Stratigraphy, mineralogy and depositional environment of the evaporite unit in the As ¸ kale (Erzurum) sub-basin, Eastern Anatolia (Turkey) Emel Abdio  glu a, * , Mehmet Arslan a , Didem Aydınçakır a , _ Ibrahim Gündo  gan b , Cahit Helvacı b a Department of Geological Engineering, Karadeniz Technical University, TR-61080, Trabzon, Turkey b Department of Geological Engineering, Dokuz Eylül University, Buca, TR-35160, _ Izmir, Turkey article info Article history: Received 9 June 2015 Received in revised form 8 July 2015 Accepted 14 July 2015 Available online 17 July 2015 Keywords: Evaporites Sabkha Secondary gypsum Anhydrite As ¸ kale sub-basin Turkey abstract The study area is situated in the As ¸ kale sub-basin where the Early-Middle Miocene aged As ¸ kale For- mation was deposited in a shallow marine to lagoonal environment, and consists of interstratifications of clastic sediments, carbonates and evaporites. The successions of the As ¸ kale Formation can be divided into four main members interfingering with one another both vertically and laterally, and composed of the sandstone-mudstone-limestone member, the evaporite member, the gravelstone-sandstone-mudstone intercalations and the limestone member. The evaporite unit comprises of secondary gypsum lith- ofacies formed by hydration of precursor anhydrite, anhydrite, gypsum-bearing limestone and claystone in the form of wedges and lenses. Massive, nodular, nodular-banded, laminated and laminated-banded gpysum lithofacieses in addition to chicken-wire and rare entrolithic structures were described, indi- cating a sabhka or a shallow water depositional environment. Alabastrine and porphyblastic textures of gypsum were identified within the all lithofacieses with abundant amount of anhydrite relics. Addi- tionally, saponite and illite/smectite, calcite and dolomite, celestite, epsomite were also observed. Suc- cessions of the As ¸ kale Formation were deposited in stable subtropical climatic conditions within rapidly subsiding sub-basin resulted in conversion of sub-basin to shallow platform and even in lagoon environment. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Turkey hosts many well characterized economically important Tertiary marine and nonmarine evaporite deposits formed within rift and foreland basins, strike-slip settings and mountain belts (e.g., Brinkmann, 1976; Palmer et al., 2004). These deposits consist of mainly gypsum, anhydrite, halite, thenardite, and glauberite (e.g., G€ okçe and Ceyhan, 1988; Çubuk, 1994; Ya gmurlu and Helvacı, 1994; Ceyhan, 1996; Gündo gan and Helvacı, 2001; Tekin et al., 2001; Çiner et al., 2002; Orti et al., 2002; Türkmen, 2004; Palmer et al., 2004; Gündo gan et al., 2005; Zeybek, 2007; Kırtıl, 2008; Yes ¸ ilova and Helvacı, 2013). The Neogene basins and sub-basins in the Eastern Anatolia of Turkey between the _ IzmirEeAnkaraeErzincan and the AssyrianeZagros suture zones (Fig. 1a) have been well documented. Previous studies have been focused mainly on stra- tigraphy, tectonic history and petroleum potential of the Neogene sediments (e.g., S ¸ eng€ or and Kidd, 1979; S ¸ aro glu and Yılmaz, 1986; Yılmaz et al., 1998; Akay et al., 1989; Tarhan, 1989; Tarhan et al., 1992; Büyükutku, 2003) but still there is a huge gap about sedi- mentology and facies features of the evaporites formed in these basins in spite of their importance reflecting fingerprints of tectonic events and climatical changes of Neo-Tethys Ocean. Thus, further investigations should be carried on the evaporites' stratigraphy and petrography in order to understand their depositional features and origin. One of the Neogene basins, the As ¸ kale (Erzurum) sub-basin have not been evaluated in terms of evaporitic successions effected by extensive tectonics and diapirism, resulted in destruction of many primary structural and textural features and causing difficulty for interpretation of their depositional environments. This paper pre- sent field geology, optical microscopy, X-ray diffraction and scan- ning electron microscopy features of the Miocene evaporite * Corresponding author. E-mail address: abdioglu@ktu.edu.tr (E. Abdio glu). Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci http://dx.doi.org/10.1016/j.jafrearsci.2015.07.013 1464-343X/© 2015 Elsevier Ltd. All rights reserved. Journal of African Earth Sciences 111 (2015) 100e112