Fjölrit RALA - 15.06.2004, Síða 80

Genesis and formation of volcanic soil in Fregrean Fields
C. Colombo 1, A. Di Cerce \ M.V. Sellitto, G. Palumbo 1 and Terribile F.2
IDip. Scienze Animali Vegetali e dell’Ambiente, Unversitá del Molise, Campobasso, Italy
Dipartimento di Scienze del Suolo della Pianta e dell’Ambiente,
Universitá degli Studi di Napoli Federico II, Portici Italy
The Volcanic soils located in the Flegrei Fields district are formed from heterogeneous
pyroclastic rocks. The origin of the Flegrei District, according to its geographic location and
to the age of the products, has been ascribed to about 30 different volcanic events begun more
than 30.000 years ago. They formed large deposits of pyroclastic products such as the
geologic formation called “Neapolitan yellow tuff’. The aim of this work was to study the
mineralogy and the geochemistry of two soils of the northem slope of Mt Gauro: the first
soil (EUR01) occurring on flat terraces and it has a specialized fruit trees (apples) land use ;
the second soil (EUR02) is located on chestnut forest at the top of Mt Gauro. On both soils
physical and chemical analysis were carried out. The profile EUR02 has been also object of
micromorphological description and mineralogical analysis (Fig. 1). The thin sections were
analysed by optical microscopy (OM) and selected areas have also been observed by scanning
electron microscope (SEM) and microanalysis (EDS) to observe the differences in the
chemical composition. All grain size fractions have been analysed by X ray diffractometry
(XRD). The pedogenetic environment of the volcanic soils studied results particularly
complex for the heterogeneity of the pyroclastic materials stratified during the intense
volcanic activity in the last 5000 years. The studied profiles have a good degree of soil
development . The profile EUR01 has slight acidity in the surface horizons (O, Al); pH
increase toward the C horizon. The EUR02 profiles (forest soil) has similar features but
higher KCl acidity.
A1
Si
Ca
Figure 1 Scanning electron images and Al, Si, Ca and K distribution map for selected grain
pumice in the thin section showing the variability in chemical composition.
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