ABSTRACT : The engineering properties of a soil depends on the composite effects of several interacting and often interrelated factors as compositional and environmental., In this research.» mincralogical composition and geotecrmical properties of Upper Pliocene deposits» collected from. Sincan, Beşevler and Kavaklıdere sites (Ankara),, are studied and correlated. The samples» inorganic clay of high plasticity (CH),, and inorganic silt of high plasticity (MH) are used as the material. Deposits consist of quartz» calcite, albite and clay minerals.- Sincan deposits contain about 20 percent montmorillonit. Montmorilionit. causes decreasing in internal friction, and shear strength of the Sincan deposits and aparts from gcotechnical properties of Beşevler and Kavaklıdere deposits.