Late Pleistocene Calcretes from Central Anatolia (Lakes Eymir and Mogan, Golbasi Basin): Comparison to Quaternary Calcretes from Turkey
Özet
This study is the first to report the radiocarbon ages, mineralogical, morphological, geochemical and stable isotope compositions of calcretes from Neogene sediments around lakes Eymir and Mogan in the Golbasi Basin of Central Anatolia. Morphologically different forms of calcretes in the Golbasi Basin include powdery, nodular, fracture infill, laminar and hardpan types. Calcite is the dominant mineral of calcrete compositions; the diagnostic features of dessication cracks, random fractures, MnO linings and dense sparitic infillings are observed. Chemical analyses show arid conditions with mean annual precipitation of <50 mm. delta C-13 compositions of the calcretes range from - 6.77 parts per thousand to -9.32 parts per thousand PDB, typical for most pedogenic calcretes, reflecting the development under seasonally arid climates and C3-dominated vegetation cover. delta O-18 values are between -5.57 parts per thousand and -7.80 parts per thousand PDB, indicating the formation from meteoric water in a vadose zone environment. The results suggest that the Middle Pleistocene was arider and warmer, favouring the formation of palygorskite in association with the different forms of calcrete occurrences; whereas the Late Pleistocene was dryer and cooler, supporting the development of calcretes.
