Abstract: The gypsum member of the upper Miocene aged Sakarya formation in the Polatli-Sivrihisar Neogene basin isrepresented by five different sub-lithofacies. These are: a) secondary massive gypsums b) primary laminatedanhydrite c) secondary laminated brecciated-nodular gypsum d) clastic gypsum (gypsum arenite) and e) chevronselenitic gypsum. Among these, massive gypsum with iron-manganese bands separated by sparse sulphur crystalsand primary laminated anhydrite with algal stromatolithic structures are important in respect of their formationmechanisms. The geochemical and geostatistical evaluation of different minerallization types from gypsumanhydrite samples of these sub-facies provide evidence of their possible source of origin. For this purpose 24samples of different types including 13 major oxides, 15 trace elements and 13 rare earth elements were analyzedand from these results the correlation coefficient values for couple elements were determined and statisticalgraphics were prepared. After these geostatistical studies, three main groups of elements were identified. Amongthese: Group-I comprised SiO , Al O , K O, Rb, ∑ Fe O , MgO, MnO, As,V, TiO , P O , Zr, Zn, Ni, Co and Cu, 2 2 3 2 2 3 2 2 5Group II comprised Ba, Sr, Mo, Pb, W, F, Au and Na O and Group III comprised CaO and SO combinations. These 2 3combinations commonly show excessive vug-filling diagenetic clay minerals and/or carbonization withinevaporites. On the other hand, the results of geochemical analysis of trace elements show higher values than thechemistry of evaporitic playa lake sedimentary environments. The reasons for these high values are considered tobe: the fact that during the evaporation process the upper Miocene paleolake was under the influence of freshground water input, variation in climatic conditions for a short period of time (like dryness and wetness), limitedreducing environmental conditions in isolated parts of the lake and post depositional hydrothermal dissolutioning.The geochemical and geostatistical evaluation of upper Miocene evaporites of the gypsum member ofSakarya formation have identified that these evaporites were deposited in a playa lake complex with differentdepositing lithologies (siliciclastics and carbonates) which were affected by paleoclimatic conditions, periodicterrestrial volcanism and syn-sedimentary tectonics.