Riverbank Deposits Research Articles

New Data on Paleogeography of Quaternary Coast Sediments of the Rivers of the European North of Russia Using Isotope-Geochemical Methods

(1) Background: The Quaternary river bank deposits of the European North of Russia contain several mollusk fossils that can give important past-climate information which is relevant to understand the evolution of climate in the Holocene period and predict future scenarios on climate change. (2) The purpose of the research: reconstruction of the main physical and chemical parameters of the habitat of mollusks based on the determination of the species of mollusks and the study of the isotope-geochemical composition of shells and their host deposits. (3) Object of study: Quaternary deposits of coastal outcrops of the rivers of the European North of Russia: Pechora Sula, Peza, bivalve shells, and their fragments. (4) Results: The revealed macrofauna complexes represented by bivalves (Arctica islandica, Hiatella arctica, Mytilus edulis, Tridonta borealis, Mya truncata, Neptunea despecta) were determined and the variations of δ13C and δ18O (‰) isotopes in the studied fossil bivalve shells were calculated. The data on the concentrations of chemical elements in fossil shells were determined and summarized. The content of elements in mollusk shells varied within the following limits: Fe 101.7−403.3 µg/g (Vastyansky Kon’, river Pechora), Mg 0.38–2.61 µg/g (Vastyansky Kon’, river Pechora), Ba 18.27–60.44 µg/g (village Oksino-River Sula), and Sr 1128.3–2275.34 µg/g (Vastyansky Kon’-village Oksino, river Pechora). The ratio between the elements varies within Ba/Sr 0.011–0.041 (village Oksino- River Sula) and Mg/Fe 0.01–0.15 (Vastyansky Kon’- village Oksino, river Pechora).

Gobi deposits play a significant role as sand sources for dunes in the Badain Jaran Desert, Northwest China

The Badain Jaran Desert has the world’s tallest dunes, but the sand sources for these dunes are unclear. Previous research suggested that the Qilian Mountains and Altai Mountains are the main sand sources, with sand transport primarily by hydrological processes. However, there is a large area of Gobi (i.e., desert pavement formed on the alluvial fans) surfaces upwind of the desert, and we hypothesized that the Gobi surface might also be a sand source. Sand geochemical characteristics can be used to identify sediment sources. To test our hypothesis, we collected 26 samples from the Gobi surface, 22 samples from sand dunes on the Gobi surface, 2 samples from dry lacustrine deposits, and 7 samples from the Heihe River’s banks. We then analyzed their geochemical characteristics and used principal-components analysis to quantify the similarity between sand source and deposition areas. We found that the Rb/Sr, Ba/Sr, Y/Zr, Rb/Zr, K/Ba, and K/Rb ratios can be used to identify the sand provenance. Based on these ratios, the geochemical characteristics for all samples were generally similar between the Gobi surface and the Badain Jaran Desert, suggesting that the Gobi surface was an important source of sand for the desert’s dunes, and can provide about 69% of the sediment for the Badain Jaran Desert. Sand was also transported by drainage from the Gobi surface into the Heihe River, where river bank deposits became an additional source of sand. Thus, both wind and hydrodynamic forces controlled the sand transport.

Geoarchaeological insights into the location of Indus settlements on the plains of northwest India

AbstractThis article presents a geomorphological and micromorphological study of the locational context of four Indus civilisation archaeological sites—Alamgirpur, Masudpur I and VII, and Burj—all situated on the Sutlej-Yamuna interfluve in northwest India. The analysis indicates a strong correlation between settlement foundation and particular landscape positions on an extensive alluvial floodplain. Each of the analysed sites was located on sandy levees and/or riverbank deposits associated with former channels. These landscape positions would have situated settlements above the level of seasonal floodwater resulting from the Indian summer monsoon. In addition, the sandy soils on the margins of these elevated landscape positions would have been seasonally replenished with water, silt, clay, and fine organic matter, considerably enhancing their capacity for water retention and fertility and making them particularly suitable for agriculture. These former landscapes are obscured by recent modification and extensive agricultural practices. These geoarchaeological evaluations indicate that there is a hidden landscape context for each Indus settlement. This specific type of interaction between humans and their local context is an important aspect of Indus cultural adaptations to diverse, variable, and changing environments.

Qualitative and quantitative assessment of gravel deposits between Aaptar and Malekhu, Central Nepal for aggregates

The Malekhu Khola is rich in sediments which are widely exposed along its banks. In recent years, river mining sites have been established and mining has been carried on to produce aggregates to meet a small portion of the market demand. Because the riverbank deposits are of heterogeneous composition, quality of the aggregate from such deposits is of main issue. This study therefore, aims to evaluate quality of river sediment to know its suitability for aggregate as raw material for various uses, and the volume of the deposit. Field observation and intensive laboratory works were carried out to evaluate aggregates. The samples of aggregates were analyzed for texture, composition, durability and physical and mechanical properties. Majority of the aggregate particles were found metamorphic rocks of the Lesser Himalaya like quartzite, schist, marble, metasandstone, amphibolites, gneiss and granite, etc. Most of the deposits were matrix-supported and the matrix was basically sandy. The majority of clasts showed bladed to disc, and were generally rounded to sub rounded. The sediment size ranged from granule to upto boulder but the modal size was of cobble grade. While tested for gradation, the coarse aggregates ranged from uniform to gap graded categories. In terms of shape, workability of aggregate was found satisfactory. Aggregate samples possessed low Water Absorption Value (0.53–1.08%) and thus low effective porosity. Aggregate Impact Value (13.40–15.70%) and Aggregate Crushing Value (17.50–19.67%) showed good soundness. Los Angeles Abrasion Value (37.00–48.40%) showed the consistent hardness of each of the samples. The low range of Sodium Sulphate Soundness Value (1.37–2.16%) indicated good resistance of aggregates against chemical weathering and frosting. The aggregates were also resistant to slaking as indicated by very high range of Slake Durability Strength Index (98.67–99.72%). Comparing with the existing Nepal Standard (NS), British Standard (BS) and American Standard of Testing Material (ASTM), the studied samples were suitable for concrete structures and unbound pavements. Six different localities were considered in the study area to estimate for resource of aggregates. The total volume of the deposits was estimated to be 392273 cubic meter.Bulletin of the Department of Geology, Vol. 18, 2015, pp. 49-58

Redistribution of pyrogenic carbon from hillslopes to stream corridors following a large montane wildfire

AbstractPyrogenic carbon (PyC) constitutes a significant fraction of organic carbon in most soils. However, PyC soil stocks are generally smaller than what is expected from estimates of PyC produced from fire and decomposition losses, implying that other processes cause PyC loss from soils. Surface erosion has been previously suggested as one such process. To address this, following a large wildfire in the Rocky Mountains (CO, USA), we tracked PyC from the litter layer and soil, through eroded, suspended, and dissolved solids to alluvial deposits along riversides. We separated deposited sediment into high‐ and low‐density fractions to identify preferential forms of PyC transport and quantified PyC in all samples and density fractions using benzene polycarboxylic acid markers. A few months after the fire, PyC had yet to move vertically into the mineral soil and remained in the organic layer or had been transported off site by rainfall driven overland flow. During major storm events PyC was associated with suspended sediments in river water and later identified in low‐density riverbank deposits. Flows from an unusually long‐duration and high magnitude rainstorm either removed or buried the riverbank sediments approximately 1 year after their deposition. We conclude that PyC redistributes after wildfire in patterns that are consistent with erosion and deposition of low‐density sediments. A more complete understanding of PyC dynamics requires attention to the interaction of post fire precipitation patterns and geomorphological features that control surface erosion and deposition throughout the watershed.

Anthropophile elements in river sediments: Overview from the Seine River, France

AbstractIn contrast to larger river systems that drain relatively pristine basins, little is known about the sediment geochemistry of rivers impacted by intense human activities. In this paper, we present a systematic investigation of the anthropogenic overprints on element geochemistry in sediments of the human‐impacted Seine River, France. Most elements are fractionated by grain size, as shown by the comparison between suspended particulate matter (SPM) and riverbank deposits (RBD). The RBD are particularly coarse and enriched in carbonates and heavy minerals and thus in elements such as Ba, Ca, Cr, Hf, Mg, Na, REEs, Sr, Ti, Th, and Zr. Although the enrichment/depletion pattern of some elements (e.g., K, REEs, and Zr) can largely be explained by a binary mixture between two sources, other elements such as Ag, Bi, Cr, Cd, Co, Cu, Fe, Mo, Ni, Pb, Sb, Sn, W, and Zn in SPM in Paris show that a third end‐member having anthropogenic characteristics is needed to account for their enrichment at low water stage. These “anthropophile” elements, with high enrichment factors (EFs) relative to the upper continental crust (UCC), display a progressive enrichment downstream and different geochemical behaviors with respect to the hydrodynamic conditions (e.g., grain size) compared to elements having mainly a natural origin. Our findings emphasize the need for systematic studies of these anthropophile elements in other human‐impacted rivers using geochemical normalization techniques, and stress the importance of studying the chemical variability associated with hydrodynamic conditions when characterizing riverine element geochemistry and assessing their flux to the ocean.

Assessing the time of final deposition of Youngest Toba Tuff deposits in the Middle Son Valley, northern India

We present optical ages for quartz and K-feldspar grains extracted from sedimentary deposits above and below Youngest Toba Tuff (YTT) at two localities in the Middle Son Valley (MSV), Madhya Pradesh, India. These ash deposits have been the focus of past palaeoenvironmental investigations that aim to understand the effects of the ~74ka Toba super-eruption on ecosystems and human populations in northern India. Age estimates from both quartz and feldspar grains post-date the Toba eruption and single-grain age distributions suggest that YTT ash-bearing sediments in the MSV are mainly composed of a mixture of recently sun-exposed, flood-transported grains and older grains from slumped river bank deposits. This study highlights the hazards of using YTT ash as an isochronous marker horizon in the MSV, and illustrates the need to independently assess the time of final deposition of reworked volcanic ash beds in sedimentary sequences used in stratigraphic correlations and palaeoenvironmental reconstructions.

Evaluation of Riverbank Hydraulic Conductivity: Implications for Groundwater Recharge

This study highlights the relationship between the hy draulic conductivity (K) of riverbank deposits and groundwater recharge in an area adjacent to a Chalk river in Hertfordshire, United Kingdom. Three locations were mapped out for Insitupermeability measurements based on geological map data indicating cha nges in superficial deposits along the river Mimram. The study area is predominated by Cretaceous Chalk and overlain by drift deposit such as glacial till and buried channel deposits which include glaciofluvial gravels,

Sources of overdispersion in a K-rich feldspar sample from north-central India: Insights from De, K content and IRSL age distributions for individual grains

Abstract Luminescence dating of individual sand-sized grains of quartz is a well-established technique in Quaternary geochronology, but the most ubiquitous mineral on the surface of the Earth—feldspar—has received much less attention at the single-grain level. In this study, we estimated single-grain equivalent dose values and infrared stimulated luminescence (IRSL) ages for K-rich feldspar (KF) grains from a fluvial sample underlying Youngest Toba Tuff (YTT) deposits in north-central India, and compared these ages (corrected for anomalous fading) with those obtained from individual grains of quartz from the same sample. Both minerals have broadly similar single-grain age distributions, but both are greatly overdispersed and most grains have ages substantially younger than the expected age of the YTT deposit (∼74 ka). Almost half (45%) of KF grains used for age calculation have fading rates statistically consistent with zero, but the age distribution of these grains is as dispersed as that of the entire population. We obtained a similar distribution of ages calculated for 51 grains using their individually measured internal K contents, which exhibited only minor grain-to-grain variation. Given the lack of dependency of single-grain ages on the measured fading rates and internal K contents, and the overall adequacy of bleaching of grains collected from a sandbar in the modern river channel, we consider the spread in ages is most likely due to mixing, at the time of deposition and after the YTT event, of potentially well-bleached fluvially-transported sediments with older grains derived from slumping of riverbank deposits. Some spread may also be due to natural variations in the IRSL properties of individual KF grains.

Preservation of bone collagen sulphur isotopic compositions in an early Holocene river-bank archaeological site

This study investigates the reliability of the sulphur isotopic compositions (δ 34S) of collagen in archaeological bones from an early Holocene river-bank site, Noyen-sur-Seine (France). The chemical composition (C, N, S) of whole bones compared to those of bones from cave sites suggests that contamination with sulphur is higher in the bones sampled from river bank deposits compared to those from caves, especially those that occur well above the water table. Sulphur content in fresh bone collagen suggests specific values for different mammal taxa, while sulphur content in reptile bones may not always be higher than those of mammals. In the early Holocene bones from Noyen-sur-Seine, the collagen has chemical characteristics within the overall range observed in modern bone collagen. However, co-variation between some diagenetic indicators, such as sulphur content and N/S in whole bone, %S in collagen, and S yield, and δ 34S values of collagen from the same species or ecological groups indicate that some diagenetic alteration may have influenced the collagen. Excluding samples possibly affected by this alteration, a difference in δ 34S is measured between freshwater and terrestrial fauna. We recommend further work on the collagen sulphur contents in different species. Moreover, whole bone chemical compositions may help to screen samples for sulphur isotopic analyses of collagen that are to be used for palaeodietary reconstructions.

A new genus and species of nothrotheriid sloth (Xenarthra, Tardigrada, Nothrotheriidae) from the Late Miocene (Huayquerian) of Peru

Abstract: The nothrotheriine sloth from riverbank deposits of the Río Acre region of Peru in western Amazonia was originally assigned toNothropus priscusBurmeister, 1882. Although relatively complete, with essentially the pes unknown, its description was accompanied only by limited information on its cranial remains. The remains of this sloth, actually of late Miocene age, were extensively prepared. Subsequent analysis indicates that its original assignment is incorrect and that it belongs to a new genus and species, which is distinguished from other nothrotheriines by the following (among other) features: notably domed braincase; depressed, narrow snout; lack of parietal/alisphenoid contact; ulna with prominently projecting anconeal process; distal position of femoral greater trochanter; medial articular condyle of femur butts against patellar trochlea. Phylogenetic analysis places the new genus and species as sister group to the (Pronothrotherium(Nothrotheriops + Nothrotherium)) clade.

Hydrological and sedimentary controls leading to arsenic contamination of groundwater in the Hanoi area, Vietnam: The impact of iron-arsenic ratios, peat, river bank deposits, and excessive groundwater abstraction

Groundwater contamination by arsenic in Vietnam poses a serious health threat to millions of people. In the larger Hanoi area, elevated arsenic levels are present in both, the Holocene and Pleistocene aquifers. Family-based tubewells predominantly tap the Holocene aquifer, while the Hanoi water works extract more than 600,000 m 3/day of groundwater from the Pleistocene aquifer. Detailed groundwater and sediment investigations were conducted at three locations exhibiting distinct geochemical conditions, i.e., i) high levels of dissolved arsenic (av. 121 µg/L) at the river bank, ii) low levels of dissolved arsenic (av. 21 µg/L) at the river bank and, iii) medium levels of dissolved arsenic (60 µg/L) in an area of buried peat and excessive groundwater abstraction. Seasonal fluctuations in water chemistry were studied over a time span of 14 months. Sediment-bound arsenic (1.3–22 µg/g) is in a natural range. Arsenic correlates with iron ( r 2 > 0.8) with variation related to grain size. Sediment leaching experiments showed that arsenic can readily be mobilized at each of the three locations. Low levels of arsenic in groundwater (< 10 µg/L) generally exhibit manganese reducing conditions, whereas elevated levels are caused by reductive dissolution under iron- and sulphate reducing conditions. Average arsenic concentrations in groundwater are twofold higher at the river bank than in the peat area. The lower levels of arsenic contamination in the peat area are likely controlled by the high abundance of iron present in both the aqueous and sediment phases. With median molar Fe/As ratios of 350 in water and 8700 in the sediments of the peat area, reduced iron possibly forms new mineral phases that resorb (or sequester) previously released arsenic to the sediment. Despite similar redox conditions, resorption is much less significant at the river bank (Fe/As(aq) = 68, Fe/As(s) = 4700), and hence, arsenic concentrations in groundwater reach considerably higher levels. Drawdown of Holocene water to the Pleistocene aquifer in the peat area, caused by the pumping for the Hanoi water works, clearly promotes reducing conditions in Pleistocene groundwater. This demonstrates that excessive abstraction of water from deep wells, i.e., wells tapping water below the arsenic burdened depth, can cause a downward shift of iron-reducing conditions and concurrently mobilize arsenic along the way. Vertical migration of reduced groundwater may also impact aquifers under natural hydrological conditions. Seepage of DOC-enriched groundwater derived from degradation of organic matter in the clayey sediments at the river bank was observed to enhance (and maintain) iron-reducing conditions in the aquifer where organic matter is scarce. Once the aquifer becomes reduced, arsenic is released from the aquifer solid-hosts but additionally derives from the arsenic-enriched groundwater seeping from the clay into the aquifer. This behaviour is an important mechanism for arsenic contamination in aquifers that might not necessarily contain enough organic matter in their sediments to induce reducing conditions independently.

Longitudinal Transportation of Suspended Solids during Floods

In light of the fact that river life is affected by sediment, nutrients and other factors on which river ecosystems are based, i t is equally importanto understandth e statuso f these factorsa s well as theirb ehaviorc hangest hat may result from river channel alterations. It has been pointed out that most of the nutrients that stored in river channels are absorbed by fine sands and transported in times of flood, before being deposited at their subsequent locations. However, the behavior during floods of such very fine sands that have absorbed nutrients has yet to be sufficiently clarified, and its earliest possible clarification is required to help further promote future river projects. This report considers the flow down process of suspended solids, based on data obtained from flood observation of the Mukawa Rivera nds ubsequents urveyo n riverbankd eposits. And the behavioro f suspendeds olidsa t the timc of a flood was reproducible using the unsteady-flow and bed variation calculation model.

A new Middle Pleistocene fauna from the Busidima–Telalak region of the Afar, Ethiopia

We report on a diverse fauna from the Busidima–Telalak region of the Afar in Ethiopia. The fossiliferous sediments are characterized by riverbank deposits. During our first field season thirty-one mammalian species were encountered. Fossils are nicely preserved and abundant. Bovids, carnivores, monkeys, and large rodents are the most common taxa. The fauna points to a Middle Pleistocene age (0.2 to 0.8 Ma). Our preliminary palaeoenvironmental reconstruction indicates that our fossil assemblage is derived from a rather wet and closed environment. This condition is unique as sites of this time period were reported to be more open and dry.

Mercury in the River Nura and its floodplain, Central Kazakhstan: II. Floodplain soils and riverbank silt deposits

A unique and serious case of mercury pollution has occurred in the River Nura and its floodplain in Central Kazakhstan, where mercury-rich wastewater from an acetaldehyde plant was discharged largely without treatment for several decades. In the river, the mercury became associated with millions of tonnes of power station fly ash, forming a new type of deposit known as ‘technogenic silt’. During spring floods these highly contaminated silts are transported downstream and are dispersed over the floodplain, leading to widespread contamination of the land. A detailed survey of the floodplain was carried out to investigate the extent of pollution and to assess the need for remediation. Total mercury concentrations in the topsoils of the floodplain ranged from near background levels to over 100 mg/kg. Mercury concentrations in river bank deposits were found to range from a mean of 73.3 mg/kg Hg in the most contaminated section of the river to a mean of 13.4 mg/kg Hg at a distance of 70 km downstream. Concentrations were lower than corresponding concentrations in the riverbed within the first 25 km from the source of the pollution, but thereafter they were significantly higher. The results show that over the past 30–40 years a large proportion of the contaminated sediments from the river was deposited on the 70 km of banks and in the floodplain below the pollution source. Topsoils of the floodplain and silt deposits located on or close to the river banks contain an estimated 53 t and 65 t of mercury respectively, with an additional 62 t in a small natural swamp which was formerly used as a waste disposal area. The contamination is serious but relatively localized, with >70% of the total amount of mercury in topsoils and >90% of mercury in river bank deposits located within 25 km from the source.

Mercury Dispersal from Lode Sources in the Kuskokwim River Drainage, Alaska

The Kuskokwim River is not industrially polluted, but it does have an anomalous mercury content due to cinnabar particles in bottom sediments near natural mineralized sources; the mercury content is rapidly diluted downstream by physical mixing with other sediments. Mercury anomalies extend the greatest distance downstream in the tributaries, the finest size fraction of bottom sediment, the river-bank deposits, the suspended sediment, and water; the last two of these categories contribute the bulk of the mercury to the marine environment.

Bank Erosion in Soils of the Lower Mississippi Valley

Bank erosion along the Lower Mississippi River is dependent on local tendencies of the river to meander and on the geology of riverbank deposits. In the Alluvial Valley, the river erodes its thalweg in sands, and sands and gravels. During the high river stage, bendway pools may be deepened 20 ft to 40 ft or more by seasonal scour. Such periodic erosion may steepen the toes of the banks from stable slopes to unstable slopes that cause subaqueous failures. The subaqueous failures may, in turn, trigger upper bank failures, affecting a layer of cohesive to partly cohesive deposits known as the topstratum. These topstratum deposits respond in certain characteristic manners to oversteepening of the bank slope. In the Deltaic Plain, the river erodes its thalweg chiefly in clays. The surge of water during the high river stage is considerably reduced by distributaries, and erosion is further reduced by the cohesive strength of the clays. Consequently, there is a comparative stability in the river channel.