Abstract

ZAPPINO, RODOLFO; CANTU, MARIO  and  BECKER, ANALÍA. Material originario y suelos enterrados en la llanura de Tucumán. Cienc. suelo [online]. 2016, vol.34, n.2, pp.303-322. ISSN 1850-2067.

Four profiles were selected in the Tucumán Plain in order to characterize the original material, evaluate its homogeneity and establish their date based on absolute dating in soils of regional representativeness. A correlation was proposed of the identified deposits through the implementation of a Normative Mineralogical Index. In all profiles average grain size is coarse silt and the materials are poorly selected. Textural analysis allowed the identification of depositional units separated by discontinuities. The original material of the present and buried soils were classified as typical loess. Dating indicated an age of 9970 ± 420 years B.C. for the base of the buried soils and 1780 ± 350 years B.C. for the present soils in the regions of the Humid-Perhumid Pedemountain Plain and Humid-Subhumid or Western Chaco Pampean plain. Normative mineralogical correlation proposed based on the Orthoclase/Anorthite index suggested a correlation that separated the present from the buried soils in all the transect. The mineralogical analysis essentially points out two populations: a majority of vulcaniclastic source which suggests an Andean contribution of rhyolitic-andesitic composition and a minor population from the crystalline basement plus the direct contribution of rain volcanic ashes of rhyolitic composition. The mineralogy found in the soil parent material clearly indicates that andean, crystalline basement and direct input from volcanic ashfall are sources that have been virtually the same throughout the Holocene.

Keywords : Original material; Sedimentology; Normative mineralogy in soils; Tucumán province.

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