International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Mineralogical, geochemical and micromorphological evaluation of the Plio-Quaternary paleosols and calcretes from Karahamzall, Ankara (Central Turkey)

Pages: 241 - 253


Abstract: We present the mineralogical, micromorphological, and geochemical characteristics of the paleosols and their carbonates from Karahamzall, Ankara (Central Turkey). The paleosols include calcretes of powdery to nodular forms and alternate with channel deposits. The presence of pedofeatures, such as clay cutans, floating grains, circumgranular cracks, MnO linings, secondary carbonate rims, traces of past bioturbation and remnants of root frag- ments are all the evidence of pedogenesis. Bw is the most common soil horizon showing subangular-angular blocky to granular or prismatic microstructures. Calcretes, on the other hand, are evaluated as semi-mature massive, nodular, tubular or powdery forms. The probable faunal and floral passages may also imply the traces of life from when these alluvial deposits were soil. The presence of early diagenetic palygorskite and dolomite together with high salinization, high calcification and low chemical index of alteration values are evidence of the formation of calcretes under arid and dry conditions. δ13C compositions of the carbonates ranging from —7.11 ‰ to —7.74 ‰ VPDB are comformable with the world pedogenic carbonates favouring the C4 vegetation; likely δ18O compositions of the carbonates are between —3.97 ‰ and —4.91 ‰ which are compatible with the paleosols formed under the influence of meteroic water in the vadose zone.

Keywords: Calcrete, paleosol, Central Anatolia, Plio-Quaternary, stable isotope, Aridity

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