Abilio de Carvalho Jr, O.

Brossard, Michel

Bruand, A.

Cornu, S.

De Souza Martins, E.

Muller, F.

Reatto, A.

Richard, G.

Silva, E.M.

Horizon / Pleins textes

Workshop on modelling of pedogenesis, October2-4, 2006, OrleansFrence
Modeling of Latosol development on geomorphic
surfaces of the Brazilian Central Plateau: First results
Reatto A.1, 2, Bruand A.2, Martins E.S.1, SlIva E.M.1, AbUio de CarvalhoJr 0.3, Brossard
M.4, Muller F.2, Cornu S.', ~Ichard G.'
1 Empresa Brasileira de Pesquisa ~opecuaria (Embrapa Cerrados), BR020, km 18, 73310-970,
Planaltina, Distrito Federal, Brazil; 21nstitut desSciences de la Terre d'Or1eans (ISTO) UMR6113
CNRSlUniversite d'Or1eans 1Aruedela Ferollerie 45071 Orleans Cedex 2, France; 3 Departamento
deGeografia, Universidade de Brasllia (UnB), 70910-000, Brasllia, Brazil,
41nstitut de Recherche pour le Developpement (IRD), UniteValpedo, BP64501, 34394 Montpellier
Cedex, France, 5 1NRAOr1eans, Unite de Science du Sol, BP20619, 45166 OlivetCedex, France.
Latosols are deeply weathered soils characteristic of the moist tropics. Many Latosols have
kaolinitic horizons ovenying more g·ibbsitic ones (Lucas, 1989), for which there has been no
satisfactory pedological explanation and why they have often been considered as a
sedimentary succession. Several hypotheses to explain this phenomenon were expressed:
biogeochemical recycling of Si by the forest (Lucas et al., 1993) or the activity of termites
(Volland-Tuduri, 2005). The objective of this study is to model the development of Latosols of
the Brazilian Central Plateau considering the respective effect of parent material, time or
biological actiVity. This plateau is constituted of the two main geomorphic surfaces: the South
American surface (Suface I) and the Velhas surface (Surface 11). In the Central Plateau, the
Latosols can be identified as Red Latosols (-28%), Yellow Red Latosols (-10%) and Yellow
Latosols (-2%), (Reatto et al., 1998; Embrapa, 1999).
Ten Latosols (L) developed in different parent materials were selected along an
approximately 350 km long regional toposequence across the South American surface (L1 to
L4) and Velhas sUrf~ce (L5 to L10) (Fig: 1). The Latosols L5 and L6 were located on the
upper Velhas surface, L7 and L8 on the intermediate Velhas surface, and L9 and L10 on the
lower Velhas surface. Samples were collected in the diagnostic horiion (Bw) of these
Latosols. Basic soil characteristics were determined on the air-dried <2 mm material
according to the Brazilian standard procedures, (Embrapa, 1997). The chemical composition
of the < 2 mm and < 2 IJm fraction was determined after fusion with lithium metaborate. The
mineralogical composition of the < 2 mm and < 2 IJm fraction was determined using X-ray
diffraction.
First results showed that the Latosols L1 to L4 from the South American surface, whose
parent materials were originated from lateritic crusts and saprolites of detritic and mafic
granUlite rocks, were gibbsitic Latosols. These Latosols were characterized by a kaolinitel
(kaolinite+gibbsite) ratio < 0.5. The kaollnite content ranged from 20 to 41 g.kg·1, the gibbsite
content from 44 to 63 g.kg·1 , the goethite content from 8 to 17 g.kg·1 and the hematite content
from 0 to 20 g.kg·1• The Latosols (L5 to L10) from the Velhas surface, whose parent materials
originated from colluvial pediments and saprolites of pelitic rocks, were kaolinitic Latosols.
They were characterized by a kaolinite/(kaolinite+gibbsite) ratio> 0.5. The kaolinite content
ranged from 40 to 65 g.kg·\ the gibbsite content from 18 to 37 g.kg·1, the goethite content
from 0 to 9 g.kg-1 and the hematite from 8 to 20 g.kg·1 •
Further analysis will consist in establishing a more detailed description of the < 2 IJm
mineralogy by using high resolution transmission electron microscopy and selective chemical
dissolutions. Indeed, 2:1 clay minerals were recognized in similar Latosols by Vo11ant-Tuduri
Session 1- Examples of longtermpedogenesis - poster 39
Worlcshop on modelling of ptJdogeMsis. OctobtN 2-4, 2~. OrleansFf'8fICtJ
(2005) and their presence in the Latosols studied remains to be established. Then, the
geochemlcal composition and assoclated mineralogy of the diagnostIc horizons will be
discussed according to the characteristics of the parent material (chemical composition,
mineralogy, density). Finalty, we will develop a model based mainly on the age of the Latosol
and the characteristics of the parent material that will account for the current characteristics
of Latosols of the Central BrazilIan Plateau.
SW-NE
1.200 m
'21.100 m
.!>
~ l.000m
i 900m
'"S 600m
lEGENQA
S.,1ace I (950. 1200m)
L2 13
Surtace 11 ( 750 . 950 m)
SuperiorLevel Intermediarylevel Inferior Level
"'0
Aren~e
Clayao MetaJithlm~e
Granul ite
t.acostre L1mes1Ol1e
LateJitic Crust (Tertiary)
Limestone (Su~or pro· Cambrian)
Metapel lle
Ouartlzlte
_ sandy Metarithlm~e
Figure 1. Position all sampling of 1he 10 Latosols (L) in each geomorphlc surface In the regional
toposequence of Central Piateau- Brazil.
References
Embrapa, 1997. Manual de m6t0dos de ansUse de solo. 2 .ed. Empresa Brasllelra de Pesqulsa
Agropecui!lr1a, Rio de Janeiro, 212 p,
Embrapa, 1999. Sistema Brasllelro de ClasslficaoAo de Solos, Empresa Braslleira de Pesqulsa
AgropeeuArla, Rio de Janeiro, 412 p.
Lueas, Y., 1989. Systemes pedologlques en Amazonie Br~slllenne. EquUlbres, d6s6qulHbres et
transformations. These de Doctorat de I'universlte de Poitlers.
Lucas, Y., Luldo, F.J., Chauvel, A, Nahon, D. s Roulller, J., 1993. The relation bet...veen biological activity of
the rain forest and mineralcomposition of soils. Science, 260, 521-523.
Reatto, A., Correla. J . R.. spers, S. T., 1998. Solos do Bloma cerrado: aspectos pedol6gicos. In: Sano, S.
M. & AJmelda, S. P. (ed.): Cerrado: ambiente e flora. Planartlna. EMBRAPA-CPAC, 47-88.
Votland-Tudun, N., 2005. Nah.lre et mode d'assemblage des constituants m1neraux et organlques dans des
Ferralsols de la r6glon des Cerrados (Br6sil). Evolution aprtlls mise en culture. PhD Thesis, Universlt&
d'Or16ans, OrIeans-France, 231 p.
40
~I CENTRE~ATIONAl1DELA RECHERCHEI I SCIENTlflQUE
INSmuTIlATIllIIALDE U\ RECHERCHE AGIlOllOIllQUI!
Editors: A. Samoueflan, S. Cornu


Workshop on modelling of pedogenesis

Workshop on modelling of pedogenesis

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