Oligocene and early Miocene charophyte flora from the Sivas Basin (Central Anatolia, Türkiye). Biostratigraphy and palaeobiogeography

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, Türkiye). The flora was extracted from 3 stratigraphic sections located in the eastern part of the Sivas Basin in the localities of Emirhan, Eğribucak, and Taşlıdere. Nine species belonging to two families (Characeae and Raskyllaceae) are identified here. The Characeae species from Emirhan and Taşlıdere (Emirhan and Karayün 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 co-occurrence of L. pinguis and Ch. molassica var. notata suggests that both the Emirhan and Karayün formations are upper Rupelian–lower Chattian (∼ 30–25 Ma). In terms of paleogeography, this flora displays a clear European affinity. The charophyte flora recovered from the Eğribucak locality (Unit 3 of the Eğribucak 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 Eğribucak Formation can be correlated with the homonymous European charophyte biozone as well as with the Mammal Neogene Zones MN1–2 (∼ 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.