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H. Emrah ERDOÐAN, Mahmut YÜKSEL Department of Soil Science, Agricultural Faculty of Ankara University, Ankara. Abstract In this study, the clay mineralogy and genesis of the soils, originated from three different parent materials, in Beypazarý, Ankara, were investigated by using some morphological, physical, chemical and mineralogical analysis. Attempts were made to clarify the mineralogical characteristics of the soils that developed on the granodiorit, marl, and basalt and to elucidate both the proportional contribution of each soil forming factors to the soils and the effect of soil formation processes on the soils. The soils developed on granodiorit and basalt were classified as Entisol order, Orthent suborder and Xerorthent great soil group and the soil developed on marl corresponded to Inseptisols order, Xerepts suborder, Haploxerepts Great Soil Group, according to the Soil Taxonomy (1999). Simectite was found to be the dominant clay mineral of both coarse and fine clay fractions of all soil samples. In addition to, kaolin, illite and mixed layered clay minerals were determined in each of three soils. It couldn't find out any differences among the compositions of clays and their ratios in the coarse and the fine clay fractions of all the soil samples. Introduction Soil is characterized by factors of soil formation. So that, it has different properties in different environment that is constituted by external factors of soil formation (Tanju,1996). For example, it is revealed that all soil formation process of the soil originated from fluvial terrace of Tormes River (Spain) doesn't have a stabile development and horizontal difference is bounded time (Alonso et al,1993). Vegetation was not developed in Arid and Semiarid region, so it has a secondary role in soil formations. Parent material has more effect on the soil formation of studied pedons in the semi arid climate region .In this study, the clay mineralogy and genesis of the soil, originated from three different parent materials. In Beypazarý, Ankara, attempts were made to clarify the mineralogical characteristics of the soil that developed on the granodýorit, marl and basalt and to elucidate both the proportional contribution of each soil forming factors to the soils and the effect of soil formation processes on the soils. Materials and Method Beypazarý is located in Ankara Province, Turkey, approximately 150 km northwest of Ankara City. Three pedons were selected to study from three different parent materials. Geology of the pedon 1 consist of Paleozoic age granadiorite layer, pedon 2 consist of upper Miocenne age marl and then Middle Miocenne age basalt. Climate in the study area is characterized by dry and hot summer and a warm, wet winter .The moisture regime is Xeric and temperature regime is Mesic. For laboratory methods: Practical size distribution was determined by hydrometer method , Free iron oxide determined by the dithionite-citrate-bicarbonate method (Soil Survey Staff, 1996); Clay samples ( < 2µm) selected from surface and removal of cementing agents and dispersion, prepared for XRD analysis after fine clay ( < 0,2µm) and coarse clay (> 0,2µm) collected by centrifugation (Jackson,1965 and Whitting et al 1986). Results The Study pedons were classification; soils that originated on granadiorit and basalt rocks are Entisol order, Orthent suborder, Xerrthent great soil grub and the other soil formed on marl parent material is classified as Inceptisol order, Xerepts suborder, Haploxerepts great grub according to the soil taxonomy. Color of Profile 1, developed from granadiorit e of volcanic rocks is 10 YR hue. Since this profile include between 48% and 59 % sand; it is the coarsest texture in all pedons soil, pH values range from 7,65 to 8,17. Lime content increased and organic matter become less thought the depth. However organic matter accumulated in Ap horizon as result of excessive fertilizing and low leaching. In generally, the CEC is lower in the surface horizon and increasing with depth as compared with subsurface horizon. As a result they are low soluble salt and CaCO3 throughout the profile depth, the soil is not affected by salt toxicity. Kaolinite that is present in Ap horizon was found considerable higher amount in fine fraction than in coarse fraction. This case indicates that kaolinite formed from weathering of smectite. Depending on this information, this soil formed on granodiorit is the beginning of soil formation. Since it is shallow and has high slope, it was thought that soil was transported by erosion. There is not a significant difference in iron oxide percentages among the horizons. This shows that physical weathering was more effective than chemical weathering in soil formation. Based on the morphological properties were examined, Profile 2 was formed on Neocene aged limestone. Along the profile, hue, value and chroma were found to be 10 YR, 5-7 and 3-4 respectively. It is the deepest in all research soils. Clay content of soil is increasing though depth but after 110 cm, this amount is slightly decreasing and texture turned to silty clay. Owing to insufficient illiviation of clay and absence of clay cutans in B-horizon of soil profile, cambic subsurface diagnostic horizon was observed. In the value of CaCO3 is high level for all horizons. However, owing to calcification Ca CO3 accumulated between 44 cm and 140 cm according to this case. It was determinate that this pedon has been still inherited from effect of parent material. Depending on the clay analysis in coarse and fine fractions of the profile, it was found that the dominant clay mineral was simectite and followed by kaolin and illite. Moreover chlorite was found in coarse clay fractions of C1k horizon and fine clay fractions of C2k horizon. Profile number 3 is formed on basalt parent rock. When the soil is air dry, hue, value and choroma are 10YR, 4-5 and 2 respectively. Soil depth is 62 cm between Ap and C-horizons. Free iron oxide percentage is high for each horizon. If we compare both horizons in 3.profile it was found that Fe2O3 is high in C horizon due to effect of parent material, high weathering degree and cracking. In addition that, another important reason for illite that commonly exsist in soil is that this mineral is resistance to weathering. Resistance to weathering is especially related to chemical evens. Conclusion Depositions don't have a significant effect on three studied soil system formed on three different parent material and loses from the soil were not observed. Very little transportation exists in three soils under semi arid climate conditions and mesic soil temperature regime, and very little changes were observed in these weathering conditions. Three soils formed on granodiorite , lime stone and basalt parent rocks in semi-arid climate conditions are also in development stage. Morphological, physical, chemical and mineralogical results of this research show that soils are young, effect of weathering on soil formation is slow, and effect of parent material is significantly important for the soil development. |