Characteristics and provenance of the loess deposits of the Gharatikan watershed in Northeast Iran

Loess and loess-like deposits cover large areas of north and central parts of Iran. Studies of shapes, inclusions, and surface textures of sand grains plus mineralogical composition and trace elements of these loesses in the Gharatikan watershed basin, located in northeast Iran, show that they had been derived from crystalline rocks (mostly granitic or granitoidic). They had been modified in glacial environment during the last glacial stage, transported in eolian suspension mode and deposited during glacial periods, when the area was a cool, arid, and poorly vegetated steppe. The loess was evidently derived from the Qaraqum desert to the north because (1) the beds become thicker and coarser-grained in that direction, (2) the deposits mostly cover northward facing hills and plains. The major and trace elements distribution patterns of the Gharatikan loesses are similar to that of Uzbekistan and Tajikistan loesses. Therefore, Gharatikan loess is the extension of the Uzbekistan and Tajikistan loesses. Changes in the petrographical characteristics of loess deposits of the Gharatikan watershed allow the reconstruction of the paleoenvironments during the periods of their formation and the detection of the trends of Pleistocene climate changes.