Vieux sols et paléosols des niveaux villafranchiens méditerranéens

Abstract

From a pedological point of view, it is necessary to distinguish two chief categories of soils associated with villafranchian levels : — Old soils, remained at the land surface, of which pedogenesis continued from Villafranchian to nowadays. The interpretation of such soils is difficult : is their strong alteration resulting from long duration of evolution or significant of villafranchian climates ? — Paleosoils, i.e. burned soils, which keep some characteristics of villafranchian climates. They permit to point out pedogenetic phases chiefly during lower and middle Villafranchian in North Africa and Spanish peninsula; however, in Italy and Greece, pedogenesis can be noted also in upper Villafranchian. Moreover, red detrital series, accumulated on piedmonts and in basins, can be considered as indirect indication of rubefacient pedogenesis. Indeed, the paleosoils associated with villafranchian levels are mostly reddish soils and have the characteristics of fersiallitic soils. On calcareous substratum, the alteration does not exceed bisiallitic stage, while on siliceous substratum, monosiallitic stage and ferruginisation are often reached, particularly in humid regions. These soils agree with hot climate, with strong seasonal contrasts. Frequent calcretes associated with these soils in dry regions rather indicate a mediterranean climate.