Weathering and the formation of hillslope deposits in the tropical highlands of Itatiaia — southeastern Brazil

doi:10.1016/0341-8162(96)00015-X

CATENA

Volume 27, Issue 2, August 1996, Pages 81-103

https://doi.org/10.1016/0341-8162(96)00015-X Get rights and content

Abstract

Deposits of cobbles and boulders found hanging on midslopes of the Itatiaia Plateau reflect tectonic reactivation and a large range of climate-controlled processes, probably including frost weathering. These processes, more efficient in detaching debris from freefaces, were replaced, at the end of the Pleistocene, by colluviation. On the lower slopes of the plateau, less coarse C_I and C_II colluvia evince the reworking of upslope materials freed in former phases of weathering or erosion. Interpretation of hillslope processes was based upon the sedimentological, mineralogical and micromorphological characteristics of colluvia. C_I may have originated in mass movements reaching deep into the regolith. C_II colluvia were probably deposited by shallow processes, which reworked initially highly evolved materials, including on the way downslope poorly weathered rock fragments.

Changes in weathering characteristics and hillslope processes suggest variations in environmental conditions of the Itatiaia Plateau since the Late Pleistocene. Coarser deposits would be associated to the wet and cold conditions of the Last Glacial Maximum. In the end of the Pleistocene, warmer and still humid conditions would have favored weathering and mass movement processes triggering the first generation of colluvia (C_I). Discontinuous stone-lines found on mid-slopes would represent a short return to colder and eventually drier conditions. In the last 8,000 years, prevailing humid climates, with temperature excursions larger than those observed at present, encompassing phases of more intense gelifraction, would explain the deposition of C_II sequences. However, such variations were not sufficient to interrupt the geochemical weathering trend toward kaolinitic and gibbsitic materials that persisted after the Last Glacial Maximum.

Environmental fluctuations of small amplitude and a decrease in the intensity of slope denudation during the Holocene seem to follow the general trend previously recognized in the neighboring highlands of Campos do Jordão.

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Weathering and the formation of hillslope deposits in the tropical highlands of Itatiaia — southeastern Brazil

Abstract

Geochimica et Cosmochimica Acta

Bol. Inst. Geol

Arq. Mus. Nac.

Bol. Paulista Geogr.

Espaços ocupados pela expansão dos climas secos na América do Sul por ocasião dos períodos glaciais quaternários

Paleoclimas

Razões da retomada parcial de semi-aridês holocênica, por ocasião do optimum climaticum

Interfacies

The paleoclimate and paleoecology of Brazilian Amazonia

Introdução

Vale do Paraíba, Serra da Mantiqueira e arredores de São Paulo

Mise en évidence de quatre phases d' ouverture de la forêt dense dans le sud est de l' Amazonie au cours des 6000 dernières années. Premières comparaisons avec d' autres régions tropicales

C.R. Acad. Sci. II

The system of continental rifts bordering the Santos basin, Brazil

Paläogeographische und paläoklimatische Aspekte des Känozoikums in Südbrasilien

Zeitschrift für Geomorphologie

Processes and environments of the Brazilian Quaternary

Observations à l'Itatiaia

Zeitschrift für Geomorphologie

Les processus d'érosion à la surface des continents

A Flora do Parque Nacional do Itatiaia

Boletim do Parque Nacional do Itatiaia

Fabric and mineral analysis of soils

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The surface of the Ice-Age Earth

Science

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Problèmes morphologiques du Brésil Tropical Atlantique

Ann. Géogr.

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O maciço do Itatiaia

Rev. Bras. Geogr.

Remarques géomorphologiques sur l'Itatiaia

Z. Geomorphol.

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Ohio J. Sci.

Novas observações sobre a glaciação pleistocênica na serra do Itatiaia

An. Acad. Bras. Ciênc.

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Late Quaternary alluvial placer development in the humid tropics: the case of the Birim Diamond Placer, Ghana

J. Geol. Soc.

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