Luigi Bruno

Human–landscape interactions in the Bologna area (Northern Italy) during the mid–late Holocene, with focus on the Roman period

Integrated sedimentological and archaeological investigations of mid–late Holocene deposits from the subsurface of Bologna elucidate the complex relationship among urban settlement, human society, geomorphology and climate change at the southern margin of the Po Plain. Above the Pleistocene–Holocene unconformity, the Holocene succession forms an intricate mosaic of alluvial deposits. Two palaeosols, spanning between about 8000–5000 cal. yr BP and 3200–1500 cal. yr BP, respectively, represent the most prominent stratigraphic markers across the study units. A huge amount of archaeological remains from the younger palaeosol enables the identification of an uninterrupted sequence of settlements from the Early Iron Age to the Late Roman period. The first permanent settlements of Iron Age took place in a topographically elevated region protected from flooding. The onset of paedogenesis during this period reflects the radical transformation of the environment by human settlements through widespread control of the river network and setting of regular patterns of irrigation channels. A period of exceptional climate stability characterized the expansion of the Roman Empire. This phase is testified by a wealth of exceptionally preserved archaeological material, including buildings, cemetery sites, streets and irrigation channels. Subsurface correlations of the Roman palaeosol enable detailed reconstruction of the Roman topography, with special focus on fluvial paths and communication routes. The decline of the Roman Empire, hit by a devastating epidemic and the barbarian invasions, was paralleled by a phase of climatic deterioration, resulting in the abandonment of rural lands and degradation of the river network, which ultimately favoured the burial of Roman settlement.

Paleosols and associated channel-belt sand bodies from a continuously subsiding late Quaternary system (Po Basin, Italy): New insights into continental sequence stratigraphy

Previous sequence-stratigraphic work has emphasized the key role of paleosols and associated sand-dominated fluvial bodies as key features for interpreting alluvial architecture. The temporal resolution of the ancient record is, however, insufficient to fully explain the complex relationship between soil formation and the evolution of fluvial systems under changing sea-level and climate conditions. In this paper, we present a detailed record of paleosol−channel belt relationships reconstructed from the subsurface of a rapidly subsiding region (Po Plain, Italy) that spans almost all of the last glacial-interglacial cycle (∼120 k.y.). The studied succession preserves a systematic bipartite zonation into a thick paleosol-bearing segment close to the basin margin and a sand-dominated interval, with vertically amalgamated channel belts, in an axial position. Individual paleosols are weakly developed and represent key stratigraphic markers that can be traced basinwide into adjacent, essentially contemporaneous, unconfined channel-belt deposits. Unlike conventional models of late Quaternary alluvial−coastal plain systems, no persistent incised valley was established in the Po system during the last glacial-interglacial cycle. Continuous accommodation was the key depositional control on alluvial stratigraphy during the prolonged (∼90 k.y.) phase of late Pleistocene sea-level fall, which led to the deposition of a thick, dominantly aggradational alluvial succession. The development of shallowly incised, short-lived valley systems took place only at the transition to glacial stages associated with substantial sea-level drop (marine oxygen isotope stage [MIS] 3-2 transition, and possibly MIS 5-4 transition). This study shows that in rapidly subsiding settings with high rates of sedimentation, incised valley systems may be replaced by aggradationally stacked, essentially nonincised fluvial bodies. In these cases, overbank packages bounded by immature paleosols represent the most likely alternative to the highly weathered interfluve paleosol predicted by classic sequence-stratigraphic models. Fourth-order sequence boundaries and lower-rank erosional surfaces may be easily confused at the ∼100 k.y. scale, and transgressive surfaces, defining the onset of retrogradation, may become the most readily identifiable sequence-stratigraphic surfaces.

High-frequency depositional cycles within the late Quaternary alluvial succession of Reno River (Northern Italy)

Palaeosol-based correlations within the Late Pleistocene-Holocene alluvial succession along the Reno River, in the southern Po Plain, enabled the identification of depositional cycles falling in the sub-Milankovitch band. Each cycle, composed of overbank and fluvial facies capped by poorly to weakly developed palaeosols, is correlatable upstream to a single fluvial terrace in the Reno River valley and to an individual channel belt close to the valley outlet. Four cycles, dated to about 15-10 (c1), 10-5.5 (c2), 5.5-1.5 (c3) and