Neogene Stratigraphy of the Bozbelen area (Çayırhan, Nallıhan) and a New Vertebrate Fossil Locality

Neogene Stratigraphy and a New Vertebrate Fossil Locality

Abstract

Within the scope of the research, we present the vertebrate fossil findings for the first time around Çayırhan (W Ankara). Fossils are only in a single locality namely Bozbelen area and its vicinity within the lacustrine sediments mostly at clayey, marly levels. The paper aims to introduce the fossil findings of this locality, which is important in terms of geoheritage and Miocene-Pliocene geological history of Türkiye, and to revise stratigraphy of the study area that is located in the Beypazarı Neogene Basin. The Miocene basin comprises various lithological units. Stratigraphy based on field observations and satellite views are from bottom to top as follows: Paleogene-aged Karabayır formation (red coloured clastics), Miocene-aged Akpınar formation (=Çayırhan formation) (rhythmic greenish tuffite, claytone, sandstone), Kırmızıtepe formation (red-coloured sandstones, conglomerates), Miocene-Pliocene aged Bozbelen formation (marls, siltstones, mudstones), Aşağıbozbelen formation (sandstones, siltstones), Yukarıbozbelen formation (sandstones, conglomerates) and Quaternary alluvium and slope deposits. The formations have lateral and vertical facies that change each other. Various teeths and broken bones of Hipparion sp., Gazellesp. and Ictitherium sp. are within the sediments of the Bozbelen formation. The age of the unit is late Miocene-early Pliocene. Reworked fossils into the lake muds and lithological features of the studied formation show a very shallow lake coast side paleoenvironment. Trace fossils and silica fillings in the muds originating from the volcanic activity are also noteworthy.