Late Miocene aquatic flora from the Yalvaç Basin (Central Anatolia, Türkiye): Biostratigraphy and paleoecology

Abstract

An assemblage of fructifications and seeds of aquatic plants (8 charophyte species and 5 seeds/fruits) from upper Miocene deposits of the Yalvaç Basin (Central Anatolia, Türkiye) is described and illustrated here for the first time. This flora has been recovered from 2 localities: a 39 m-thick sedimentary sequence near the village of Balcı, dominated by limestones related to well-developed, alkaline, and deep lake; and a 252 m-thick borehole (SK–2) near the village of Şarkikaraağaç, dominated by organic claystones and marls formed in a context of palustrine and shallow lake conditions. Both sequences are within the Göksöğüt Formation (upper Miocene–Pliocene). The assemblage at Balcı is dominated by gyrogonites of the genus Sphaerochara cf. intricata, Chara vulgaris, Chara cf. aspera, Lychnothamnus duplicicarinatus, and Lychnothamnus cf. barbatus subsp. megalicarpus. Gyrogonites from the lower part of the SK–2 borehole at Şarkikaraağaç are very diverse and well-preserved. The assemblage is composed of Sphaerochara intricata, Chara vulgaris, Chara globularis, Chara cf. hispida, Chara cf. aspera, Nitellopsis (Tectochara) etrusca, and Lychnothamnus duplicicarinatus. Several seeds/fruits of aquatic and helophytic plants occur associated with this charophyte flora, including Ceratophyllum, Aldrovanda, Scirpus, Ranunculus and Typha. The dominance of the species N. (T.) etrusca suggests that the base of the sedimentary sequence at Şarkikaraağaç is late Miocene, most probably Vallesian-Turolian in age. Likewise, the occurrence of Lychnothamnus cf. barbatus subsp. megalicarpus at the base of the Balcı sequence indicates that it probably dates back to the Turolian age. The facies assemblage and the associated fossils such as ostracods from both Balcı section and the SK–2 borehole indicate that palustrine and lacustrine conditions prevailed in the Yalvaç Basin during the late Miocene. The lake was stable, oligotrophic and oligohaline in the central part of the basin, while the water table fluctuated along the lake's edges where palustrine vegetated conditions prevailed. The species N. (T.) etrusca and L. duplicicarinatus and L. barbatus subsp. megalicarpus are being reported for the first time in Anatolia, providing significant information about the distributional pattern of these biostratigraphically significant taxa.