Comparison of pre-AD 79 Roman paleosols in two contrasting paleo-topographical situations around Pompeii (Italy)

Two transects of 13 stratigraphical cross-sections were studied and 7 pre-AD 79 Roman paleosols were analysed in two contrasting paleotopographical situations northwest (Boscoreale) and south (Moreggine) of ancient Pompeii. The pre-AD 79 paleosol properties were characterised and compared identifying individual paleocatenary relationships between soil parameter values and the paleo-landscape position along the two transects. Furthermore, between the two study areas, pronounced differences in the paleosol characteristics were revealed. Most notably, they seem to be related to the presence or absence of post-burial groundwater influence in the originally terrestrial pre-AD 79 paleosols. Under the recent influence of groundwater dynamics the paleosols are characterised by: (i) higher amounts of organic carbon and nitrogen, (ii) a darker Munsell color of the top soil, (iii) lower amounts of calcium carbonate, (iv) increased sulphate concentrations together with a decreased pH value and (v) redoximorphic features in the overlying AD 79 pumice layer. Moreover, the different thickness of the AD 79 pyroclastic deposits that buried the pre-AD 79 paleosols reflects the volcanogenic processes that took place during the explosive eruption of Somma-Vesuvius in AD 79.