Tezin Türü: Doktora
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Jeoloji Mühendisliği Bölümü, Türkiye
Tezin Onay Tarihi: 2011
Tezin Dili: İngilizce
Öğrenci: Ceren Küçükuysal
Danışman: ASUMAN GÜNAL TÜRKMENOĞLUÖzet:
The major goal of this study is to define the paleoclimatic conditions in Ankara region during Plio-Pleistocene period by evaluating the mineralogical and geochemical proxies carried from the paleosols and their calcretes. The field observations, mineralogical, micromorphological, geochemical and stable isotope investigations were all conducted to achieve a paleoclimatic approach. As pedogenic minerals in calcretes, presence of dolomite with palygorskite in the Karahamzalı section and calcite with palygorskite in the Bala section together with high salinity and calcification values reveal the semi-arid and dry climatic conditions. The geochemical signatures of the paleosols are consistent with each other indicating low clastic input during the dry seasons favouring the formation of calcretes. The δ13C and δ18O values indicate the formation of calcretes from percolating soil-water under predominantly C4 to C3:C4 association type vegetation. Temperature calculations show that paleoclimatic conditions favouring the formation of calcretes in the region are semi-arid and seasonally dry with approximately 25°C soil depositional temperature. This study is the first to give both a radiometric age data to the calcretes of Central Anatolia, Ankara and document their stable isotope compositions. Dated calcretes having ESR ages of 419±69ka and 761 ±120ka point the formation during Middle Pleistocene when Mid-Brunches Event (MBE) was happened and the periodicity changed affecting the climatic control over the European continent. Like the Mediterranean calcretes, this study suggests that calcretes in the study area started to develop with MBE warmth between Marine Isotope Stages of 13- 11 and 19-17.