Abstract: The studied Kirmir formation (Late Miocene-Pliocene) consists of alternation of gypsum and clay ey beds, which are conformably underlain by Bozbelen formation (sandstone, conglomerate, mudstone) and Sanycw limestones, and disconformably overlainby alluvium and tallus breccia of Pleistocene age.The unit includes three different fades, based on sedimentary properties of gypsum; 1) Individual gypsum beds inter bedded withgreen clays, 2) Scattered gypsum crystals and bassanite within an organic rich mudstone, 3) Massive gypsum with thin clay laminations. All these fades respectively reflect the different conditions of Neogene lake basin deposition: 1) Open lake with short evaporitic phases, 2) Marginal swamps with evaporitic ground water, 3) Closed lake with evaporitic lake water. These different stages ofgypsum occur ences primarily resulted from climatic changes from humid to arid. Tectonic is also thought to play a role on the regression of the lake area.