Geology and Origin of Clay Deposits at Orta (Çankırı) Area

Abstract

Kaolinitic clay layers interbedded with lignite seams are observed in the Orta (Çankırı) area. In order to reveal the genesis of these clays, geological, mineralogical, petrographical and micromorphological studies were carried out in the vicinity of the clay deposits and in their surrounding country rocks. Rock samples were examined by means of optical microscope, X-ray powder diffractometer and scanning electron microscope. Kaolinitic clays were formed in the clayey and silly Orta formation of Pliocene age. These elastics were transported and deposited by streams in a lacustrine environment located on a paleotopographic depression. The country rocks providing detritic materials which mainly consist of smectite comprise pyroclastic rocks (Kepezinkaş, formation) and lava flows (Naltepe basalt). In addition to this, some data indicating the development of smectite related to the authigenic processes were also obtained. It is concluded that the clay layers were formed by the transformation of smectite to kaolinite in an acid swamp environment.