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 b een derived from crystalline rocks (mostly granitic or granitoidic). They h ad been modified in glacial environment during the last glacial stage, tran sported in eolian suspension mode and deposited during glacial periods, whe n the area was a cool, arid, and poorly vegetated steppe. The loess was evi dently derived from the Qaraqum desert to the north because (1) the beds be come thicker and coarser-grained in that direction, (2) the deposits mostly cover northward facing hills and plains. The major and trace elements dist ribution patterns of the Gharatikan loesses are similar to that of Uzbekist an and Tajikistan loesses. Therefore, Gharatikan loess is the extension of the Uzbekistan and Tajikistan loesses. Changes in the petrographical charac teristics of loess deposits of the Gharatikan watershed allow the reconstru ction of the paleoenvironments during the periods of their formation and th e detection of the trends of Pleistocene climate changes. (C) 2001 Elsevier Science B.V. All rights reserved.