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    Base surge deposits, eruption history, and depositional processes of a wet phreatomagmatic volcano in Central Anatolia (Cora Maar)
    (ELSEVIER SCIENCE BV, 2007) Gencalioglu-Kuscu, Gonca; Atilla, Cuneyt; Cas, Ray A. F.; Kuscu, Ilkay
    Cora Maar is a Quaternary volcano located to the 20 km northwest of Mount Erciyes, the largest of the 19 polygenetic volcanic complexes of the Cappadocian Volcanic Province in central Anatolia. Cora Maar is a typical example of a maar-diatreme volcano with a nearly circular crater with a mean diameter of c. 1.2 km, and a well-bedded base surge-dominated maar rim tephra sequence up to 40 m in thickness. Having a diameter/depth ratio (D/d) of 12, Cora is a relatively "mature" maar compared to recent maar craters in the world. Cora crater is excavated within the andesitic lava flows of Quaternary age. The tephra sequence is not indurated, and consists of juvenile clasts up to 70 cm, non-juvenile clasts up to 130 cm, accretionary lapilli up to 1.2 cm in diameter, and ash to lapilli-sized tephra. Base surge layers display well-developed antidune structures indicating the direction of the transport. Both progressive and regressive dune structures are present within the tephra sequence. Wavelength values increase with increasing wave height, and with large wavelength and height values. Cora tephra display similarities to Taal and Laacher See base surge deposits. Impact sags and small channel structures are also common. Lateral and vertical facies changes are observed for the dune bedded and planar bedsets. According to granulometric analyses, Cora Maar tephra samples display a bimodal distribution with a wide range of Md-phi values, characteristic for the surge deposits. Very poorly sorted, bimodal ash deposits generally vary from coarse tail to fine tail grading depending on the grain size distribution while very poorly sorted lapilli and block-rich deposits display a positive skewness due to fine tail grading. (c) 2006 Elsevier B.V. All rights reserved.
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    Hydrogeochemical properties of CO2-rich thermal-mineral waters in Kayseri (Central Anatolia), Turkey
    (SPRINGER, 2006) Afsin, Mustafa; Kuscu, Ilkay; Elhatip, Hatim; Dirik, Kadir
    The present study highlights the hydrogeological and hydrogeochemical characteristics of the CO2-rich thermal-mineral waters in Kayseri, Turkey. These waters of Dokuzpinar cold spring (DPS) (12-13 degrees C), Yesilhisar mineral spring (YMS) (13-16 degrees C), Acisu mineral spring (ACMS) (20-22.5 degrees C), Tekgoz thermal spring (TGS) (40-41 degrees C), and Bayramhaci thermal-mineral spring (BTMS) (45-46.5 degrees C) have different physical and chemical compositions. The waters are located within the Erciyes basin in the Central Anatolian Crystalline complex consisting of three main rock units. Metamorphic/crystalline rocks occur as the basement, sedimentary rocks of Upper Cretaceous-Quaternary age form the cover, and volcanosedimentary rocks Miocene-Quaternary in age represent the extrusive products of magmatism acting in that period. All these units are covered unconformably by terrace and alluvial deposits, and travertine occurrences have variable permeability. Dokuzpinar cold spring, YMS and ACMS localized mainly along the faults within the region have higher Na+ and Cl- contents whereas TGS and BTMS have higher amounts of Ca2+ and HCO3-. The high concentrations of Ca2+ and HCO3- are mainly related to the high CO2 contents resulting from interactions with carbonate rocks. Whereas the high Na+ content is derived from the alkaline rocks, such as syenite, tuff and basalts, the Cl- is generally connected to the dissolution of the evaporitic sequences. These waters are of meteoric-type. BTMS deviates from meteoric water line. The content is related to the increases in the 6180 compositions due to mineral-water interaction (re-equilibrium) process. CO2-dominated YMS and ACMS with low temperatures have higher mineralizations. Yesilhisar mineral spring, ACMS, TGS and BTMS are oversaturated in terms of calcite, aragonite, dolomite, goethite and hematite, and undersaturated with respect to gypsum, halite and anhydrite. Yesilhisar mineral spring, ACMS and BTMS are also characterized by recent travertine precipitation. Dokuzpinar cold spring is undersaturated in terms of the above minerals. The higher ratios of Ca/Mg and Cl/HCO3, and lower ratios of SO4/Cl in BTMS than TGS suggest that TGS has shallow circulation compared to BTMS, and/or has much more heat-loss enroute the surface. The sequence of hydrogeochemical and isotopic compositions of the waters is in an order of DPS > YMS > ACMS > TGS > BTMS and this suggests a transition period from a shallow circulation to a deep circulation path.