Yalvaç ve Ilgın Karasal Neojen Havzalarında (Güneybatı Anadolu) Ostracoda Taksonomisi ve Biyostratigrafisi: Ostrakodlara Dayalı Eskiortamsal-Eskiiklimsel Yaklaşımlar

Abstract

Regional tectonism during the late Cenozoic triggered the development of many sedimentary basins in northern Taurids. These basins include the continental Yalvaç and Ilgın basins, which contain economical coal seams within the Neogene basin infillings. Within the scope of the study, it is aimed to determine ostracod fauna assemblages along the lacustrine successions of Yalvaç and Ilgın basins, and to perform detailed paleoenvironmental/paleoclimatic and biochronological evaluations on the deposition environments and ages of the units by using of ostracods and other faunal/floral findings. In this context, 14 measured stratigraphic sections and 2 borehole cores gathered from the deposits of Yalvaç (Yarıkkaya and Göksöğüt formations) and Ilgın (Kumdöken, Aşağıçiğil, Belekler and Dursunlu formations) basins are evaluated.

Within the systematic paleontology studies, 40 genera and 90 taxa of ostracods belonging to 7 ostracod families are identified. 38 known species and 1 known subspecies are identified within the taxa. Moreover, 7 new species (Cyprinotus turcica n. sp., Heterocypris granuloreticulata n. sp., Heterocypris yalvacensis n. sp., Herpetocyprella posterotruncata n. sp., Herpetocyprella posterocornuta n. sp., Psychrodromus seni n. sp. ve Metacypris gokcenae n. sp.) are diagnosed and proposed. In addition, 44 of the 90 taxa are left open to nomenclature.

Paleoenvironmental/paleoclimatic evaluations and age interpretations are carried out by using ostracods and other faunal/floral findings along the Neogene and Quaternary sequences of the Yalvaç and Ilgın basins. It is determined that the lower-middle parts of the Yarıkkaya Formation (Yalvaç Basin) was deposited in stagnant and permanent sublittoral?-profundal lacustrine conditions. It is revealed that the upper parts of the formation was deposited under the subtropical climatic conditions in a freshwater-oligohaline littoral lacustrine environment which also contains paleomires. Additionally, the age of the Yarıkkaya Formation is suggested as late early (middle Orleanian)–early middle (late Orleanian) Miocene according to micro mammals, ostracods and palinoflora. It is revealed that carbonate-dominated parts of the Göksöğüt Formation (Yalvaç Basin) were deposited in stagnant/slow-flowing, freshwater-oligohaline and permanent littoral lacustrine conditions. It is revealed that the coal-bearing middle and upper parts of Göksöğüt Formation were deposited under the cool climatic conditions in vegetation-rich, stagnant/slow flowing, neutral-slightly alkaline, oligo-mesotrophic and littoral lacustrine environment containing paleomires. It is also determined that freshwater-oligohaline aquatic conditions fed by flows were common during the deposition and water level decrease and relative salinity increase were prevailed during some periods. Additionally, the age of the Göksöğüt Formation is suggested as late Miocene-Pliocene according to ostracod and palinoflora assemblages.

It is determined that the sequence overlying the lower coal levels of the Kumdöken Formation (Ilgın Basin) were deposited in a stagnant and temporary pond (freshwater?) with paleomires. Sequoioxylon sp. suggests that the paleomire that forms the upper coal levels was accumulated in an eutrophic wet forest mire under humid and rainy climatic conditions. It is found that the sequence overlying the upper coal levels was deposited in vegetation-rich, stagnant/slow flowing, mesotrophic-eutrophic and very shallow freshwater aquatic conditions (pond/lake). Additionally, the age of the lower and upper coal-bearing levels of the formation is proposed as early Miocene according to obtained ostracod taxa. It is determined that the middle-upper parts of the Aşağıçiğil Formation (Ilgın Basin) was deposited in spring-fed, vegetation-rich, stagnant/slow flowing, freshwater-oligohaline and permanent littoral lacustrine conditions during the late middle?–early late Miocene. It is revealed that the fine clastics-dominant part of the Belekler Formation (Ilgın Basin) was deposited in a freshwater-oligohaline temporary and/or permanent lake (pond?) environment during the late Miocene?-Pliocene. It is found that the paleomire of the coals in the lower parts of Dursunlu Formation (Ilgın Basin) was accumulated in flow-fed, eutrophic and slightly salty lacustrine (pond?) conditions. It is also determined that the overlying levels of the formation were deposited in vegetation-rich, stagnant/slow flowing, freshwater-oligohaline and permanent littoral lacustrine (pond?) conditions. It is revealed that the basin was fed with flows and relatively cold aquatic conditions were prevailed. Additionally, ostracod assemblage indicates that coal-bearing level of the Dursunlu Formation was deposited during the early Pleistocene.