Subrecent charophyte flora from Çeşmealti (Izmir Gulf, Western Turkey): Palaeoecological implications

Abstract

A charophyte assemblage from lower Holocene sediments in Çeşmealtı (Izmir Gulf, Turkey) is described and illustrated for the first time here. This assemblage is composed of well-preserved gyrogonites and oospores of Lamprothamnium papulosum, which occur in association with seeds of Ruppia cf. maritima and up to eight ostracod species and 22 benthic foraminiferal taxa. The fossil assemblage was extracted from five clay intervals of the SK-2 borehole. The presence of monospecific assemblages of L. papulosum indicates that very shallow (up to 1 m deep), brackish, alkaline, and oligotrophic waters prevailed in the gulf under strong seasonality (marked cyclical changes in humidity and/or temperature). The dominance of germinated gyrogonites suggests that the water salinity of the lagoon decreased during the humid season, reaching at least 10‰. The associated ostracod fauna supports the palaeoenvironmental conditions inferred from the flora. Despite the gulf receiving considerable freshwater input, it remained semiconnected to the sea, as indicated by the diverse foraminifera assemblage. The availability of freshwater in the Izmir Gulf during the early Holocene Climatic Optimum, between ∼9000 and 5000 years BP, might have played an important role for the first human settlements in the area dating back 5500 years BP.