The development of Central Anatolian Cenozoic basins such as Sivas, Çankırı, and Tuz Gölü was related to a series of geological processes that occurred after the closure of the northern branch of the Neo-Tethyan Ocean (Şengör and Yılmaz, 1981;Dirik et al., 1999) (Figure 1). An assemblage of ophiolite mélange related to the İzmir-Ankara-Erzincan suture zone crops widely out in eastern and northeastern parts of the basin (Tatar, 1982;Cater et al., 1991). The Sivas Cenozoic Basin is located on three crucial continental plates. These are the Central Anatolian massif in the west, Pontide Thrust Belt in the north, and Tauride-Anatolian Block in the south. On the other hand, older geological units are exposed in the southern part of the basin. They belong to the suture zone of the Inner Tauride Ocean, which was opening and closing between the Jurassic and the Cretaceous/Paleocene periods (Oktay, 1982;Görür et al., 1984;Tekeli et al., 1992). Since the geological structure of the Sivas Basin is so interesting, many researchers have carried out multidisciplinary studies on the basin (
Introduction The Miocene is an epoch in earth history before the development of the Northern Hemisphere ice sheet. It was characterised by transgression-regression events leading to the opening and closing of seawater in Europe (Rögl, 1998; Zachos et al., 2001; Meulenkamp and Sissingh, 2003). The early Miocene, which is the main subject of this study, is a critical period between Oligocene mainly "icehouse" climates and the middle Miocene climatic optimum (MMCO) (Flower and Kennet, 1994). Some authors indicated that relatively warm and ice-free conditions persisted during the early Miocene (Zachos et al., 1997; Mosbrugger et al., 2005). Conversely, other authors claimed that this warm period was stopped by several cooling and glaciation events, especially for the high latitudes (
Planktonic and benthic foraminifera are described from the Middle Eocene-Lower Miocene successions in the Sivas Basin, Central Anatolia. An integrated foraminiferal zonation provides new age assignments in terms of a great number of taxa for the studied sections. Four biostratigraphical intervals are first recorded based on the concurrent ranges of sporadically occurring but well preserved planktonic foraminiferal assemblages. The first interval characterized by the co-occurrences of Acarinina bullbrooki, Truncorotaloides topilensis and Turborotalia cerroazulensis is referable to the E11 Zone of late Lutetian-early Bartonian. An assemblage yielding Paragloborotalia opima accompanied by Globigerinella obesa forms a basis for the late Chattian O5 Zone. The successive interval corresponds to the late Chattian O6 Zone indicated by the presence of Globigerina ciperoensis and Globigerinoides primordius along with the absence of Paragloborotalia opima. The early Aquitanian M1 Zone can be tentatively defined based mainly on the assemblage of Globigerina, Globigerinella, Globoturborotalita and Tenuitella. The biostratigraphical data obtained from the benthic foraminifera assign the studied sections to the SBZ 21-22, SBZ 23 and SBZ 24 ranging in age from Rupelian to Aquitanian. The SBZ 23 and 24 are well constrained biozones by the occurrences of Miogypsinella complanata and Miogypsina gunteri, respectively, whereas the SBZ 21-22 defined by nummulitids and lepidocylinids in the Tethyan Shallow Benthic Zonation is characterized dominantly by peneroplids, soritids and miliolids in the studied sections. Benthic foraminiferal assemblages suggest different paleoenvironments covering lagoon, algal reef and shallow open marine whereas planktonic foraminifera provides evidence for relatively deep marine settings on the basis of assemblages characterized by a mixture of small-sized simple and more complex morphogroups indicative for intermediate depths of the water column.
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