Occurrence of pyroclastic material in soils of three sectors of western Santa Cruz

Abstract

Main features of cineritic parent material from soils from central-western Santa Cruz Province were studied with special attention in the spatial variability, relative participation as parent material, and their influence in soil genesis. Study area is located between 49°00'-49°36'S and 73°30'- 72°00'W from LagoViedma to Península de Maipú in Lago San Martín. Andisols, Aridisols, Entisols, Spodosols, Histosols, Inceptisols and Mollisols soils profiles were recognised and studied. Ash and lapilli participation is a common feature in all observed soils. Pyroclastic materials are intercalated as thin layers or mixed with other sandy sediments of fluvial, glaciofluvial- glaciolacustrine or aeolian origin. Since morphodynamics is high as well as the variability of the geomorphic process, mixing of soils parent materials is a remarkable feature in all studied area. The characterization of the pyroclastic material was done based on mineralogical studies and geochemical analyses. Five different ash layers samples were sampled. Mineral determination was done in 74-125 m sand fraction. Lithic volcanics predominates followed by plagioclase crystaloclasts and, in lesser amount, volcanic glass. The analysed tephras when compared with data from other sources show a close correlation with Lautaro, Hudson, and Mont Burney volcanic products.