Differentiation among geomorphological processes in a mountain hydrographic basin by means of soils analyses
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Data di Pubblicazione:
2020
Citazione:
Differentiation among geomorphological processes in a mountain hydrographic basin by means of soils analyses / A. Masseroli, I. Bollati, M. Pelfini, L. Trombino. ((Intervento presentato al convegno EGU Assembly 2020 : March, 4th - 8th tenutosi a online nel 2020.
Abstract:
Mountains regions are usually characterized, according to their geological and structural setting,
by an articulated relief, where gravity and water-driven processes occur with an increasing
intensity following glaciers retreat. Denudation processes affecting mountain slopes may vary
according to local conditions controlled by different factors (e.g., lithology and structural setting of
bedrock, climate, relief features).
The succession of slope stability and instability phases can be registered in the soil record as
paleosols or buried surfaces. Therefore, an exhaustive investigation of soils and paleosols could
provide information to infer the spatial-temporal variation of the denudation/deposition
processes.
The main aim of this study is the reconstruction of the dynamic interplay between erosion and
sedimentation that have been characterizing the landscape evolution of the Buscagna Stream
hydrographic basin (Veglia-Devero Natural Park, Central-Western Italian Alps) during the Late
Holocene. The basin is characterized by an evident asymmetry between the valley slopes in terms
of lithology (calcschists on the southeastern slope versus ortogneiss, micaschists and spots of
ultramafic rocks on the northwestern slope), and by a structural control on the relief. This
differentiation is also responsible for the great landforms variability and the geomorphic dynamics
dissimilarities between the slopes.
In order to reconstruct the different dynamics affecting the slopes, 11 soil profiles were
investigated by means of field and laboratory (on both mineral and organic constituents)
characterizations; the soil profiles were selected in different morphological contexts, along two
downslope transects on the two sides of the valley.
The results show that the investigated soil profiles are characterized by different soil units,
identifiable by the presence of grain size discontinuities and/or stone lines or buried organic
horizons. The presence of different pedological units underlines the occurrence of separate events
of pedogenesis alternated to phases characterized by slope instability and intensification of
denudation and related degradation/aggradation processes. Moreover, the soils recorded in a
different way the instability phases occurred in the two opposite flanks of the hydrographic basins,
underlining changes in predominant erosion processes, which are also related to the varying
bedrock both in term of lithology and structural settings.
In particular, on the southeastern slope characterized by a calcschists parent material and by less
steep slopes i) the gravity erosion processes are less intense; ii) the presence of vegetation cover
and a developed soil promote the slope stability. Whereas, on the northwestern slope
characterized by gneiss and micaschists and locally by ultramafic rocks and high relief energy i) the
soils have recorded many instability phases in term of sequences of buried surfaces; ii) the
presence of coarse slope deposits only partially colonized by vegetation predispose to slope
instability. The characterization of soil mineral component underlines the presence of different
material sources, linked to action of a variety of agents (e.g., gravity, water, snow, wind), which
have contributed to landscape evolution in term of sediment erosion, transport and deposition.
Finally, this research highlights the role of soil as useful archive for retracing the geomorphological
processes responsible for high altitude areas landscape evolution. (EGU2020-749)
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Elenco autori:
A. Masseroli, I. Bollati, M. Pelfini, L. Trombino
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