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Seqüência Latossolo Amarelo - Podzólico Amarelo - Areias Quartzosas sob material da formação barreiras na região de Tucuruí, estado do Pará Oxisol-Ultisol-Entisol sequence developed from clayey material near Tucuruí region, Pará state, Brazil

By J.A.M. Demattê, R.R. Aloisi and J.L.I. Demattê

Abstract

Estudou-se uma seqüência de Latossolo Amarelo-Podzólico Amarelo-Areia Quartzosa desenvolvida em sedimentos da Formação Barreiras. A área se localiza no sul do Pará, nas proximidades entre Tucuruí e o Rio Moju, distando 65km da Usina Hidroelétrica de Tucuruí. Foi escolhida uma encosta de aproximadamente 1500 metros formada por Latossolo na parte alta e Podzólico Amarelo na encosta, ambos argilosos, terminando em amplo vale de fundo arenoso, com forte hidromorfísmo. Os regimes de temperatura são isohipertérmico e hipertérmico e os de umidade ústico e áquico, nas partes elevadas e fundo do vale, respectivamente. Foram abertas quatro trincheiras ao longo da encosta e feitas oito tradagens para apoio. O material de origem é representado pela caolinita. Verificou-se que a diferenciação lateral dos solos: Latossolo Amarelo na parte alta, Podzólico Latossólico na encosta e Areia Quartzosa no fundo do vale, pode ser devida principalmente a processos de remoção e/ou destruição de finos (argila silicatada + óxidos). O encharcamento temporário e a gleização acentuada, exerceram papel preponderante na diferenciação da seqüência estudada.<br>The objective of this work was to study the genesis of an Oxisol-Ultisol-Entisol sequence, developed from sediments of the Barreiras Formation in the Tucurui region. The area is located about 65 km from Tucurui. In this area a soil topo sequence was selected, represented by a clayey oxisol in the higher parts, a clayey ultisol in the middle part, ending in an ample valley of sandy botton, with strong hidromorphism. The temperature regimes are isohyperthermic and hyperthermic and the moisture regimes are udic and aquic, in the higher parts and valley botton, respectively. Four profiles were examined and auger samples were taken in eight representative sites. The parent material is represented by clayey sediments from the Barreiras Formation. Chemically, the soils are leached with high aluminum saturation, dominated by kaolinite clay minerals. In the higher parts of the sequence the textura! gradient is similar and the iron oxides are mainly in crystalline forms. Downslope the textural gradient increases and the iron forms are less crystalline. At the valley botton the process of the fine fraction loss (also due to the hydromorphism) is completed remaining a sandy deep mantle. The iron oxides dissapear, remaining the kaolinite in smaller proportion. The soil sequence evolution may probably be developed by the degradation of the latossolic clayey material of the higher portions of the landscape

Topics: Seqüência de solos, Latossolos Amarelos, Formação Barreiras, região de Tucuruí, Soil sequence, Oxisol, Barreiras Formation, Tucuruí region, LCC:Agriculture (General), LCC:S1-972, LCC:Agriculture, LCC:S, DOAJ:Agriculture (General), DOAJ:Agriculture and Food Sciences
Publisher: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz"
Year: 1994
DOI identifier: 10.1590/S0103-90161994000200022
OAI identifier: oai:doaj.org/article:193f376ef65c47e88e6dfebb016c3307
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