SEDIMENTOLOGICAL CHARACTERISTICS AND FACIES OF THE EVAPORITE-BEARING KIRMIR FORMATION (NEOGENE), BEYPAZARI BASIN, CENTRAL ANATOLIA, TURKEY

A thick sedimentary sequence comprising fluvial, lacustrine and volcan o-sedimentary rocks is present in the Neogene Beypazari Basin, central Anatolia. These units display considerable lateral facies variation a nd interfinger with alkaline volcanic rocks along the north-eastern ma rgin of the basin. The uppermost Miocene Kirmir Formation contains num erous evaporite horizons. The evaporite sequence is up to 250 m thick and may be divided into four lithofacies. In ascending stratigraphical order these are: (1) gypsiferous claystone facies, (2) thenardite-gla uberite facies, (3) laminar gypsum facies and (4) crystalline gypsum f acies. These facies interfinger with one another laterally along a sec tion from the margins to central parts of the basin. The lithological and sedimentological features of the Kirmir Formation indicate fluvial , saline playa mudflat, hypersaline ephemeral playa lake and very shal low subaqueous playa lake depositional environments, which probably we re influenced by alternating semi-arid and evaporative conditions.