Evaluation of a Cenozoic Lacustrine Basin-Hançılı formation (Kalecik-Ankara) and its paleoenvironment and paleoclimate analysis based on mineral facies

Aker, Serdar
The major purpose of this study is to evaluate the paleoenvironmental and paleoclimatological conditions during the Middle Miocene-Early Pliocene in Kalecik-Ankara by using mineralogical and geochemical proxies from Hançılı Formation. To achieve a high-resolution paleoclimate data, 2 stratigraphic sectioning and 1 continous core drilling were examined. Field studies were followed by analytical techniques on the selected representative samples. The mineralogical compositions of the bulk samples and the minerals of the clay fractions were determined by X-ray diffractometer. Scanning electron microscopic analyses were also carried on the specific samples which have the potential to define the important microstructural units. The major and trace elemental compositions were determined by X-ray fluoresence spectrometer. Additionally, the stable isotope compositions of the samples selected from the continous core drilling on Hançılı formation were among the major proxies to gather a paleoenvironmental and paleoclimatrological approach. All the proxies employed for this study clearly indicate that mineralogical and geochemical signatures are consistent with each other and can be used for paleoclimatic interpretations. The stable isotope values point that C4 plants were dominant during the deposition of Hançılı Formation, while evaporation caused the development of alkaline environment which is seasonally dry with depositional temperature approximately between 25-30°C. During deposition, lava flowand tuff were deposited due to the volcanic activity in the vicinity of the lake. Based on this volcanism, economical bentonite deposits were originated. The lake at which the Hançılı formation was deposited, completed its development in a time to time silicate rich and salty-alkaline anvironment.