Non-allophanic Andosols of Trindade Island, south Atlantic : a new soil order in Brazil.
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2020
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The pedological studies carried out so far in Trindade Island (TI) have obtained
patchy evidences of allophane, without detailed mineralogical and micromorphological
studies to confirm the occurrence of Andosols in TI. Therefore, in this study, the
mineralogical, micromorphological, physical and chemical characterization of four soil
profiles from Vulcão do Paredão (P1) and Morro Vermelho formations (P2, P3, and P4)
were carried on the latest volcanic events in Brazil from Trindade Island (TI) with the
aim of to evaluate the presence of Andosols in this oceanic island. Profiles P1 and P2 are
developed on pyroclastic bombs, and show, respectively, A-Bi- C and decapitated A-C
horizons, whereas P3 and P4 are developed on lapillitic and bomb pyroclasts, show A-C
horizons. The soil profiles have a reddish and brownish clayey matrix, are highly friable
and show a plastic consistency. Their microstructures are granular, single grain and
intergrain microaggregate, in which aggregates display an undifferentiated b-fabric.
The mineralogical constituents of the bulk fraction are biotite, hematite, magnetite,
ilmenite, pyroxene, olivine, halloysite, goethite, anatase, and rutile. The clay fraction
is marked by the presence of halloysite, ferrihydrite, and little amounts of allophane.
All soils presented andic properties and can be classified as non-allophanic Andosols.
In addition, micromorphological features closely resemble those reported in Andosols
from other volcanic islands from elsewhere. The predominance of halloysite in the clay
fraction formed by alteration of sideromelane, suggests that allophane would be an
intermediate phase of this rapid transformation favored by the wet climate conditions
of the highest parts of TI.
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Volcanic islands, Andic properties, Andisols, Halloysite
Citação
MATEUS, A. C. C. et al. Non-allophanic Andosols of Trindade Island, south Atlantic: a new soil order in Brazil. Revista Brasileira de Ciência do Solo, v. 44, artigo e0200007, jul. 2020. Disponível:https://www.scielo.br/j/rbcs/a/3mXnZGzJPFFm5Fs4jrz7yKb/?lang=en>. Acesso em: 15 mar. 2023.