Pedological (micromorphological and chemical) investigation in an archaeological site of the Early Bronze Age: the case study of Palma Campania (southern Italy): Soil properties of the last 9000 years in a plain close to Vesuvius

Archaeological records from excavations of the last forty years in the Campania region (southern Italy) attest an intense human occupation from the Early Bronze Age (EBA) to the present day. Findings of the cultural sphereof the EBA, known asfacies of Palma Campaniain the southern Italy, have beenwidelyburied by the pyroclastic deposits of the Vesuvius Pomici diAvellino eruption (3945yrcalBP).Because of the exceptional importance and preservation of the relicsfoundin the excavation of the 1995in Balle/Pirucchi locationat Palma Campania (Naples),a detailed (micromorphological and chemical) soil study was carried out oni) avery deepsoil chronosequence (approximately 9 m), composed of soil and pyroclastic deposits dating from the Pomici di Mercato eruption (8890 yrcal BP) until the present day and ii) a wide (4500 m2) paleo-surface belonging to the EBA. As shown by the chemical (i.e. organic matter– OM, cation exchange capacity– CEC, pH, ammonium oxalate extractable Al and Fe–Alo+0.5Feo index, organic and inorganic phosphorous fractions – OP and IOP) and physical (i.e. particle size distribution - PSD) properties, allsoils of the sequence i) formed by weathering of volcanic materials,ii) satisfy the requirements for Andosolclassification,iii) are markedly different in terms ofdepth, degree of andic properties and chemical fertility, iv) show micromorphological features (e.g. clay and silty coatings, laminar features, iron segregations, weathering rims,ecc.) indicatingspecific weathering environments.Moreover, the comparison of selected soil properties, such as Alo+0.5Feo index(essential for Andosols) and OM,andthe estimated pedogenetic times (EPT), calculated on the basis of the volcanological markers,withthe climatic conditions by the literature,highlights a markedrelationship between the degree of development of those properties (i.e. their content) in the soils of Palma Campania and the humidity/aridity of the environment. These resultsencourage furtherapplications aimed to use these soil propertiesas proxy for the reconstruction of past climatic conditions in volcanic environments. The soil properties measured in the different areas of the EBA paleo-surface showed very consistent with both archaeological findings and reconstructed agricultural uses. Indeed, the very high OP content, along with the enrichment of OMin the soils of the North and Central sectors are in accordance with the pasture and agricultural activities, respectively,suggested by the numerous chaotically scattered animal track sand the parallel furrows of “strip” cultivation, while both OP and OM are markedly lower in the coetaneous soil analyzed along the soil chronosequence, where no anthropic or animal traces were found. Regarding to the controversial interpretation about the use of the South area, peculiar pedological features and chemical properties strongly suggest the anthropic genesis for the ancient micro-topography.Indeed, the presence of a broken soil structure, horizontal planar pores and vertical orientated laminar aggregates in a massive structure reveal a process of deeply mixing and strongly compacting soil horizons to form micro-relieves and micro-concavities. High O Pand OM content are found at 7-25 cm below the soil surface, probably as a consequence of manuring and ploughing. Further abandonment and waterlogging of the area are consistent with the presence of Phragmites footprints,previously found during the archaeological survey, and absence of a specific shape of ploughing traces