Nature, origin, transport and deposition of andosol parent material in south-central Chile (36-42°S)
Nature, origin, transport and deposition of andosol parent material in south-central Chile (36-42°S)
Date
2007-07
Authors
Bertrand, Sebastien
Fagel, Nathalie
Fagel, Nathalie
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Keywords
Andosol
Volcanic ashes
Volcanic glasses
Allophane
Chile
Volcanic ashes
Volcanic glasses
Allophane
Chile
Abstract
The andosols of south-central Chile (36-42°S) are developed on yellow-brown loams that cover the
region with a thickness of several meters. In the literature, several hypotheses concerning the
nature, origin, mode of transport and deposition of the andosol parent material have been advanced
but no general agreement has been found. In this paper, we test these hypotheses by analyzing new
representative outcrops located around Icalma (38°50’S) and Puyehue (40°40’S) lakes by a plurimethodological
approach. Our data demonstrate that the andosol parent material has the typical
mineralogical and geochemical signature of the regional volcanism and that these deposits are postglacial
in age. The grain size of the deposits and the morphology of the coarse grains evidence that
most of these particles haven’t been re-transported by wind but are direct volcanic ash falls
deposited throughout the Late Glacial and Holocene. Because of the prevailing westerly winds,
most of them have been transported to the East. Following the deposition of the volcanic particles,
weathering and pedogenetic processes have transformed part of the volcanic glasses and
plagioclases into allophane and have wiped out the original layering. This work demonstrates that
most of the andosols that occur in the Andes and in the eastern part of the Intermediate Depression
of south-central Chile are developed on volcanic ashes directly deposited by successive volcanic
eruptions throughout the Late Glacial and Holocene.
Description
Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in CATENA 73 (2008): 10-22, doi:10.1016/j.catena.2007.08.003.