Chemical weathering indices applied to soils developed on old lake sediments in a semi-arid region of Turkey

Abstract

Climate is a major influence on weathering processes affecting soil parent materials.Important contributors to soil formation in arid and semi-arid climatic zones are thediurnal cycles of solar heating and cooling that cause mechanical or physicaldisintegration of rock or parent materials, and wind-blown sands that score and abradeexposed rock surfaces. By using the Soil Taxonomy classification system, the initial aim ofthis study was to carry out a pedological evaluation for four soil profiles, classified as XericHaplocalcid and Xeric Haplocambid, formed on different parent materials (limestone, marland old alluvial deposits) under the same conditions, including topography andvegetation, in a semiarid region. The second stage was the exploration of the similaritiesand differences in the classifications resulting from either the pedogenic processes, orfrom other factors, by determining the degree of soil weathering using geochemical data.To achieve this, soil samples were collected from the horizons to investigate theirmineralogical, geochemical and physiochemical properties. The study also consideredother features, such as the pedogenic evolution of soils, through the use of weatheringindices, namely the Chemical Index of Alteration (CIA), Chemical Index of Weathering(CIW), Base/R2O3 Ratio, Weathering Index of Parker (WIP) and Plagioclase Index ofAlteration (PIA). The results clearly showed that soil development at the Altınova StateFarm at Konya in the Central Anatolia region of Turkey is due to slow pr ogressiveweathering. For this case, the main indicators are secondary calcium carbonate illuviationand weak structural development with a weathering ratio of silicon to aluminium greaterthan two in all profiles.