Physical and chemical characteristics of soils formed on ophitic and sedimentary materials in mediterranean climate
2007
López Lafuente, Antonio | González Huecas, Concepción | Valverde Asenjo, Inmaculada
The present study was carried out on seven soils developed on a diapiric formation in the north of Spain. Three of them were formed on volcanic materials (ophites) and four on sedimentary materials (marls and gypsums) of the Upper Triassic age in a Mediterranean climate. Morphological, physical, chemical, and mineralogical properties of the soil were evaluated. Profiles derived from ophitic materials had thick dark A horizons with a fine granular structure and a high organic C content, were coarse textured, and had a degree of base saturation of the cation exchange complex higher than 50%. Responses to the NaF test were low and delayed, giving results of pH NaF2 min of greater than 9.4, phosphate retention of less than 22.2%, and the Alo% + 1/2 Feo% relation of less than 2, showing the scarcity of amorphous compounds. The predominant clay minerals were biotite, chlorite, and smectite. Profiles developed on the sedimentary material showed the influence of the original material, being lighter in color with fine and medium textures and a saturated cation exchange complex. The predominant clay minerals were biotite and chlorite. The low rainfall of less than 650 mm, together with the nature of the original materials, resulted in a low intensity of pedogenic processes, giving rise to poorly developed soils that represent the first stages in their present evolution. Profiles derived from ophites were classified as Entic and Typic Haploxerolls. Those formed on clay marl materials were classified as Typic Xerorthents and those on gypsum marls as Gypsic Haploxerepts. (Soil Science 2007:172:396-412)
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