Taxonomy, Stratıgraphic and Palaeogeographic Distribution and Palaeoenvironment of Charophytes Flora of Neogene Continental Sediments Around Ilgın (Konya)- Yalvaç (Isparta) (Central Anatolia/Türkiye)

Abstract

The basins of Yalvaç and Ilgın have provided a diverse charophyte assemblage ranging in age from Late Miocene to Early Pleistocene. Up to 16 known taxa have been described and illustrated in this Ph.D thesis. Moreover, 11 taxa have been identified and kept in open nomenclature (limited populations and bad preservation). This flora provides valuable information about charophyte palaeoecology, relative age of several lithological units (biostratigraphy) and charophyte palaeobiogeography. The flora recovered in lacustrine rocks (marls and limestones) and palustrine facies (organic rich marls and lignites) of the Göksöğüt Formation (Balcı section and SK–2 borehole at Şarkikaraağaç, Yalvaç Basin) is constituted by 8 taxa: Sphaerochara cf. intricata, Sphaerochara sp., Chara vulgaris, Ch. globularis, Chara sp., Lychnothamnus duplicicarinatus, L. barbatus subsp. megalicarpus, and Nitellopsis (Tectochara) etrusca. This assemblage indicates that the Göksöğüt Formation can be correlated with the European charophyte biozone of Nitellopsis (Tectochara) etrusca, which is upper Miocene–lowermost Pliocene in age (most provably Vallesian). Associated to these charophyte flora a rich assemblage of microfossils has been found including 4 taxa of fruits/seeds of aquatic and halophytic herbaceous plants as well as gastropods and ostracods. The charophyte flora extracted from the Miocene palustrine deposits (organic rich claystones) and lacustrine rocks (marls, limestones) and tufas of the Aşağıçiğil Formation in the Ilgın Basin (stratigraphic sections of Kiresendere, Çiğil, Yukarıçiğil) is composed of 13 taxa including Sphaerochara ulmensis, Sph. miocenica, Chara vulgaris, Ch. globularis, Ch. molassica var. molassica, Ch. molassica var. notata, Ch. multispira, Ch. pappii, and 5 indeterminate species of Chara. The charophyte assemblage from the section of Çebişli (Belekler Formation) provides up to 5 badly preserved taxa: Sphaerochara intricata, Sphaerochara sp., Chara cf. vulgaris, Ch. cf. multispira, and Lychnothamnus sp. The charophyte assemblage from the Aşağıçiğil Formation can be correlated with 5 European charophyte bizones of Riveline et al (1996): Chara notata, Rantzieniella nitida, Stephanochara berdotensis, Nitellopsis (Tectochara) ginsburgi, and the base of Nitellopsis (Tectochara) etrusca. These biozones range in age from the upper Oligocene (Upper Chattian) until the upper Miocene (Tortonian). However, the occurrence of Sphaerochara miocenica suggests that the Aşağıçiğil Formation is middle-late Miocene in age (Serravalian). These results are in agreement with previous biostratigraphical works performed in the area based on ostracods. Also, in the same Ilgın Basin, the charophyte flora from the lower Pleistocene palustrine and lacustrine sediments of Dursunlu is constituted by 11 species i.e. Sphaerochara intricata, Sph. prolifera, Chara vulgaris, Ch. globularis, Ch. hispida, Ch. pappii, Ch. molassica var. notata, Chara sp.1–2, Lychnothamnus barbatus var. antiquus, and Nitellopsis obtusa. Associated to this flora a rich assemblage of microfossils have been found including 7 species of fruits/seeds of aquatic and halophytic herbaceous plants, 16 species of gastropods (12 freshwater and 4 terrestrial taxa), 6 species of ostracods, 7 fish taxa, and remains of herpetofauna (toad, frog, turtle and snake). The ecological requirements of the charophyte assemblage (dominated by living species) indicated that during the Günz glaciation the Ilgın Basin was occupied by a very shallow eutrophic lake with a dense palustrine vegetation belt, which evolved to a shallow (2–15 m deep), stable, oligotrophic, alkaline and oligohaline lake. The here–studied Neogene charophyte flora display a wide palaeogeographic distribution mainly in south European and Middle East peri–Mediterranean basins. This distribution suggests that a certain degree of floral homogeneity exists during the Miocene and Pleistocene in the Mediterranean region, following a latitudinal climatic control.