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Holocene prodelta lobes are key sedimentary archives of environmental change that can be used effectively for high-resolution palynological investigations, as they: (i) consist almost entirely of mud, (ii) represent stratigraphically expanded successions, and (iii) are strictly related to river dynamics, thus reflecting vegetation changes in river catchments. In this study, we focussed on the ~20 m-thick prodelta succession of the modern Po Delta (NE Italy), fed by two river branches (Volano and Goro) that were mostly active during the past two millennia, a period of rapid acceleration of natural resources' exploitation and climate variability. Forty-eight samples with mean temporal resolution of 50 years were analysed. Eleven ecological groups and four pollen zones were identified, with distinct peaks of the secondary-primary pollen ratio marking major floods during the Volano-Goro lobe switching and the Little Ice Age. Five vegetation phases were detected since the 1st century AD. In the framework of a patchy natural-cultural landscape, patterns of wetland expansion/contraction reflect the combined effect of cool-wet oscillations (LALIA – Late Antique Little Ice Age), land management (reclamations) and river avulsion. Forest dynamics document warm conditions during the so-called 'Roman Climate Optimum' and 'Medieval Warm Period', although minor cool-wet episodes occurred in tune with solar minima, and bipartite climate conditions (cool-moist followed by cool-dry) characterized the LALIA. Since the 14th century, despite human-induced forest shrinking, peaks of montane vegetation followed a centennial-scale cyclicity likely influenced by solar minima and major plagues. [ABSTRACT FROM AUTHOR]

Pollen and spore records in prodeltaic sediments hold significant potential for reconstructing paleoecologic and paleoclimatic evolution. However, uncertainties in these reconstructions arise from millennial-scale prodelta evolution, which dominates stratigraphic development and consequently influences sedimentary processes and/or pollen provenance. Here we explore the intricate relationship between pollen/spore records and prodelta stratigraphic evolution, using established seismic stratigraphy and ten sediment cores (five new, five from literature) within both the proximal and distal (mud belt) parts of the Huanghe (Yellow River) prodelta. In the proximal region, dominant lobate stratigraphic development, accompanied by shifts in river mouth and depocenter, leads to variations in pollen assemblages and contents within individual cores and differences in vertical pollen distribution across core sites. Transport distance appears to be a key factor, with arboreal pollens, particularly saccate ones (e.g., Pinus), positively correlating with the distance from the river mouth in their percentages within a single delta lobe, while non-arboreal and non-saccate arboreal pollens show higher percentages within shorter transport distances, despite longer distances leading to decreased total pollen concentrations. Likely due to the total pollen concentration after extended long-distance transport, this pattern is not observable in the distal mud belt. Subsurface stratigraphy in this mud belt reveals a complex pollen provenance characterized by Artemisia-Ulmus-Chenopodiaceae-Pinus, with non-arboreal pollens in dominance. Therein, non-arboreal pollens are not consistent with deposition from long-distance transport, and Ulmus pollens are uncommon in the western Bohai Sea. Interestingly, surface sediments in the mud belt display a different assemblage, characterized by Pinus-Artemisia-Quercus, consistent with the nearby Luanhe River prodelta, suggesting recent pollen supply from nearby sources, possibly due to the recent abandonment of the mud belt. Additionally, an energetic longshore transport/erosional regime reduces pollen content at the mud-belt margins and create pollen sinks (with the highest concentration) in the mud patch (accumulation area) within the erosion-dominated region adjacent to the mud belt. Our findings confirm that stratigraphic evolution, alongside hydrodynamic conditions and pollen provenance, governs pollen assemblages in deltaic/prodeltaic sediments. They can provide insights for palynological and pollen-based paleoclimatic and paleoecologic studies in other deltas. [ABSTRACT FROM AUTHOR]

This paper describes the ichnology and sedimentology of the middle Berriasian sedimentary succession of the Sidi Khalif Formation outcropping in Jebel Meloussi, Central Tunisia. The succession records deltaic progradation above outer shelf deposits and shows the vertical stacking of thickening and coarsening-upward parasequences dominated by hummocky cross-stratification, parallel lamination and abundant gutter casts. The mudstones and the thinly bedded fine-grained sandstones of the prodelta are characterized by scarce and low diverse horizontal trace fossils of the impoverished distal Cruziana ichnofacies, including cf. Thalassinoides, Phycosiphon, Planolites, Helminthoidichnites and cf. Helminthoidichnites. In contrast, trace fossils of the wave-dominated delta-front are dominated by deposit-feeding ichnotaxa, such as Rhizocorallium commune, Arenicolites isp., R. ?jenense, Thalassinoides and Planolites, which represent the proximal Cruziana ichnofacies. The lack of bioturbation structures in the amalgamated hummocky cross-stratification beds of the delta front is mostly related to the high frequency and/or high intensity episodic erosional amalgamation and deposition associated with storms. The difference between Rhizocorallium ichnospecies help to depict the erosional discontinuities bounding parasequences. The transgressive surfaces (TS) are characterized by R. ?jenense and by R. commune. [ABSTRACT FROM AUTHOR]

The combined use of the meiofauna (benthic foraminifers and ostracods) and geochemical data from three cores, recovered in distinct bathymetric sectors of the southern Adriatic shelf (Apulia, SE Italy), provides new insights on the relationships between shallow-marine environments, sediment fluxes and eutrophication trends over the last ∼7000 years. The stratigraphic distribution of meiofauna assemblages allows distinguishing a variety of facies associations, accumulated at proximal (Manfredonia Gulf), intermediate and distal shelf sectors. Spatial-temporal facies trajectories mainly reflect changes in fluxes of fine-grained, inorganic and organic particles at the seafloor. Major palaeoenvironmental shifts are paralleled by stratigraphic variations of Cr-Ni values, which represent effective provenance tracers for the Adriatic region. The correlation between the meiofauna content and trace-metal concentrations documents the link between the type of substrate (organic matter-OM and grain-size) and sediment provenance along the bathymetric profile and through time. After 6000 yr B.P., the gulf, partly sheltered by the Gargano Promontory, experienced the first increase in OM fluxes (transition from open-bay to prodelta). This turnaround occurred under the progressive change in sediment supply from southern Apennine source-rocks, poor in trace metals, to a mixed contribution including northern sources, enriched in chromium and nickel (mafic/ultramafic rocks of the Po River catchment) via the SSE-directed longshore drift. Alongside, prodelta clays in lateral transition to mud-belt deposits accumulated in the adjacent open shelf under the steady influence of the longshore drift. Finally, since ∼2000 yr B.P. a pervasive subaqueous delta system developed across the study area in response to increased sediment load by Po + Apennine rivers, likely induced by enhanced anthropic pressure during Roman times. This study highlights the key role played by the sediment routing system, coastal morphology and human land-use on shelf facies patterns and eutrophication trends, even in areas hundreds of km away from the main fluvial mouths. • Shallow-marine facies, meiofauna and sediment provenance are closely related. • Beyond water depth, meiofauna reflect organic content and grain-size sea bottom. • Longshore drift coupled with coastal morphology drives shelf facies patterns. • Human land-use can fuel environmental changes on shelves far from major deltas. [ABSTRACT FROM AUTHOR]

Analyses of benthic foraminiferal assemblages were carried out on sediment samples collected in the Gulf of Patti (NE Sicily, Tyrrhenian Sea), where high sedimentation rates in front of the Mazzarrà River led to the growth of a prodelta. The frequency of riverine sedimentary fluxes is testified by the widespread occurrence of erosional and depositional bedforms indicative of high-energy processes on the prodelta slope.The frequency of riverine sedimentary fluxes suggests the widespread occurrence of erosional and depositional bedforms indicative of high-energy processes on the prodelta slope. The study aimed to assess the spatial distribution of benthic foraminiferal assemblages and sediment grain size along different sectors of this prodelta to define any relationship between the foraminiferal assemblages, the environmental gradients and the sedimentary processes. In particular, we focused on the role of the highly energetic impulsive torrential inputs that dominate the depositional environment and likely affect food supply and its control on the foraminiferal density and biodiversity. The dominance of opportunistic agglutinated taxa associated with hyaline eutrophic species is a distinctive character likely related to organic matter enrichment and physical disturbance associated with inputs from torrential rivers.

Abstract The Boreal Valanginian to Barremian foraminiferal succession of the Rurikfjellet Formation in central Spitsbergen is applied to stratigraphic zonation, analyses of depositional conditions and developing a sequence stratigraphic model. The study is based on the Janusfjellet section where the formation is 204 m thick, and represents a depth range from upper bathyal to prodelta top. It contains a continuous benthic foraminiferal succession permitting distinction of five assemblage zones. The assemblages are almost entirely agglutinated and reflect calcium carbonate depletion, which appears as an overall feature of Mesozoic Boreal seas superimposed on other, but more local restricting factors such as salinity and food supply. Close taxonomic similarities within the Boreal Realm are revealed by comparison of the Janusfjellet foraminiferal faunas to those of other pan-Arctic sites. The lower half of the Janusfjellet section contains a significant faunal component comparable to modern bathyal faunas and Late Cretaceous to Paleogene flysch-type assemblages indicating upper bathyal to offshore shelf depths. In the upper half of the section increased diversities are created by enhanced food supply in middle shelf setting. This is succeeded by increasing deltaic impact leading to hyposaline environments reflected by low species diversities. Changing foraminiferal biofacies trends through the Janusfjellet section are portrayed in the framework of the third order transgressive–regressive Wimanfjellet Sequence. Its transgressive systems tract was deposited mainly at upper bathyal depths with maximum flooding surface in the lower (Valanginian) part of the Rurikfjellet Formation. The regressive systems tract reveals an upward shoaling succession from upper bathyal conditions, through marine shelf to hyposaline prodelta setting. Highlights • Agglutinated foraminifera are used to zonation of Valanginian to Barremian deposits of Spitsbergen. • Carbonate depletion appears as a regional feature of the Boreal Ocean, superimposed on local restricting factors. • Outlining of depositional conditions from bathyal depth, through marine shelf to delta margin • Application foraminiferal facies tends to interpret changing environments in a transgressive-regressive sequence. [ABSTRACT FROM AUTHOR]

Ichnological, sedimentological and geochemical analyses were conducted on the Eocene Frysjaodden Formation in order to interpret palaeoenvironment prodelta sediments in the Central Basin of Spitsbergen. Phycosiphon incertum is the exclusive ichnotaxon showing differences in size, distribution, abundance and density, and relation to laminated/bioturbated intervals. Large P. incertum mainly occur dispersed, isolated and randomly distributed throughout the weakly laminated/non-laminated intervals. Small P. incertum occur occasionally in patches of several burrows within laminated intervals or as densely packed burrows in thin horizons in laminated intervals or constituting fully bioturbated intervals that are several centimetres thick. Ichnological changes are mainly controlled by oxygenation, although the availability of benthic food cannot be discarded. Changes in oxygenation and rate of sedimentation can be correlated with the registered variations in the Bouma sequence of the distal turbiditic beds within prodeltal shelf sediments.

On Gökçeada Island, the Mezardere Formation is dominated by the prodelta facies composed mostly of light grey, thinly bedded, fissile calcareous mudstones and siltstones, which mostly display parallel lamination or rarely ripple lamination. These sediments are intercalated with isolated thin beds of very fine- or fine-grained slightly muscovitic sandstones, which display parallel lamination in the lower part and ripple lamination in the upper part, or only ripple lamination. Thicker sandstone beds, referred to as mouth bars, are present in places. The prodelta sediments are poorly bioturbated (ii = 0–1), but moderately diverse trace fossils occur on some bedding surfaces, including 22 ichnotaxa referred to 13 ichnogenera and three trace fossils left in open nomenclature. The impoverished trace fossil assemblages are typical of deltaic sediments, but paucity of the trace fossils and poor bioturbation of the prodelta sediments in the Mezardere Formation is striking. The typically marine ichnoataxa are rare or absent in most outcrops. This trace fossil assemblage, resembling theMermiaichnofacies, suggests a strong brackishness of the palaeoenvironment; however, the occurrence ofBichordites kuzunensisin one outcrop suggests local and temporal normal marine conditions referred to as salinity fluctuations. [ABSTRACT FROM AUTHOR]

Thin-bedded delta-front and prodelta facies of the Upper Cretaceous Ferron Notom Delta Complex near Hanksville in southern Utah, USA, show significant along-strike facies variability. Primary initiation processes that form these thin beds include surge-type turbidity currents, hyperpycnal flows and storm surges. The relative proportion of sedimentary structures generated by each of these depositional processes/events has been calculated from a series of measured sedimentological sections within a single parasequence (PS6-1) which is exposed continuously along depositional strike. For each measured section, sedimentological data including grain size, lithology, bedding thickness, sedimentary structures and ichnological suites have been documented. Parasequence 6-1 shows a strong along-strike variation with a wave-dominated environment in the north, passing abruptly into a fluvial-dominated area, then to an environment with varying degrees of fluvial and wave influence southward, and back to a wave-dominated environment further to the south-east. The lateral facies variations integrated with palaeocurrent data indicate that parasequence 6-1 is deposited as a storm-dominated symmetrical delta with a large river-dominated bayhead system linked to an updip fluvial feeder valley. This article indicates that it is practical to quantify the relative importance of depositional processes and determine the along-strike variation within an ancient delta system using thin-bedded facies analysis. The wide range of vertical stratification and grading sequences present in these event beds also allows construction of conceptual models of deposition from turbidity currents (i.e. surge-type turbidity currents and hyperpycnal flows) and storm surges, and shows that there are significant interactions and linkages of these often paired processes. [ABSTRACT FROM AUTHOR]

Identifying facies and paleoenvironmental interpretation of the rock record is complicated due to the interplay of independent variables (i.e. wave-, river- and tidal-input) in marginal- and shallow-marine environments. This study integrates sedimentology and ichnology to characterize the depositional environments of the Lower Cretaceous Wabiskaw Member. The deltaic and strand plain shoreface-offshore deposits of Wabiskaw Member of Clearwater Formation of northeast Alberta provide an excellent case study to evaluate the ichnological and sedimentological characteristics associated with laterally and vertically variable stresses in wave-influenced nearshore settings. The Wabiskaw Member is studied using four sedimentary facies associations (Ten sedimentary facies). Facies association 1(FA-1) consists of massive, sharp-based mudstones and lenticular sandstone with small-scale soft-sediment deformation features, syneresis cracks and small-scale oscillation ripples. The ichnological suite mainly includes small grazing and deposit-feeding traces, representing the Phycosiphon Ichnofacies. Facies association 1(FA-1) is interpreted to record deposition in a prodeltaic setting. Facies association 2 (FA-2) is fine-to-medium-grained sandstone and thin mudstone with current, oscillation and combined flow ripples. The low angle and trough cross-beds, soft-sediment deformation structure, mud chips and coal debris are common. The trace fossil suite includes sporadically distributed deposit-feeding traces belonging to the Rosselia Ichnofacies. This facies association is interpreted to be deposited in the delta front to a mouth bar setting. Facies association 3 (FA-3) is gray to bluish-gray mudstone with minor sandstone interbeds (massive, planar parallel to hummocky cross-stratified). FA-3 is moderate to highly bioturbated. The ichnodiversity and abundance is high with dominant horizontal and subordinate vertical traces, including the dominance of deposit and detritus feeding traces representing the archetypal Cruziana Ichnofacies ichnological suite. Facies association 3 (FA-3) is interpreted as being deposited in a storm-influenced offshore environment. Facies association 4 (FA-4) is upper fine to fine-grained glauconitic sandstone with minor mudstone interbeds at the base. Physical sedimentary structures including massive and planar (horizontal and low angle), hummocky, and swaley crossing-stratification. FA-4 is heavily burrowed with a diverse suite of horizontal and vertical traces of deposit and detritus-feeding structures, representing a proximal expression of Cruziana Ichnofacies. Facies association 4 (FA-4) represents distal lower to middle shoreface deposition. The Wabiskaw Member deltaic (prodelta-delta front) deposits, producing characteristic sedimentological-ichnological signatures, distinguishing these deposits from related strand plains. In addition to characteristic deltaic traits (e.g. soft-sediment deformation structures, fluid mud and syneresis cracks), these deposits commonly contain comparably stressed low-diversity and diminutive trace-fossil suites. On the other hand, fully marine strand plain shoreface-offshore complexes are characterized by comparably robust trace fossils with high ichno-diversity and bioturbation intensities. [Display omitted] • Ichnologic-sedimentologic approach to refine palaeoenvironmental interpretations. • Ichnological response to stresses provides insight into depositional conditions. • Deltaic and shoreface deposits produce distinctive trace fossils characteristics. • Ichnological characteristics indicate a trend from deltaic to offshore-shoreface. • Integrated ichnology-sedimentology: a robust palaeoenvironmental tool. [ABSTRACT FROM AUTHOR]

Plastic pollution affects all oceans and sequestration of plastics in sediments is considered its ultimate sink. We report evidence of macroplastic burial retrieved within a sediment core collected at 38 m depth at the mouth of the Mazzarrà River, a torrential river able to carry a large amount of sediment during seasonal flash-floods. Two macroplastic items were found at 68 and 255 cm below the core top (corresponding to the seafloor). Their association with terrestrial vegetal debris and their inclusion in decimetre-thick sandy/silty intervals showing coarsening- and fining-upward trends, suggest that they were deposited by hyperpycnal flows possibly triggered by flood events. These findings testify the potential of sedimentary flows in burying macroplastic at depth below the seafloor, especially in nearshore prodelta environments. Furthermore they raise the quest on the magnitude of macroplastic storage in the subsurface and on the lack of specific devices and strategies for their reckoning. • Macroplastic items retrieved within a sediment core collected in a prodelta deposit. • Two items were found at 68 and 255 cm below the core top (i.e. the seafloor). • Plastics were enclosed in sandy sediments and associated with vegetal debris. • Plastics were transported and buried by river flood-generated hyperpycnal flows. [ABSTRACT FROM AUTHOR]

Determining sediment transport direction in ancient mudrocks is difficult. In order to determine both process and direction of mud transport, a portion of a well-mapped Cretaceous delta system was studied. Oriented samples from outcrop represent prodelta environments from ca 10 to 120 km offshore. Oriented thin sections of mudstone, cut in three planes, allowed bed microstructure and palaeoflow directions to be determined. Clay mineral platelets are packaged in equant, face-face aggregates 2 to 5 μm in diameter that have a random orientation; these aggregates may have formed through flocculation in fluid mud. Cohesive mud was eroded by storms to make intraclastic aggregates 5 to 20 μm in diameter. Mudstone beds are millimetre-scale, and four microfacies are recognized: Well-sorted siltstone forms millimetre-scale combined-flow ripples overlying scoured surfaces; deposition was from turbulent combined flow. Silt-streaked claystone comprises parallel, sub-millimetre laminae of siliceous silt and clay aggregates sorted by shear in the boundary layer beneath a wave-supported gravity flow of fluid mud. Silty claystone comprises fine siliceous silt grains floating in a matrix of clay and was deposited by vertical settling as fluid mud gelled under minimal current shear. Homogeneous clay-rich mudstone has little silt and may represent late-stage settling of fluid mud, or settling from wave-dissipated fluid mud. It is difficult or impossible to correlate millimetre-scale beds between thin sections from the same sample, spaced only ca 20 mm apart, due to lateral facies change and localized scour and fill. Combined-flow ripples in siltstone show strong preferred migration directly down the regional prodelta slope, estimated at ca 1 : 1000. Ripple migration was effected by drag exerted by an overlying layer of downslope-flowing, wave-supported fluid mud. In the upper part of the studied section, centimetre-scale interbeds of very fine to fine-grained sandstone show wave ripple crests trending shore normal, whereas combined-flow ripples migrated obliquely alongshore and offshore. Storm winds blowing from the north-east drove shore-oblique geostrophic sand transport whereas simultaneously, wave-supported flows of fluid mud travelled downslope under the influence of gravity. Effective wave base for sand, estimated at ca 40 m, intersected the prodelta surface ca 80 km offshore whereas wave base for mud was at ca 70 m and lay ca 120 km offshore. Small-scale bioturbation of mud beds co-occurs with interbedded sandstone but stratigraphically lower, sand-free mudstone has few or no signs of benthic fauna. It is likely that a combination of soupground substrate, frequent storm emplacement of fluid mud, low nutrient availability and possibly reduced bottom-water oxygen content collectively inhibited benthic fauna in the distal prodelta. [ABSTRACT FROM AUTHOR]

Surface sediments (fraction <63 μm) from the source to the mouth of the Rječina, short (18.3 km) karst allogenic river in Croatia, which is an important source of drinking water, were studied to investigate their mineral (by XRD) and chemical (by ICP-MS) composition to check possible anthropogenic influence at the lower course due to paper industry and mills, and in the prodelta area from untreated municipal sewage and the large harbor of Rijeka town. In all analyzed sediment samples and in the sandstone source, rock quartz is a major mineral, while feldspar and mica group minerals are less abundant. Chlorite is a minor or trace mineral in all samples. Calcite and dolomite are abundant in the river prodelta, reflecting changes in bedrock lithology from flysch to carbonates. In river sediments, Fe is the most abundantly analyzed element, while Ca is the most abundant in prodelta sediments. Concentrations of Al, Mn, Ni, Cr, Co, La and Nd decrease downstream, while Mg, S, Na, B, Pb, Zn, As, Sn, U, Mo, Hg and Ag have relatively higher concentration in prodelta sediments. The results are compared with sediments of other rivers in the area: Raša, Rižana and Dragonja, as well as with those of the Rosandra Creek (Italy). Sediments in the Raša River showed similar behavior as those in the Rječina, as the highest concentration of metals was found in the restricted upper part of the estuary, characterized by rapid deposition of clay particles and terrestrial sedimentary organic matter. The comparison also showed that the most contaminated were the sediments from the Rižana, followed by those from the Rječina and Rosandra Creek, which had similar results. Among the studied elements, As was present in all sediment samples at concentrations >6 ppm that might have the lowest toxic effects. At the lower Rječina and in prodelta sediments, Pb was also present at slightly elevated concentrations (>31 ppm) that could cause such effects. Concentrations of Zn in the prodelta correspond to those occurring in moderately polluted sediments (90-200 ppm). In the prodelta sediments, Hg is slightly below toxicity threshold (1 ppm), while Ag is present at toxicity threshold (0.5 ppm) or close to it. Rječina River could act as a good illustrative example for behavior of toxic metals in allogenic karstic rivers, in which accumulation of anthropogenically introduced pollutants usually occurs in their estuaries, as a result of transport and deposition of fine particles. [ABSTRACT FROM AUTHOR]

The Holocene morpho-stratigraphic evolution of a compound submarine deltaic system linked with the Antas and Almanzora Rivers on the narrow (< 5 km) shelf along the Palomares margin (southeastern Iberia) has been reconstructed from the integrated analysis of geomorphology, seismo-stratigraphy and sedimentology. The shelf morphology is characterized by a 3–4 km wide deltaic body off the Almanzora River, where seafloor undulations and gullies are present. Larger and more incised gullies, crescent-shaped bedforms and pockmarks are recognizable at or close to the head of shelf-indenting canyons associated with the Almanzora-Garrucha canyon system. The seismo-stratigraphy displays a strong and irregular basal reflector overlain by a sedimentary wedge, showing variable thicknesses (1–25 m) and seismic characteristics along and across the shelf. The main depocenter of this wedge is not located off the Almanzora River mouth (i.e., the main sedimentary input in the study area) but along the southern shelf encompassing the Almanzora and Antas Rivers. Grain-size and sand compositional analyses show that silty sand with high terrigenous content (mostly quartz and mica) is mainly found on the submarine deltaic body. In contrast, sandy silt with variable ratios between terrigenous and biogenic contents is retrieved from the canyon head and associated gullies as well as from the surrounding mid-outer shelf. The evolution of the Antas-Almanzora compound delta has been divided into three evolutionary stages, mainly driven by the interplay between paleo-topography and riverine and marine processes and modulated by sea level changes during the Holocene. The origin of the present-day morphological features is also discussed, again highlighting a complex interaction between sedimentary gravity flows (mainly flash flood-generated hyperpycnal flows), storm-waves and shelf currents, fluid seepage and retrogressive slope failures. [ABSTRACT FROM AUTHOR]

Abstract: The Barcelona continental shelf is part of a 6–20 km wide canyon-bounded shelf located off the city of Barcelona (NE Spain). This study integrates newly acquired high-resolution single channel seismic reflection profiles and available lithological information of the Barcelona shelf to describe its late Quaternary architecture and the role of global glacio-eustatic fluctuations and local factors in its development. Four major sequence boundaries are identified throughout the seismic dataset. They are tentatively correlated with the four last 4th order (100–120 ka) high-amplitude late Quaternary glacio-eustatic lowstands. Most of the stratigraphic record is formed by falling stage systems tracts with forced-regressive deposits, which confers a general progradational vertical stacking pattern. Transgressive systems tracts are represented by continuous units confined directly off river sources and on previously eroded surfaces. Stillstand deposits are difficult to recognize in the available dataset. The uppermost seismic unit corresponds to the Holocene shore-parallel Besos and Llobregat joint prodelta affected by the prevailing south-westward circulation. The general architecture of the late Quaternary Barcelona shelf deposits is determined by global glacio-eustatic cycles. However, the lateral variability of the seismic units depends largely on local factors such as (i) the position of sediment sources (essentially the Llobregat River); (ii) differential subsidence and, especially, sediment compaction; (iii) erosive processes such as canyon incision, mass wasting or wave base dynamics; and (iv) underlying geomorphic restrictions. [Copyright &y& Elsevier]

Abstract: Fluxes of the heavy metals chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), lead (Pb), cadmium (Cd) and zinc (Zn) delivered by rivers to the Gulf of Lion (NW Mediterranean Sea) were estimated over a three year study of the River Rhone and its smaller tributaries. Most of the particulate metal fluxes (80–90%) delivered by these rivers occurred within a very short period of time (less than 12%), a typical trend for the Mediterranean environment, where highly contrasting hydrological regimes were observed over the year. Temporal and spatial variations in the fluxes of these particulate metals were driven by the fluxes in both water discharge and suspended particulate matter load. On the shelf, these particulate metal fluxes, largely arising from the Rhone watershed, were two to ten times more important than those resulting from atmospheric deposition. Co, Cr and Ni in the rivers and on the shelf surface sediments were mainly natural and associated with the finest particles. Cd and Phosphorus appeared to be associated with the silt fraction and to be enriched in the prodelta areas. Pb, Zn and Cu were more closely associated with the organic matter content and also showed enrichment in the organic rich prodeltaic sediments. Anthropogenic influences diminished offshore, except for Pb and Zn which could be supplied from the atmosphere by man-made aerosols. Although most of the metals tended to be enriched in the prodelta areas, these did not constitute a permanent sink due to resuspension processes affecting these shallow depths. A resuspension experiment conducted on sediment cores from the Rhone prodelta demonstrated that metal deposited on the surface layer, especially those associated with the organic matter, may be resuspended; this should be taken into account for a complete understanding of the biogeochemical cycle of these metals. [Copyright &y& Elsevier]

Abstract: Statistical sequential analysis was performed on a series of sediment cores collected from the Têt prodelta in the Gulf of Lions, northwestern Mediterranean Sea, between October 2003 and October 2004. Seabed changes during that period were correlated to hydrodynamic conditions (waves and currents) and river discharge. Low sediment supply prevents full preservation of new sediment strata on this low-accumulation prodelta located on a microtidal, storm-dominated inner shelf. Severe meteorological events caused a rapid succession of erosion and deposition phases. For example, the December 2003 flood and storm produced a flood layer deposit that persisted for 2 months with only slight transformations due to early diagenesis and/or bioturbation, until a new storm event eroded this layer. A typical sedimentary sequence was observed for the secular deposits composed of a 10-cm-thick sandy layer overlaying siltyclayey layers. These characteristic features were used to analyse the last millennia sedimentary record of the Têt prodelta. The low preservation of freshly deposited sediments and variable sedimentation rates during the last millennia period yield a sedimentary sequence formed by the outcropping of muddy prodeltaic units intersected by heterogeneous siltysandy units similar to those formed under present day hydrodynamic conditions. No flood layer was found related to catastrophic flooding of the last century in the sedimentary record. The Little Ice Age (∼1550–1850 AD) probably favoured the formation of a well-developed muddy prodelta in the mouth of the Têt River. Later on, the decrease of sediment supply by rivers due to climate change and/or human activities (damming, irrigation), and the increase of the number of high-energy storms reaching the coast, induced a coarsening of the top sediment layer on this prodelta. This modern change of the substrate is also observed in the composition of benthic biota found in the substrate. [Copyright &y& Elsevier]

Abstract: The Barcelona continental shelf, off the city of Barcelona (NE Spain), is a relatively narrow canyon-bounded shelf in the northwestern Mediterranean Sea. Three medium-size rivers (Tordera, Besós and Llobregat) and several ephemeral rivulets flow into this margin. Two main domains have been recognized in the Barcelona shelf: (i) a modern, river-influenced area, and (ii) a relict, sediment depleted area, both affected by a variety of human impacts. A detailed geomorphologic study based on multibeam bathymetry and backscatter data, high resolution seismic profiles, and surface sediment samples allowed mapping and interpreting the main distinctive seafloor features on the Barcelona shelf. Modern sedimentary features reveal that the Llobregat River is the main sediment source of the Barcelona prodeltaic shelf. High-discharge fluvial events result in the formation of suspended sediment plumes and sediment waves on the shelf floor. Relict (late Pleistocene–Holocene) sedimentary features reflect that an important shift occurred in the seashore direction between MIS 4 and MIS 2, and that recent neotectonic reactivation has created a set of seafloor faults. The Barcelona inner and middle shelf is severely impacted by anthropogenic activities such as the enlargement works of the Port of Barcelona, sewage pipes, dredging, anchoring and trawling. [Copyright &y& Elsevier]

Abstract: The Ba Lat River is the major distributary of the Red River system in North Vietnam. To assess the recent to subrecent depositional processes in the Ba Lat prodelta, a detailed sediment analysis was conducted. Bottom samples were collected during two field surveys, one in the dry season (winter) and one in the wet season (summer). A steep frontal prodelta slope is characterized by very rapid sedimentation (tens of cm per year) of muddy sediments under influence of the turbid river plume. Beyond direct influence of the river plume the bottom slope decreases and bottom transport by the prevailing southward directed currents becomes important. Coarse-grained tempestites alternate with the dominating muddy sediments. Downcore changes in the 234Th activities indicate that the subaqueous delta progrades to the southwest, with erosion and reworking of older sediments occurring north of the present outlet. The southwestward progradation is also encountered in the trend of 210Pb activities indicating that this process has continued for at least 100 years. Avulsion of the Ba Lat outlet in 1973 has led to a decrease in sedimentation rates north of the Ba Lat outlet. [Copyright &y& Elsevier]

Abstract: The study, which is based on repetitive bathymetric surveys, assesses changes and effects of one of the most important floods recorded in the Rhône Delta area: bottom morphology and sediment distribution in the Rhône outlet after the December 2003 flood are discussed by comparison between Digital Terrain maps (DTMs) of November 2003 and January 2004. The post-flood morphology shows that the whole of the system is active, mainly in the east. The channel of the Rhône has been hollowed out on the left bank by more than 5 m, the eastern coast of the mouth has retreated 400 m, the mouth-bar has prograded 200 m and the slope of the delta front has increased by 0.19°. The overlay of pre- and post-flood DTMs makes it possible to estimate the total volume deposited in the [0 to −20 m] zone as +7.8×106 m3 (i.e. 0.88 m3 m−2), which corresponds to 4×106 t of sediment. These values are compared with the average annual volume of 0.47×106 m3 yr−1 of sediment deposited in this zone between 1995 and 2003, as well as the average sediment load estimated at the Arles station (50 km upstream) for this flood event (3.1×106 t to 5.3×106 t). The acquisition of bathymetric measurements immediately before and after a major flood allows more than a simple morphological description; in addition, an analysis of the solid load transfer processes towards the prodelta is achievable. Three mechanisms are highlighted. Most of the material eroded in the channel and supplied to the delta front corresponds to fine sediment that drape homogeneously over the pre-flood morphology of the delta front. The transit of the coarsest sediment (primarily sand) is slowed down in the channel of the Rhône: this sediment builds up in relatively small areas, leading to the formation of gullies on the prodelta slope. The gullies have fixed positions and disappear gradually towards the west, following the progressive migration of the active band towards the east. These old features are not reactivated by floods occurring after their formation. During the flood, only a small volume of coarse sediment bypasses through the gullies, and the fine deposits are remobilised rapidly or compacted. Flood input concerns essentially the delta front, which traps 90% of the fluvial solid discharge between 0 and 20 m depth. The coarse prodelta supply is then due mainly to mass movements of unconsolidated material deposited beforehand on the top of the delta front. Consequently, the main nourishment of the prodelta does not occur directly during and/or immediately after a flood event, but is delayed by sediment being temporarily trapped on the delta front. [Copyright &y& Elsevier]

Abstract: Large quantities of sediment introduced by rivers especially during flood events lead to the formation of prodeltaic structures characterized by fine-grained deposits in the proximal area of the shelf. According to their mean grain size, it is largely admitted in the literature that these deposits mainly stand below the storm wave base. In the Gulf of Lions (NW Mediterranean), however, our data show that these muddy sediments also exist above the storm wave limit, in the uppermost unit of the Holocene prism. The purpose of this work is therefore to draw a detailed sedimentological and geochemical portrait of these units, and to discuss the processes involved in the sedimentation and remobilization of these sediments. Our results show that the fine particles accumulate earlier in the inner-shelf in front of the nearby rivers, in association with the chemical elements which are commonly associated with this grain size fraction (e.g. organic carbon, radionuclides, and heavy metals). This accumulation probably mainly occurs during storm and flood events. The early deposits are then exposed to resuspension events and can actively participate to the distribution of fine-grained sediment in the entire margin by advective transfers via the benthic nepheloid layer. These fine-grained nearshore prodeltas are a common feature of the Mediterranean deltaic systems and mark the frontal processes that occur at the continent/sea interface of non-tidal seas. Our results especially point out the potential use of heavy metals as markers of the tracking of riverine sediments, which is naturally an important condition when evaluating the ultimate fate of land-derived pollutants in the marine realm. But also more fundamental studies on the understanding of sedimentological processes and reconstruction of margin stratigraphies should consider these deposits as functional units for the distribution of platform sediments. [Copyright &y& Elsevier]

A high-resolution pollen study (136 samples) has been performed on the KTR05 core (738 cm long) located in the modern Grand Rhone prodelta. The objectives were (1) to evaluate the palynological and sedimentological record quality of a prodelta in comparison with fluvial inputs 12) and to quantify lost sediment (resuspensions) in this area. The core covers more than the last thirty years. By comparison with the modern pollen rain both in the Rh&ocric;ne delta and in the mid-drainage basin (Lyon), a seasonal forcing in pollen deposition has been demonstrated. Monthly pollen successions can be evidenced in a well preserved sequence, providing an estimate of the true sedimentation rate (60 cm.yr-1. Importance of disturbed or incomplete sequences suggests that most of the sediment first deposited in the prodelta (around 2/3) bas been resuspended. Sedimentological and palynological data record not only seasonal but fluvial impact. The progressive shift of the prodelta has been evidenced firstly with sedimentology and secondly with palynology. Despite high fluvial impact, pollen grains in the KTR05 core are representatives of the vegetation of the Rhone drainage basin. The apparent homogeneity of the pollen spectra evidences the high reliability of palynology applied on prodeltaic area, at least in a microtidal environment. [ABSTRACT FROM AUTHOR]

Abstract: On the Adriatic shelf, a large field of seafloor and subsurface undulations (typically 300 m wide, 2.5 m high, and several km long, parallel to the bathymetric contour) affects the progradational clinoforms of the late Holocene prodelta wedge above a regional downlap surface that shows evidence of deformation and fluid escape. The undulations are associated with mud reliefs that occur farther seaward in elongated swarms perpendicular to the regional slope and to the crests of the undulations. A quantitative measurement of key morphobathymetric parameters (such as wavelength, height, asymmetry and wave-form indexes) was performed on 13 selected seismic-reflection profiles perpendicular to the undulations; these measurements are determined with respect to water depth or downslope distance from the shallowest undulation. The results highlight substantial differences from deep-water sediment waves; these differences include: (1) most undulations show a staircase morphology with sub-horizontal upslope limbs of 100–300 m delimited seaward by sharp edges and steep downslope limbs; (2) landward- or upslope-dipping limbs do not develop; (3) there is no consistent downslope decrease in wavelength or amplitude as opposed to most cases of sediment waves related to overflowing turbidity currents; (4) there is a consistent downslope loss in crest continuity approaching areas where mud reliefs and sediment deformation are evident at the seafloor; (5) many of the undulations show differences in angle of climb and in some cases a single undulation at the seafloor results from the burial and merger of more undulations in the underlying section. These differences compared to bottom current or turbidity current sediment waves are augmented by the observation that the Adriatic shallow-water undulations are also typically associated with gas-charged sediment, fluid escape, sediment deformation and localised failure planes. It is therefore suggested that seafloor undulations evolved in response to sediment deformation and were successively amplified by differential deposition from bottom currents crossing an irregular seafloor. In general, we feel that case-by-case solutions should be found to explain the origin and evolution of seafloor wavy features, based on the geologic/stratigraphic setting, the recognition of possible weak layers and the co-existence of a variety of other deformation geometries that may occur within or adjacent to the field of wavy features. The Adriatic example can reinforce recent suggestions that besides purely depositional bedforms there exist also wave-like deformation structures and multi-process sediment waves [Faugères et al., 2002. Multi-process generated sediment waves on the Landes Plateau (Bay of Biscay, North Atlantic), Marine Geology, 182, 279–302]. [Copyright &y& Elsevier]

To better explore the potential of Holocene subaqueous deltas as sedimentary archives, we quantitatively examined the benthic foraminiferal content of the muddy wedges belonging to three major Western Mediterranean deltas: Po Delta (N Adriatic Sea), Arno Delta (Ligurian Sea) and Rhône Delta (Gulf of Lions). The application of multivariate analyses (R-mode cluster, nMDS) on a regional dataset allowed defining six Mediterranean assemblages of taxa whose distribution, through time and space, is guided by the distance from the feeding mouths and by the balance of power between river and sea processes at the sea floor. At each site, the stratigraphic distribution of multivariate faunal data efficiently tracks the main changes in riverine fluxes and hydrodynamic levels, leading to a robust evaluation of (dis-)similarities in delta growth patterns. The dominant role of fluvial processes invariably emerges from the Po record, pointing to a river-dominated regime; whereas the foraminiferal fauna in the Arno and Rhône deltas indicates a wave-dominated regime with an intense redistribution of the river load by wind-driven currents throughout the Holocene. The distribution patterns of benthic foraminiferal assemblages in the multivariate space allow the identification of six biofacies, reflecting specific subaqueous environments that typify the Mediterranean shelves under different delta regimes: i) inner shelf; ii) deep-water mud belt; iii) shallow-water mud belt; iv) distal, river-dominated prodelta; v) distal, wave-dominated prodelta and vi) proximal prodelta. These biofacies can be a useful palaeoenvironmental tool for the interpretation of ancient, shallow-marine muddy successions belonging to the western Mediterranean stratigraphic record. The stratigraphic-based multivariate approach applied in this work can strongly support the analysis of subaqueous delta successions, developed even under different delta regimes and difficult to unravel from sedimentological features alone. • Six foraminiferal assemblages typify Holocene subaqueous deltas of W Mediterranean. • Distance from the feeding mouths and delta regime guide foraminiferal distribution. • Multivariate data stress similarities and dissimilarities in delta growth trends. • Foraminiferal biofacies are a powerful tool for interpreting shallow-marine muds. [ABSTRACT FROM AUTHOR]

Benthic ostracods and foraminifers are commonly applied as paleoenvironmental indicators in shallow marine successions, ignoring that individual meiofaunal groups could provide distinct information. We aim to shed light on the distinct paleoecological record of benthic ostracods and foraminifers by analyzing the shallow marine Holocene succession of the Po Delta (Italy) in a sequence stratigraphic fashion. Multivariate elaborations connecting the modern North Adriatic reference set to fossil data allowed to investigate community dynamics, obtain quantitative estimates of (paleo-)environmental drivers and assess the meiofaunal response to coastal and delta dynamics through time and space under the influence of allogenic and autogenic factors. Benthic ostracods and foraminifers easily discern transgressive (TST) and highstand (HST) systems tract, and also discriminate between locations at different distance from paleo-river mouths under highstand conditions. Specifically, community changes reflecting shifts in delta regimes at distal locations suggest that lobe-fringe deposits are more indicated for paleoenvironmental purposes. We emphasize that a deep knowledge of the analyzed datasets should drive the interpretation of multivariate outputs, as reconstructed values from significantly similar deposits could be inappropriate, and the lack of true modern analogs could reflect authentic differences in community composition, or either pitfalls in the modern reference set. Our results show that ostracods evidence depositional regimes determined by the interplay of sediment supply and hydrodynamic energy in relationship with the position from main river outlets; on the other hand, foraminifers highlight changes in riverine inputs in terms of organic matter. Our findings demonstrate that shallow marine benthic ostracods and foraminifers provide distinct but complementary paleoecological information, and their integration allows to achieve high-resolution reconstructions. • Integration of paleoecology and sequence stratigraphy • Depositional regimes indicated by benthic ostracods • Organic matter from riverine inputs by benthic foraminifers • Delta dynamics reflected in the shallow-marine benthic meiofauna • Critical evaluation of multivariate outputs [ABSTRACT FROM AUTHOR]

Analyses of benthic foraminiferal assemblages were carried out on sediment samples collected in the Gulf of Patti (NE Sicily, Tyrrhenian Sea), where high sedimentation rates in front of the Mazzarrà River led to the growth of a prodelta. The frequency of riverine sedimentary fluxes is testified by the widespread occurrence of erosional and depositional bedforms indicative of high-energy processes on the prodelta slope.The frequency of riverine sedimentary fluxes suggests the widespread occurrence of erosional and depositional bedforms indicative of high-energy processes on the prodelta slope. The study aimed to assess the spatial distribution of benthic foraminiferal assemblages and sediment grain size along different sectors of this prodelta to define any relationship between the foraminiferal assemblages, the environmental gradients and the sedimentary processes. In particular, we focused on the role of the highly energetic impulsive torrential inputs that dominate the depositional environment and likely affect food supply and its control on the foraminiferal density and biodiversity. The dominance of opportunistic agglutinated taxa associated with hyaline eutrophic species is a distinctive character likely related to organic matter enrichment and physical disturbance associated with inputs from torrential rivers. [ABSTRACT FROM AUTHOR]

Hyperpycnal flows have been widely described in different lacustrine and marine environments but sedimentary structures and fossil content in hyperpycnites often offer limited information about the palaeoenvironmental conditions. This limitation can be improved by ichnological analysis, which has been recently used as a tool to differentiate between different type of subaqueous deposits, even though still only a few detailed ichnological studies on hyperpycnites exist. In order to bridge this gap in knowledge, a 50 m-thick package of terrestrial organic debris-rich, dominantly structureless and well-sorted sandstone bodies alternating with burrowed siltstones (Upper Miocene, Betic Cordillera, Spain) is here analyzed. This study is based on observations of a well-exposed outcrop and cores from a well drilled just behind the outcrop to bridge field-scale observational gaps. Two type of sandbodies were typified on the basis of their stratigraphic architecture, physical sedimentary structures, and ichnofacies in the fine-grained deposits embedding them: (1) Lobate to channelized-top sandstones embebbed into silty sands with dominant highly variable degree of bioturbation by Taenidium and Schaubcylindrichnus (depauperate Cruziana ichnofacies) and interpreted as proximal marine sustained hyperpycnites in prodelta settings; and (2) channelized-lobate (cut-and-fill sequence) sandstones embebbed into siltstones with dominant Nereites and Phycosiphon (Nereites ichnofacies) interpreted as distal hyperpycnites developed in offshore settings. The studied succession is interpreted to represent the progradation of a sandy hyperpycnal system along a prodelta to starved offshore setting with high variability in grain-size, benthic food and oxygen content. Results of this study suggest that a multi-scale analysis focused on trace fossils and physical sedimentary signatures is needed to get a better understanding of these river-derived sustained-flow turbidites (hyperpycnites) that are less well known than their conventional surge-type turbidite counterparts. • Trace fossils allow to refine the depositional setting of marine hyperpycnites. • Prodeltaic lobe-to-channel-type hyperpycnites are linked to depauperate Cruziana ichnofacies. • Offshore channelized-lobe-type hyperpycnites are linked to Nereites ichnofacies. [ABSTRACT FROM AUTHOR]

During IODP Expedition 369, a 690 m thick succession of silty claystone spanning the early Turonian to the late Santonian was encountered at Site U1512 in the Bight Basin, offshore southern Australia. Stacking patterns, sedimentary facies and palynological assemblages reveal that the succession was rapidly deposited with hyperpycnal and hypopycnal flows in a marine prodelta setting, which was subject to basin restriction. The dominance of clay-rich facies and phytoclasts in the succession was likely the result of a major river system delivering a high sediment load into the Bight Basin when a warm, wet climate prevailed. A combination of high sedimentation rates (19–272 m/Myr) and accelerated subsidence prevented the delta from rapidly prograding into more distal regions of the basin. The complete Turonian to Santonian mudstone succession yields low total organic carbon (~1 wt%) and Type IV kerogens. However, palynofacies assemblages become progressively marine in character and total organic carbon values vary between 1 and 1.5 wt% with depth. This may indicate that the base of the hole at Site U1512 was close to potential organic-rich black shales associated with Ocean Anoxic Event 2. Low amplitude and irregular reflections on seismic data and disparities between biostratigraphic zonations suggest the upper 350 m of the Turonian to Santonian succession may represent a mass movement that happened during the Pleistocene. This study reveals that Site U1512 material likely represents a near-stratigraphically complete marine mudstone succession from high paleolatitudes, as well as the only depositional record that was fully cored from the Bight Basin. • 690 m thick Upper Cretaceous mudstone succession sampled in the Bight Basin. • A near-stratigraphically complete mudstone succession from southern high latitudes. • Deposited by hyperpycnal and hypopycnal flows in a marine prodelta setting. • Upper 350 m may represents a mass movement that occurred during the Pleistocene. • Implications for predicting source and reservoir rocks in the basin. [ABSTRACT FROM AUTHOR]

We investigated the distribution of ostracoda and benthic foraminifera from the shallow (<40 m water depth) river-influenced North Adriatic shelf. Combining faunal and environmental data from a sub-set of literature databases (Breman, 1975; Jorissen, 1988), we recognised the main environmental drivers for ostracoda (grain-size and bathymetry) and benthic foraminifera (organic matter concentration). Integrating these benthic groups, we identified five depositional settings dependent on the relative position from the main source of riverine material: the Po River. Near the Po Delta, where high fluxes of sediment occur, taxa tolerant to organic-rich muddy substrates and oxygen deficiency are abundant (Palmoconcha turbida , Leptocythere ramosa , Ammonia tepida , Ammonia parkinsoniana , Nonionella turgida). Downdrift of the delta, ostracoda discriminate between shallow sandy substrates (Semicytherura incongruens , Xestoleberis spp.) subject to longshore currents and deeper clayey environments (S. incongruens , Palmoconcha turbida), whereas benthic foraminifera are monotonous being represented by taxa tolerant to moderate organic matter concentrations (A. parkinsoniana , A. tepida , Aubignyna perlucida). The mud-loving Cytheridea neapolitana and Bulimina denudata , tolerating high organic matter fluxes, characterise the 20–40 m deep mud-belt subject to the major accumulation of riverine material. Updrift, sandy substrates with low organic matter are typified by S. incongruens , Pontocythere turbida and Milioloidea. Out of the fluvial influence (water depth > 20 m), diversified meiofaunal assemblages occur with ostracoda discriminating sediment-starved areas enriched in sand. Our results demonstrate that the combined use of ostracoda and benthic foraminifera represents a powerful tool for the depositional characterisation of river-influenced shelves and to achieve detailed palaeogeographical reconstructions from shallow marine successions. • Integration of ostracoda and benthic foraminifera from the North Adriatic shelf • Ostracoda and benthic foraminifera respond to distinct environmental drivers • Combine meiofauna to detect and refine river-influenced depositional environments [ABSTRACT FROM AUTHOR]