Search

The relationships between pedogenetic processes and fluvial-coastal dynamics in the Po Plain have been reconstructed through sedimentological analysis and correlation of ca. 170 core data chronologically constrained by 376 radiocarbon dates. Vertically stacked, weakly developed paleosols within Upper Pleistocene and Holocene mud-prone strata testify to intermittent pedogenesis, periodically interrupted by overbank sedimentation. Individual paleosols are laterally traceable for tens of km and exhibit A-Bk-Bw, A-Bk or A-Bw profiles. Strati graphically ordered 14C calibrated ages from A organo-mineral horizons testify to slow aggradation during 4-6 thousand years-long exposure periods. Burial ages, with an error of few centuries, are provided by plant debris at the top of A horizons.Millennial-scale climate oscillations and glacio-eustasy are the main drivers of the pedo-sedimentary evolution of the area during the last 50 kyr. Upper Pleistocene paleosols (P1-P3) developed in well-drained floodplain environments, during relatively warm periods.Paleosol burial occurred during colder phases. High-sediment supply during the Last Glacial Maximum hindered pedogenesis and led to the accumulation of 3-10 m-thick overbank strata. Widespread soil development (paleosol PH) occurred at the end of Last Glacial Maximum, following the retreat of Alpine glaciers and the afforestation of Apennine drainage basins. At distal locations, paleosol PH was progressively buried under estuarine sediments during the Holocene phases of post-glacial sea level rise. Beyond the area of marine influence, burial ages of paleosol PH change from a place to another without specific spatial trends and reflect upstream fluvial sedimentation dominated by avulsions and deposition of spatially restricted alluvial units. Holocene (H1-H2) paleosols show a poor correlation potential and laterally variable degree of maturity that reflect avulsive sedimentation patterns and crevassing. This paper provides insights on the timing and mechanisms of formation and burial of weakly-developed paleosols. The outcomes of this research are applicable to similar Quaternary alluvial systems, and may help interpreting ancient paleosolbearing successions.

Framed into a robust stratigraphic context, multivariate analyses on the Holocene palaeobiological record (pollen, benthic foraminifers, ostracods) of the Po coastal plain (NE Italy) allowed the investigation of microtidal ecosystems variability and driving parameters along a 35-km-long land–sea transect. Millennial-scale ecosystem shifts are documented by coeval changes in the meiofauna, reflecting variations in organic matter–water depth (shallow-marine environments) and degree of confinement-salinity (back-barrier settings). In-phase shifts of vegetation communities track unsteady water-table levels and river dynamics in freshwater palustrine areas. Five environmental–ecological stages followed one another crossing four tipping points that mark changes in relative sea level (RSL), climate and/or fluvial regime. At the culmination of Mediterranean RSL rise, after the 8200 event, remarkable growth of peatlands took place in the Po estuary, while low accumulation rates typified the shelf. At the transgressive–regressive turnaround (~7000 cal a bp), the estuary turned into a delta plain with tidally influenced interdistributary embayments. River flow regime oscillations after the Climate Optimum (post-5000 cal a bp) favoured isolation of the bays and the development of brackish wetlands surrounded by wooded peatlands. The youngest threshold (~800 cal a bp), which led to the establishment of the modern delta, reflects a major avulsion of the Po River.

Understanding Quaternary dynamics of delta-coastal plains across multiple glacial-interglacial cycles in the Milankovitch band (~100 kyrs) is crucial to achieve a robust evaluation of possible environmental response to future climate-change scenarios. In this work, we document the long-term bio-sedimentary record of core 204 S16 (~205 m long), which covers a wide portion of the post-MPR (Mid-Pleistocene Revolution) interval, taking advantage of the highly subsiding context of the SE Po Plain (NE Italy). Detailed facies characterization through an integrated sedimentological and meiofauna (benthic foraminifers and ostracods) approach allowed for the identification of a repetitive pattern of alluvial deposits alternating with four fossiliferous, paralic to shallow-marine units (Units 1–4). The transgressive surfaces identified at the base of these units mark major flooding events, forced by Holocene (Unit 4), Late Pleistocene (Unit 3) and Middle Pleistocene (Units 1, 2) interglacials. Distinct stratigraphic patterns typify the Middle Pleistocene interval, which includes coastal-marine (tidal inlet and bay) deposits. In contrast, lagoonal sediments record the maximum marine influence in the Late Pleistocene-Holocene succession. As a whole, the meiofauna tracks a regressive trend, with the deepest conditions recorded by the oldest Unit 1 (MIS 9/11 age?).

Peat horizons are characteristic features of delta plains worldwide. In this study, we tested the use of peat-based correlations to assess the deformation of Holocene strata in the Po coastal plain (Northern Italy). The Holocene stratigraphy, about 30km inland from the modern coastline consists of a peat-bearing, estuarine and deltaic succession, up to 23m thick. Through the analysis of 31 core data and 100 piezocone penetration tests, we identified and mapped three 10–40cm-thick peat layers (T1–T3) dated to 6.6–5.8, 5.5–5.0 and 3.3–2.7cal kyr BP respectively. These peat horizons were found to be suitable stratigraphic markers within the Holocene succession over an area of about 200km2. The mid-late Holocene palaeogeography, reconstructed through high-resolution peat correlation, supported by 72 radiocarbon dates, highlights a typical upper delta plain environment, with ribbon-shaped distributary channels and swamp interdistributary areas. Peat layers are inclined towards E-NE with gradients that increase downsection from ~0.016% (T3) to 0.021% (T1). The gradient of the oldest peat horizon is one order of magnitude larger than the slope of the modern delta plain (~0.0025%). We infer that peat horizons accumulated during periods of low sediment supply mainly controlled by autogenic processes and were deformed after deposition. Differential compaction of underlying sedimentary strata and recent tectonic activity of the buried Apenninic thrust systems are the most likely drivers of strata deformation. Based on isochore maps, we document that higher sedimentation rates in topographically depressed areas compensated, in part at least, the ongoing deformation, keeping unaltered the topographic gradient and the depositional environment. This study demonstrates that peat-based correlation and mapping can shed lights on the mechanisms of strata accumulation and deformation in deltaic settings, constituting a robust basis for reconstructing delta evolution.

Weakly developed paleosols from two distinct interfluve surfaces of Late Pleistocene age provide excellent keys to high-resolution stratigraphic correlation and may serve to trace large-scale genetic packages (systems tract equivalents) across the continental portion of the Po Basin. Twenty-four paleosol profiles from 17 sediment cores were identified and characterized for bulk-geochemical analysis. X-ray fluorescence data were used to trace the degree of weathering. Paleosols, 0.5–1.5 m thick, are pedogenically altered floodplain deposits, developed over time spans of a few thousand of years and mostly partitioned into A-Bk horizons. The most notable paleosol features are dark, organic-matter-rich and carbonate-free mineral surface horizons (A) that overlie bright calcic horizons (Bk) typified by the accumulation of secondary carbonates in the form of pedogenic nodules. Paleosol profiles exhibit a homogeneous geochemical signature that fingerprints a moderate degree of weathering, with little strike- and dip-oriented variability across the different study localities. Plots of Al-normalized calcification and base loss indices against depth reveal systematic increasing values from intensely altered A horizons to underlying Bk horizons. These trends reflect consistent patterns of Ca translocation from surface horizons deeper into the profile, with significant to almost complete Ca removal from A horizons through leaching and accumulation in Bk horizons. Selected trace element ratios (Ba/Sr, Rb/Sr), redox-sensitive trace elements and Zr contents display opposite, up-profile increasing trends that reflect Sr loss in A horizons, with selective Zr concentration in residual minerals. Vertical trends in element ratios are laterally extensive and consistent on a regional basis and represent key pedochemical/stratigraphic markers that can be traced over great distances (tens of kms) throughout the inland portion of the basin. Through quantitative assessment of the degree of weathering, geochemical profiling provides high potential for robust subsurface paleosol correlation that might not be captured by visual core descriptions alone.

Despite increased application of subsurface datasets below the limits of seismic resolution, reconstructing near-surface deformation of shallow key stratigraphic markers beneath modern alluvial and coastal plains through sediment core analysis has received little attention. Highly resolved stratigraphy of Upper Pleistocene to Holocene (Marine Isotope Stage 5e to Marine Isotope Stage 1) alluvial, deltaic and coastal depositional systems across the southern Po Plain, down to 150 m depth, provides an unambiguous documentation on the deformation of previously flat-lying strata that goes back in time beyond the limits of morphological, historical and palaeoseismic records. Five prominent key horizons, accurately selected on the basis of their sedimentological characteristics and typified for their fossil content, were used as highly effective stratigraphic markers (M1 to M5) that can be tracked for tens of kilometres across the basin. A facies-controlled approach tied to a robust chronology (102 radiocarbon dates) reveals considerable deformation of laterally extensive nearshore (M1), continental (M2 and M3) and lagoon (M4 and M5) marker beds originally deposited in a horizontal position (M1, M4 and M5). The areas where antiformal geometries are best observed are remarkably coincident with the axes of buried ramp anticlines, across which new seismic images reveal substantially warped stratal geometries of Lower Pleistocene strata. The striking spatial coincidence of fold crests with the epicentres of historic and instrumental seismicity suggests that deformation of marker beds M1 to M5 might reflect, in part at least, syntectonically generated relief and, thus, active tectonism. Precise identification and lateral tracing of chronologically constrained stratigraphic markers in the(14)C time window through combined sedimentological and palaeoecological data may delineate late Quaternary subsurface stratigraphic architecture at an unprecedented level of detail, outlining cryptic stratal geometries at the sub-seismic scale. This approach is highly reproducible in tectonically active Quaternary depositional systems and can help to assess patterns of active deformation in the subsurface of modern alluvial and coastal plains worldwide., Sedimentology, 68 (1), ISSN:0037-0746, ISSN:1365-3091

Large volumes of peatland deposits characterise the Holocene stratigraphy of the Po Plain. A combination of sedimentological and pollen-based paleoenvironmental analyses enables recognition and stratigraphic correlation of small-scale (2–5 m thick) packages of peat-bearing strata, stacked rhythmically in a retrogradational to progradational set and bounded by chronostratigraphically significant surfaces. Across these repetitive lithofacies successions, the proportion of facies-controlled palynomorphs is used as a diagnostic signature to characterise marine flooding surface equivalents (helophytes and hydrophytes) and shoaling-upward (terrestrialization) trends (trees and mesophilous herbs) that record systematic variations in groundwater table associated with increasing/decreasing accommodation. Paludification surfaces at the base of peats delineate the updip (freshwater) equivalents of brackish/marine flooding surfaces recognized at seaward locations atop peat layers (give-up transgressive surfaces). Peat beds exhibit maximum thickness in aggradational strata of the lowermost highstand systems tract, above the maximum flooding surface (MFS). An extrinsic control due to eustatic rise can be inferred for peat development in transgressive deposits: peats, in particular, reveal warmer climates at flooding surfaces (specifically around the MFS) that invariably coincide with rapid shifts to deeper depositional environments. Under highstand conditions, autogenic mechanisms affected base-level changes in the paralic swamps. At this stratigraphic level, peat-bearing strata primarily reflect subtle changes in accommodation due to distributary-channel avulsion, subsidence, and peat autocompaction. Detailed patterns of Holocene peat distribution on millennial timescales can help decipher multiple high-resolution accommodation cycles developed in the rock record on sub-seismic scales, resulting in an improved stratigraphic analysis and prediction of chronologically less constrained non-marine successions.

Despite the growing employment of Remote Sensing (RS) techniques in paleoenvironmental studies, the stratigraphic interpretation of RS-derived paleodrainage traces is still an open issue, as their relation to subsurface is largely unexplored. Here we applied a multi-data analysis approach, including publicly available optical images from different satellites (Landsat, ASTER, Sentinel, Hyperion), LiDAR-derived Digital Terrain Model (DTM), soil reflectance spectra and facies core data, which succeeded in revealing a paleodrainage system buried beneath a 200-sq km wide wetland (the Mezzano Lowland-ML) of the Po coastal plain (northern Adriatic Sea, Italy). Data integration in a GIS environment allowed the 3D mapping of numerous and temporally persistent meandering traces. From distal to proximal locations, the RS-derived traces show a hierarchical organization, in terms of sinuosity and width, and form a dense and dendritic pattern typical of a tidally-influenced system. Surface and subsurface cross-investigation of two meandering traces through soil reflectance spectra and core stratigraphy reveal that these landforms represent the surface expression of buried channels that eroded the underlying lagoonal succession, with lateral transition to intertidal deposits. LiDAR-detected micro-morphologies related to paleomeanders evolution strongly influenced the spatial distribution of mid-late Holocene peat-bearing lithofacies (i.e., salt marsh and swamp), and hence soil moisture distribution, inducing the sharp radiance contrasts (traces) detected by satellite sensors on the surface. On-trace areas invariably lack peat deposits and record the top of 3–4 m-thick channel-fill sands, some 2–4 m below the ground level. In contrast, out-of-trace areas are characterized by organic-rich soils that cap a 2.5–3.5 m-thick succession of intertidal-supratidal peat deposits, accumulated in depressed areas lateral to the channel-levee complex. We conclude that in the early stage of Po Delta construction, between ca. 6000–2500 cal yr BP, two distinct tidal-influenced drainage networks fed the Mezzano Lowland lagoon under a predominantly autogenic control. These findings indicate the suitability of a low-cost RS-stratigraphic approach to improve the reconstruction of past paleogeographic scenarios buried beneath deltaic lowlands, shedding new light on the evolution trends of coastal landforms, environments and sedimentary patterns under highstand conditions.

To understand the complex stratigraphic response of a coastal depositional system to rapid eustatic rise and sediment inputs, the evolution of the Adriatic coastline and Po River system, during the post-glacial (Holocene) transgression, was investigated. The landward migration and evolution of a wave-dominated estuary was mapped, based on an extensive data set comprising 14 boreholes, 28 core descriptions and 308 piezocone tests, chronologically constrained between 11·5 and 7·0Âkyr bp by 137 radiocarbon dates. Palaeogeographic maps reveal temporal differences in retrogradational geometries and mechanisms that likely underpin shoreline retreat. The Po estuary initially developed within a shallowly incised valley and then spread onto the interfluves. Between 11·5 and 9·2Âkyr bp the Po fluvial system became avulsive/distributive and wetlands developed in topographically depressed areas. The shoreline retreated at a mean rate of ca 10ÂmÂyear−1, between 9·2Âkyr and 7·7Âkyr bp, following a stepped trajectory at the centennial scale. After 7·7Âkyr bp, bayhead deltas started to prograde and partially filled the estuary. The overall stratigraphic architecture is interpreted to reflect the sedimentary response of the coastal depositional system to the main pulses of early Holocene eustatic rise. The influence of antecedent topography, partly due to local subsidence, was dominant at the time of initial transgression. Basin morphology influenced sediment dispersal and partitioning. Sediment supplied by the Po River was trapped within the estuary, whereas coastal sand bodies at the estuary mouth were fed by alongshore currents and by reworking of older barriers. High-resolution age control that ties facies evolution to independently constrained eustasy provides direct data to test models of short-term coastal retreat under conditions of relative sea-level rise, and makes this case study a useful analogue for the interpretation of ancient marginal-marine, retrogradational systems where only stratal geometries are available.

Sequence stratigraphy, typically used for hydrocarbon exploration in ancient strata, can be applied to late Quaternary successions to decipher complex spatial relations among their aquifers. Late Pleistocene-Holocene strata of the Po Basin were investigated using a sequence stratigraphic approach to produce a highresolution model for guiding groundwater exploitation. Because facies tend to be diachronous across depositional basins, facies analysis was done within the conformable intervals of strata revealed by sequence stratigraphy to accurately interpret and map coeval lateral facies relations. Volumetric assessments, sand-distribution mapping, hydraulic characterization of facies, and spatial variations of hydraulic parameters revealed two aquifer systems: The lowstand systems tract (LST) and the highstand systems tract (HST) vertically separated by an aquitard, the transgressive systems tract (TST). The LST aquifer consists of amalgamated fluvial sands (average transmissivity: 3.5 E-3 m2/s [37.7 E-3 ft2/s]) with considerable width (>25 km [>16 mi]) preferentially elongated downstream. The widespread TST aquitard is dominated volumetrically (~57%) by low-permeability estuarine deposits. The HST aquifer (average transmissivity: 5.4 E-5 m2/s [58.1 E-5 ft2/s]) is 5-10 km (~3-6 mi) wide, elongated parallel to the modern shoreline. Sequence stratigraphic analysis at the parasequence scale revealed an almost unprecedented level of detailed insight into aquifer (or aquiclude) dimensions and the complex distribution of hydraulic parameters in the subsurface, showing that similar facies have different permeabilities depending on systems tract. In contrast, lithostratigraphic mapping obscures subsurface connectivity and directional trends and hasminimal predictive power away from control. These insights should be useful for guiding correlation and mapping of the deep subsurface and for hydrocarbon reservoir modelers.

Eight stratigraphic transects, 40–140 km long reveal, for the first time on a regional scale, a comprehensive picture of facies architecture of the highly preserved Late Pleistocene-Holocene sedimentary succession from the rapidly subsiding Po Basin. Facies analysis and pollen-based correlation, supported by radiocarbon, electron-spin resonance and optically stimulated luminescence dates, enabled the attribution of distinct stratigraphic intervals to Marine Isotope Stages (MIS) 6 to 1. Basin-scale facies changes appear to have been driven mostly by glacio-eustatic oscillations falling in the Milankovitch band (∼100 ky). The MIS 5e coastal wedge was tracked continuously beneath the modern shoreline, for over 110 km along strike. Along-dip (west-east) stratigraphic correlation over 140 km revealed the characteristic landward transition from shallow-marine and coastal facies to lagoonal, swamp, and floodplain deposits. The MIS 5d-MIS 2 stratigraphic succession, up to 95-m-thick, records the stepped, basinward shift of facies related to the post-MIS 5e sea-level fall. In particular, lagoon and swamp facies mark minor transgressions (Substages 5c and 5a), whereas thick floodplain deposits and laterally extensive (>40 km) fluvial channel-belts, up to 30 m thick, characterized the glacial periods (MIS 4 and MIS 2). The Holocene (MIS 1) coastal wedge shares many similarities in terms of facies architecture and geometry with its MIS 5e counterpart, though maximum landward marine incursion during the MIS 5e transgression was 10 km farther inland (36 km inland of modern shoreline). Organic-rich (freshwater swamp) environments developed > 100 km landwards of the present-day coastline. The MIS 5e-MIS 1 succession of the Po Basin displays an exceptional thickness, up to 130 m. Minimum values (∼20 m) are recorded close to the Apennine margin and above the buried actively growing anticlines. The spatial distribution and geometry of the MIS 5e-MIS 1 strata, as well as rapidly varying subsidence rates (from 0.2 to 1.0 mm/y) reflect the strong influence of the structural setting (location of major thrust fronts) over the creation/destruction of accommodation.

Though clinothem geometry represents a key control on fluid flow in reservoir modelling, tracing clinothem boundaries accurately is commonly limited by the lack of sufficiently precise outcrop or subsurface data. This study shows that in basin systems with strongly heterogeneous compositional signatures, the combination of bulk‐sediment geochemistry and benthic foraminiferal distribution can help identify clinothem architecture and generate realistic models of 3D deltaic upbuilding and evolution. Middle‐late Holocene deposits in the Po Delta area form an aggradational to progradational parasequence set that reveals the complex interaction of W–E Po Delta progradation, S‐directed longshore currents (from Alpine rivers) and Apennines rivers supply. Unique catchment lithologies (ophiolite rocks and dolostones) were used to delineate basin‐wide geochemical markers of sediment provenance (Cr and Mg) and to assess distinctive detrital signatures. The geochemical characterization of cored intervals across different components of the sediment routing system enabled a direct linkage between clinothem growth, transport pathways and provenance mixing to be established. On the other hand, abrupt microfaunal variations at clinothem boundaries were observed to reflect the palaeoenvironmental response to sharp changes in sediment flux and fluvial influence. This study documents the ability of an integrated geochemical and palaeoecological approach to delineate three distinct sources (Po, Alps and Apennines) that contributed to coastal progradation and to outline the otherwise lithologically cryptic geometries of clinothems that using conventional sedimentological methods it would be virtually impossible to restore.

Although general trends in transgressive to highstand sedimentary evolution of river-mouth coastlines are well-known, the details of the turnaround from retrogradational (typically estuarine) to aggradational–progradational (typically coastal/deltaic) stacking patterns are not fully resolved. This paper examines the middle to late Holocene eustatic highstand succession of the Po Delta: its stratigraphic architecture records a complex pattern of delta outbuilding and coastal progradation that followed eustatic stabilization, since around 7·7calkyrbp. Sedimentological, palaeoecological (benthic foraminifera, ostracods and molluscs) and compositional criteria were used to characterize depositional conditions and sediment-dispersal pathways within a radiocarbon-dated chronological framework. A three-stage progradation history was reconstructed. First, as soon as eustasy stabilized (7·7 to 7·0calkyrbp), rapid bay-head delta progradation (ca 5myear−1), fed mostly by the Po River, took place in a mixed, freshwater and brackish estuarine environment. Second, a dominantly aggradational parasequence set of beach-barrier deposits in the lower highstand systems tract (7·0 to 2·0calkyrbp) records the development of a shallow, wave-dominated coastal system fed alongshore, with elongated, modestly crescent beaches (ca 2·5myear−1). Third, in the last 2000years, the development of faster accreting and more rapidly prograding (up to ca 15myear−1) Po delta lobes occurred into 30m deep waters (upper highstand systems tract). This study documents the close correspondence of sediment character with stratal distribution patterns within the highstand systems tract. Remarkable changes in sediment characteristics, palaeoenvironments and direction of sediment transport occur across a surface named the ‘A–P surface’. This surface demarcates a major shift from dominantly aggradational (lower highstand systems tract) to fully progradational (upper highstand systems tract) parasequence stacking. In the Po system, this surface also reflects evolution from a wave-dominated to river-dominated deltaic system. Identifying the A–P surface through detailed palaeoecological and compositional data can help guide interpretation of highstand systems tracts in the rock record, especially where facies assemblages and their characteristic geometries are difficult to discern from physical sedimentary structures alone.

Geochemistry, sediment provenance, and the Holocene paleoenvironmental evolution of the Southern Po River coastal plain (Italy) were examined based on the geochemical analysis of 279 sediment samples from 35 cores. The Holocene succession is subdivided into four major facies associations: back-barrier, transgressive barrier, shallow-marine, and beach-ridge deposits. Bulk chemical composition shows remarkable differences between facies associations, and the poly-modal behavior in the related frequency curves suggests distinct sources of sediment. Using MgO and Ni as geochemical tracers, changes in sediment provenance were assessed with the aim to reconstruct the Holocene paleoenvironmental evolution of the area. The Po River and the Apenninic rivers represented the main sources of sediment during the early stages of transgression and highstand sea-level conditions, whereas transgressive barrier and early shallow-marine facies associations exhibit a clear North Adriatic river (eastern Alpine) provenance. The Holocene paleoenvironmental evolution of the study area, between about 10 ky and the present, indicates the presence of a bypass zone in front of the Po River mouth between 9 and 6 ky BP. At that time, sediment supplied by the North Adriatic rivers was transported southward by the longshore drift, bypassed the weak Po River influx and accumulated close to the Apennines. Comparison between Holocene facies associations and current back-barrier and shallow-marine sediments confirms that the present-day basin circulation is similar to the one that acted during the last episode of sea-level rise.

Pocket penetrometer measurements, though commonly listed as accessory components of core descriptions, are almost totally ignored in shallow subsurface stratigraphic analysis. In this study, we prove that, if properly calibrated with core data, pocket penetration tests may serve as a quick and inexpensive tool to enhance high-resolution (palaeosol-based) stratigraphy of unconsolidated, late Quaternary non-marine deposits. A palaeosol sequence, made up of 12 vertically stacked, weakly developed palaeosols (Inceptisols) dated to the last 40 ky cal BP, is reconstructed from the subsurface of the southern Po Plain. The individual palaeosols exhibit flat to slightly undulating geometries and several of them can be tracked over distances of tens of km. They show substantially higher compressive strength coefficients than all other fine-grained, alluvial (floodplain) facies, being typified by distinctive penetration resistance, in the range of 3.5–5 kg/cm2. Along the palaeosol profiles, A and Bk horizons demonstrate consistent difference in relative compressive strengths, the highest values being almost invariably observed at the A/Bk boundary. Palaeosols are rarely described in conventional stratigraphic logs, and just a small proportion of them is likely to be identified by geologists with no specific sedimentological training. Through core–log calibration techniques, we document that vertical profiles of penetration resistance measured in the field can be used as an efficient method for palaeosol identification, and thus may represent a strategy for predicting stratigraphic architecture from limited core descriptions or poor-quality field logs. This technique allows to optimize the contribution of all available stratigraphic information, expanding significantly the coverage of well-described, one-dimensional core data. Copyright © 2014 John Wiley & Sons, Ltd.

Holocene deposits exhibit distinct, predictable and chronologically constrained facies patterns that are quite useful as appropriate modern analogs for interpreting the ancient record. In this study, we examined the sedimentary response of the Po Plain coastal system to short-term (millennial-scale) relative fluctuations of sea level through high-resolution sequence-stratigraphic analysis of the Holocene succession. Meters-thick parasequences form the building blocks of stratigraphic architecture. Above the Younger Dryas paleosol, a prominent stratigraphic marker that demarcates the transgressive surface, Early Holocene parasequences (#s 1–3) record alternating periods of rapid flooding and gradual shoaling, and are stacked in a retrogradational pattern that mostly reflects stepped, post-glacial eustatic rise. Conversely, Middle to Late Holocene parasequences (#s 4–8) record a complex, pattern of coastal progradation and delta upbuilding that took place following sea-level stabilization at highstand, starting at about 7 cal ky BP. The prominent transgressive surface at the base of parasequence 1 correlates with the period of rapid, global sea-level rise at the onset of the Holocene (MWP-1B), whereas flooding surfaces associated with parasequences 2 and 3 apparently reflect minor Early Holocene eustatic jumps reported in the literature. Changes in shoreline trajectory, parasequence architecture and lithofacies distribution during the following eustatic highstand had, instead, an overwhelming autogenic component, mostly driven by river avulsions, delta lobe switching, local subsidence and sediment compaction. We document a ∼1000-year delayed response of the coastal depositional system to marine incursion, farther inland from the maximum landward position of the shoreline. A dramatic reduction in sediment flux due to fluvial avulsion resulted in marine inundation in back-barrier position, whereas coastal progradation was simultaneously taking place basinwards. We demonstrate that the landward equivalents of marine flooding surfaces (parasequence boundaries) may be defined by brackish and freshwater fossil assemblages, and traced for tens of kilometers into the non-marine realm. This makes millennial-scale parasequences, whether auto- or allogenic in origin, much more powerful than systems tracts for mapping detailed extents and volumes of sediment bodies. The Holocene parasequences of the Po coastal plain, with strong age control and a detailed understanding of sea-level variation, may provide insight into the driving mechanisms and predictability of successions characterized by similar depositional styles, but with poor age constraint, resulting in more robust interpretations of the ancient record.

The occurrence of vinyl chloride (VC) is often a main concern at sites contaminated with chlorinated solvents due to its high degree of toxicity and carcinogenicity. VC occurrence in aquifers is most often related to the degradation of higher chlorinated ethenes or ethanes and it is generally detected in plumes along with parent contaminants. However, specific combination of stratigraphic, hydrogeologic and geochemical conditions can enhance the degradation of parents and lead to the formation of plumes almost entirely composed of VC (i.e. VC-only plumes). This paper investigates the causes of VC-only plumes in the aquifers below the city of Ferrara (northern Italy) by combining multiple lines of evidence. The City of Ferrara is located on an alluvial lowland, built by the River Po, and is made up of alternating unconsolidated sandy aquifer and silt-clay aquitard deposits of fluvial origin. This region has been strongly impacted by prior industrial activities, with the occurrence of chlorinated compounds at several sites. VC-only plumes with uncertain source location were found at two contaminated sites. The source zone of a third plume composed of chloroethenes from PCE to VC was investigated for high resolution depositional facies architecture and contaminant distribution (contaminant concentration and Compound Specific Isotope Analysis – CSIA). The investigation suggested that degradation of PCE and TCE takes place during contaminant migration through peat-rich (swamp) layers related to the Holocene transgression, which locally act as a “reactor” for stimulating degradation with the accumulation of VC in the strongly reducing environment of the peat. Regional-scale stratigraphic architecture showed the ubiquitous occurrence of swamp layers at distinct stratigraphic levels in the investigated system and their apparent linkage to the in situ creation of the VC-only plumes.

A buried paleovalley system, up to 2 km wide and exceeding 50 m in relief, made up of multiple cross-cutting depressions incised into the Lower Pleistocene bedrock, is reported from the central Adriatic coastal plain at the mouth of Biferno River. Through a multi-proxy approach that included geomorphological, stratigraphic, sedimentological and paleontological (benthic foraminifers, ostracods and molluscs) investigations, the facies architecture of distinct, superposed valley fills is reconstructed and their relative chronology established along a transverse profile with extremely high data density (average borehole spacing 75 m). Regional tectonic uplift appears as the major controlling factor of initial (Middle Pleistocene) river down-cutting and paleovalley formation. In contrast, glacio-eustatic fluctuations drove fluvial-system response over the last 120 ky, when valley incision was primarily induced by the last glacial base-level lowering and climatic forcing. A fragmented record of coastal and shallow-marine deposits is available for the lower paleovalley fill, which is penetrated by a limited borehole dataset. Multiple erosion phases probably related to the post-MIS 5e sea-level fall are reconstructed from the upper paleovalley fill, where a buried fluvial terrace succession is identified a few tens of meters below the ground surface. The flat surfaces of two buried fluvial terraces suggest longer-term, stepped relative sea-level fall, and are correlated with fluvial incisions that took place possibly at the MIS 5/4 transition and at the MIS 3/2 transition, respectively. A laterally extensive gravel body developed on the valley floor during the Last Glacial Maximum. During the ensuing latest Pleistocene–early Holocene sea-level rise the Biferno paleovalley was transformed into an estuary. Upstream from the maximum shoreline ingression, the vertical succession of well-drained floodplain, poorly-drained floodplain, and swamp deposits evidences increasing marine influence in the estuary, in response to continuing sea-level rise. The interfluves were drowned around 8 cal. ky BP, when brackish conditions developed in the study area. Decreasing marine influence in the uppermost 15 m of the paleovalley fill suggests the onset of the modern delta: when the rate of sea-level rise was overwhelmed by sediment supply, delta progradation took place.

High-resolution investigation of a ~Â 120-km-long transect along the course of the modern Po River, northern Italy, revealed marked changes in alluvial architecture across the Pleistocene–Holocene boundary. Along the whole transect, a 20- to 30-m thick sheet-like succession of Late Pleistocene fluvial sands is invariably overlain by silt and clay deposits, with isolated fluvial bodies of Holocene age (

International audience; Teaching how to map the geomorphology of an area cannot be performed in a satisfying manner only in the lecture room, but requires practical exercises both in the laboratory and in the field. A preliminary study of existing geological maps, geomorphological legends and symbols used in Italy and of the landslide inventory preceded a detailed four-day-long field mapping campaign carried out by students in the framework of their MSc course on ‘Geomorphological Mapping’ at Bologna University. The Geomorphological Map at 1:5000 produced by some of these students is presented in this paper.The study area is located in the northern Apennines, a few kilometres East of Bologna, along the Idice Valley (N-Italy). Lithologies are mainly composed of clayey and marly sequences ranging in age from Cretaceous to Plio-Pleistocene, sands and sandstones of Pleistocene age, and Messinian gypsum, these last being the most resistant rocks.Besides the greater scale used in this map, allowing for a more detailed representation of the mapped features, this map also shows the recent evolution of landslides in this actively mass wasting area.