ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

Bulk density is shown to be a very significant control on
fluid uptake. The final dry mass (including absorbed salts)
is shown to be positively correlated with both wet dimensions
and final dry dimension. The various solutions were
shown to have differential effects on the mass and linear
dimensions of the samples, as demonstrated by significant
variation in final dry mass of the samples, and both wet
and final dry dimensions of the sample blocks.
Tests have been carried out to determine the effects of the
different saline solutions on the compressive strength of the
test cubes after varying periods of immersion. Results indicate
that there is a small but significant differential effect
which is likely to increase with increasing immersion time.
Chemical analysis of the experimental saline solutions has
also been carried out using inductively coupled plasma
spectrometry and ion chromatography, to determine the
uptake of anions by the rock and to establish whether any
significant loss of particular cations occurs from the rock
during immersion. Initial results suggest the latter effect is
relatively small but that it may also increase with duration
of immersion.
CRISTINE MUGGLER 1 ,2 & PETER BUURMAN 1
Soil genesis and landscape evolution in Sao Sebastiiio da
Vitoria, Minas Gerais, Brazil
1 Department of Soil Science and Geology,Wageningen Agricultural
University, p.o. box 37,6700 AA Wageningen, The Netherlands
2 Departamento de Solos, Universidade Federal de Vicosa,
36570-000 Vicosa, Minas Gerais, Brazil
The geomorphic evolution of the south-east Brazilian landscape,
is considered to be a sequence of dissections and
planations due to climatic changes, superposed on differences
in lithology. The evolution comprises a number of
unstable (truncation of soils; accumulation of slope material),
and stable (undisturbed soil formation) phases, which'
combined with the overall stability of the landscape, resulted
in deep soils of a polygenetic nature. In addition to
climatic changes, it is likely that tectonic activity during the
Tertiary and Quaternary contributed to the landscape disruption
and rebuilding. This implies that the dominating
Oxisols will have been more or less affected by erosional
reprises that resulted in cycles of soil formation in a landscape
rejuvenation scenery.
In order to unravel the link between gemorphic history
and phases of soil formation, an area located in Sao Sebastiao
da Vit6ria, centre south part of the state of Minas Gerais,
was selected for investigation. The main lithologies
are fine textured metamorphic rocks (phyllites and fine
schists), and the climate is a Tropical Highland climate,
with an average annual temperature of 19-20 °C, and average
annual precipitation of 1,400 mm with 4 to 6 dry
months. Topographic and weathering soil sequences were
sampled, and the soils were studied by means of chemical,
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mineralogical and micromorphological analyses in order to
draw conclusions on their development stages. A set of soil
profiles sampled in an catena that cuts through the Oxisol
deep into the saprolite, has deeper and redder soils at the
top, and yellow and shallower soils downslope.Their macromorphology
suggests at least two phases of soil formation.
But the redder soils at the summit level, which are
remnants of the last stable landscape surface, show relicts
of homogenised soil materials that already represent more
than one soil formation phase.Vertical sequences sampled
in a recent gully nearby the catena show a more complex
soil development. They show that the former landscape
was affected by gully formation and filling, which was interrupted
by at least a short phase of soil formation, witnessed
by the presence of buried root layers. As a consequence,
the present-day Oxisols have developed on both
metapelites and younger sediments. Former gullies have
been filled up by sediments in which (various phases of)
paleosols had developed. Now they are virtually invisible
because of the Oxisol overprint. It suggests that gullies formed
by erosion and/or tectonic activity in a planated landscape
were filled up in more than one sedimentary and soil
formation phases, and eventually overprinted by a phase of
Oxisol development. The last landscape incision removed
most of the Oxisol cover and was followed by the present
soil formation resulting in yellower soils in the slopes. So,
climatic changes causing dissections and planations together
with tectonic reactivation giving origin to small sedimentary
basins are likely the main geomorphic processes
intervening in the formation and evolution of the soils in
the studied area.
JEAN-LOUIS MUGNIER\ PASCALE LETURMY\
EDOUARD CHALARON 2 , BERNARD DELCAILLAU 3 ,
PASCALE HUYGHE 1, GEORGE MASCLE 1 & GERARD VIDAL 4
Morphology and geodynamics of the outer thrust belt
of Western Nepal
1 Laboratoire de Geodynamique des Chaines Alpines et ESA CNRS
5025, rue Maurice Gignoux, 38031 Grenoble, France
2 INRs Ceoressource, 2535 boulevard Laurier, CP 7500 St Foy,
G1V4C7,Quebec, Canada
3 Departcment de Geographie, Universite de Caen,
Esplanade de la paix, b.p. 5186, 14032 Caen, France
4 UMR CNRS 5570, ENS Lyon, 46 allee d'Italie, 69364, Lyon, France
Comparisons between digital elevation data, structural
field data and predictions of a numerical model («Wedge»)
are used to improve the understanding of the landscape
and geodynamics of the Outer thrust belt of Western Nepal.
The «Wedge» model is based on incorporation of discontinuities
in the critical wedge model, a cinematic
forward model of serial cross sections and a linear diffusion
algorithm that simulates superficial transport. «Wedge»
predicts , from a set of mechanical, geometrical and