Formation Of Delta Research Articles

Early History of the Formation of the Ancient Delta of the Syr Darya and its settlement (according to archaeological data till the 1st millennium AD)

The article discusses the history of settled agricultural cultures in the Eastern Aral Sea Region, which should be studied considering the hydrographic factor due to their close connection to the functioning of the Amu Darya and Syr Darya delta channels. In the ancient delta of the Syr Darya, four systems of channels are distinguished: the Inkar Darya, Zhana Darya, Kuvan Darya and Prakuvan Darya systems. It has been proven that the southern Inkar Darya system and the northernmost Prakuvan Darya system already functioned in the Neolithic and Bronze Ages. In the Early Iron Age, the Saka tribes inhabited the ancient Syr Darya delta. In the second half of the 1st millennium BC. the regime of flooding of the southern delta channels changed. Some sections of the watercourse in the middle reaches of the Inkar Darya died off, primarily in its southern channel, by the middle of the 1st millennium BC. At the same time, a more straightened latitudinal channel of the Zhana Darya was formed. In the southern part of the delta, on the latitudinal channels of the Zhana Darya and the oxbow lakes of the Inkar Darya, favorable conditions were created for the formation of a settled agricultural and pastoral culture, with economy based on transhumance and irrigation farming. Such was the Chirik Rabat archaeological culture, which, according to researchers, was formed on the basis of the Saka culture. At the same time, it was formed under the influence of the ancient agricultural cultures of Central Asia.

Evolution of the facies development of the Knurów deposit (USCB) based on the microlithotypes analysis

This paper presents the first attempt to reconstruct the facies development of the entire Carboniferous coal deposit with an area of 38.50 km2, in the western part of the Upper Silesian Coal Basin based on microscopic microlithotype analysis. For this purpose, eight coal seams in the Knurów deposit were sampled. Samples were taken from all stratigraphic series of exploited seams and exploratory boreholes. This paper reconstructs the transition of environments between eight coal seams extracted in the active Knurów coking coal mine in the Upper Silesian Coal Basin, using microlithotype analysis of the whole seam basis on the fifty coal samples. Facies diagrams proposed in the literature by other researchers were used to reconstruct the depositional environments. The dominant microlithotypes in the coking coal of the Knurów deposit are vitrite (in the range from 19.96 vol% for coal seam No. 504 to 42.96 vol% for coal seam No. 355) and duroclarite (in the range from 20,57 vol% for coal seam No. 410 to 33,65 vol% for coal seam No. 405/1). The distribution of the samples indicates two dominant peat-forming environments. These are telmatic reed moor rich in duroclarite and telmatic forest moor rich in vitrite. This indicates a transitional environment between forest swamp and herbaceous swamp. Thus, the deposit evolved from the paralic to limnic facies. The formation of the river delta caused the progradation of terrestrial environments into the sea and the formation of extensive mires fed mainly by groundwater connected to the river system. Over time, the deposit changed from a reed facies to a forest facies. Periodically, the mires were flooded with waters formed in the proximal lacustrine delta by rising water levels or delta subsidence. The remnants of this phenomenon are interbeds in coal seams resembling macroscopic sapropelic coal rich in the clay matters and gelinite. These are layers containing vitrite in the range of 52.99–59.06 vol% and mineral matter in the amount of 19.76–34.59 vol%. The evolution of the basin proceeded from the paralic to limnic stage. The main factor determining the evolution of the mire was the existing river system with periodically variable activity and intensity.

Changes within the P681 residue of spike dictate cell fusion and syncytia formation of Delta and Omicron variants of SARS-CoV-2 with no effects on neutralization or infectivity

The rapid spread and dominance of the Omicron SARS-CoV-2 lineages have posed severe health challenges worldwide. While extensive research on the role of the Receptor Binding Domain (RBD) in promoting viral infectivity and vaccine sensitivity has been well documented, the functional significance of the 681PRRAR/SV687 polybasic motif of the viral spike is less clear. In this work, we monitored the infectivity levels and neutralization potential of the wild-type human coronavirus 2019 (hCoV-19), Delta, and Omicron SARS-CoV-2 pseudoviruses against sera samples drawn four months post administration of a third dose of the BNT162b2 mRNA vaccine. Our findings show that in comparison to hCoV-19 and Delta SARS-CoV-2, Omicron lineages BA.1 and BA.2 exhibit enhanced infectivity and a sharp decline in their sensitivity to vaccine-induced neutralizing antibodies. Interestingly, P681 mutations within the viral spike do not play a role in the neutralization potential or infectivity of SARS Cov-2 pseudoviruses carrying mutations in this position. The P681 residue however, dictates the ability of the spike protein to promote fusion and syncytia formation between infected cells. While spike from hCoV-19 (P681) and Omicron (H681) promote only modest cell fusion and formation of syncytia between cells that express the spike-protein, Delta spike (R681) displays enhanced fusogenic activity and promotes syncytia formation. Additional analysis shows that a single P681R mutation within the hCoV-19 spike, or H681R within the Omicron spike, restores fusion potential to similar levels observed for the Delta R681 spike. Conversely, R681P point mutation within the spike of Delta pseudovirus abolishes efficient fusion and syncytia formation. Our investigation also demonstrates that spike proteins from hCoV-19 and Delta SARS-CoV-2 are efficiently incorporated into viral particles relative to the spike of Omicron lineages. We conclude that the third dose of the Pfizer-BNT162b2 provides appreciable protection against the newly emerged Omicron sub-lineages. However, the neutralization sensitivity of these new variants is diminished relative to that of the hCoV-19 or Delta SARS-CoV-2. We further show that the P681 residue within spike dictates cell fusion and syncytia formation with no effects on the infectivity of the specific viral variant and on its sensitivity to vaccine-mediated neutralization.

Facies Analysis and Paleoenvironmental Reconstruction of Well X, Onshore Niger Delta, Nigeria

Biofacies and lithofacies analysis of one hundred and ninety-two (192) ditch cutting rock samples from well x, onshore Niger Delta was carried out for the purpose of the paleoenvironmental reconstruction of the rock succession. The objectives were to identify the lithofacies units and species of foraminifera and to use both quantitave and qualitative foraminiferal assemblage to recognise the benthonic foraminiferal biofacies and integrate both results for delineation of paleobathymetric and paleoenvironmental settings of sediments penetrated by well x interval studied. The rock samples were prepared through wet-sieve analysis with 63µm mesh sieve size, and subsequently through dry-sieve analysis with 250µm and 500µm mesh sieve sizes. The prepared rock samples were analyzed to generate data for sedimentological grain-size analysis and foraminifera biofacies assemblages. The grain-size analysis provided lithofacies associations, sand/shale ratio and sorting/gradational profile for the studied intervals of well-x while the micropaleontological analysis identified a total of ninety-three (93) well preserved foraminiferal species from which three (3) biofacies associations were delineated. The biofacies include: Ammonia beccarii, Ammonia beccarii/Bolivina scalprata miocenica, and Haplophragmoides compressa/ Valvulina flexilis biofacies indicating Shallow Inner Neritic, Inner- Middle Neritic, and Outer Neritic – Upper Bathyal paleoenvironment respectively. The result of the sand/shale ratio and lithofacies associations indicated penetration into the Agbada Formation of the Niger delta and deposition within shallow to deep marine paleoenvironmental settings, predominantly as channels, intercalated with overbank and distal bar/bay deposits. Synthesis of the biofacies and lithofacies indicated stratigraphic development between coastal deltaic and upper bathyal paleowater depths.

ფოთის პორტის ახალი მოლოს გავლენა სანაპირო ზოლის ლითოდინამიკურ პროცესებზე

In the city of Poti and its maritime region, for several decades there have been of environmental and geomorphological problems, which have been caused by anthropogenic interventions in this region. The impact of the breakwater of the new port of Poti on lithodynamic processes in the coastal zone is discussed in the paper. The sediment mass constancy equation is used in numerical experiments to determine the velocities of overbank and bank-driven sediment transport. To solve this equation, we use the finite element method and Crank–Nicolson schemes. According to calculations, 1,500,000 m3 of sediment migrates along the Nabada delta's banks, 850,000 m3 south of the delta to the harbor, and 65,000 m3 north of the delta to Khobiskal. The remaining 2,500,000 m3 is moved along the shore in a westerly direction before being dumped on the sea's underwater slope. After the new breakwater is built, all fine sediment movement in that direction will be stopped, and solid sediment will start to settle to the north of the new breakwater. Eventually, this will cause the southern branch of the Nabada Canal to become blocked. The total flow of water from the Nabada canal will be transferred to the northern branch, and the formation of a new delta will begin there.

Modelling study on the sediment dynamics and the formation of the flood-tide delta near Cullendulla Beach in the Batemans Bay, Australia

The first 3-D current-wave-sediment coupled model of the semi-exposed estuary Batemans Bay, New South Wales, Australia, was developed in our study based on the Finite Volume Coastal Ocean Model (FVCOM). Our study explored the hydrodynamics, sediment dynamics and morphology change inside the Batemans Bay under large wave events. The modeled monthly-averaged residual flow, sediment flux and suspended sediment concentration with a combined tidal and wave forcing in the inner bay were significantly different to those only with tidal forcing, this is because the storm wave events can generate wave-induced currents and large bottom stresses, influencing the sediment transport. In addition, the morphology change of the flood-tide delta (FTD) inside the Batemans Bay under wave effects was also investigated in this study. According to previous studies, the FTD is a sediment deposit located on the landward side of tidal inlets, formed by the incoming tidal currents and ocean waves, which is an important morphology coastal feature influencing the sediment exchange with adjacent beach systems. Yet, the dynamic processes of FTDs have not been fully understood and explored quantitatively in sheltered estuaries. Based on our model results, the FTD near Cullendulla Beach is controlled by wave effects and was in an equilibrium status: when the FTD was eroded deeper to a critical value (about 2 m) by waves, sedimentation occurred. The rocky headland adjacent to the FTD contributed to the formation of the FTD due to sheltering effects, and the FTD actually developed at the ‘wave shadow areas’ behind the headland in Batemans Bay, which were dominantly controlled by sheltering effects. Despite being termed a ‘Flood-Tide Delta’, ‘Tide’ here is misleading, and a new name of ‘Wave Shadow Shoal’ should be given to describe such wave-dominated coastal features. In conclusion, this study demonstrated that waves played the dominant role in the hydrodynamic processes, sediment transport and morphology change in Batemans Bay.

Unmanned aerial vehicles (UAVs) as a tool for hazard assessment: The 2021 eruption of Cumbre Vieja volcano, La Palma Island (Spain)

Monitoring for assessment of natural disasters, such as volcanic eruptions, presents a methodological challenge for the scientific community. Here, we present Unmanned Aerial Vehicles (UAVs) as a feasible, precise, rapid and safe tool for real time monitoring of the impacts of a volcanic event during the Cumbre Vieja eruption on La Palma Island, Spain (2021). UAV surveys with optical RGB (Red-Green-Blue), thermal and multispectral sensors, and a water sampling device, were carried out in different areas affected by the lava flow, including the upper volcanic edifice and the lava delta formed on the coastal fringe of the island. Our results have provided useful information for the monitoring of the advance of the lava flow and its environmental consequences during the volcanic emergency. Our data shows how La Palma island's growth, with the formation of a new lava delta of 28 ha and a total volume of lava injected into the sea of 5,138,852 m3. Moreover, our Digital Elevation Model (DEM) simulated, with a 70 % accuracy, the probabilistic simulation of the possible path followed by the lava flow in the vicinity of the fissure from which the magma emanates. In addition, significant changes of seawater physical-chemical parameters were registered in coastal surface waters by the in situ seawater samples collected with the automatic water sampling device of our UAV. The first meters of the water column, due to the instant evaporation of the seawater in contact with the hot lava, produce an increase of temperature and salinity of up to 4–5 °C and up to 5 units, respectively.

Biosynthesized δ-Bi2O3 Nanoparticles from Crinum viviparum Flower Extract for Photocatalytic Dye Degradation and Molecular Docking.

Bioinspired delta-bismuth oxide nanoparticles (δ-Bi2O3 NPs) have been synthesized using a greener reducing agent and surfactant via co-precipitation method. The originality of this work is the use of Crinum viviparum flower extract for the first time for the fabrication of NPs, which were further calcined at 800 °C to obtain δ-Bi2O3 NPs. Physicochemical studies such as FTIR spectroscopy and XPS confirmed the formation of Bi2O3 NPs, whereas XRD and Raman verified the formation of the cubic delta (δ) phase of Bi2O3 NPs. However, HRTEM revealed the spherical shape with diameter 10–20 nm, while BET studies expose mesoporous nature with a surface area of 71 m2/gm. The band gap for δ-Bi2O3 NPs was estimated to be 3.45 eV, which ensured δ-Bi2O3 to be a promising photocatalyst under visible-light irradiation. Therefore, based on the results of physicochemical studies, the bioinspired δ-Bi2O3 NPs were explored as active photocatalysts for the degradation of toxic dyes, viz., Thymol blue (TB) and Congo red (CR) under visible-light irradiation. The study showed 98.26% degradation of TB in 40 min and 69.67% degradation of CR in 80 min by δ-Bi2O3 NPs. The photogenerated holes and electrons were found responsible for this enhancement. Furthermore, molecular docking investigations were also performed for δ-Bi2O3 NPs to understand its biological function as New Delhi metallo-β-lactamase 1 (NDM-1) [PDB ID 5XP9] enzyme inhibitor, and studies revealed good interaction with various amino acid residues and found good hydrogen bonding with a fine pose energy of −3.851 kcal/mole.

Remote Sensing and Field Survey Data Integration to Investigate on the Evolution of the Coastal Area: The Case Study of Bagnara Calabra (Southern Italy)

Coastal areas worldwide are the result of a weak balance between man and the natural environment. They are exposed to strong anthropogenic pressure and natural hazard events whose intensity has increased in recent decades. In this frame, the satellite and drone monitoring systems as well as field survey are key tools to learn about the factors responsible for coastal changes. Here we describe the formation and dismantling of a fan delta at Sfalassà Stream mouth, Calabria Region (Southern Italy) to shed light on the environmental drivers modelling this coast. The flood event of 2 November 2015 placed approximately 25,000 m3 of coarse sand and gravel sediments in a few hours forming a fan-shaped delta, while three main storm surges, occurring from November 2015 to January 2016, caused its dismantling. Sentinel 2 images and several photographs captured the gradual erosion of fan delta highlighting its complete dismantling in about 3 months. The eroded sediments only partially feed the neighbouring beaches, as they were rapidly funnelled several hundred metres seaward by submarine channels whose heads cut back up at depths <10 m. This analysis showed that observing systems with high spatial and temporal resolution provide the proper knowledge to model the processes that characterise this transitional environment. They are fundamental tools for coastal zone management, which aims to ensure the sustainability of coastal zones by mitigating the effects of erosion and flooding.

Changes in Organic Carbon Delivery to the Yangtze River Delta Over the Last 2000 Years

Natural processes and anthropogenic activities are vital in dictating the amount and character of organic carbon (OC) input into large river deltas and adjacent shelves. Previous studies have indicated that sediment from the Huanghe River (HR) has significantly affected the formation of the northern Yangtze River subaqueous delta (YRD) over the past several hundred years. However, whether this process has changed sedimentary OC burial in the YRD remains unclear. A sediment core was collected from the YRD in 2018 CE for optically stimulated luminescence and 210Pb dating as well as grain size, total OC, total nitrogen, and stable-isotope analyses to investigate temporal changes in sedimentary OC over the past 2000 years. The results indicate that changes in terrestrial OC inputs to the YRD have been controlled mainly by the East Asian summer monsoon and anthropogenic influences in the past 2000 years. However, the decreased terrestrial OC inputs after 1385 CE, have been significantly affected by increased contribution of HR sediment to the YRD when the HR lower courses shifted to enter the southern Yellow Sea. This study demonstrates that sediment source changes should not be neglected in analyses of mechanisms and variations in OC burial in estuarine and coastal areas.

The Li stance on precipitation in Al\u2013Li-based alloys: an investigation by X-ray Raman spectroscopy

Decomposition and precipitation processes in a binary Al–Li alloy and a technical Al–Li–Cu–Mg alloy were investigated using differential scanning calorimetry and X-ray Raman spectroscopy (XRS). The formation of delta ’ and T1 precipitates in the Al–Li and the T8 heat-treated Al–Li–Cu–Mg alloy, respectively, was confirmed using DSC. The XRS measurements complemented by simulated spectra allowed for probing specifically Li and its environment within the Al matrix. Based on linear combination fits of the XRS spectra, the relative contributions of delta ' and T1 precipitates were quantified. These results are in agreement with estimates of the relative amount of Li taking part in the precipitation process. Difficulties and limitations of the application of XRS to Al alloy systems are also discussed.

Changes within the P681 Spike Residue of the Polybasic Motif Dictate Fusogenicity and Syncytia Formation of Delta and Omicron Variants of SARS- CoV-2 with No Effects on Neutralization or Infectivity

Changes within the P681 Spike Residue of the Polybasic Motif Dictate Fusogenicity and Syncytia Formation of Delta and Omicron Variants of SARS- CoV-2 with No Effects on Neutralization or Infectivity

Role of dew points and Fe pre-coats on the galvanizing and galvannealing of dual phase steel

In this study, the galvanizing and galvannealing ability of dual phase steel sheet (DP 590), with and without Fe pre-coatings, is investigated with varying dew points using a hot dip process simulator (HDPS). Good quality defect free adherent galvanized coating on the substrate surface is obtained by appropriate selection of the inter-critical annealing atmosphere consists of N2-5%H2 gas mixture with +10 °C dew point without substrate pre-coating. However, the production of defect-free coating on DP 590 substrates is highly challenging when the substrates are without any pre-coating. It is observed that the selective oxidation of manganese on the substrate surface during intercritical annealing is primarily responsible for the appearance of bare spots on the galvanized surface in case of the coated specimen produced without pre-coating. A significant improvement in the reactive wetting behaviour between the liquid zinc alloy and pure Fe results in defect free adherent coatings (both galvanized and galvannealed) with electrodeposited Fe pre-coating on the substrate surface irrespective of dew points. Both the galvannealed specimens prepared with and without iron pre-coatings, exhibit partial passive-active metal characteristics in potentiodynamic polarization corrosion test. Iron pre-coating on the substrate surface is observed to improve the quality of galvannealed coatings by reducing defects and enhancing the formation of more compact and dense delta (δ) phase compared to galvannealed coatings produced without pre-coating under identical conditions. This leads to the improvement in corrosion resistance of galvannealed coating produced with pre-coating by lowering the corrosion potential and corrosion current density compared to that of galvannealed specimens produced without iron pre-coating.

Yellow River's Contribution to the Building of Yangtze Delta During the Last 500 Years ‐ Evidence From Detrital Zircon U‐Pb Geochronology

AbstractThe Yangtze Delta (YD), as one of the world mega deltas, its formation process has long been the subject of research. Previous study has proposed a remote connection of the Yellow River (YR) to the building of the YD over the past 600–400 years. However, complex source‐sink routing system of the YD sediment and lack of diagnostic provenance tools have hampered further understanding of this process. Inferred from detrital zircon U‐Pb geochronology, this study revealed an increased and significant contribution of the reworked YR sediment to the YD (up to 26%) since ca. 500 a during the period YR shifted its lower courses and entered the southern Yellow Sea. This study not only highlights the impact of human activity on the formation of the world's large delta but also addresses the intricate interplay between neighboring deltas through marine dynamics, for example, alongshore and tidal currents.

The interaction of buoyant coastal river plumes with mangrove vegetation and consequences for sediment deposition and erosion in a tidal environment

To identify the drivers of sediment deposition within a mangrove-lined river delta, we developed a three-dimensional numerical model in an idealized domain. Our model system is based on the Firth of Thames, a modern flat-fronted, bay-head deltaic system, in the Hauraki Gulf, in the North Island of New Zealand. The interactions of the buoyant river plume with mangroves are examined, including sediment deposition and erosion patterns. The morphological study presented here is restricted to cohesive sediments, whose patterns are observed after 4 months of morphological evolution. For the non-vegetated case, represented by a spatially uniform roughness, sediment deposited throughout the central model domain with a formation of a cuspate delta at the river mouth. However, in the vegetated case (with vegetated areas represented by an enhanced and spatially varying roughness coefficient), sediment deposition occurred in the regions of forests and flats, whereas the fringe areas experienced erosion. The sediment deposition patterns along cross-sections were qualitatively consistent with field observations from the Firth of Thames. Analysis of the across-transect and along-transect momentum balances demonstrates that the predominant balance between the bottom shear stress and baroclinic pressure gradient largely controls the sediment deposition in the riverine sections of the domain. However, close to the center of the plume, vertical advection promotes suspension of the sediments in the fringe region during the flood tide.

Sedimentological variability and depositional environment of the Anthemountas River (Northern Greece) during the Late Pleistocene and Holocene

Research has shown that fluvial systems exhibit a rapid response to extreme events, such as floods or climate-tectonic interplay, the evidence of which is recorded in fluvial sediments. This article provides new data and insights into the reconstruction of the Anthemountas River depositional environment. The study was conducted with granulometric analysis and with the lithostratigraphic and chronostratigraphic description of approximately 20000 yr B.P., the area's most extended sedimentary sequence to date. The evolution of the Anthemountas River Valley during the Late Pleistocene and Holocene is closely linked to tectonic activity and changes in the sea-level and climate. The interpretation of grain size cumulative curves, frequency curves, and the Passega C-M diagram is used in conjunction with the textural parameters of the sediments to obtain information about the means of transport and the intensity of environmental conditions. In addition, the loss on ignition method was used to estimate two parameters; organic matter and carbonates. Chronostratigraphic details were also obtained from the A.M.S. dating of charcoal samples. The analysis has identified the Late Pleistocene aggradation materials and the transition to the Holocene. Sedimentation can be described as a fluvial valley-fill sequence with periodical in-channel, off-channel, and floodplain series. After 3500 cal. B.P., the area is affected by the possible formation of a bay-head delta, with fluvial-dominated sands and the development of stable floodplains. Finally, the fluvial records of the Anthemountas River reveal phases of hydrological activity and stability.

Biogeomorphic succession in a fluvial-lacustrine delta of the Middle Paraná River (Argentina): Feedbacks between vegetation and morphodynamics

The Leyes' Delta lies at the Middle Paraná River, the second-largest fluvial system in South America, and it is being quickly formed into the Setúbal fluvial lake, Argentina. In the context of the Fluvial Biogeomorphic Succession theory, our aim was to better understand interactions between physical and biotic processes contributing to the formation of the Leyes' Delta. We studied the genesis, morphologic development, and vegetation in three groups of its deltaic islands with contrasting formation ages. Different methodologies were applied. Genesis and morphologic development were interpreted from time-series of satellite images and aerial photography obtained from 1974 to 2014. Then landforms and vegetation communities were mapped on the most current images, and they were corroborated and characterized during fieldwork. Our results evidence that the three island groups (Channel crevasse splay islands, Delta bar-plain islands, and Delta front islands) were formed via two different geomorphic processes, determining differences in the initial vegetation colonization. Eight fluvial-lacustrine landforms and eight vegetation communities, both differently represented among the island groups, currently characterize these islands. The species richness accumulation curves and beta diversity showed that the morphodynamic activity can be as important in the floristic composition of the deltaic islands as formation ages. The floristic composition differed statistically among island groups. After identifying three of the four phases of the FBS, we concluded that even though the morphodynamic activity under which islands were formed determined differences in the initial vegetation colonization, under similar subsequent levels of morphodynamics the resulting vegetation heterogeneity tends to be similar even under contrasting genesis. Among the vegetation types, Lotic prairies would play a key role in the morphologic evolution of the deltaic islands, therefore, their distribution and interactions with flow and sediments should be considered during the studies of social ecological systems as the Leyes' Delta, in Santa Fe, Argentina.

The glaciovolcanic evolution of the Copahue volcano, Andean Southern Volcanic Zone, Argentina-Chile

Glaciovolcanism produces distinctive features that are useful paleoclimate proxies for the distribution of past ice sheets and glacier extent. The Copahue volcano located in the Andean Southern Volcanic Zone, Argentina-Chile, is an active composite volcano known to have glaciovolcanic features such as lava bodies with glassy margins and anomalous cooling fractures. However, the emplacement conditions of these products and the influence of Pleistocene glaciations on the evolution of the Copahue volcano remains poorly understood. In this contribution, we propose a model for glaciovolcanic evolution of the Copahue volcano based on the analysis, interpretation, and mapping of its products. Ten lithofacies are described on the eastern flank of Copahue volcano exhibiting several examples of glaciovolcanism. The evolution of the Copahue volcano can be divided into two main sequences: the Ancient Sequence (S1) and the Young Sequence (S2), separated by a major erosive phase. The S1 (early-middle Pleistocene-late Pleistocene) consists of an initial subaerial effusive stage followed by a major glaciovolcanic stage, during which a thick ice cap existed and the edifice grew beneath an englacial lake with the eventual formation of a lava-fed delta. The S2 (late Pleistocene-Present) is defined by mainly effusive activity during periods of glacial advance and retreat recorded by an alternation of unconfined subaerial lavas and ice-confined lavas. The evolution of the Copahue volcano therefore indicates two glaciations in the Copahue-Caviahue area during the late Pleistocene, in contrast to a single glaciation. Based on the glacial history in the area we associate the first glaciation with the end of Marine Isotope Stage 3 (57–29 ka) and/or the Last Glacial Maximum period (26.5–19.0 ka), and the second less-extensive glacial period with the Antarctic Cold Reversal (14.5–12.9 ka).

Rapid consolidation characteristics of Yellow River-derived sediment: Geotechnical characterization and its implications for the deltaic geomorphic evolution

The Yellow River, which presently discharges into the western Bohai Sea, has been widely recognized as having one of the highest sediment loads on Earth. Understanding the consolidation characteristics of Yellow River-derived sediments is critical for improving our knowledge of the riverine sediment transport, depositional processes, and evolution of the Yellow River Delta morphology. In this study, we conducted in situ experiments from 2004 to 2008 at an abandoned subaqueous delta lobe (Diaokou lobe) in order to investigate the consolidation process of the sediments. Our results show that the initial consolidation of Yellow River-derived sediment is a rapid process when the excess pore-water pressure caused by sediment aggradation can completely dissipate in ~1500 min. The change in the physical and geotechnical properties during the consolidation endows the sediments with a certain shear strength. However, due to the hydrodynamic conditions, the distribution of the sediment strength is both temporally and spatially inhomogeneous. Furthermore, a hard layer can develop at the depths of 10–30 cm and the adjacent layer can become a potential sliding surface. This study offers some insight into the formation and evolution processes of the Yellow River Delta's sedimentary and geomorphic forms.

A Multi-Proxy Reconstruction of Environmental Change in the Vicinity of the North Bay Outlet of Pro-Glacial Lake Algonquin

We present a multi-proxy study of environmental conditions during and after the recessional phases of pro-glacial Lake Algonquin in the vicinity of the North Bay outlet, Great Lakes Basin. Data presented comes from a new sedimentary profile obtained from the Balsam Creek kettle lake c. 34 km north-east of the city of North Bay. This site lies close to the north-east margin of the maximum extent of the post-Algonquin lake sequence, which drained through the Ottawa-Mattawa valley system. Our data are presented against a Bayesian age-depth model, supporting and extending regional understanding of vegetation succession in this part of north-east Ontario. The core profile provides a minimum age for the formation of the glacial outwash delta in which the kettle is set, as well as tentative timing for the Payette (post-Algonquin) lake phase. We highlight two discrete intervals during the Early Holocene, with modelled mean ages of: 8475–8040 cal. BP (332–316 cm) and 7645 cal. BP (286 cm), when climatic aridity affected the growth of vegetation within the kettle vicinity. Association with volcanic activity is posited. Cryptotephra dating to 7660–7430 cal. BP (mean age: 7580 cal. BP) is chronologically and geochemically assigned to the Mazama climactic eruption, while an earlier ash accumulation 8710–7865 cal. BP is tentatively sourced to an unknown eruption also in the Cascades region of Oregon. Outside of these periods, the Balsam Creek sequence shows considerable habitat stability and a character akin to that seen at more southerly latitudes. On this evidence we propose that access to reliable resources within kettle features could have aided the initial colonisation of northern Ontario’s environmentally dynamic early post-glacial landscape.