Abstract

ORGEIRA, María Julia et al. Rock magnetism in soils of the Pampean plain, Buenos Aires province, Argentina: Linking climate and magnetic behaviour. Rev. mex. cienc. geol [online]. 2009, vol.26, n.1, pp.65-78. ISSN 2007-2902.

Results of the study of Argiudolls in two localities (Zárate and Verónica) of the Pampean plain, Argentina, are presented in this contribution. This is a typical area covered by loess. The magnetic studies carried out allowed to determine the presence of detrital magnetite and titanomagnetite, as well as maghemite, pedogenic goethite and superparamagnetic particles (SP). In Verónica soils, a depletion of ferromagnetic minerals is recorded. The dominant process in these soils has been the reductive loss of detrital magnetite and titanomagnetite. This is associated with a greater degree of evolution of the soil, which is determined by the concentration and type of detected clays. The higher clay concentration in these soils facilitated reducing conditions and a greater loss of detrital magnetic particles. The loss is reinforced under poor drainage conditions. In the poorly drained soil of Zárate, a concentration of magnetic particles is observed in the Bt horizon, which is associated with an illuviation process. The well drained soil of the same locality shows neoformation of SP particles. These particles would have an ephemeral life until a new wet period in the annual cycle occurs. Although some characteristics of the magnetic signal appear reinforced by the conditions of drainage, this aspect does not seem to be too significant, at least in the Pampean region with low topographic gradients.

Keywords : environmental magnetism; soils; argiudoll; Pampean plain; Argentina.

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