RECHARGE FROM TWO DEEP .. sampling points were analyzed for major anions, cations and potential pollutants. The 50 mL sample collected from each point was first acidified in the field by nitric acid to drop the pH level below 2. This prepared sample was then analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for major cations and several trace elements, such as aluminum, arsenic and iron in Canadian ACME Laboratories. The 500 mL water sample collected from each sampling point was used for major anions analysis such as chloride, nitrate, sulfate, and bicarbonate ions. The bicarbonate analysis was performed by titrimetric techniques, whereas the remaining anions were analyzed by ion chromatography (IC) in the Dokuz Eylul University laboratories. Finally, the 1000 mL water samples collected from five selected springs and surface waters were tested for S3H (tritium) in the isotope laboratories of Hacettepe University, Turkey. A tracer test was conducted with 1 kg of Uranine by injecting into the Subatan sinkhole and monitoring from Camyayla and Pitrak springs. RESULTS AND DISCUSSION KARSTIFICATION OF MARBLES Structural mapping and speleological studies were conducted in sinkholes in Bozdag marble area to determine the marble aquifer karstification features. Joint systems are important pathways of ground water flow. The layers and faults are found to be concentrated at 174/24 and 260/35 directions in the marble unit. The discontinuity aperture was found to vary between 1-50 mm in the surface. The dips of the main discontinuities are near vertical and generally run in N-S directions. The main fault system is N-S directed and controls several small horst and graben systems in the area and separates several marble blocks from one another in the study area. Ayvacik, Subatan and Camyayla poljes were developed along the main N-S directed fault system in the Bozdag Mountain region as shown in Fig. 2 and 3. The main karst features of the study area are Ayvacik and Subatan sinkholes developed along the N-S directed small graben faults. All surface waters within enclosed poljes drain into the marble unit through these sinkholes. Based on the speleological survey, the length and depth of the Ayvacik sinkhole were found to be 1575 m and 239 m, respectively. The Ayvacik sinkhole descends in a spiral form along the vertical fault zone as show in Fig. 4. Ayvacik sinkhole can be divided into three main morphological structures. The first section starts from the surface to the depth of 100 m with a vertical slope that consists big shafts and caves with very dense small fracture system in the massive marble unit (Fig. 4). The second morphological feature continues from to 100 m down to the depth of 200 m at a slope angle of 20°. The second section has very complex morphological features like labyrinths that include enlarged fracture zones and narrow passages. In addition, there is a big hall in this section, whose height varies between 25 m to 30 m and total area is approximately 1500 m2. This hall consists of mainly marble with intercalations of medium to small thick mica-schist layers. The third morphological unit consists of very small fracture zones and a narrow shaft with a mild slope ending at the depth of 239 m with a siphon. It consists of marble units including very thick mica and calc-schist layers. Similarly, the Subatan sinkhole occurs along the N-S running faults within the Subatan polje. Total depth of Subatan sinkhole is 150 m (Fig. 5). Subatan sinkhole developed through the marble and schist contact zone controlled by the graben fault and ends at a similar siphon feature. These results indicate that Subatan and Ayvacik sinkholes end at the bottom of the marble layer, creating bottom siphons. These siphons are also filled with sediments including sands, clays and silts as well as organic material coming from the surface agricultural lands. HYDROCHEMICAL CHARACTERISTIC The results of chemical analysis of the water samples collected from surface waters (SP1, SP2 and SP3) and some important karst springs (SP4, SP5, SP6, and SP7) in the study area (Fig. 2) are presented in Tab. 1. The range of pH values for all samples is between 7.11 and 7.96, indicating neutral to weak alkaline waters. The temperature values range from 11.2 to 14.5 °C. The electrical conductivity value varies from 281 to 373 mS/cm. The physical characteristics of these waters show slightly alkaline and low mineral content as seen Tab. 1. Water chemistry of the marble aquifer are dominantly Ca-HCO3. The surface water samples were found to differ from the spring waters; while Na and K were predominant elements in the surface waters, Ca and Mg were the major ions in the spring waters. Since marble is dolomitic, the dissolution of dolomite increased the Ca and Mg ions in the spring waters. Na was found to be at concentrations between 4.24 to 12.72 mg/L. The highest Na value was observed in the surface water and a high level K concentration was also ACTA CARSOLOGICA 44/2 - 2015 207 CELALETTIN $IM$EK, BIROL KAYA, AHMET ALKAN, FATIH BÜYÜKTOPQU, NECDET TÜRK & YALQIN ARISOY Fig. 4: Cave map of the Ayvacik sinkhole (Simsek et al. 2010). obtained in the surface water (Tab. 1). SO4 concentration ranged from 2.99 to 47.93 mg/L, with highest value observed in S6 sampling point. The nitrate concentrations in the surface and spring waters were between 0.1 and 25.3 mg/L. The highest nitrate concentration was found in the surface water and the spring water at sampling point of SP2. It is known that main nitrate sources in groundwater are mineral deposits, soils, agricultural fertilizers, biota and sewage (Evangelou 1998). Since nitrogenous materials are rare in the geological materials, presence of nitrate in the groundwater is due to anthropogenic activity. Therefore, some fertilizers from the agricultural activities play very important role in deteriorating the surface water quality in the Ayvacik and Subatan enclosed poljes. Chemical analysis results of the water are shown on a Schoeller's semi-logarithmic diagram in Fig. 6. From the Schoeller's semi logarithmic diagram, it is clear that the surface water samples taken from SP1, SP2 and SP3 locations have similar chemical characteristics (Fig. 6). Fig.5: Cave map of the Subatan sinkhole (Simsek et al. 2010). 206 ACTA CARSOLOGICA 44/2- 2015 HYDROGEOLOGY AND HYDRO CHEMISTRY OF MARBLE AQUIFER WITH POINT RECHARGE FROM TWO DEEP .. P o s rs VO vo 5 ro 8 rs VO vo 5. 5. 5. Mn mg/L 0.004 0.031 0.015 0.00 OO'oeO 0.008 0.0001 0.002 t o H 1 6 Fe S o o 0.0' o 0. 0.0 0.0 6 o 0. 0.0 0.0 o mg/L uo 0 o o m o o r^ 0 o o 5 0 o o 5 O o 4 o o 5 0 o o 3 0 o o 0.01 0. 0. 0. 0. 0. 0. 0. 0. mg/L 0.029 0.01 0.01 0.002 0.003 0.058 0.008 0.007 rs o cT IS1 mg/L 44.94 11.98 47.93 8.98 5.99 29.96 14.98 2.99 8 a: mg/L 147.6 139.1 73.2 187.9 185.4 4 t 2 rs 2 235.5 C mg/L 13.0 o 13.0 o 00 o K 10.0 o vo o Ln Mg mg/L rs Ln Ln 00 vo H r^ 00 H vo .8 .6 .7 vo vo .2 .2 .9