Estuarine Sand Research Articles

Sand Dunes as a Nature‐Based Solution to Mitigate Salt Intrusion in Stratified Estuaries

AbstractSalt intrusion in estuaries can pose a threat to drinking water extraction, irrigation, industries, and ecology. Key factors influencing the salt intrusion length include freshwater river flushing and vertical salt mixing. This study investigates the potential of estuarine sand dunes, that is, large‐scale rhythmic patterns, to serve as a nature‐based solution to mitigate salt intrusion. To this end, we adopt a two‐dimensional vertical (2DV) modeling approach, which numerically solves the flow and salt transport in an idealized single‐channel estuary. By varying the tidal amplitude and river discharge, three types of estuaries are modeled; a salt wedge, a strongly stratified and a strain‐induced periodic stratification estuary. Two types of dune configurations are considered: ’depth‐neutral’ dunes (preserving mean water depth) and ’deepening’ dunes (crest level equal to original bed level, rest of dune profile entirely below). Model results demonstrate that the presence of dunes can effectively reduce the salt intrusion length by several kilometers, compared to the scenario without dunes. Systematically varying dune geometry demonstrates that steeper (higher and shorter) dunes yield a stronger reduction in the salt intrusion length. Deepening dunes have the potential to generate sufficient mixing to overcome the adverse effects of channel deepening and, as such, can mitigate salt intrusion while maintaining navigability. As a naturally existing bedform, estuarine sand dunes present a promising nature‐based solution against salt intrusion without compromising accessibility to seaports.

Discerning sediment provenance in the Outer Banks (USA) through detrital zircon geochronology

Detrital zircon data from modern barrier island and estuarine environments in the Outer Banks (Atlantic Coast, USA) were statistically compared to sands from nearby rivers to assist in determining source-to-sink pathways. Fluvial samples, collected from near the Fall Line contact between the Appalachian Orogen and sediments of the coastal plain, all have age unique distributions, making them ideal for tracing provenance. Three samples from the Atlantic foreshore showed high similarities to one another, as well as to three samples from the estuarine (back-barrier) Pamlico and Albemarle Sounds. Mixture modeling with multiple data reduction methods and three different statistical tests for similarity consistently indicated that the nearby Potomac River was the primary source for all Atlantic foreshore and estuarine zircons, followed by minor contributions from the James River in some models. The models indicate little or no sediment contribution from the Susquehanna, Roanoke, Tar, Neuse, Cape Fear, and Peedee Rivers. Both Atlantic foreshore and estuarine sands are therefore interpreted to have initially originated from Appalachian bedrock to the north of their present-day location, and subsequently to have been transported southward through the Chesapeake Bay watershed before deposition in Virginia and North Carolina. Prior to barrier island formation in the last several thousand years, differing geomorphology of the Chesapeake Bay facilitated southward movement of sediments from its constituent rivers via longshore drift, where they were deposited in coastal settings on the mainland. The modern barrier islands, formed during the most recent post-glacial transgression, may be reworked from these deposits, but may also include a contribution from sediments that were derived more recently from relict deposits on the shelf. Oceanographic and sedimentological evidence suggests that movement of sand-sized grains from southern rivers across the back-barrier sounds is unlikely. These findings can assist with coastal resilience planning and resource management in a region under severe threat from climate change and rising sea levels.

Sediment texture and geochemistry as predictors of sub-depositional environment in a modern estuary using machine learning: A framework for investigating clay-coated sand grains

Sedimentary cores from the Ravenglass Estuary lack some of the sedimentary structures which can be seen in other estuarine sands due to their unconsolidated nature, making it difficult to meaningfully interpret depositional environments using standard sedimentological facies analysis. Here we explore how sediment texture, obtained from laser particle size analysis, and geochemistry, obtained from portable X-ray fluorescence, can be used independently, or in combination, to automatically classify sub-depositional environment and estuarine zone in a modern estuary. We have adapted an established Extreme Gradient Boosting workflow to select the most informative geochemical elements to be included in a training set to automatically classify sub-depositional environment at the surface of the Ravenglass Estuary, NW England, UK. Models that are trained exclusively on textural data significantly outperform those that use geochemical data when classifying sub-depositional environment but are comparable when classifying estuarine zone. However, the combination of textural and geochemical data in training sets improves model performance in all but one class when compared to separate textural and geochemical models. We have applied surface-calibrated combined textural and geochemical models to classify palaeo sub-depositional environment in three cores obtained from a tidal flat in the Ravenglass Estuary that are interpreted to record initial outer estuary deposition which transitioned to an inner estuary setting dominated by deposition from suspension. The subsurface classifications provide a framework to investigate the occurrence of reservoir quality-preserving detrital grain coats which vary in abundance as a function of sub-depositional environment at the surface. A review of literature suggests that the mixed flat sub-depositional environment is an ideal target for optimum clay grain coat occurrence, and we show that this sub-depositional environment is reliably identified by all models. We also discuss the implications of the modelling, how it compares to other machine learning approaches to understand reservoir quality in ancient systems, and how the workflow may be adapted for application to reservoir core. This study demonstrates value in utilising textural and geochemical data in conjunction with machine learning methods to help reveal the environmental evolution of marginal marine sands.

MIGRATION AND WELDING OF AN ESTUARINE BARRIER-SPIT DRIVEN BY DELTA EVOLUTION AND STORMS

As sea levels rise globally in response to anthropogenic climate change, coastal depositional systems that persist in dynamic equilibrium with accommodation space, sediment supply and hydrodynamic processes may begin to respond by redistributing sediment, causing erosion or migration of landforms that may have appeared as stable over previous decades to centuries. In contrast, systems that have adjusted to inherited or changing boundary conditions over historical times offer insights on the modes and timescales of potential future change in remobilised coastal systems. We investigate the coupled evolution of an estuarine sand barrier-spit and tidal delta over the past century, focusing on storm-driven erosion and overwash during recent decades that triggered recurrent barrier migration (rollover), ultimately welding it to the bedrock valley framework. Historical aerial photographs and recent high-resolution satellite and aerial imagery are analysed to map morphological change and calculate decadal trends in shoreline and barrier migration. Ocean wave and water level conditions between image dates capturing notable responses are analysed using wave and tide records from nearby measurement stations.

A preliminary study on the mechanism of the Liangzhu culture’s migration across the Yangtze river

The Liangzhu culture (5300–4200 cal BP) was the most famous Neolithic culture of who settled near the lower reaches of the Yangtze River in China. The core and initial distribution area of Liangzhu originated around Taihu Lake, located on the south bank of the Yangtze River delta. Recently, archaeological studies believe that the Jianghuai area and Huanghuai area north of the Yangtze River are also important distribution areas of Liangzhu culture. The route for Liangzhu culture migrating across the Yangtze River is inferred as follows: One would have crossed the Yangtze River from Nanjing-Zhenjiang belt and continued to migrate northward; while the other would have crossed the River near the estuary before moving north along the ancient coastline to the Jianghuai during the late period of Liangzhu, or crossed the Yangtze River from the east of the present Beijing-Hangzhou Grand Canal to Jianghuai and Huanghuai. According to the formation of the Yangtze River delta during the Holocene and the evolution of the estuarine sand bar, it is believed that there were large shoals in the Yangtze River channel in the middle-Holocene. The Liangzhu ancestors around 5000 cal BP had the ability of making canoes over 8 m. Based on the archaeological research of the Neolithic period, the evolution of the Yangtze River channel in the Holocene, the history of ancient Chinese shipbuilding, and the modern examples of crossing the Yangtze River with boat, it can be concluded that the present Changzhou–Jiangyin–Zhangjiagang line should be the main and reasonable route for the Liangzhu culture migrating across the Yangtze River.

Concurrent 21. Presentation for: Conceptual model of the Lower Permian Kingia Sandstone (northern Perth Basin, Western Australia) as an alternative energy resource

Presented on Thursday 19 May: Session 21 The geothermal potential of the Kingia aquifer in the northern Perth Basin has been identified. In order to further assess resource potential, the occurrence, conditions, and properties of the Kingia Sandstone have been considered further. A new regional correlation supports the Kingia Sandstone being a regionally extensive unit deposited along the northern margin of the syn-depositional Dandaragan Trough. The unit is part of a falling-stage to lowstand system containing lower and upper shoreface, coastal, beach, and estuarine sands. Gross Kingia Sandstone thickness varies from 16 m on flanking terraces to at least 71 m in the basin depocenter. At depth, reservoir properties are preserved where iron-rich clay grain coatings inhibit cementation and preserve primary porosity. In such cases, net reservoir ranges from 3 to 58 m thick (18 m mean) and net porosity range is 12–19 p.u. (15 p.u. mean). The prevailing geothermal gradient is ~37°C/km with heat flow in excess of 90 mW/m2. Resultant Kingia aquifer temperatures exceed 115°C. Given the presence of hot, porous Kingia aquifer, the potential for geothermal power generation is strong. Production of Kingia brine to surface facilities allows for power conversion via established binary Organic Rankine Cycle (ORC) technology. A scalable Kingia opportunity could help to meet Western Australia’s decarbonisation aspirations by contributing to the replacement of coal-fired and gas-fired power plants, plus supply of low-carbon power to local urea, hydrogen, and gas projects. An enhanced understanding of Kingia porosity distribution, reservoir compartmentalisation, flow performance, and ultimate energy delivery remain key uncertainties subject to future de-risking activities. To access the presentation click the link on the right. To read the full paper click here

Conceptual model of the Lower Permian Kingia Sandstone (northern Perth Basin, Western Australia) as an alternative energy resource

The geothermal potential of the Kingia aquifer in the northern Perth Basin has been identified. In order to further assess resource potential, the occurrence, conditions, and properties of the Kingia Sandstone have been considered further. A new regional correlation supports the Kingia Sandstone being a regionally extensive unit deposited along the northern margin of the syn-depositional Dandaragan Trough. The unit is part of a falling-stage to lowstand system containing lower and upper shoreface, coastal, beach, and estuarine sands. Gross Kingia Sandstone thickness varies from 16 m on flanking terraces to at least 71 m in the basin depocenter. At depth, reservoir properties are preserved where iron-rich clay grain coatings inhibit cementation and preserve primary porosity. In such cases, net reservoir ranges from 3 to 58 m thick (18 m mean) and net porosity range is 12–19 p.u. (15 p.u. mean). The prevailing geothermal gradient is ~37°C/km with heat flow in excess of 90 mW/m2. Resultant Kingia aquifer temperatures exceed 115°C. Given the presence of hot, porous Kingia aquifer, the potential for geothermal power generation is strong. Production of Kingia brine to surface facilities allows for power conversion via established binary Organic Rankine Cycle (ORC) technology. A scalable Kingia opportunity could help to meet Western Australia’s decarbonisation aspirations by contributing to the replacement of coal-fired and gas-fired power plants, plus supply of low-carbon power to local urea, hydrogen, and gas projects. An enhanced understanding of Kingia porosity distribution, reservoir compartmentalisation, flow performance, and ultimate energy delivery remain key uncertainties subject to future de-risking activities.

Root Traits and Erosion Resistance of Three Endemic Grasses for Estuarine Sand Drift Control

In southern Taiwan, rivers sporadically cease to flow and dry up in winter. The exposed dry riverbeds are very vulnerable to wind erosion. The strong northeast monsoon often induces serious estuarine sand drift and fugitive dust, which cause damages to agricultural crops, human health and infrastructures. Giant reed (Arundo formosana), common reed (Phragmite australis) and the wild sugarcane (Saccharum spontaneum) are pioneer grass species in estuary areas. They have great potential to reduce wind erosion and control windblown dust on agricultural lands. Nevertheless, their root traits, biomechanical characteristics and wind erosion resistance have not been investigated. In this research, the root traits were investigated utilizing the hand digging technique and the WinRHIZOPro System. Root pullout resistance and root tensile strength were estimated using vertical pullout and root tensile tests. Wind tunnel tests were executed to evaluate the wind erosion resistance using six-month-old plants. The results demonstrated that the growth performance and root functional traits of S. spontaneum are superior to those of A. formosana and P. australis. Additionally, the root anchorage ability and root tensile strength of S. spontaneum plants are notably greater than those of A. formosana and P. australis plants. Furthermore, the results of the wind tunnel tests showed that the wind erosion resistance of A. formosana is remarkably higher than those of S. spontaneum and P. australis. This study demonstrates that A. formosana and S. spontaneum are superior to P. australis, considering root traits, root anchorage ability, root tensile strength and wind erosion resistance. Taken together, our results suggest that S. spontaneum and P. australis are favorable for riverbed planting, while A.formosana is applicable for riverbank planting in estuary areas. These results, together with data on the acclimation of estuarine grasses in waterlogged soils and brackish waters, provide vital information for designing planting strategies of estuary grasses for the ecological engineering of estuarine sand drift control.

Syn-depositional oil seeps in the Late Albian Paddy Member of the Peace River Formation (Early Cretaceous), north-central Alberta

Abstract Controversy exists regarding the timing of emplacement of oil in the giant Athabasca and Peace River oil sands. Bitumen-cemented sandstones are present in the late Albian Paddy Member of the Peace River Formation; some cemented sandstones formed burrowed firmgrounds and reworked intraclasts, showing that oil was reaching surface by about 101–102 Ma. Estuarine and shallow-marine sandstones of the Paddy Member are exposed on the Peace and Heart rivers in the vicinity of the town of Peace River. Bitumen-cemented sandstone occurs in four stratigraphic settings: 1) An in-situ cement forms locally bedding-transgressive, sheet-like masses in cross-bedded estuarine sandstone; 2) A bitumen-cemented and heavily burrowed layer, 30–60 cm thick, lies immediately beneath a marine transgressive surface and shows that oil infiltrated downward into, and cemented, the upper surface of a shoreface sandbody. The firm sand was subsequently exhumed by transgressive erosion, fractured and burrowed by arthropods; 3) Rounded pebble- to cobble-sized clasts of bitumen-cemented sand lie on the floor of a tidal channel, and the channel floor surface is also stained and burrowed. This case suggests floating oil infiltrated the channel floor at low tide, subsequently hardening prior to erosion and burrowing; 4) Rounded cobble-to boulder-size clasts of bitumen-cemented sandstone, up to 1 m wide and 0.5 m thick, lie on a regional marine ravinement surface cut on the uppermost Paddy shoreface sandstone. The sand was permeated with oil, top-down, then oxidized to form a tough bitumen cement. The bituminous sand was subsequently scoured by waves during marine transgression to form a boulder lag that is enclosed in transgressive marine claystone. All four of these examples show that oil was reaching the Earth’s surface during Paddy time where it infiltrated porous sands to a depth of several decimetres, subsequently degrading and oxidizing to form a tough ‘asphalt pavement’ that attracted a burrowing firmground fauna and was eroded into cohesive intraclasts weighing many tens of kilograms. Pyrolysis proved the bitumen cement to be degraded oil, but it was not possible to identify the source-rock using gas chromatography-mass spectrometry. The Paddy ‘asphalt pavements’ are comparable to cements that form in beach sediments in the wake of catastrophic spills from tanker groundings. A direct analogue is provided by Eocene estuarine sediments in Dorset, U.K. There, bitumen-cemented estuarine sands also formed firmgrounds and intraclasts on channel-floor and marine transgressive surfaces.

Reworking activity of the thalassinidean shrimp Trypaea australiensis Dana, 1852 (Decapoda: Pleocyemata: Callianassidae) in an Australian estuary: A pilot study

Abstract Trypaea australiensis Dana, 1852 is the predominant bioturbating thalassinidean shrimp on the east coast of Australia. It is, like other large bioturbators, generally considered an important ecosystem engineer. The sediment particle reworking rate of thalassinideans, a key parameter in benthic biogeochemical modelling, nevertheless remains unknown. We have for the first time quantified particle reworking by a population of T. australiensis living in fine estuarine sand. The particle reworking rate was monitored for 18 days using coarse sand as a new tracer approach followed by analyses of grain-size distribution in the sediment to a depth of 24 cm. Burial depth (BD, cm) over time (t, days) followed the relationship BD = 0.3002 × t for an average population density of 96 individuals m–2, equivalent to a sediment displacement of 1.1 m3 m–2 yr–1 (11.4 liters individual–1 yr–1). The individual-specific particle reworking by this thalassinidean is higher than that reported for most other key bioturbators, and its engineering impact on estuarine sediments therefore has potentially large consequences for biodiversity and ecosystem functioning.

Gravitational Circulation as Driver of Upstream Migration of Estuarine Sand Dunes

AbstractSand dunes are large‐scale rhythmic bed patterns commonly occurring in sandy shelf seas, estuaries and rivers. Field observations of sand dunes in the Gironde estuary (France) have suggested that the gravitational circulation may cause seasonal reversal of asymmetry, which is linked to migration direction. In this study, we aim to unravel the influence of gravitational circulation on the migration of estuarine sand dunes. To this end, we present an idealized process‐based sand dune model with tide and river forcing, and the addition of a longitudinal salinity gradient (imposed diagnostically) that induces gravitational circulation. Linear stability analysis shows the emergence of dunes from a flat bed and confirms that reversal of dune migration may occur, provided the gravitational circulation is sufficiently strong compared to the river flow velocity. Lastly, we show that the migration direction of estuarine sand dunes is not necessarily the same as the direction of net sediment transport.

The Late Quaternary geological history of the lower Sydney estuary (Australia)

Sydney estuary is a dendritic, drowned river valley on the mid-east coast of Australia and comprises an upper and central section of narrow, sinusoidal channels and embayments and a wide, more marine lower estuary. The current work considered only the lower estuary.Minimal research has been undertaken into the structure of the lower Sydney estuary and previous attempts to integrate geologic and geophysical information are limited. The current study combines previously uninterpreted seismic records and poorly-accessible borehole data into a Late Quaternary history of the lower estuary.High-resolution, continuous reflection seismic (212-line km) interpretation matched borehole-based stratigraphy reasonably well. A bedrock paleo-valley deepened from approximately 40 m below present sea level (bpsl) at the Sydney Harbour Bridge (SHB) to > 90 m bpsl at the estuary mouth. Stratigraphy was dominated by two estuarine sequences, which, in the lower part of the estuary comprised mainly fine-grained, organic-rich sediments with peat, that manifest as multiple, strong dark and light-reflectors on seismic. At the SHB, the upper estuarine sequence developed into a transgressive marine to tidal delta deposit. A thin veneer (up to 10 m) of Modern estuarine sands mantled most of the lower estuary. The elevation of the estuarine sediments at approximately present-day levels and at 20 to 30 m bpsl respectively, strongly indicated deposition during periods of high-level marine transgression, i.e. the Last Interglacial (Marine Isotope Stage, MIS 5.5) event at 130 kyPB to 115 kyBP and the Penultimate Interstadial event (MIS 5.1 at 110–80 kyBP), respectively.Late Pleistocene aeolian sands contributed sediment in the south of the estuary, and remobilisation may have dispersed these sediments more widely. Present-day bathymetric features frequently reflected subsurface erosional structures due to starvation of bedload sediment.

Sedimentary characteristics and evolution process of the Huangqiao sand body in the Yangtze River Delta, China

Sea-level rise and reduced sediment loads have caused erosion in the Yangtze River Delta, which is one of South Asia's largest deltas. Scholars have not reached a consensus regarding the origin and timing of the Yangtze River Delta formation, mainly because of the scarcity of cores at the bottom of the delta. In this study, we recovered three sediment cores from the Huangqiao sand body. We systematically analyzed their parameters, including sedimentary characteristics, down-core changes in grain size, benthic foraminifera and ostracod assemblages, AMS14C dating, and optically stimulated luminescence dating. We also integrated our results obtained with data from previously studied cores of the Yangtze River Delta. Four depositional systems were identified in the Huangqiao sand body: a fluvial system dated 12–10 ka that includes sandy gravel in incised valleys and hard clay in paleo-interfluves; an estuary dated 10–7.5 ka that is characterized by sand-mud couplets in valleys and tidal floodplains in the other regions; a deltaic system dated 7.5–4 ka; and a delta or estuary dated 4–0 ka, which included tidal flat and delta plains. The stratigraphic architecture and origin of the paleo-Yangtze estuary (bottom of the delta) were mainly controlled by Holocene sea-level changes. The timing of transgression at the bottom of the Yangtze River Delta was different due to differences in the post-glacial paleontography during the early Holocene. Compared to the Yangtze River Delta records, the Huangqiao sand body lies between 7.5 and 4 ka. The age of the main body was affected by sea-level fluctuations and developed from 5 to 4 ka with sediment loads carried by the Yangtze River. The Huangqiao sand body is not an estuarine sand body but a sand body formed in a tide-dominated delta. This study provides new evidence for interpreting the origin and evolution of the Yangtze River Delta.

Sedimentary transition of the Yangtze subaqueous delta during the past century: Inspiration for delta response to future decline of sediment supply

How the Yangtze delta responds to riverine sediment decline has become a hot research topic and an urgent issue to be addressed, especially after the impoundment of the Three Gorges Dam in 2003. This study investigated sedimentary features through the sediment granularity of surficial samples and short cores over the entire Yangtze subaqueous delta, aiming to better understand the spatial response of the subaqueous delta to sediment supply decline and local hydrodynamic adjustment of the estuary. The results show that four sedimentary zones of estuarine sand bar (Zone I), prodelta (Zone II), delta-shelf transition zone (Zone III) and residual sand (Zone IV) are distributed from the estuary to the shelf, characterised by first fining from zone I to zone II, and then coarsening from zone II to zone IV on grain size of surficial sediments. In the past few hundred years, the subaqueous delta has been generally prograded seaward following this sedimentary system spatially, manifested by generally fining upwards in the cores of the main subaqueous delta. However, sediment coarsening occurs on the top of the cores in the delta-shelf transition zone (Zone III), implying a recent retrogradation process. Based on the results of 210Pb and 137Cs, the sedimentary transition from progradation to retrogradation occurred since 1950s and was intensified after 1980s in the north part of Zone III, mainly caused by channel shrinking of the North Branch and riverine sediment decline. Comparatively, such a sedimentary transition is not significant in the south part of Zone III. But it is worth noting that surficial coarsening in the core (of the south part of Zone III) is probably related to drastic sediment decline since 2003 when the Three-Gorges Dam closed, which means that the Yangtze subaqueous delta has probably been in a full sedimentary transition. The sedimentary transition of the north subaqueous delta can provide an insightful reference for the sedimentary response of the Yangtze delta to further decline of sediment supply in the future.

Experimental formation of clay-coated sand grains using diatom biofilm exopolymers

Abstract In sedimentary environments, clay and sand are segregated by hydrodynamic processes. Yet, clay coats, thin clay envelopes lining sand grains, are abundant in modern and ancient coastal sedimentary deposits. Here, we present laboratory experiments in which we produced clay-coated quartz sands similar to those observed in modern and ancient estuarine sands. These coats were produced at ambient temperature by mixing exopolymeric substances (EPS) derived from intertidal diatom biofilms with clay minerals and quartz reference materials. The imaging of sediment-EPS mixes using cryo–scanning electron microscopy and atomic force microscopy demonstrated that EPS form organic bridges between clay and quartz. The physicochemical properties of the EPS were characterized independently through wet chemical assays and Fourier transform infrared spectroscopy. The results indicated that several EPS components (e.g., proteins, polysaccharides) had a potential to complex with quartz and clay. Our findings provide novel insights in the importance of biofilms in the aggregation of clay and sand. Detrital coats from ancient estuarine sandstones show textural similarities to the experimental clay-EPS complexes and could be considered as biosignatures of biofilm development and EPS production in past environments.

Early Pleistocene conifer macrofossils from Happisburgh, Norfolk, UK, and their environmental implications for early hominin occupation

Continuing coastal erosion in the vicinity of Happisburgh in north Norfolk has revealed archaeological sites documenting early human presence during at least two episodes in the Early and early Middle Pleistocene. At Happisburgh 3, the oldest archaeological site in northern Europe (approximately 900,000 years old) finds include at least 80 flint artefacts and human footprints associated with abundant, well-preserved organic remains. The deposits consist of gravels and estuarine sands and silts contained within a complex of channels, which accumulated in the estuary of a large river, probably the ancestral River Thames. The environmental remains reflect a slow-flowing tidal river, at the limit of tidal influence, and a grassland valley bordered by conifer-dominated woodland. Analyses of the pollen, wood, cones and leaves have identified a diversity of coniferous taxa, with some unexpected central and southern European elements (Pinus mugo ssp. mugo, Pinus mugo ssp. rotundata and Juniperus thurifera) indicating a type of coniferous woodland no longer present in Europe today. Here we present the conifer finds and their environmental implications. A new multi-proxy consensus palaeoclimate reconstruction, using conifer and beetle mutual climatic ranges, confirms and refines previous indications of a more continental climate than today, with significantly colder winters. These results provide a new perspective for understanding the climate and environment encountered by Early Pleistocene hominins at the northernmost limit of their range.

Quantifying effects of water and sediment regulation scheme on the sand bar in the yellow river estuary in 2014

Water and sediment regulation scheme (WSRS) is an annual water conservancy project which aims to alleviate sand depositions and reduce flood risks in the Yellow River of China since 2002. There are few researches on the sand bar within Yellow River tail channel and its estuary from each WSRS effect, though these relative researches are important to be carried out for a better understanding of WSRS. By interpreting two GF-1 satellite images in the end of 2013 and the start of 2015 after carefully controlling some potential bias factors from the change of water level, precipitation or tidal, we compared and analyzed the change of sand bars by one WSRS implemented in 2014 in this paper. Our results indicated this WSRS changed obviously the area/shape of sand bars. It made the area of the river sand bar decreased totally by 5.55 km2, while the estuarine sand bar increased by 2.08 km2. And it achieved the highest scour efficiency (90.11%) in the straight channel, but it achieved the lowest scour efficiency (44.71%) in the more bends channel. From the prospect in the change of estuarine sand bar, the west side area increased, while the east side area shrank. There were some broken small sand bars on the north side and they were forming a large sand bar.

Multi-Decadal to Short-Term Beach and Shoreline Mobility in a Complex River-Mouth Environment Affected by Mud From the Amazon

On the 1500 km-long mud-dominated Guianas coast of South America, between the mouths of the two mega-rivers, the Amazon and the Orinoco, debouch numerous small rivers draining the humid tropical/equatorial Guiana Shield. The geomorphic development of the mouths of these rivers reflects interactions among water discharge, fluvial sediment load, and the alongshore migration of Amazon-derived mud banks alternating with inter-bank areas. The mouth of the Maroni River, astride the French Guiana-Suriname border, shows advanced estuarine infill and geomorphic development characterized by a western (downdrift) side comprising numerous recent cheniers and an eastern (updrift) side bound by an old (> 2000 years B.P.) chenier. A multi-decadal analysis of the beach bounding this chenier shows little net overall mobility notwithstanding significant decadal to sub-decadal variation. The overall stability reflects the diversion of sand supply from the Maroni River towards the downdrift coast and limited sand supply by the smaller Mana River further east, and the south bank of which was contiguous with this beach. The variability in beach multi-decadal mobility reflects the influence, on waves, of alongshore-migrating banks (strong wave dissipation, limited beach mobility) and inter-bank areas (limited wave dissipation, larger beach mobility), highlighted by a comparison, in the current bank phase, of offshore and inshore waves. Erosion of the beach between 2011 and 2017 coincides with the sealing of the mouth of the Mana by muddy progradation in 2011 and mouth relocation several kilometers eastward. The morphodynamics of the beach and shorter-term fluctuations in budget are related to: (1) interaction with estuarine sand dunes mobilized by strong tidal currents on the adjacent shallow shoreface, (2) the influence of the Maroni channel, and (3) rapid encroachment of the leading edge of the shore-attached mud bank on the eastern part of the beach. The beach morphodynamics and evolution highlight, thus, embedded levels of influence: the Maroni at the local scale, and the net westward sediment-transport system and bank and inter-bank alternations that affect the Guianas coast at a regional scale. The recent erosion poses a threat to the local communities by reducing beach space available for recreation and turtle-nesting.

Compositional variation in modern estuarine sands: Predicting major controls on sandstone reservoir quality

Primary depositional mineralogy has a major impact on sandstone reservoir quality. The spatial distribution of primary depositional mineralogy in sandstones is poorly-understood and consequently empirical models typically fail to accurately predict reservoir quality. To address this challenge, we have determined the spatial distribution of detrital minerals (quartz, feldspar, carbonates and clay minerals) in surface sediment throughout the Ravenglass Estuary, UK. We have produced, for the first time, high resolution maps of detrital mineral quantities over an area that is similar to many oil and gas reservoirs. Spatial mineralogy patterns (based on x-ray diffraction data) and statistical analyses revealed that estuarine sediment composition is primarily controlled by provenance, i.e. the character of bedrock and sediment drift in the source area. The distributions of quartz, feldspar, carbonates and clay minerals are primarily controlled by the grain size of specific minerals (e.g. rigid versus brittle grains) and estuarine hydrodynamics. The abundance of quartz, feldspar, carbonates and clay minerals is predictable as a function of depositional environment and critical grain-size thresholds. This study may be used, by analogy, to better predict the spatial distribution of sandstone composition, and thus reservoir quality in ancient and deeply-buried estuarine sandstones.

Influence of Oil Sands Composition on Bitumen Quality During Non‐Aqueous Bitumen Extraction from the Athabasca Deposit

ABSTRACTThe aim of the present work is to identify the most important species affecting a non‐aqueous bitumen extraction process and bitumen quality. This investigation was carried out on four petrologic end member samples from Syncrude's North Mine collected in 2012 (NM12), i.e., marine claystone (MC), marine sand (MS), estuarine claystone (EC), and estuarine sand (ES). Each end member was separately mixed with cyclohexane at a ratio of 40:60 (cyclohexane:end member), and the bitumen‐cyclohexane solutions were collected at different settling times (1–30 min). These solutions were analyzed to determine the amount, particle size distribution, and mineralogical composition of suspended fine solids (SFS), water content, as well as the bitumen content using a focused beam reflectance measurement (FBRM) particle size analyzer, Karl Fischer (KF) titration, x‐ray diffraction (XRD), quantitative XRD (QXRD), and elemental analysis. The SFS was composed of mainly illite and kaolinite after cyclohexane extraction from MC, MS, EC, and ES. Although mixed layer expandable clay minerals (i.e., illite‐smectite and kaolinite‐smectite) were identified in the original clay, end members (EC and MC), illite‐smectite, and kaolinite‐smectite were not observed in the SFS of the bitumen‐cyclohexane solutions obtained from the four petrologic end members. The SFS content and bitumen quality of the bitumen product were affected slightly but significantly by the end member composition and settling time, respectively. Illite and kaolinite were identified as the main minerals in the SFS of the bitumen products after relatively long settling times.