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    Depositional stages of the Egribucak inner basin (terrestrial to marine evaporite and carbonate) from the Sivas Basin (Central Anatolia, Turkey)
    (SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2017) Kangal, Ozgen; Ozgen Erdem, Nazire; Varol, Baki Erdogan
    The Sivas Cenozoic Basin and coeval Central Anatolian basins such as Cankiri and Tuz Golu are characterized by both marine and terrestrial sediments ranging in age from the Eocene to early Miocene. The evaporite regime here generally appeared during the late stage of Eocene transgression and persisted through the Oligocene time. However, marine-induced Oligocene evaporites are less known because of less paleontological evidence and regional tectonics and salt diapirism that mostly caused the destruction of their original stratigraphic positions. The Egribucak area studied here, located about 25 km southeast of Sivas, provides a well-stratified key section to shed light on the depositional history of the Oligocene marine evaporite (coastal lagoon or sabkha complex) and other associated carbonate and siliciclastic units. The Egribucak succession has a thickness of approximately 400 m and rests on thick fluviatile sediments commencing with red beds (mudstone, sandstone, and gravelly sandstone), and upwards, terrestrial gypsums are present within the red units as thin beds that are overlain by thick marine gypsum beds with rhythmical alternations of gray and green colored sandstone-marly limestone and limestone. The limestones alternating with the thick gypsum beds are rich in benthic foraminifers yielding a Rupelian-Chattian age. At the top of the section evaporites disappeared and lagoon-type limestone turned into thick platform carbonate dated as Oligocene-early Miocene. The Egribucak succession shows a wide variety of depositional environments ranging from terrestrial to restricted marine to open marine from bottom to top. The short periods of the lithological alternations from siliciclastic to carbonate and evaporite indicate that the evaporite environment was not consistent through the Oligocene period. This would be formed as a marginal evaporite environment, presumably a coastal lagoon/sabkha affected by seasonal variations with arid and humid periods as well as eustatic sea-level changes. The Oligocene transgression culminated in the area with the deposition of platform-type carbonates and it continued during the early Miocene.
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    Oligocene and early Miocene charophyte flora from the Sivas Basin (Central Anatolia, Turkiye). Biostratigraphy and palaeobiogeography
    (Elsevier, 2025) Sanjuan, Josep; Demirci, Elvan; Kangal, Ozgen; Ozgen-Erdem, Nazire
    A rich charophyte assemblage is described and illustrated here from the Upper Paleogene-Lower Neogene lacustrine and palustrine rocks of the Sivas Basin (central Anatolia, Turkiye). The flora was extracted from 3 stratigraphic sections located in the eastern part of the Sivas Basin in the localities of Emirhan, Egribucak, and Taslidere. Nine species belonging to two families (Characeae and Raskyllaceae) are identified here. The Characeae species from Emirhan and Taslidere (Emirhan and Karayun formations) are diverse and the assemblage is represented by Sphaerochara ulmensis, Sphaerochara sp., Chara molassica var. notata, Ch. cf. pappii, Chara sp., Hornichara sp., Lychnothamnus pinguis forma major and Nitellopsis (Tectochara) merianii. Several of these species display a wide biostratigraphic range in Europe spanning from the early Oligocene to middle Miocene. The cooccurrence of L. pinguis and Ch. molassica var. notata suggests that both the Emirhan and Karayun formations are upper Rupelian-lower Chattian (similar to 30-25 Ma). In terms of paleogeography, this flora displays a clear European affinity. The charophyte flora recovered from the Egribucak locality (Unit 3 of the Egribucak Formation) is composed of the single species Rantzieniella nitida which displays a limited biostratigraphic range within the Aquitanian (early Miocene). Accordingly, Unit 3 of the Egribucak Formation can be correlated with the homonymous European charophyte biozone as well as with the Mammal Neogene Zones MN1-2 (similar to 24-21 Ma). Moreover, the occurrence of this index species in central Anatolia confirms its Eurasian distribution highlighting the usefulness of R. nitida in intercontinental basin correlation.
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    Palaeontological evidence and sedimentary facies in a lower Miocene (Aquitanian) succession from the Bingol minibasin (Sivas Basin), Central Anatolia
    (SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2018) Akkiraz, Mehmet Serkan; Kangal, Ozgen; Ozgen Erdem, Nazire; Buyukmeric, Yesim; Dogruoz, Cihan
    The results of palaeontological (palynological and mollusc) and sedimentological analyses of the lower Miocene deposits from the Bingol minibasin, a part of the Sivas Basin, are exhibited to define the vertical shifts in sedimentation environments and plant covers, linking to eustasy. The presence of index species Corbulomya (Lentidium) aquitanica suggests an Aquitanian age for the studied succession, which can be divided into three informal units: a lower unit, a middle unit, and an upper unit. Fine-grained sediments of the lower unit were deposited in a low sea-level setting due to high quantities of terrestrial palynomorphs. This unit is overlain by the middle unit, coralgal limestone, which marks the first initiation of Aquitanian transgression. Continuing shallow marine settings in the upper unit gave rise to deposition of coarse to fine-grained sediments. Palynological data were recovered from the fine-grained sediments of the lower and upper units. A total of 35 spore and pollen taxa were recorded, including 2 spores from ferns, 5 gymnosperms, 26 angiosperms, 1 group of undifferentiated dinoflagellate cysts, and 1 fresh water alga of Botryococcus sp. The pollen spectrum is dominated by coniferous forest, mainly undifferentiated Pinaceae, and herbaceous communities including high quantities of Poaceae and Chenopodiaceae-Amaranthaceae, with minor contributions of Ephedra sp., Caryophyllaceae, and Asteraceae subf. Asteroidae. High sea-level conditions, which started with sedimentation of the middle unit, survived during the deposition of the upper unit due to being overwhelmingly dominated by dinocysts. Thermophile plants including Avicennia sp., Engelhardia sp., Myrica sp., Sapotaceae, Cyrillaceae-Clethraceae, and Reveesia sp. along with relatively high quantities of xerophytes and the quantitative palaeoclimate values imply a subtropical and dry palaeoclimate.
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    Planktonic and benthic foraminiferal biostratigraphy of the Middle Eocene-Lower Miocene successions from the Sivas Basin (Central Anatolia, Turkey)
    (SLOVAK ACAD SCIENCES GEOLOGICAL INST, 2016) Hakyemez, Aynur; Ozgen-Erdem, Nazire; Kangal, Ozgen
    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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    Systematics and biostratigraphy of Oligocene (Rupelian-Early Chattian) foraminifera from lagoonal-very shallow water limestone in the eastern Sivas Basin (central Turkey)
    (INST GEOLOSKA ISTRAZIVANJA, 2013) Sirel, Ercument; Ozgen-Erdem, Nazire; Kangal, Ozgen
    The aim of the present work is to describe the Oligocene (Rupelian-early Chattian) shallow water larger foraminifera from central Turkey (Sivas Basin). Among them is a new miliolid genus, Sivasina n. gen. SIREL & OZGEN-ERDEM (type species Sivasina egribucakensis n. gen. n. sp. SIREL & OZGEN-ERDEM), which occurs in the Egribucak, Bakimli, Tuzlagozu and Caygoren sections (E of Sivas). One new Rupelian-early Chattian lagoonal very shallow water peneroplid species Peneroplis flabelliformis n. sp. SIREL & OZGEN-ERDEM from the Egribucak, Tuzlagozu and Caygoren sections and Rupelian lagoonal two new peneroplid species Coscinospira sivasensis n. sp. SIREL & OZGEN-ERDEM, Coscinospira elongata n. sp. SIREL & OZGEN-ERDEM from the Egribucak section (E of Sivas), two new Rupelian very shallow water alveolinid species Praebullalveolina oligocenica n. sp. SIREL & OZGEN-ERDEM and Praebullalveolina minuta n. sp. SIREL & OZGEN-ERDEM from the Bakimli section are described and figured. Furthermore, details on several already known Oligocene species are given (soritids: Praearchaias diyarbakirensis SIREL, Praearchaias minimus SIREL, Archaias kirkukensis HENSON, Archaias asmaricus SMOUT & EAMES; austrotrillinids: Austrotrillina brunni MARIE). In addition, the biostratigraphy of four studied sections is discussed.