Modern Po Research Articles

Phylogenetic and biogeographic history of brook lampreys (Lampetra: Petromyzontidae) in the river basins of the Adriatic Sea based on DNA barcode data.

The Adriatic brook lamprey, Lampetra zanandreai Vladykov 1955, was described from northeastern Italy. Its distribution is thought to include left tributaries of the River Po and the river basins of the Adriatic Sea from the River Po to the River Isonzo/Soča in Italy, Switzerland and Slovenia. It also shows a geographically isolated distribution in the Potenza River on the Adriatic slope in Central Italy. Lampetra from the Neretva River system in Croatia and Bosnia and Herzegovina and the Morača River system in Montenegro that were previously identified as L. zanandreai were recently described as a new species Lampetra soljani Tutman, Freyhof, Dulčić, Glamuzina & Geiger 2017 based on morphological data and a genetic distance between the two species of roughly 2.5% in the DNA barcoding gene cytochrome oxidase I (COI). Since DNA barcodes for L. zanandreai are only available for one population from the upper Po River in northwestern Italy, we generated additional COI nucleotide sequence data of this species from Switzerland, northeastern and central Italy comprising near topotypic material and obtained GenBank sequences of the species from Slovenia to better assess the evolutionary history of the two brook lamprey species in the river basins of the Adriatic Sea. Our data show a low sequence divergence of <1% between L. zanandreai from Switzerland, northeastern and central Italy and Slovenia and the Balkan species L. soljani. However, members of the population previously identified as 'L. zanandreai' from northwest Italy are genetically highly divergent from those of L. zanandreai and likely belong to an undescribed species, L. sp. 'upper Po'. The presence of a unique and highly divergent brook lamprey lineage in the upper Po River suggests that L. zanandreai and Lampetra sp. 'upper Po' may have evolved in separate paleo drainages during the formation of the modern Po Valley subsequent to marine inundations in the Pliocene.

Evolution of the Po–Alpine River System during the Last 45 Ky Inferred from Stratigraphic and Compositional Evidence (Ostiglia, Northern Italy)

The stratigraphic and compositional study of three sediment cores recovered close to the Po River near Ostiglia provides clues on changes in fluvial dynamics at the transition from the last glacial to the present interglacial. Upper Pleistocene units are dominated by sands with high content in volcanic lithics, denoting high sediment supply from the south-Alpine fluvio-glacial tributary system. The Early–Mid Holocene unit, peat-rich and barren in fluvial sands, results from low sediment supply and waterlogging, encompassing the maximum marine ingression. The Late Holocene unit, characterized by fluvial-channel sands with lower content in volcanics and relatively abundant metamorphic lithics, records the Po River sedimentation since the Late Bronze Age. Late Holocene sands show a lower content in siliciclastic lithic fragments (supplied mainly by Apennine tributaries) compared to modern Po River sands. This distinctive composition could reflect the diversion of Apennine sediments into a southern Po River branch during the Late Bronze Age and into an Apennine collector flowing south of Ostiglia during Roman times and the Middle Ages. The integrated stratigraphic-compositional methods used in this study permitted to reconstruct the major climate-related changes in sediment dispersal and may be potentially applied to other alluvial and coastal settings.

8 - Actors and Institutions in Urban Politics in Nigeria: Agege (Lagos) Since the 1950s

Unlike Lagos Island and Mushin, for example, Agege, a multi-ethnic and densely populated ward of metropolitan Lagos (originally an autonomous settlement, has suffered relative neglect in the extensive literature on Lagos. This article analyses the dynamics of power relations among the various interest groups, personalities and institutions in this ‘ward’ of Lagos since the 1950s. Combining chronological and thematic approaches, it outlines the evolution of the commu- nity and its local government system since the nineteenth century, examines the interactions of traditional and modern institutions (chieftaincy and modern po- litical offices at the local government level), the dynamics of inter-tier (state– local government) relations, the composition and activities of interest groups (specifically, religious, occupational, ethnic, youth and residential associations), and the management of common facilities (markets) and problems (communal conflict and insecurity). The study co pares Agege with a similar ward, Ajegunle, which this author has also studied.

From rapid coastal collapse to slow sedimentary recovery: The morphological ups and downs of the modern Po Delta

As is the case with many deltas in the world, the Po Delta (Italy) and its barrier systems have experienced severe modifications over the last century as a consequence of anthropogenic subsidence and river input decrease. The interruption of subsurface fluid withdrawals in the early 1960s created an opportunity to evaluate the effects of the subsequent subsidence decrease along the 11 km of beaches and 45 km of barrier islands of the Po Delta, and improve the understanding of coastal system response to relative sea level rise. To this aim, shoreline and bathymetric multi-decadal dataset were coupled with the local rate of subsidence and classified with a geomorphic - response approach. From 1954-78, a mean shoreline variation of −224 m (−9.34 m y−1) occurred under high rates of subsidence (14–43 mm y−1) with a diffuse process of landward barrier rollover (up to 1124 m), frequently associated with break-up. This phase is evidenced by the diffuse sinking of the shoreface (up to 4 m), the negative upper shoreface sediment budget and the parallel drowning of the cross-shore profiles highlighted by the 1968–2008 bathymetric dataset. Despite the loss of altimetry and shoreline retreat being almost irrecoverable, during the period from 1978 to 1996 and 1996 to 2014 barrier islands experienced a stabilisation in response to a decrease in the subsidence rates down to 6 mm y−1. The mean rates of shoreline changes (−0.25 and + 1.51 m y−1 respectively) are the results of different local behaviour with progressively dominant longshore processes and progradation at the most active fluvial branches. The most recent bathymetric data (2008–2014) confirm this reversal trend, both in the altimetry differences and in the upper shoreface sediment budget. This trend is at odds with signals from many of the world's deltas and represents an important issue for the present and future coastal management and adaptation plans.

Sediment dispersal pathways in the Po coastal plain since the Last Glacial Maximum: Provenance signals of autogenic and eustatic forcing

AbstractWe examined downstream trends in sediment composition within the modern Po River system and defined provenance changes within a selected sector of the Upper Pleistocene to Holocene coastal plain in response to paleogeographic reorganisation during the last glacial‐interglacial cycle. Sediment composition of the Upper Pleistocene to Holocene alluvial and coastal plain succession overlaps with the modern petrofacies, suggesting that ancient fluvial sand was sourced from a dynamic river system attributable to a distal paleo‐Po with episodic sediment input from South Alpine and Apennine rivers. In the wave‐dominated estuarine depositional system developed under transgressive conditions, Po‐derived detritus mixed in the coastal system with sediment fed by Central/Eastern Alpine rivers, which was redistributed southwards by alongshore currents. A similar, mixed composition of late Holocene highstand depositional systems reflects the progradation of Po delta lobes (similar in composition to Po River sands) and adjacent strandplains (typified by sediment mixing due to alongshore transport). Compositional variability across the main stratigraphic surfaces suggests that autogenic processes (e.g. marine reworking, sedimentary mixing, delta switching/abandonment) in turn influenced by glacioeustasy, controlled the development of the transgressive and highstand Po Plain succession. This study clarifies the effect of fluvial‐marine interaction during the Holocene evolution of the Po coastal system and can be used as a model to interpret the evolution of many mixed‐delta types and Quaternary successions that shows alternating river‐flood and wave‐dominated deposits.

Ephemeral rollover points and clinothem evolution in the modern Po Delta based on repeated bathymetric surveys

AbstractReconstructions of ancient delta systems rely typically on a two‐dimensional (2D) view of prograding clinothems but may miss their three‐dimensional (3D) stratigraphic complexity which can, instead, be best documented on modern delta systems by integrating high‐resolution geophysical data, historical cartography, core data and geomorphological reconstructions offshore. We quantitatively compare three precisely positioned, high‐resolution multi‐beam bathymetry maps in the delta front and pro delta sectors (0.3 to 10 m water depth) of Po di Pila, the most active of the modern Po Delta five branches. By investigating the detailed morphology of the prograding modern Po Delta, we shed new light on the mechanisms that control the topset to foreset transition in clinothems and show the temporal and spatial complexity of a delta and its pro delta slope, under the impact of oceanographic processes. This study documents the ephemeral nature of the rollover point at the transition between sandy topset (fluvial, delta plain to mouth‐bar) and muddy seaward‐dipping foreset deposits advancing, in this case, in &gt;20 m of water depth. Three multibeam surveys, acquired between 2013 and 2016, document the complexity in space and time of the topset and foreset regions and their related morphology, a diagnostic feature that could not be appreciated using solely 2D, even very high‐resolution, seismic profiles. In addition, the comparison of bathymetric surveys gathered with one‐year lapses shows the migration of subaqueous sand dunes on the clinothem topset, the formation of ephemeral cut‐and‐fill features at the rollover point (few m below mean sea level), the presence of collapse depressions derived by sagging of sediments and fluid expulsion (possibly induced by storm waves) on the foreset, and splays of sand likely reflecting gravity flows on the lower foreset. Though the modern Po Delta is anthropogenic in many respects, its subaqueous clinothem can be studied as a scale model for ancient clinothems that are less resolved geometrically and far less constrained chronologically.

Trace-element and Nd-isotope systematics in detrital apatite of the Po river catchment: Implications for provenance discrimination and the lag-time approach to detrital thermochronology

Detrital thermochronology is often employed to assess the evolutionary stage of an entire orogenic belt using the lag-time approach, i.e., the difference between the cooling and depositional ages of detrital mineral grains preserved in a stratigraphic succession. The impact of different eroding sources to the final sediment sink is controlled by several factors, including the short-term erosion rate and the mineral fertility of eroded bedrock. Here, we use apatite fertility data and cosmogenic-derived erosion rates in the Po river catchment (Alps–Apennines) to calculate the expected percentage of apatite grains supplied to the modern Po delta from the major Alpine and Apenninic eroding sources. We test these predictions by using a cutting-edge dataset of trace-element and Nd-isotope signatures on 871 apatite grains from 14 modern sand samples, and we use apatite fission-track data to validate our geochemical approach to provenance discrimination. We found that apatite grains shed from different sources are geochemically distinct. Apatites from the Lepontine dome in the Central Alps show relative HREE enrichment, lower concentrations in Ce and U, and higher 147Sm/144Nd ratios compared to apatites derived from the External Massifs. Derived provenance budgets point to a dominant apatite contribution to the Po delta from the high-fertility Lepontine dome, consistent with the range independently predicted from cosmonuclide and mineral-fertility data. Our results demonstrate that the single-mineral record in the final sediment sink can be largely determined by high-fertility source rocks exposed in rapidly eroding areas within the drainage. This implies that the detrital thermochronology record may reflect processes affecting relatively small parts of the orogenic system under consideration. A reliable approach to lag-time analysis would thus benefit from an independent provenance discrimination of dated mineral grains, which may allow to proficiently reconsider many previous interpretations of detrital thermochronology datasets in terms of orogenic-wide steady state.

Benthic foraminifera as a key to delta evolution: Acase study from the late Holocene succession of the Po River Delta

Benthic foraminifera from stratigraphically expanded, late Quaternary prodelta successions of the Po Delta plain reveal small-scale paleoenvironmental variations within lithologically homogeneous deposits formed under conditions of rapid sedimentation (ca. 6 cm/yr). A detailed paleoenvironmental reconstruction was obtained comparing benthic foraminifera with shallow-water assemblages from the modern Po Delta. The integration with sediment geochemistry and radiocarbon dates was also tested to detect short time-scale delta dynamics controlled by autogenic factors. Core 7 records the development of an inner-shelf environment (interval A), replaced by a prodelta with strong fluvial influence, shown by the sharp increase in Ammonia tepida and Ammonia parkinsoniana (interval B). These taxa are replaced by Aubignyna perlucida (interval C) which indicates a major mouth shift (Ficarolo avulsion). Subsequent abrupt increases in A. tepida and A. parkinsoniana document a step-like progradation of the Po di Goro delta lobe (intervals D and E). In the seaward Core 1, possible minor mouth shifts are recorded by a sharp increase in A. tepida and A. parkinsoniana, paralleled by Cr/Al2O3 depletion. The upper portion of both prodelta successions includes stacked flood layers formed near the river mouth, as indicated by scarce A. tepida and A. parkinsoniana.

Contrasting alluvial architecture of Late Pleistocene and Holocene deposits along a 120-km transect from the central Po Plain (northern Italy)

High-resolution investigation of a ~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 (<9.4cal ka BP). The Holocene succession displays consistent downstream changes in facies architecture: well-drained floodplain deposits are transitional at distal locations to increasingly organic, poorly drained floodplain to swamp facies associations. Thick paludal facies extend continuously up to 60km landward of the Holocene maximum marine ingression, about 90km from the modern shoreline. Based on 28 radiocarbon dates, the abrupt change in lithofacies and channel stacking pattern occurred at the transition from the last glacial period to the present interglacial, under conditions of rapid sea-level rise. The architectural change from amalgamated, Late Pleistocene sand bodies to overlying, mud-dominated Holocene units represent an example of chronologically well-constrained fluvial response to combined climate and relative sea-level change. The overall aggradational stacking pattern of individual channel-belt sand bodies indicates that high subsidence rates continuously created accommodation in the Po Basin, even during phases of falling sea level and lowstand.

Tracing the drainage change in the Po basin from provenance of Quaternary sediments (Collina di Torino, Italy)

Quantitative provenance analysis of the Quaternary sediments from the Collina di Torino and the Po alluvial plain was assessed by using statistical techniques. This method, based on high-resolution heavy mineral analysis on modern and ancient sands processed by compositional biplot and linear mixing model, allowed reconstruction of the drainage change of the western Po River and its tributaries in the last 1 Ma. Mineralogical and statistical analyses discriminate three groups in the Quaternary samples. Sediments from the Po alluvial plain are rich in garnet, epidote and minor amphiboles. Detritus from the western slope of the Collina di Torino is characterized by epidote-rich assemblages, actinolite, blue-green hornblende and chloritoid. Heavy minerals from sediments of the northwestern slope include epidote-group minerals, glaucophane and hypersthene. A linear mixing model was used to compare detrital modes from modern and Quaternary detritus, and to identify the best modern analogue for any sample of ancient sedimentary deposit. Statistical analysis indicates that the first mineralogical group compares best with detritus of the modern Po River. Detritus from the second and third group compare best with sediments of the modern Dora Riparia River and Stura di Lanzo River, respectively. These results outline how the distribution of the Middle-Late Pleistocene fluvial deposits of the Collina di Torino is linked with the ancient Alpine watercourses, before the shifting of the Po River on the northern edge of the hill. During the Middle Pleistocene, rivers draining the Piedmont Zone of the Western Alps (PaleoDora Riparia and PaleoStura di Lanzo rivers) ran across the hill, while the PaleoPo River, which drained the Dora Maira Massif (Internal Massif), flowed to the south of the Collina di Torino. At the end of the Pleistocene, the PaleoPo River was diverted to the north to its present-day position in the alluvial plain. This case history shows how quantitative provenance analysis based on orogenic sediments is the key to reconstruct Quaternary drainage evolution of the foreland basin.

THE APPLICATION OF A SUBTIDAL FORAMINIFERA-BASED TRANSFER FUNCTION TO RECONSTRUCT HOLOCENE PALEOBATHYMETRY OF THE PO DELTA, NORTHERN ADRIATIC SEA

This study evaluates the potential of a foraminifera-based transfer function to reconstruct the Holocene paleobathymetric evolution of the Po Delta area (northern Adriatic Sea). The Northern Adriatic Transfer Function (NATF) is based upon the largest modern Adriatic database existing in the literature (Jorissen, 1988). The performance of the NATF suggests a strong relationship between observed and foraminifera-predicted water depths (r2jack = 0.95) with relatively precise reconstructions (RMSEP = ~5 m) within the depth range of 8 to 100 m. We applied the NATF to a fossil marine succession in 40-meter-long core from the southern part of the modern Po Delta. The transfer function produced a shallowing-upward trend of paleowater depths from about 30 to 10 m within the interval of 5500-400 cal yr BP. The deepest reconstructed water depths (>18 m) are from the inner shelf deposits at the base of the marine succession (~29–27 m core depths). The transition to a prodelta setting at 4700 cal yr BP is associated with oscillations in water-depth reconstructions and should be treated with caution because of the unstable and complex paleoenvironmental conditions. Thereafter, from core depths of ~27 to 15m, shallower paleowater depths(<18 m) characterize the prodeltaic succession that was deposited as the Po Delta system developed. The shallowest paleowater depths (11–8 m) characterize the uppermost deposits, in line with the shallowing-upward, progradational trend. These results suggest that subtidal foraminifera-based transfer functions can be useful tools in reconstructing the paleobathymetric history of subsurface deposits in modern deltaic systems.

Late Quaternary palaeoenvironmental evolution of the Adriatic coastal plain and the onset of Po River Delta

Despite abundant geologic literature about the Po coastal plain, stratigraphic architecture beneath modern Po River Delta is virtually unknown. In this paper, combined sedimentological, micropalaeontological and geochemical investigations of three continuous cores (cores 1 to 3), about 40 m thick, enable for the first time the detailed reconstruction of subsurface stratigraphy in the Po River Delta area, along with its late Quaternary palaeoenvironmental evolution. Lowstand deposits, formed during the Last Glacial Maximum, are expressed as a fining-upward succession of fluvial-channel and related overbank deposits, capped by a stiff, overconsolidated horizon. Above this unconformable surface, the lower post-glacial succession (transgressive systems tract or TST) is less than 7 m thick and includes a deepening-upward succession of back-barrier, shoreface and inner-shelf deposits. On the other hand, the overlying highstand systems tract is considerably thicker (up to 27 m) and comprises the bulk of recent delta progradation ( i.e., vertically stacked prodelta, delta front and delta-plain deposits). Stratigraphic correlations within early transgressive, back-barrier deposits show vertically stacked, thin shallowing-upward successions, reflecting an internal subdivision of TST into small-scale parasequences. The homogeneous shallow-marine clay that accumulated at the turnaround from transgressive to highstand conditions can be palaeontologically differentiated into two packages ( Miliolidae-dominated and Ammonia/Cribroelphidium-dominated), reflecting open-marine and river-influenced conditions, respectively. Timing of maximum marine ingression (maximum flooding surface-MFS) is recorded within the open-marine clays at about 5500 calibrated yr BP by minor changes in microfauna. Geochemical characterization of Core 1 testifies that distinct changes in sediment provenance accompanied the palaeoenvironmental evolution of the study area under changing relative sea-level conditions. At lowstand times, the study area was an alluvial plain under the influence of Adige River, as suggested by comparatively high Ba/Al values within pre-Holocene fluvial deposits. Increasing upward values of Cr/Al 2O 3 and Ni/Mg within TST suggest an increasing sediment provenance from the Po River during early stages of transgression, via the longshore drift. The onset of modern-age Po Delta in the study area is precisely identified in Core 1 at 25.10 m depth, and has a distinctive, double signature. In terms of microfaunal assemblages, Po River sediments are clearly marked by the development of a characteristic foraminiferal association dominated by the opportunistic species Nonionella turgida, a taxon typically abundant in the marginal zone of present northern Adriatic Sea mud-belt. Po River deposits are also fingerprinted by a peculiar geochemical composition, corresponding to maximum Cr and Ni concentrations.

Benthic foraminiferal evidence of sediment supply changes and fluvial drainage reorganization in Holocene deposits of the Po Delta, Italy

Detailed benthic foraminiferal analyses performed on the Holocene subsurface deposits of modern Po Delta evidenced a complex palaeogeographic evolution. Hierarchical R- and Q-mode cluster analyses allowed to distinguish four assemblages indicative of different marine environments and sub-environments. Temporal and spatial distribution patterns of benthic foraminifers reflect changes in Po River discharge during delta evolution. The capability of foraminiferal assemblages to track nutrients and sediment supply oscillations permitted to recognize four main evolutionary phases (A–D), which took place after the maximum marine transgression (ca. 5500 cal yr BP). Prodelta and delta front deposits are accumulated in the western part of the study area between the first stages of progradation and the late Middle Ages (ca. 10th century AD); these are paralleled, in a more distal position, by open-marine sedimentation, replaced upward by prodelta sediments (phases A and B). Owing to the combined effect of a major avulsion (Rotta di Ficarolo) and the Adriatic circulation patterns, an organic-rich zone developed in the eastern part of the present Po Delta at the transition to the Modern Age (phase C), around 600 cal yr BP. For the fist time a fossil mud-belt, although its marginal fringe, along with its peculiar microfossil content ( Nonionella turgida assemblage), is recorded beneath a modern delta plain. During the recent past an outstanding rate of sedimentation affected the Po Delta, as clearly evidenced by the deposition of 14 meters fine-grained prodelta sediments between 600 and 380 cal yr BP. Prodelta deposits were finally replaced by delta front sands after the Porto Viro cut (ca. 350 cal yr BP), which marked the onset of Modern Delta (phase D).

Climatic signature of cyclic fluvial architecture from the Quaternary of the central Po Plain, Italy

Detailed investigation of middle-upper Quaternary deposits from central Po Plain was carried out on the basis of integrated sedimentological and pollen analyses of a 114 m-long core, and stratigraphic correlations of well data. Stratigraphic architecture of alluvial strata beneath modern Po River reveals distinctive cyclic changes in lithofacies and channel stacking patterns. Each cycle includes basal, silt–clay overbank deposits with thin and lenticular fluvial-channel sands, with upward transition to increasingly amalgamated and more laterally extensive fluvial-channel sand bodies. Lower cycle boundaries, corresponding to the top of laterally extensive fluvial complexes, are locally associated with organic-rich, paludal clays. Pollen records show distinctive cyclic changes that parallel facies architecture. Overbank deposits in the lower parts of cycles are invariably associated with forest expansions. These indicate that major phases of channel abandonment and widespread floodplain aggradation took place at the onset of warm-temperate (interglacial) climatic conditions. The middle portions of cycles record transition to pollen associations diagnostic of glacial periods. Lack of pollen data from sandy facies prevents climatic characterization of laterally extensive fluvial bodies in the upper parts of cycles. On the basis of the overall stratigraphic framework, internal facies architecture and distinctive pollen attributes, the cycles identified in the subsurface of the study area are interpreted to fall in the Milankovitch (100 ka) band, and inferred to be correlative with the transgressive–regressive sequences recently recognized in the coeval successions of the Po coastal plain.

Palaeomagnetic and rock magnetic analysis of Holocene deposits from the Adriatic Sea: detecting and dating short-term fluctuations in sediment supply

We present palaeomagnetic and rock magnetic results from five cores collected in the basin of the Adriatic Sea. Four cores (PRAD2-4; KS02-246; CSS00-23 and CSS00-07) were collected along a shore-parallel transect whereas the fifth core (AMC99-01) was retrieved in the central Adriatic in 250 m water depth, on the floor of the Meso-Adriatic Depression. After alternating field demagnetization, the natural remanent magnetization (NRM) directions show a characteristic and primary magnetization of the sediments that is representative of secular variation of the geomagnetic field. By combining 14C dating and the ages of magnetic inclination features, it has been possible to establish an age—depth model for all of the cores. Precise identification of the secular variation features provides a refined chronology that allows us to quantify short-term changes in sediment flux from the Adriatic catchment as well as changes in sediment routing within the basin. Rock magnetic parameters indicate a homogeneous magnetic mineralogy dominated by fine-grained magnetite. Variations in both concentration and grain-size related magnetic parameters reflect changes in sediment supply between glacial and interglacial stages, as well as changes in environmental conditions. Selective dissolution of magnetic grains is associated with the formation of sapropel S1 during the first part of the Holocene, although the duration of the anoxic interval varies between cores. A significant modification in sediment supply characterizes the late-Holocene deposits with a marked increase in sedimentation rate occurring during the last few centuries. We interpret this as a far-reaching response to the rapid construction of the modern Po delta under increasing anthropogenic impact.

Inverse modeling of post Last Glacial Maximum transgressive sedimentation using 2D-SedFlux: Application to the northern Adriatic Sea

A coupled simulation of the hydrologic model HydroTrend and the stratigraphic model 2D-SedFlux is applied to transgressive deposits in the north Adriatic Sea area over the last 21,000 years. Synthetic sediment discharge from the Po River, which increases more than 70% during late Pleistocene compared to those during Holocene due to glacier melt and enlarged drainage area, is employed in the simulation of sediment deposition by the process based, forward model, 2D-SedFlux. Paleo-morphology is reconstructed in a pseudo-inverse manner by comparing the predicted deposit distribution and the modern morphology. Accommodation for thick, prograding deposits in the modern Po delta and the Po lowstand delta are created by drawing back the modern bathymetric profile. The bathymetric profile is then adjusted for aggradational deposits. These sequential simulations produced a likely profile of the paleo-morphology, which had accommodation matching with the sediment supply. Evaluation of effects of waves, however, suggested that the predicted rate of sediment input was too low to produce a prograding delta. A good match with the observation of the modern Po delta was achieved when further adjustments in basin width was properly made.

Cover Picture: Macromol. Symp. 239/2006

Cover: Advancement in modern po lymer technologies such as photo‐electronics, pharmaceutical and biomedical fields, biodegradable systems and specific composites are increasingly interrelated. Urgent demands are apparent for new, eco‐efficient, advanced polymer systems, the development of which requires interdisciplinary knowledge. The common thinking of scientists specialized in certain segments of polymer science and technology was strongly initiated by the 8th International Symposium on Polymers for Advanced Technologies (PAT 2005) held in Budapest, September 2005.Convergent concepts can be seen in the developments of materials to be used as pharmaceuticals, biomaterials, polymer composites, fire retarded polymers, membranes, conductive systems and fuel cells. The presented unusual ways for various technologies of advanced polymer systems may initiate further research activities in the near future.Responding to the demand for better understanding of the advanced materials the conference covered the mechanistic and technological aspects of syntheses, composite and nanocomposite formation, and behaviour of polymeric materials in biomedical environment. As an example, the picture shows an SEM micrograph of carbon nanofibers in sPP (filler content: 0,6 %), taken from the contribution by W. Kaminsky.

The modern Po Delta system: Lobe switching and asymmetric prodelta growth

The modern Po Delta system, comprising five main delta lobes, has been investigated by integrating VHR seismic surveys, recorded offshore from water depths as shallow as 5 m to the toe of the prodelta in about 30 m, with accurate historical cartography extending back several centuries. Previous studies give sedimentological and geochronological information from precisely positioned sediment cores. This combined historical and stratigraphic reconstruction of the modern Po prodelta allows volumetric reconstructions indicating an average sediment load of 9.4 10 6 t yr − 1 for Po di Pila and Po di Goro-Gnocca lobes. This estimate is remarkably consistent with the total sediment load of 11.5 10 6 t yr − 1 available for parts of the last century from a gauge station at the apex of the delta plain (in Pontelagoscuro). These integrated stratigraphic studies allow to explain the key characters of the Po delta system: a) the marked asymmetry of the whole delta-prodelta system reflecting prevailing sediment dispersal to the south of each individual delta outlet; b) the shore-parallel overlapping of successive prodelta lobes fed by distinct river outlets of ever changing relative importance; c) the delta outlets being artificially forced in a fixed position so that natural avulsion is prevented and delta lobes undergo headland retreat leaving a marked erosion on the prodelta; d) the presence of prodelta lobes showing widespread “cut-and-fill” features (ranging from 100 to 300 m and depths up to 4–5 m filled with massive silt to very fine sand) offshore of short-lived very active distributary channels (e.g.: Po di Tolle lobe) and suggesting that, in some particular interval, short-lived episodes of submarine erosion are induced by catastrophic increases in river discharge (of natural origin or induced by human maintenance). The seismic stratigraphy of the modern Po Delta documents that markedly distinct prodelta architectures form when a newly activated lobe is located updrift (north, in this case) or downdrift (south) of the one that is retreating: in the first case the abandoned lobe becomes sheltered by the new, rapidly advancing, one; in the opposite case the retreating lobe is updrift and a substantial portion of the sediment is cannibalized and transported to the new lobe, downdrift.

Extremely Shallow-water Morphobathymetric Surveys: The Valle Fattibello (Comacchio, Italy) Test Case

A morphobathymetric survey has been carried out of a coastal lagoon south of the modern Po delta (Valle Fattibello, Comacchio). Acquisition of bathymetric data in such an extremely shallow water environment (more than 80% of the area lies between 0 and ) 1m ) faces technical difficulties that led to the development of ‘ad hoc’ solutions. Methods to obtain morphobathymetric and reflectivity maps of the lagoon are presented, including descriptions of data acquisition and processing. ‘Ground-truthing’ of the reflectivity data, provided by analysis of sediment samples, allowed description of the sediment distribution within the lagoon, and the imaging of sedimentary features. Combined analysis of morphobathymetry and reflectivity maps identified arcuate, sand-rich features not in equilibrium with the present-day ‘low energy’ regime of the lagoon. These features might constitute the substratum over which the lagoon system has been formed, not completely overprinted by anthropogenic and biogeochemical processes at the lagoon bottom.The system we have developed could be used on board remote-controlled or autonomous vehicles that could perform rapid, low-cost surveys and collect data useful for quantitative estimates of sedimentary dynamics. Rapidity and low-cost are important conditions for carrying out periodical surveys, and taking a series of ‘snapshots’ of the lagoon bottom. This would allow predictive geological models on sediment budgets of these complex environments, characterized by multiple sediment sources and sinks that are difficult to quantify.

Styles of Failure in Late Holocene Highstand Prodelta Wedges on the Adriatic Shelf

On the continental shelves of the northern Mediterranean basin, the late Holocene highstand systems tract (HST) prograded un- der the influence of major rivers, after the attainment of the present sea-level highstand (about 5.5 cal kyr BP). On the Adriatic shelf, the thickness distribution of the late Holocene HST reflects the location of major deltas on the western side of the basin and the geostrophic cir- culation, which prevents a more uniform sediment dispersal toward the center of the basin. Very high sediment accumulation rates (1 to 10 cm/year) resulted in the construction of a HST depocenter up to 35 m thick. This shore-parallel depocenter is affected by failure of limited displacement over as much as 40% of its extent. Gas impregnation is common in the topset region and occurs at very shallow levels (a few meters) below the sea floor. Five areas are characterized by a variety of sea-floor and subsurface crenulations. Although locally some of these crenulations have an intriguingly regular geometry, sediment failure is the most plausible mechanism for their formation. Sediment failure better explains the large variety of geometries that characterizes the coastal mud prism of the late Holocene HST. Furthermore, we observe that these crenulations occur only where the downlap surface at the base of the HST is disrupted and affected by geometries that are con- sistent with fluid escape processes. This relationship suggests that the basal surface acts as a weak layer for sediment failure. Failure occurred in variable water depths from the northern slope of the modern Po prodelta (10-20 m water depth) to the narrow shelf offshore Bari (40-110 m water depth). In all these areas the proximal part of the HST prodelta wedge is intensely gas-charged. The thickness and age of the sediment sections affected by failure are slightly differ- ent from place to place but appear everywhere younger than 5.5 cal kyr BP. Where failure affects the entire HST the detachment occurs on the downlap surface at its base. Failure geometries characterize the head region whereas compressional features, such as pressure ridges and mud diapirs, dominate in the toe region, ranging in depth between 70 and 110 m. Where failure is limited to the upper few meters of the HST, there is a clear lithologic change (decrease in carbonate fraction and grain size) across the basal surface. This lithological change reflects a switch in sediment supply from local Apennine rivers (below) to Po- derived mud; this change occurred at the onset of the Little Ice Age, documenting the indirect control of short-term climate change and hu- man impact on sediment architecture. The deformations affecting the late Holocene HST in the various areas show differences in internal geometry, but appear everywhere to be characterized by limited downward displacement and can be attri- buted to shear-dominated retrogressive failure. It is suggested that some degree of consolidation occurred immediately after mobilization, possibly induced by the escape of fluids. Nowhere has failure evolved into disintegration and flow, likely because the type of cyclic loading that triggered it was not prolonged over a long enough interval. Short-lived radionuclides in the uppermost stratigraphic layers, which postdate the failure in the area offshore Ortona, allowed us to quantify systematic changes in sediment accumulation rates as a func- tion of the underlying deformed sea floor. In areas of wavy sea floor, troughs show sediment accumulation rates of greater than 16 mm/yr, a figure that is fourfold the rate measured on the flanks of the troughs.