Tableland soil of North-Eastern Brazil:characterization, genesis and classification
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Date
1986
Authors
Barrera, Daniel
Journal Title
Journal ISSN
Volume Title
Publisher
State University of Ghent
Abstract
The coastal low level tablelands of the State of Alagoas are located in the north-eastern region of Brazil between 8° 25' and 10° 20' south latitude, and from 35° 10’ to 37° 15' west longitude of Greenwich. These surfaces formed by Tertiary Sediments are flat or slightly undulated with slopes rarely higher than 4%.
It enjoys a tropical climate with a dry summer and a constant temperature throughout the year. The dominant vegetation is formed by the so-called "Atlantic Forest", presenting also minor areas of "Cerrado". Nine profiles corresponding to the soil types present in, a) the well drained surfaces of the tablelands - which classify as Oxisols, Ultisols and Oxisol-Ultisol intergrades -, and b) in poorly drained depressions - classified as Spodo-sols -, were selected for this work.
The influence of the morphogenesis of the landscape and the topographical location on soil development is evident from the soils studied. The properties of the soils are strongly related to geomorphic processes. The soils were characterized in terms of their morphological, physico-chamical, mineralogical and micromorphological properties. The sedimentological analysis of the sand fraction(63 - 2000ym) was also carried out. The mineralogy of the sand fraction is similar in all profiles. The light minerals are dominant ( 91-98% ) and almost
entirely composed of quartz grains and no more than traces of feldspars. In the heavy fraction the opaques are dominant, ( 84-92% ); among the transparent minerals zircon dominates, followed by tourmaline and rutile. The composition of the clay fraction is also very similar throughout the region, dominated by kaolinite and minoramounts of gibbsite and oxi-hydroxides of iron and aluminium.
With the sole exception of profile 2, all the soils are developed from highly uniform parent materials. At the sametime the parent materials of the different soils are also mutually very similar from sedimentological point of view.
" Selective erosion 11 of fine soil components as a consequence of run-off is throughout the plateaux the dominant morphogenetic process, which influences the physico-chemical properties, the classification and the distribution of the soils in the landscape. The micromorphological analysis indicates similar features
among the dominant soils of the area; and that the illuviation of clay is present in all profiles, which however is not manifested as clay skins in the field as a result of poor structure development. The soils were classified according to Soil Taxonomy, FAO/UNESCO, the Brazilian System of Soil Classification
and under the I.N.E.A.C. ( Zaire ) System.
Description
Keywords
Tableland soil, Genesis, Classification, Soils, North-Eastern Brazil, Micromorphology