A pedological case study of volcanoclastically impacted landscapes: The Vesuvian Avellino air-fall deposits, Southern Italy

Volcanic sediments are involved in both stratigraphic architecture and pedological environment of the impacted surfaces. Volcanic deposits are widespread in the southern Italian region of Campania, generating extensive tephrostratigraphic and pedological studies. Nevertheless, the pedogenetic effects of the distribution of volcanic sediments have not been fully investigated. The implications of tephra burial and composition on pedogenetic processes have been studied by comparing soil profiles in two different locations influenced by the pumice fall-deposit from the Vesuvian Avellino eruption (about 3360 years BP): Mt. Somma volcano and Mt. Arciano. The latter forms part of the carbonate Campanian Apennines, where the carbonate rock has been excluded from the main pedogenetic processes, due to emplacement of pyroclastic products. Among the described soils on Mt. Somma, the analyzed soil profile was extracted from an earlier work (see the text for the pertinent citation). For the investigation, soil morphological, mineralogical, chemical and lithological properties were determined. On Mt. Somma, the pedogenesis from the Avellino pumices was prevented by their rapid and massive burial by other volcanic sediments. In the absence of overlying materials on Mt. Arciano, the Avellino pumices provided a homogeneously developed soil with well-expressed andic soil properties. In this environment, the pumice substratum was also enriched in the glassy fraction as an effect of selection caused by the pyroclastics during the air-fall distribution. The results indicated the distance directly and indirectly influencing the pedogenesis, due to its implications on both the potential burial processes and the lateral variation in the pedogenetic substratum.