Climate control on stacked paleosols in the Pleistocene of the Po Basin (northern Italy)

Abstract

Paleosols are recurrent features in alluvial successions and provide information about past sedimentary dynamics and climate change. Through sedimentological analysis on six sediment cores, the mud-dominated succession beneath the medieval 'Two Towers' of Bologna was investigated down to 100 m depth. A succession of weakly developed paleosols (Inceptisols) was identified. Four paleosols (P1, P2, P3 and PH) were radiocarbon-dated to 40-10 cal ka BP. Organic matter and CaCO 3 determinations indicate low groundwater levels during soil development, which spanned periods < 5 ka. The development and burial of soils, which occurred synchronously in the Bologna region and in other sectors of the Po Plain, are interpreted to reflect climatic and eustatic variations. Climatic oscillations, at the scale of the Bond cycles, controlled soil development and burial during Marine Isotope Stage (MIS) 3 (P1 and P2). Rapid sea-level oscillations probably induced soil development at the MIS 3/2 transition (P3) and favored burial of PH after 10 ka BP. Weakly developed paleosols in alluvial successions can provide clues to millennial-scale climatic and environmental variations. In particular, the paleosol-bearing succession of the Po Plain represents an unprecedent record of environmental changes across the Late Pleistocene (MIS 3 and 2) in the Mediterranean region.

Trunk river and tributary interactions recorded in the Pleistocene–Holocene stratigraphy of the Po Plain (northern Italy)

“…Unlike deeply weathered reddish soils (McCarthy & Plint, 1998;Abels et al, 2013;Kraus et al, 2015), these palaeosols show evidence of only incipient pedogenesis (Amorosi et al, 2014(Amorosi et al, , 2017a. In Inceptisols, the characteristics of secondary calcite (evolutionary stages 2 and 3 of Gile et al, 1981;Machette, 1985) are consistent with exposure periods of a few thousand years (Bruno et al, 2020a). Entisols likely result from exposure periods of a few hundred years (Kraus, 1999).…”

“…The widening of the Po channel-belt resulted in the cannibalization of mud deposits, which were transferred 400 km downstream of the study area to the lowstand prograding complex (Pellegrini et al, 2018), and in the reduction of the potential area for Apennine-rivers sedimentation. Preserved Apennine sediments are thin palaeosol-bounded overbank strata, whose deposition was controlled by millennialscale climate oscillations (Bruno et al, 2020a). From the analysis of 80 radiocarbon dated soil profiles, Bruno et al (2020a) documented that palaeosol burial occurred during cold periods, when a more open herbaceous vegetation favoured erosion in the Apennine drainage basins and sediment transfer to the alluvial plains.…”

“…Preserved Apennine sediments are thin palaeosol-bounded overbank strata, whose deposition was controlled by millennialscale climate oscillations (Bruno et al, 2020a). From the analysis of 80 radiocarbon dated soil profiles, Bruno et al (2020a) documented that palaeosol burial occurred during cold periods, when a more open herbaceous vegetation favoured erosion in the Apennine drainage basins and sediment transfer to the alluvial plains.…”

Deformation patterns of upper Quaternary strata and their relation to active tectonics, Po Basin, Italy

“…Palaeosols M2 and M3 have been chronologically anchored to temporally discrete palaeoclimatic events that coincide with rapid shifts from relatively warm to colder phases (Bruno et al. , 2020). In particular, M2 caps a set of closely‐spaced, weakly developed palaeosols (Fig.…”

Late Glacial and Holocene buried black soils in Emilia (northern Italy): genetic and paleoenvironmental insights

“…In northern Italy, the majority of the sites studied from a paleoenvironmental perspective are hilly and mountain settings, mainly lacustrine environments characterized by continuity of sedimentation (e.g., Vescovi et al 2010;Joannin et al 2013, and references therein). On the other hand, case studies performed in wide alluvial plains with high discontinuous sedimentation rates are rare (Ravazzi et al 2006;Marchesini et al 2017;Bruno et al 2020;Marcolla et al 2021). In this framework, during recent decades, excavation for building and engineering activities in the eastern Po Plain (northern Italy) targeted stratigraphic sequences that were well constrained from archeological and chronological points of view (Bianchini et al 2014(Bianchini et al , 2019Cacciari et al 2017;Vittori Antisari et al 2011, 2013a.…”