Genesis and preservation of patterned ground in permafrost non-affected soils – Central Apennines, Italy

Abstract

Several research have been focused on the polygenetic origin of patterned ground soils, ascribing to the freeze-thaw cycles the driving mechanism in the sorted features genesis. Therefore, this type of soils may be considered strictly associated with permafrost-affected areas because freezing and thawing of soil are generally related to the seasonal frost and/or the occurrence of the active layer. Since permafrost can reach mid-latitudes depending on local microclimatic conditions, the Majella Massif (central Apennines, Italy) gained interest because of the presence of periglacial landforms (rock glaciers, kettle holes, and patterned ground), although no direct observations and measurements indicating the occurrence of permafrost have been reported. This work was aimed to determine the genesis and preservation of patterned ground on the Majella Massif through monitoring of soil and air temperatures and derived parameters, and soil characteristics.Results suggested that permafrost was absent at a depth <2 m. However, this did not exclude the presence of deep and sporadic permafrost, as a relict form of a shallower permafrost present in ancient climatic phases. Although during these phases permafrost-driven processes were probably responsible for the formation of the patterned ground, nowadays the preservation and reorganization of this periglacial form is driven by phenomena including superficial freeze-thaw cycles and snow redistribution due to wind. Specifically, the preservation of the miniature patterned ground has been ascribed to shallower phenomena related to the water-holding capacity of the soil and to freeze-thaw cycles of the upper soil layers, which resulted in differential frost heave and segregation of coarse fragments and fines.