Genesis, mineralogy, and geochemistry of soil profiles developed on volcanic materials under semi-arid conditions from Central Anatolia-Turkey /Genesis, minearologia y geoquimica de perfiles de suelo desarrollados con material volcanico bajo condiciones semiaridas en Anatolia Central, Turquia

Pedogenesis of volcanic soils has been studied broadly in humid regions, but very little data are present regarding these soils in arid and semi-arid regions of Turkey. This research aimed to assess the pedological processes and investigate the physical, chemical, and mineralogical characteristics of soil profiles developed from volcanic parent material. The studied soils were not classified as Andisol because they lack andic properties. The results showed that sand and coarse silt fractions exceeded 30%. The bulk density was higher than 0.90 [grcm.sup.-3] in all profiles. In general, phosphate retention was low, higher than 25% in profiles but lower than 85% in all profiles. The Al + [.sub.[1/2]] [Fe.sub.d] percentages were lower than 2% in all profiles. Selective extraction (Na-Pyrophosphate, Ammonium Oxalate, Na-Dithionite) indicated that soils lack noncrystalline minerals, such as allophane, imogolite, and iron humus complexes. The only noncrystalline minerals in high quantities are Al-humus complexes and small amounts of ferrihydrite. X-ray diffraction indicated that smectite, kaolinite and illite were dominant minerals in the clay fraction. Among the studied profiles, profiles 1 and profile 4 are classified as vitrandic Haploxerept, profile 2 as vitrandic haploxerolls, and profile 3 as vitrandic Xerorthent. The results indicated that the dominant soil-forming processes include the following: 1. desilication and the eluviations of base cations and Al from the solum; and 2. transformation of iron and aluminum from the sand and silt-size fractions into secondary clay and crystalline Fe minerals. The major factors determining soil genesis on Mt. Karacadag appear to be climate and topography affected by the leaching regime and weathering rates. Keywords: Karacadag; Andisols; Weathering; Elemental losses; Allophane; Andic soil properties. La pedogenesis de los suelos volcanicos se ha estudiado ampliamente en regiones humedas, sin embargo hay muy poca informacion sobre estos suelos en las regiones aridas y semiaridas de Turquia. Este trabajo se enfoca en evaluar los procesos pedologicos y en investigar las caracteristicas fisicas, quimicas y mineralogicas de perfiles de suelo desarrollados con materiales volcanicos. Los suelos estudiados no fueron clasificados como Andisoles porque carecen de propiedades andicas. Los resultados muestran que las arenas y las fracciones de arena granulada exceden el 30 %. La densidad del volumen fue mayor a 0.90 [grcm.sup.-3]