(PALEO)PEDOLOGICAL SURVEY ON OLD TERRACES IN NORTH-WEST ITALY (VAL SESIA)

A double transect in the low Sesia valley, from the river bed to the upper oldest terraces (named “Baragge”), towards east and west, has been recognized on the geological maps: the crono-topo-sequence could be attributed to a fluvioglacial terraces chain, dated since the Middle Pleistocene. In order to verify this attribution and increase knowledge to a greater detail, a geopedological survey has been undertaken by means of soil profiles excavation, on the different morphological surfaces, additionally supported by frequent auger controls. Description, sampling and analysis of soil horizons allowed to produce a broad data set for a complete characterization of the geopedological aspects of the studied area. Field and laboratory work has brought two levels of results: 1° Level: Land survey concluded by a soil map (1:50.000 scale) 2° Level: Analytic investigation for a better characterization of the chrono-topo-sequence. The analytical protocol was constituted by: grain size and routine pedological analyses, heavy minerals determination, X-ray fluorescence and X-ray diffraction, micromorphology of soil thin sections, in order to use the most significant (paleo)pedological indexes (i.e. soil development index, percentage of original content of elements remaining, parent material uniformity index…). The final results can be summarised as follows: 1. The quantitative characterization of the chrono-topo-sequence; 2. An improved focus on pedogenesis factors in the Quaternary paleoenvironment of Northern Italy; 3. A tentative methodological contribution to define and classify paleosols; 4. An unusual data set as support of a soil map, which can be utilized to derive, with high precision, suitability maps, useful for land planning according to agricultural and environmental targets; 5. A strict interaction between quaternary geologist and pedologist with exchange of information and methodological confrontation.