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Título

SEDIMENTOLOGICAL AND PALEOPEDOLOGICAL PATTERNS IN HOLOCENIC SUCESSION OF SERRA DO PASMAR, DIAMANTINA (MG): PALAEOSOLS AND CLIMATE VARIATIONS.

Resumo

The object of this work is the analysis of an outcrop of Holocene paleosols identified in Serra do Pasmar, Diamantina (MG).From macromorphological description, geochemical analysis by X-Ray Fluorescence, with ANOVA by Kruskal-Wallis test, and C14 dating, five geological intervals were identified:  (i) the first interval is 1.5 m, dated 7401±33 years BP, and constituted of very fine-grained sand with 12% of organic carbon and tree stumps. This paleosol is interpreted a Histossol developed in an old swamp, and it indicates a surface water table; (ii) the second interval is 1.5 m thick and it is constituted of white and dark gray sand intercalations; (iii) the third interval consists in a paleosol, 2.5 m thick, organized in A-E-Bh-Bs-C horizons, and interpreted as Spodosol, indicating decrase of the water table. The A horizon is dated 1589±27 years BP. The E horizon is eluviated horizont. In Bh, Very dark grey color (5Y3/1), and concentration of Al2O3 indicates the iluviation of organic matter and Al. In horizon Bs the high concentrations of Fe2O3 showed illuviation of Fe and forming Bs horizon;(iv) the fourth interval is 0.3 m thick, consists of fine-grained sands, deposited by unconfined flows; (v) the fifth is 0.2 m thick, is current soil, a Entisol, with horizon A, identified as Ochric epipedon. Si, Mg, Ca, Na, K, Ti and P, presented values very close to each other, showing balanced distribuition in the intervals. Al is high on spodic horizon Bh, and Fe in spodic horizon Bs. In Kruskal-Wallis test no significant differences in geochemical distribution, with all elements having values >0.05. The first and third intervals testify pedogenesis and stability of the landscape in humid climate, whereas less humid and drained conditions characterise the third interval. The second and fourth intervals correspond to deposits produced by extreme precipitation events probably in drier climate conditions,  and the last interval testifies an abrupt dropping of the ground water.

Palavras-chave

soil morphology; holocene paleosols; unconfined flow deposits.

Instituição financiadora

National Council for Scientific and Technological Development (CNPq).