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    Cretaceous-Tertiary (K-T) boundary evaporites in the Malatya Basin, eastern Turkey
    (Springer, 2015) Ayyildiz, Turhan; Varol, Baki; Onal, Mehmet; Tekin, Erdogan; Gundogan, Ibrahim
    The Malatya basin is situated on the Anatolid-Torid plate of the Neo-Tethys Sea. Evaporites were deposited in the northwestern part of the Malatya basin, which is referred to as the Hekimhan sub-basin. Although the Gunduzbey sub-basin in the southeastern Malatya basin has coeval deposits, it contains no evaporate deposits. The evaporite is most likely the result of the last transgressive-regressive cycle of the Late Cretaceous Sea. The pre-evaporitic unit is represented by the carbonate platform deposit of the Loftusia banks, which partly underwent dolomitization and overlies the deep marine sediments. Celestite-bearing algal limestone was deposited directly below the gypsum-dominated evaporate unit in association with the organic-rich mudstone. Evaporite sedimentation took place in various types of environments, such as marginal shallow subaqueous with the association of sabkha-coastal lagoon and deeper subaqueous. It is assumed that the tectonic evolution of the basin margin, which occurred during the latest stage of the Cretaceous regression, was responsible for the environmental restriction leading to evaporate sedimentation under arid/semiarid climatic conditions. The Sr-87/Sr-86 ratios obtained from 38 samples of the gypsum and celestite-bearing limestones (11 samples) range between 0.707817 and 0.707980 and between 0.707783 and 0.707864, respectively. The delta S-34 values range from +19.5 to +22.4 aEuro degrees, and the delta O-18 values range from +9.6 to +12.7 aEuro degrees. These isotopic signatures correspond to that of Late Cretaceous/Early Paleocene (Cretaceous-Tertiary boundary) marine water. However, celestite exhibit(s) relatively higher delta S-34 and Sr-87/Sr-86 values than expected marine values, which could be a result of contribution of diagenetic fluid into the celestite-precipitated environment.
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    Sedimentology and geochemistry of the middle Miocene playa lake evaporites in the Gurun Basin (S of Sivas), Central Anatolia, Turkey
    (Springer, 2008) Onal, Mehmet; Helvaci, Cahit; Tekin, Erdogan; Ayyildiz, Turhan
    The Gurun basin is a half graben filled by alluvial, fluvial and playa-lake deposits of the Gurun Formation accumulated under the N-S direction extensional tectonic regime and volcanic rocks. The Gurun Formation is divided into four members such as the Kavak, Gokpinar, Cayboyu and Terzioglu members, and the Cayboyu Member has two different evaporitic occurrences such as selenitic and satin spar. During the first phase of evaporite deposition, selenitic gypsum crystals in 5 to 15 cm thick layer within the dolomitic mudstones were formed. The second evaporitic phase consists of four different levels of cavity filling within the sandstones and shale alternation at the upper part of sequence originated as 5 to 10 cm sized satin-spar gypsum crystals with white colored, partly orientated, fibrous-radial shaped. XRF major, minor and some rare elements analyses (La, Ce, Ta, W and U) and low Sr-87/Sr-86 (parts per thousand) and delta S-34 (CDT) values indicate that meteoric and volcanic solution occasionally mixed with the lake water. In addition, low delta O-18 (SMOW) values in the continental evaporate could be interpreted as mixing of fresh water with the playa lake environment. Selenitic gypsum in the Cayboyu Member of the Gurun Formation was precipitated from ground water-brine water rich in humic acid during periodic desiccations of in the shore-lake plain.