Data/hora: 04/06/2024 14:05:25

Biblioteca(s): | Embrapa Pantanal.
Data corrente: | 28/08/1995
Data da última atualização: | 15/05/2017
Autoria: | RIGHI, D.; CONINCK, F. de.
Título: | Mineralogic evolution in hydromorphic sandy soils and podzols in "Landes du Medoc", France.
Ano de publicação: | 1977
Fonte/Imprenta: | Geoderma, v.19, p.339-359, 1977.
Idioma: | Inglês
Conteúdo: | Soils of the nearly level "Landes du Medoc" in southwestern France have a pattern of alternating bodies of hydromorphic podzols (Haplaquods) and low humic hydromorphic soils (Psammaquents). The soils are formed in a sedimentary mantle of coarse, quartzose sands with a slight microrelief consisting of low, elongated ridges and shallow, intervening trougs. The water table is at shallow depths throughout the plain, even at the surface in places. the podzols on the crests of the low ridges have distinct A2 and demented B2h horizons. Podzols persist down the sides of ridges but going downslope first lose the A2 horizon and then the cementation of the Bh horizon. Soils in the shallow troughs have A1 and Cg horizons without B horizons. The fine silt (2-20 um) and clay (0-2 um) fractions of the parent sands constain primary trioctahedral chlorite, mica, feldspars, and quartz, with the last mineral predominant. During soil development, the first three minerals undergo weathering at different rates and to different extends. Chlorite is most strongly weathered, followed in order by plagioclases and K-minerals. In the fine silt fraction, weathering seems to occur mostly by fragmentation of particles. In the clay fraction, the phyllosilicates successively form irregularly interstratified minerals with contractible but not expandable vermiculitic layers, interstratified minerals with contractible and expandable smectitic layers and finally smectites. The extent to which the silicate minerals are weathered becomes progressively greater from the low humic hydromorphic soils to the podzols with driable Bh horizons to the podzols with cemented Bh horizons. Smectite is present only in the A2 horizons of these last podzols. The aluminium released by weathering of silicate minerals is translocated in part in the form of organo-metal complexes into the Bh horizons of the podzols. Greatest concentrations of Al are associated with coatings of monomorphic organic matter on mineral grains in the cemented Bh horizons, in which some Al has also crystallized into gibbsite. That mineral was not detected in friable B horizons of podzols nor in the low humic hydromorphic soil. Contrary to expectation, the mobile Al did not enter interlayer spaces of expanding 2:1 clay minerals.
Palavras-Chave: | Evolucao; Evolucao mineralogica; Franca; Hidromorfica; Hydromorphic sandy soils; Landes du Medoc; Mineralogic evolution.
Thesagro: | Mineralogia; Solo.
Thesaurus Nal: | France; Podzols.
Categoria do assunto: | --
Registro original: | Embrapa Pantanal (CPAP)

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