Soil chronosequences on Quaternary marine terraces along the northwestern coast of Calabria (Southern Italy)

Two soil chronosequences, representative of four orders of marine terraces from Early to Late Pleistocene, have been studied along the Tyrrhenian coast of northern Calabria, in Southern Italy. All soil profiles show a high degree of weathering, although the degree of soil evolution varies according to the age of each terrace. The soils are characterized by reddish to reddish brown colors, clayey textures, abundant clay coatings, slickensides, Fe–Mn features or calcium carbonate concretions. The dominance of kaolinite and illite among phyllosilicate clay minerals in all soil horizons, the intense depletion in CaCO3, Na and K, and the severe etching of quartz crystals in the older soils all record a highly leached pedogenic environment that is progressively more intense from younger to older soils. Despite the carbonate bedrock, quartz, feldspar and mica minerals also occur, suggesting a partly allochthonous, eolian origin of the parent material. The major pedogenic features and their formative processes occurred polycyclically on the different orders of marine terraces, and we interpret the soils to have mainly developed during repeated Quaternary interglacials. Some surface A and Bw horizons show quite different features, suggesting a clear change in pedogenetic processes and possibly in climate and duration of soil formation. These horizons have the typical field appearance of volcanic soils with andic properties (brown colors, loamy textures, high porosity, low bulk density, high water retention, thixotropy). The occurrence of very small volcanic glass fragments and the possible presence of short-range order aluminosilicate minerals confirmed some pyroclastic supply during soil formation.