Revisiting the genesis of red Mediterranean soils

Authors: NICOLAS FEDOROFF, MARIE-AGNES COURTY

Abstract: This work, aside from being a classical discussion on the processes of rubefaction and illuviation, is an attempt to cross the abundant literature on red Mediterranean soils (RMSs) written by pedologists, and also by paleopedologists and geologists, with the climatic frame established by paleoclimatologists for the Quaternary. Such an approach leads us to consider that the development of the RMSs was discontinuous, occurring during periods of environmental stability, i.e. interglacials, characterized by a humid climate (precipitations exceeding evapotranspiration) with dry and hot summers. The impact of glacial intervals on the RMS covers is presently only partially documented. Aeolian processes during atmospheric instability episodes played a dominant role; however, hydric erosion and resedimentation cannot be ignored. Severe wind storms have reworked the RMS covers locally, but long distance dusts were also incorporated into the soils. Outbursts are proposed to explain the disruption observed in pre-Holocene red B horizons. Calcite from aeolian dusts was dissolved in surface horizons and recrystallized in deeper horizons in the form of discrete features and calcrete. During the more humid phases of these intervals, RMS became waterlogged in presently humid areas of the Mediterranean basin. The impact of frost on the RMS covers has been exaggerated. Precise correlations between the climatic fluctuations identified by paleoclimatologists and features and facies in the soil covers generated during the glacial intervals are almost impossible to establish.

Keywords: Rubefaction, illuviation, behavior of red Mediterranean soils during glacial intervals

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