Abstract: The young fluvial sediments exposed at the northern part of the Büyük Menderes Graben have been assigned to latest Plioceneand Pleistocene on the basis of Arvicolidae. These constitute the first mammal findings explaining the age of the sediments at thenorthern part of the Büyük Menderes Graben and the tectonism which controlled the sedimentation. The evolutionary stages of thearvicolids may suggest the presence of four biochronologic units in the time interval between late Villanian and Toringian.