Palaeontological evidence and sedimentary facies in a lower Miocene (Aquitanian) succession from the Bingol minibasin (Sivas Basin), Central Anatolia

Abstract

The results of palaeontological (palynological and mollusc) and sedimentological analyses of the lower Miocene deposits from the Bingol minibasin, a part of the Sivas Basin, are exhibited to define the vertical shifts in sedimentation environments and plant covers, linking to eustasy. The presence of index species Corbulomya (Lentidium) aquitanica suggests an Aquitanian age for the studied succession, which can be divided into three informal units: a lower unit, a middle unit, and an upper unit. Fine-grained sediments of the lower unit were deposited in a low sea-level setting due to high quantities of terrestrial palynomorphs. This unit is overlain by the middle unit, coralgal limestone, which marks the first initiation of Aquitanian transgression. Continuing shallow marine settings in the upper unit gave rise to deposition of coarse to fine-grained sediments. Palynological data were recovered from the fine-grained sediments of the lower and upper units. A total of 35 spore and pollen taxa were recorded, including 2 spores from ferns, 5 gymnosperms, 26 angiosperms, 1 group of undifferentiated dinoflagellate cysts, and 1 fresh water alga of Botryococcus sp. The pollen spectrum is dominated by coniferous forest, mainly undifferentiated Pinaceae, and herbaceous communities including high quantities of Poaceae and Chenopodiaceae-Amaranthaceae, with minor contributions of Ephedra sp., Caryophyllaceae, and Asteraceae subf. Asteroidae. High sea-level conditions, which started with sedimentation of the middle unit, survived during the deposition of the upper unit due to being overwhelmingly dominated by dinocysts. Thermophile plants including Avicennia sp., Engelhardia sp., Myrica sp., Sapotaceae, Cyrillaceae-Clethraceae, and Reveesia sp. along with relatively high quantities of xerophytes and the quantitative palaeoclimate values imply a subtropical and dry palaeoclimate.