Mineralogical and Stable Isotope Properties of Carbonate Minerals in Tuz Gölü Basin (turkey): Paleoenvironment Assessment

Abstract

The study area is located south of the Tuz Gölü Basin in the Central Anatolia. The investigated carbonate minerals are deposited in the Neogene lacustrine sediments. Alternations of halite, carbonate, sulfate minerals and clay-enriched levels have been observed in the ten different drillings made in the study area. The aim of this study is to investigate the properties of carbonate minerals closely related to evaporite minerals, e.g. halite and sulfate minerals. The carbonate minerals commonly observed in the region are dolomite and magnesite which are generally micritic and parallel to bedding and also, they have reticulated structures. The thickness of the carbonate minerals precipitate ranges from mm to dm, and the carbonates have been located as a matrix around other minerals in some levels. The thick carbonate levels indicate to rise of lake level or dilution of the water in the lake. In this study, four carbonate facies have been identified as microbial carbonate facies, sparitic facies, pelloidal facies and oolitic facies. Microbial carbonate facies show quite shallow environments and enriched cyanobacteria. The facies are overlain by generally sparitic cemented peloidal limestones. The Mg/Ca ratio of carbonates is quite high and these high values can be explained by dedolomitization processes. The Sr values of the carbonates range from 115-6216 ppm. The δ18O and δ13C isotope values of the dolomite samples from TG6, TG3 and TG2 drillings range from -3.38 to +5.74 ‰, and -10.78 to +0.04 ‰, respectively. Besides, δ18O and δ13C values of magnesite-rich samples vary between 7.57 and 10.46 ‰ and -4.82 and -9.49 ‰. Isotopic values, sedimentological and geochemical data of carbonates indicate that the deposition environment has sometimes been influenced by atmospheric events, wave activity and water level changes, and also biological activities are highly effective in shapka environment.