Late Glacial-Holocene genesis of Andosols from the Seaca-Tãtarca (South Gurghiu Mountains, Romania)

The purpose of the research presented here was to find an answer for the possible origin and mode of deposition of soil parent materials for Andosol formation and to link the soilscape variability to the various soil forming factors since the Last Glaciation. Soil formation was studied along a 20‐km climo‐toposequence in the Miocene Andesitic area of the South Gurghiu Mountains (Romania). Six representative soil profiles were chosen from a larger geopedological study on the western slope of the Seaca‐Tãtarca volcano. Based on the macromorphological, micromorphological and chemical properties it was possible to say that the soil profiles are composed of two major types of soil material: a relict type, with a crystalline clay fraction; and a recent type with an amorphous colloidal fraction. It was found that the present‐day distribution of the Andosols on the Seaca‐Tãtarca volcano must be related to the rejuvenation of the soil parent material by processes of aeolian input of frost‐shattered volcaniclasts and by a glacial reworking. It appears that the extension of the glaciated areas during the Pleistocene could have been larger than concluded from geomorphological studies. General Carpathian glacial features are closely related to the altitudinal distribution of the Carpathian Andosols. At the present climatic optimum, the soils of Seaca‐Tãtarca are influenced by pedogenetic processes of freeze‐thaw, oxido‐reduction, strong leaching and internal colluviation, strong accumulation of organic matter and considerable biological activity. Those Andosols that are located in special microtopographic positions with stronger water percolation tend to evolve towards Podzols.