THE ROLE OF PALEOSOLS IN PALEOENVIRONMENTAL STUDIES: GENESIS AND DEVELOPMENT OF APENNINE MOUNTAIN SOILS DURING THE HOLOCENE.
Tesi di Dottorato
Data di Pubblicazione:
2016
Citazione:
THE ROLE OF PALEOSOLS IN PALEOENVIRONMENTAL STUDIES: GENESIS AND DEVELOPMENT OF APENNINE MOUNTAIN SOILS DURING THE HOLOCENE / G.s. Mariani ; tutor: L. Trombino ; coordinator: E. Erba. DIPARTIMENTO DI SCIENZE DELLA TERRA "ARDITO DESIO", 2016 Feb 10. 28. ciclo, Anno Accademico 2015. [10.13130/g-s-mariani_phd2016-02-10].
Abstract:
The aim of this research is to conduct an investigation on the soils, paleosols and landforms of the area of Mt Cusna ridge (Northern Apennines - Italy) in order to define the relationship between geomorphic evolution and soil development, to characterise the main pedogenetic processes and factors acting on soils in past and present times, and to provide new information to understanding the Holocene climatic variations in the area. For this purpose, several sets of field, laboratory and microscopic analyses were carried out.
A comprehensive survey of the study area allowed the production of a geomorphological map (scale 1:10000, attached to this thesis) expanding and revising the existing cartography (Panizza et al., 1982). At the same time, also the soils were surveyed and described, in order to provide a detailed characterisation of the soil types of the area. Selected soil profiles were sampled and underwent a wide set of laboratory analyses, including measurements of pH, exchangeable bases and cation exchange capacity (CEC), organic carbon content, total nitrogen and exchangeable phosphorus; along these iron oxides were investigated with the measurement of total iron and its extractable forms; grain size analyses and x-ray diffractions on the clay fraction were also carried out; finally, micromorphology of soil thin sections and SEM observations and analyses were also carried out on a subset of significant horizons.
Geomorphological survey results allowed to compare the active and inactive processes. Glacial and periglacial processes, though mainly inactive since the beginning of the Holocene, still give an important forcing on the present landscape through their deposits, produced during the Last Glacial period. During the Holocene, different phases of stability and instability could be detected from the activation an reactivation of slope dynamics as the result of both climate fluctuations and structural constraints. The result is a very diversified landscape in which erosion and deposition alternate in space and time. The present day conditions are characterised by a prevalence of washout and erosion activity, mainly on lithologies more susceptible to surface processes.
Soils were attributed to different landscape units, highlighting differences in processes and development between them. Degree of pedogenesis, in fact, varies from weakly developed soils on the highest and steeper areas to deep and more weathered profiles at lower elevations and/or on flatter surfaces. Among the latter, the presence of a paleosurface, characterised by the presence of paleosol units truncated and buried by colluvial deposits, has been detected in the stable areas above 1650 m a.s.l..
Laboratory geopedological analyses showed how soil in the area are characterised by being mainly silty-clayey, with low values of pH and organic C which tends to concentrate at the surface and in many cases also in the uppermost horizon of buried soil units. Iron oxides are usually present in its crystalline form, with some exceptions in peculiar soils. The crystalline/total iron ratio (weathering index) is generally low, higher inside paleosurface buried units. Clay fraction mineralogy shows the presence of quartz and chlorite inherited from parent material; neoformed clay minerals consist in illite and mixed layer clays.
Micromorphological analysis mainly involved paleosurface horizons. Colluvial units show the presence of variable quantities of pedorelicts (Brewer, 1967) in their groundmass, as well as features pointing to multiple depositional events. The buried unit shows different phases of clay illuviation relatable to environmental changes. In flat areas a 2Ab horizon is found between the two units, showing accumulation of excrements and organic mate
Tipologia IRIS:
Tesi di dottorato
Keywords:
paleosols; geomorphology; soil analysis; soil micromorphology; Northern Apennines; Holocene; paleoenviroment
Elenco autori:
G.S. Mariani
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