Sea Delta Research Articles

Moving beyond the Framing Impasse in the Aral Sea Delta: Vernacular Knowledge of Salinization and Its Potential for Social Learning towards Sustainability

Moving beyond the Framing Impasse in the Aral Sea Delta: Vernacular Knowledge of Salinization and Its Potential for Social Learning towards Sustainability

Trace metal partitioning in the parnaíba delta in dry season, equatorial coast of Brazil

Trace metal concentrations in the particulate fractions (MP), dissolved fractions (MD) and sediments (MS), such as Ba, Cu, Co, Cr, Pb, Ni and Zn, were determined during the dry season of the largest open sea delta of Americas, the Parnaíba River Delta (Brazil). This study aimed to comprehend the distribution, dynamic changes of metal speciation and environmental quality index of trace metals in the particulate fractions and subsurface sediments in scenario of major marine influence over the delta. The trace metals bound to suspended particulate material (SPM) from weathering the drainage basin exhibited a removal trend under increases in salinity and pH. Desorption influenced the partitioning of BaMP, ZnMP, NiMP, CoMP, CuMP, and the adsorption and precipitation of PbMP and CrMP to the surface sediments. The organic matter contents in the sediments acts as an important geochemical carrier of these contaminants, and the dissolved organic carbon influences the binding of PbMD in the subsurface waters. The geoaccumulation index (Igeo) plays a crucial role in revealing potential contamination with ZnMP contents and weak association to this fraction. These results make possible the assessment of ecological risk by metal contamination and global pollution mitigation in coastal tidal estuaries under intensive physical mixing along the equatorial coast.

Hydro‐geomorphological and sedimentological processes along the major fluvial‐lacustrine delta of the Paraná River (Argentina): Their role in floodplain construction

AbstractRiver‐dominated sea deltas have been thoroughly studied by different authors. In these environments the interrelationships of the hydro‐sedimentological variables between river, tides, and waves, among others, are the main factors controlling the delta formation. However, few studies have focused on the deltaic processes in river–lagoon environments and even fewer in large river floodplains (defined here as a fluvial‐lacustrine delta, FLD) and their role in floodplain construction.This study provides a comprehensive and novel analysis approach combining satellite imagery treatment and aerial photographs with detailed field measurements of sediment samplers, cores, and acoustic techniques applied to quantify flow and discharge distribution along main, secondary, floodplain channels, and lagoon systems under different hydro‐sedimentological conditions. All data allow a full description of deltaic processes and the main variables that control the evolution of the major FLD located along the Middle Paraná River floodplain (Argentina). These results show: (i) pre‐existing local geology elements affect the deltaic processes; (ii) the hydro‐sedimentological behaviour of the main channel and its connection with the floodplain channels and independent basin systems affects the delta evolution; (iii) the dynamics (temporally and spatially) of sediment transport input and the interaction with lagoons produce different delta front bars planform and composition; (iv) periods of mean and high water levels play a key role in delta evolution; and (v) the rapid vegetation growth above the formed bars favours the sedimentation of fine material, producing permanent changes and leading to floodplain construction. Particularly, our findings suggest a complex interrelationship between the different factors in this particular environment, such as hydrology, local geology, main/secondary and floodplain channels, sediment supply, sediment transport modes, vegetation, and free surface slopes. All these factors act together in a complex manner, providing unique features to the FLD system that could help us better understand the floodplains construction in large river systems worldwide.

Contributions from the main river of the largest open sea delta in the Americas to the CO2 fluxes

In this study, we sampled for the first time the main channel of the Parnaíba Delta, the largest open sea delta in the Americas, and two of its secondary channels, during the rainy season. Continuous measurements of pCO 2, temperature, salinity, and wind velocity were taken, while subsurface water samples were collected to analyze for dissolved oxygen, pH, total alkalinity, dissolved organic carbon, and its isotopic, chlorophyll-a, and nutrients. The spatial variability of pCO 2 along the different channels showed the existence of distinct drivers of CO2 dynamics in the area. The correlation of pCO 2 in freshwater samples with dissolved oxygen and chlorophyll-a indicated the incidence of organic matter decomposition and primary production in the main channel and mangroves, while the highest salinity samples evidenced the control of carbonate equilibrium in the river mouth. Our data also indicated an important influence of the river discharge on the carbon dynamics of the estuary, with around 73% of the CO2 emissions in the estuary estimated to be from riverine CO2. The strong river effect in the estuary was also supported by the low salinities (0.04–26.37), pH (7.09 ± 0.36), and total alkalinity (328 ± 530.46 μmol kg −1), typical from fluvial waters. The estuary was supersaturated in CO2 and behaved as a strong source, with an average flux of 194.1 ± 135.1 mmol m−2 d−1.

Retracted] Infrared Spectroscopic Measurement of Dissolved Organic Matter and Nanomaterials in Water Based on Parallel Factor Algorithm

Infrared spectroscopy can separate carbon sugars and amino sugars that have collapsed in soil water very quickly. In this study, the midinfrared (MIR) and near‐infrared (NIR) spectra collected from soil water isolates or soil masses are sentenceless, assessing different agricultural groupings of flooded carbon and aminosaccharides. Soil was collected from five fields in two regions in western Canada and two regions in eastern Canada, where least squares backslide (PLSr) was inadequate. The inverted model of DOC recovery at the Eastern Peace River estuary can provide the optical functionality of traditional systems. The introduction of overflow DOCs from various sources rather than distance meters has been found to be a major contributor to the complexity of optical neighborhoods, resulting in a bias in DOC evaluation. The impact of voluntary DOC liability on the relationship between DOC and CDOM can be forgotten at a critical turn in the CDW. A slightly mitigating approach can overlook the impact of voluntary DOC responsibility on the relationship between DOC and CDOM. CDW is responsible for the continued responsibility of the Subei coastal currents for the normal material of the former Yellow Sea Delta, for the warm West Coast currents of the Yellow Sea for the materials of the Yellow Sea, and for the materials of the Changjiang Basin. The results of this study more thoroughly assess the state differences of DOM inputs from different sources within the CDW to determine the magnitude of the impact on DOC evaluation across the East China Sea CDOM. It suggests that it is necessary.

Effects of Clay Mineral Composition on the Dynamic Properties and Fabric of Artificial Marine Clay

Marine clays are easily affected by different mineral composition in cyclic load-based geological hazards. Therefore, based on analyzing the mineral composition of natural marine clay, it is the key to predict the dynamic properties of natural materials under cyclic loading by using quantitated artificial marine clay. In this study, the marine clay found in the South China Sea deltas was investigated. Based on the results of geological conditions and mineral composition analyses, raw non-clay minerals (such as quartz, albite) and clay minerals (such as Na-montmorillonite and kaolinite) were used to produce artificial marine clay, the dynamic properties of which were studied from the impact of mineral composition. Dynamic triaxial laboratory testing for artificial marine clay comprising various clay minerals was performed under identical test conditions. The artificial marine clay with high montmorillonite content exhibited slower development of strain, more sluggish growth in pore water pressure, more rounded hysteresis curves, greater stiffness, and more prolonged viscous energy growth than the clay with low montmorillonite content. In addition, the flocculated fabric of the artificial marine clay with high montmorillonite content demonstrated sufficient pore space changes, more uniform pore distribution, and larger specific surface area than the dispersed fabric of the clay with low montmorillonite content. The factors arising from the influence of montmorillonite may lead to microstructural and fabric changes, hinder the development of pore water, and increase intergranular contact stiffness as well as delay the cyclic strain amplitude at the breakpoint of viscous energy dissipation. In general, the results presented in this study confirm that clay minerals, especially montmorillonite, have significant influence on the dynamic properties of large strain.

Basin-scale land use impacts on world deltas: Human vs natural forcings

Abstract A new global database of 86 deltas and river basins was analyzed to investigate the relative importance of deforestation and land use changes versus natural forcings in determining long-term total delta size. Results show that mean river flow and shelf slope were the most important variables, whereas population density and sediment load had a much lower importance. Deforestation and other variables related to land-use generally had a very small effect, but were more influential in a subset comprising Mediterranean and Black Sea deltas. As most deltas have developed over thousands of years, the much shorter-lived anthropogenic signals from deforestation and other landscape perturbations have had only secondary impact on the total area of deltas. Also, delta progradation is strongly influenced on sand deposition, whereas anthropogenic impacts on sediment load have more often impacted mostly the finer sediment being deposited offshore (prodelta deposits) or in the deltaic plain. These data disproves the hypothesis that delta size and growth is strongly influenced by human forcings, particularly for larger deltas, since Holocene delta building is mainly determined by natural forces. However, humans are influencing the geomorphology of deltas, particularly over the last century when the Anthropocene nature of deltas has become manifest. A more precise terminology is proposed to clarify concepts such as “human-made”, “human-engineered” or “human-influenced” deltas.

Generation, migration, entrapment and leakage of microbial gas in the Dutch part of the Southern North Sea Delta

Understanding the shallow gas system is critical for assessing its potential as an energy source, for evaluating the possible hazard of shallow gas for drilling and wind farm locations and for evaluating the effect of gas emissions at the seabed on marine ecosystems and climate. This paper presents the key elements and processes of the microbial shallow gas system in the Plio-Pleistocene Dutch Southern North Sea Delta based on recent findings from different projects. Geochemical and carbon isotopic composition of shallow gas occurrences in the delta are indicative of a microbial origin of the gas. Shallow gas mainly occurs in stratigraphic traps and stacked anticlinal structures above salt structures, as indicated by identified direct hydrocarbon indicators on seismic, such as bright spots. Organic matter in the delta deposits is of predominantly land plant origin with TOC values varying between <1% and 5%, and mostly between 1 and 2%. Simulations of temperature and burial history in combination with dedicated 1D simulations of microbial gas generation reveal that gas generation in the delta started in Early Pleistocene Calabrian times and is still ongoing. Simulated volumes of gas generation are more than enough to fill published estimated volumes of shallow gas prospects in the delta. The geometry of the E-W prograding delta sequences and the close interbedding of interglacial silty/sandy and glacial clayey/silty sediments focus gas migration updip through the foresets towards the topsets of the delta sequences, and ultimately into the anticlinal stacked traps. Grain-size based calculations of the permeability and capillary seal capacity of clayey/silty seals of the stratigraphic and anticlinal traps provided first estimates of permeability values ranging from 2.8E-20 m2 to 1.1E-18 m2 and capillary seal capacity values between 10m and 24m. Comparison of gas column heights derived from grain-size based calculations, cross plots of neutron and density logs and pressure measurements, with trap heights derived from seismic bright spots suggests that many traps in stacked bright spots are not filled to structural spill point. This suggests that filling of the stacked reservoirs is not related to fill-spill migration, but rather to leakage through the top seal. In absence of fault and fracture zones crossing the seal, this leakage is related to the capillary seal capacity and permeability of the top seal. The leakage extends, locally, to the seabed. The microbial gas system in the delta today is a highly dynamic system driven by ongoing burial of the delta sediments and microbial gas generation. © 2018

The First Hop: Use of Beaufort Sea Deltas by Hatch-Year Semipalmated Sandpipers

River deltas along Alaska’s Beaufort Sea coast are used by hatch-year semipalmated sandpipers (Calidris pusilla) after leaving their terrestrial natal sites, but the drivers of their use of these stopover sites on the first “hop” of fall migration are unknown. We quantified sandpiper temporal distribution and abundance as related to food resources at three river deltas during the beginning of their fall migration (post-breeding period) to compare the habitat quality among these deltas. We conducted population counts, sampled invertebrates, and captured birds to collect blood samples from individuals for triglyceride and stable isotope analyses to determine fattening rates and diet. Patterns of sandpiper and invertebrate abundance were complex and varied among deltas and within seasons. River deltas were used by sandpipers from late July to late August, and peak sandpiper counts ranged from 1000 to 4000 individuals, of which 98% were hatch-year semipalmated sandpipers. Isotopic signatures from blood plasma samples indicated that birds switched from a diet of upland tundra to delta invertebrate taxa as the migration season progressed, suggesting a dependence on delta invertebrates. Despite differences in diet among deltas, we found no differences in fattening rates of juvenile sandpipers as indicated by triglyceride levels. The number of sandpipers was positively associated with abundance of Amphipoda and Oligochaeta at the Jago and Okpilak-Hulahula deltas; an isotopic mixing model indicated that sandpipers consumed Amphipoda and Oligochaeta at Jago, mostly Chironomidae at Okpilak-Hulahula and Spionidae at Canning. Regardless of the difference in sandpiper diets at the Beaufort Sea deltas, their similar fattening rates throughout the season indicate that all of these stopover sites provide a critical food resource for hatch-year sandpipers beginning their first migration.

Natural Disturbance Shapes Benthic Intertidal Macroinvertebrate Communities of High Latitude River Deltas

Unlike lower latitude coastlines, the estuarine nearshore zones of the Alaskan Beaufort Sea are icebound and frozen up to 9 months annually. This annual freezing event represents a dramatic physical disturbance to fauna living within intertidal sediments. The main objectives of this study were to describe the benthic communities of Beaufort Sea deltas, including temporal changes and trophic structure. Understanding benthic invertebrate communities provided a baseline for concurrent research on shorebird foraging ecology at these sites. We found that despite continuous year-to-year episodes of annual freezing, these estuarine deltas are populated by a range of invertebrates that represent both marine and freshwater assemblages. Freshwater organisms like Diptera and Oligochaeta not only survive this extreme event, but a marine invasion of infaunal organisms such as Amphipoda and Polychaeta rapidly recolonizes the delta mudflats following ice ablation. These delta sediments of sand, silt, and clay are fine in structure compared to sediments of other Beaufort Sea coastal intertidal habitats. The relatively depauperate invertebrate community that ultimately develops is composed of marine and freshwater benthic invertebrates. The composition of the infauna also reflects two strategies that make life on Beaufort Sea deltas possible: a migration of marine organisms from deeper lagoons to the intertidal and freshwater biota that survive the 9-month ice-covered period in frozen sediments. Stable isotopic analyses reveal that both infaunal assemblages assimilate marine and terrestrial sources of organic carbon. These results provide some of the first quantitative information on the infaunal food resources of shallow arctic estuarine systems and the long-term persistence of these invertebrate assemblages. Our data help explain the presence of large numbers of shorebirds in these habitats during the brief summer open-water period and their trophic importance to migrating waterfowl and nearshore populations of estuarine fishes that are the basis of subsistence lifestyles by native inhabitants of the Beaufort Sea coast.

Natural and anthropogenic emissions of N and P to the Parnaíba River Delta in NE Brazil

The Parnaiba River Delta is the largest open sea delta in the Americas, having a unique ecological importance for the conservation of wildlife and fisheries resources. However, little is known about the biogeochemistry of this ecosystem. This study estimates N and P emissions to the delta using emissions factors, calibrated with field samples and N and P concentrations in different compartments of the delta. The estimated loads totaled 14.517 t N year−1 and 8.748 t P year−1, indicating that anthropogenic N and P emissions outweigh natural emissions by approximately 5 and 10 times, respectively. The activities that contribute the most to this result are livestock farming, agriculture and the release of untreated domestic sewage. The flows of N and P from the estimated loads corresponded to 339 kg N km−2 year−1 and 204 kg P km−2 year−1, so the region can be classified as “meso-active” and “eury-active” with regard to the transfer of nutrients. These results are consistent with the coastal megabasin design (COSCATs) proposed by Meyback et al. (2006). This article presents a first approach to the calculation of an estimated annual emissions inventory of N and P for the lower basin of the Parnaíba River and its coastal region, representing an approach that has been satisfactorily used in assessing the sensitivity of estuarine systems in northeastern Brazil.

Salt on the move: Multi stage evolution of salt diapirs in the Netherlands North Sea

After more than half a century of research, the dynamics of salt tectonics in the North Sea remains a contentious issue with unresolved questions regarding triggering and driving mechanisms. The North Sea is now covered by high-quality 3D seismic datasets which allow new insights into the interplay between salt tectonics and sedimentation. These insights are of both regional geological, societal and exploration interest as well as more widely applicable as analogues for salt tectonics in frontier regions such as the South Atlantic salt basins. A high quality 3D seismic volume from the Netherlands North Sea is used to show the thick and mobile Zechstein halite sequence of Late Permian age remobilized in several phases into complex salt structures. Early stage structural evolution was dominated by Triassic NNE–SSW and NW–SE trending salt ridges. Salt tectonic reorganization was triggered by regional shortening in the Campanian. Salt was transferred both laterally and vertically, creating salt anticlines and tall asymmetrical salt diapirs. Vertical growth of the tallest salt diapirs continued in pulses in the Plio-Pleistocene likely driven by increased sediment input from southern North Sea delta systems. The most recent deformation affects Late Pleistocene and Holocene sediment and could have impacted on the landscapes of Meso-Lithic human occupied sites. The recent activity of some salt domes should be considered when planning repositories for gas and nuclear waste.

Patterns of Cenozoic sediment flux from western Scandinavia

AbstractThe significance of variations in the sediment flux from western Scandinavia during the Cenozoic has been a matter of debate for decades. Here we compile the sediment flux using seismic data, boreholes and results from other publications and discuss the relative importance of causal agents such as tectonism, climate and climate change. Western Scandinavia, the northern British Isles and the Faeroe‐Shetland Platform were significant sediment sources during the Paleocene, which is well founded in tectonic causes related to the opening of the North Atlantic. From the Eocene and onward, variations in the sediment flux from western Scandinavia correlate better with climate and climate change. During the Eocene, sediment production was low. From the late Eocene onward, increased seasonality may have contributed to stimulating the sediment flux. Significant climatic cooling episodes correlate with Oligocene deposits in the North Sea, the post‐mid‐Miocene Molo and Kai Formations of the Norwegian Shelf, the southern North Sea delta system and large volumes of the Late Pliocene‐Holocene Naust Formation. The sediment flux from Scandinavia during the Cenozoic is in general agreement with the detrital flux to the world's oceans. Furthermore, the large variations in the size of sediment catchment areas as well as the possibility of submarine and glacial erosion must be incorporated to understand regional variations in climate driven sediment flux.

Early and Middle Pleistocene landscapes of eastern England

This paper reviews the pattern of climate and environmental change in eastern England over the period of the Early and Middle Pleistocene, focussing especially upon northern East Anglia. Particular attention is given to the climate and tectonics that have brought about these changes and the distinctive geology, topography and biology that has developed. Throughout, an attempt is made to describe the new models that have been proposed for the Early and Middle Pleistocene of eastern England, and explain the reasons for these changes. The Early Pleistocene experienced relatively high insulation and relatively low magnitude climatic change and is represented primarily by non-climatically forced processes in the form of tidal current- and wave-activity which formed shallow marine deposits. It is possible to recognise a tectonic control in the distribution of deposits of this age because the surface processes do not have the power to remove this signature. The early Middle Pleistocene was dominated by higher magnitude climatic change involving, occasionally, climatic extremes that ranged from permafrost to mediterranean. The landscape at this time was dominated by the behaviour of major rivers (Thames, Bytham, Ancaster) and extensive coastal activity. In the latter part of the early Middle Pleistocene and the Late Middle Pleistocene the climate experienced major changes which resulted in periods of lowland glaciation and short intervals when the climate was warmer than the present. Details of tectonic activity are difficult to identify because they are removed by powerful surface processes, but it is possible to infer uplift focussed on the major interfluves of central England and subsidence in the North Seas basin. In the areas of glaciation the landscape changed radically from an organised terrain dominated by large rivers and extensive shallow coastal zones to complex, with small valleys, disrupted drainage and often discontinuous river, slope and coastal deposits. Likewise the switching off of the North Sea Delta and the opening of the Strait of Dover, separating Britain from continental Europe can be attributed to the onset of lowland glaciation. The case is made that eastern England was glaciated four times during the Middle Pleistocene: during MIS 16, 12, 10 and 6, and attention is given to recent evidence contradicting this model. Over the period of the Middle Pleistocene there is evidence for high biomass production occurring over short intervals coinciding with the climatic optima of MIS 19, 17, 15, 13, 11, and 7c, 7a and during most of these warmer periods, extending back to c. 750ka (MIS 19/17), there is evidence in the region for the brief appearance of humans.

Pre-Anglian fluvial and coastal deposits in Eastern England: lithostratigraphy and palaeoenvironments

Clast lithology and derived microflora are used to provide a basis for correlating pre-Anglian fluvial and coastal deposits in eastern England and to provide a lithostratigraphic framework for these Early and early Middle Pleistocene sediments. Three fluvial systems are recognised. (i) The Thames, which drained an area from Wales through midland England to the Thames basin and southern East Anglia. The catchment was truncated over the period concerned and the western headwaters diverted to other river systems. (ii) The Bytham river which drained midland England and the southern Pennines and reached the southern North Sea delta in the region of north central East Anglia. This river extended its catchment over the period concerned. (iii) The Ancaster river which drained the southern Pennines and received sediment from northeast England. Each of these catchments contributed sediment to the southern North Sea delta/estuary and contributed to the lithologies of the Red, Norwich, and Wroxham Crag formations. The lithostratigraphic subdivisions are based on the fact that: (i) the Pliocene and Early Pleistocene rivers and the equivalent Red and Norwich Crags are characterised by far-travelled microflora which was transported in suspension and a locally derived clast assemblage transported as bedload , and (ii) the later Early and early Middle Pleistocene rivers and the equivalent Wroxham Crag are characterised by a far-travelled microflora and a far-travelled clast assemblage. Variations in the amount and composition of far-travelled materials is determined by the relative importance of the three river systems. This provides a basis for identifying different formations of the Thames river sediments (older Sudbury Formation and younger Colchester Formation) and different members of the Wroxham Formation (Dobb's Plantation Member: local material with minor components of Thames and Ancaster river sediments; How Hill Member: local material with major components of Thames and Ancaster river sediments; Mundesley Member with major components of Bytham river sediments). These lithostratigraphic units are related to established North European biostratigraphy and Oxygen Isotope stratigraphy. The factors forcing the changes in river energetics are explained in terms of the relative importance of geomorphic processes operating within the river catchments determined by the patterns of Milankovitch orbital forcing .

Spatial and Temporal Controls on the Development of Southern North Sea Delta Systems during the Late Tertiary and Quaternary

Spatial and Temporal Controls on the Development of Southern North Sea Delta Systems during the Late Tertiary and Quaternary