Sand Accumulation Research Articles

Retreating ice sheet caused a transition from cold-dry to cold-humid conditions in arid Central Asia

Water is critical for ecological systems in arid regions, making it imperative to understand how moisture in arid Central Asia (CA) responds to anthropogenic warming. The oscillation of warming and cooling events since the Last Glacial Maximum (LGM, ∼24–19.5 ka) provides a window for exploring the relationship between moisture and temperature. Employing 109 luminescence ages derived from eight sand dune sediment cores in the Bayanbulak Basin in the CA, this study endeavors to reconstruct the evolution of sand accumulation, and by extension, moisture dynamics. We found that pre-Holocene sand accumulation was predominant during the LGM and Heinrich Stadial 1 (HS1, ∼18–14.6 ka), indicative of a cold-dry climate prevailing during these two cold stages. During the Holocene, sand accumulation during Early Holocene is significantly stronger than that during Middle-late Holocene, supporting a long-term wetting trend. Additionally, this study reveals that the colder Little Ice Age (LIA, ∼0.55–0.2 ka) exhibited a wetter condition compared to the warmer Medieval Warming Period (MWP, ∼1–0.55 ka), indicating a cold-humid climate during the LIA. Corroborated by TraCE-21ka (Transient Climate of the Last 21,000 Years) simulation, we propose that diminished evaporation over North Atlantic during the LGM and HS1 potentially led to a reduction in water vapor transported by westerlies to the CA. During the Middle and Late Holocene, increased evaporation over North Atlantic, attributed to decreased ice sheet, westerlies intensity became the primary limiting factor. Notably, stronger westerlies during the LIA could have contributed to elevated moisture levels compared to the MWP. These findings not only resolve the debate surrounding the transition from cold-dry to cold-humid conditions but also enhance our comprehension of future moisture variations.

Noise reduction performance and maintenance time of porous asphalt pavement

The noise reduction performance of porous asphalt (PA) pavement is significantly influenced by the presence of air voids, which act as sound absorbers. However, factors such as traffic-induced compaction and clogging due to the accumulation of dust, sand, and debris can alter the morphology and quantity of these voids, consequently compromising noise reduction effectiveness. In this study, a comprehensive investigation into the noise reduction capabilities and maintenance requirements of porous asphalt pavement was conducted by a novel approach. Initially, a three-dimensional structural model of the PA mixture was constructed using X-ray computed tomography. Subsequently, this model was integrated into finite element analysis software to develop a "tire-pavement-air" coupled model. It is important to note that in our numerical approach, we have made several simplifications. For instance, the "tire-pavement-air" coupled model was simplified within the air model is set to fully absorbing boundary condition (*Nonreflecting), and the pavement material was assumed to be linear elastic to ensure computational efficiency and convergence of the model. The findings revealed that as the air-void content increased, the average sound pressure level (SPL) of tire/pavement noise exhibited a gradual decrease. Furthermore, when air voids became obstructed due to factors like rainwater and clogging materials, the SPL of tire/pavement noise initially increased with rising air-void content before subsequently decreasing. Notably, porous asphalt with an air-void content of 20 % demonstrated relatively effective noise reduction capabilities. Based on simulation results obtained under varying conditions, including rainfall and clogging, critical thresholds for air-void content were identified to determine recommended maintenance time for PA pavements. Specifically, an air-void content of 17 % was proposed as the threshold for cleaning maintenance, while a content of 14 % was suggested as an indicator for failure alert, respectively. These findings contribute valuable insights into optimizing the design and maintenance strategies for porous asphalt pavements to enhance their noise reduction performance and prolong their functional lifespan.

UAV REMOTE SENSING APPLICATIONS IN BEACH-CLIFF SYSTEM MONITORING OF MORPHODYNAMIC PROCESSES

This study aims to evaluate the morphodynamic changes in a beach-cliff system in northeastern Brazil using high resolution data collected by UAV-SfM techniques to understand the geomorphic changes of the coastal landscape. The study used the Geomorphic Change Detection (GCD) method applied to short-term monitoring. This method uses Digital Elevation Models (DEMs) to determine the morphological changes in terms of both erosion and deposition through DEMs of Difference (DoDs). The difference gridded models are acquired by drone-based remote sensing, which can accurately and efficiently provide ultra-high resolution imagery and digital surface model data to measure volumetric changes. The geomorphic changes are observed on high resolution maps. The multi-temporal analysis revealed significant volumes of erosion and deposition throughout the beach-cliff system over the study period. In the first interval (May/2021 - November/2021), the cliff recorded -8,715 m³ of erosion and 2,816 m³ of deposition, with the beach sector showing erosion in 86% of its area. In the second period (November/2021 - March/2022), more severe erosion rates were observed on the cliff, reaching -10,853 m³ with 51% of its area eroded, while the beach showed the opposite behavior to that previously analyzed, with 73% of the beach experiencing an accumulation of sand and a positive balance of 5,960 m³. The results of this study can be fruitful in identifying the different of geomorphology hazards, coastal impacts of cliff urbanization and in the use of remotely piloted aircraft in coastal monitoring. Furthermore, the results indicate that the management of the beach-cliff system must be integrated and never dissociated, as is generally done by coastal managers. Keywords: Geomorphometry; DEMs; Drone-Based Remote Sensing; Mass Movement; Elevation and Volumetric.

Erosion and Deposition Patterns Over a Wind‐Blown Sand Dune Behind a High Vertical‐Type Sand Fence

ABSTRACTSand dunes are the primary factor influencing wind‐sand disasters. To explore the evolution law of wind‐blown sand dunes surrounding high vertical‐type sand fences along desert railways, numerical simulation analyses based on computational fluid dynamics coupled with a discreet element method of the wind‐sand flow field and sand particles trajectories around sand fences were conducted. The focus of this study was the Yandun section of the Lanzhou‐Xinjiang Railway in Xinjiang, China (42.38°N, 93.95°E). By combining ERA5 wind data with field measurements and monitoring, a three‐dimensional coupling model was established. According to the results of L9 (33) orthogonal tests, the sensitivity of the three factors to the evolution of sand dunes can be ordered as wind speed > porosity > height, indicating that wind speed is closely related to sand dune evolution (p < 0.05). The results of single‐factor tests indicate that the structure of wind‐sand flow fields, sand accumulation patterns, and sand particle movement trajectories vary significantly under different wind speeds. The sand accumulation rates on the windward slope of the sand dune are 29.67%, 25.91%, and 20.04%, while on the leeward slope, these rates are 40.33%, 34.09%, and 29.96%, respectively. The obtained information on the evolution law of sand dunes surrounding high vertical‐type sand fences provides a scientific basis for wind‐sand prevention measures along railways in desert regions.

Implementation of Controlled Floods for Sediment Management on the Colorado River in Grand Canyon Under Aridification

ABSTRACTIn addition to supplying water for agriculture, cities, and industry, the Colorado River traverses the Colorado Plateau, including several of the most unique and valued National Parks and Recreation Areas in the United States. Although the water needs of these landscapes were not considered at the time water allocations were first negotiated, these needs were recognized in subsequent legislation and policy. Management goals address a range of aquatic and riparian resources, including fine sediment (sand, silt, and clay) which, in Grand Canyon, is important for ecological, cultural, and recreational resources. Over ~30 years, stakeholders, resource managers, and scientists collectively developed operational strategies for sediment management to meet goals outlined by an adaptive management program. However, prolonged drought, or “aridification,” resulting in declining runoff and the lowest reservoir storage elevations in decades has challenged those strategies. The paradigm for sustainable sediment management relies on (1) sand accumulation on the bed of the Colorado River during periods of sediment‐rich tributary floods from summer/fall thunderstorms, and (2) dam‐released controlled (artificial) floods, referred to as High‐Flow Experiments (HFEs), to redistribute the accumulated sand to rebuild eroded bar and floodplain deposits. The management protocol, which specifies narrowly defined sand accumulation periods and HFE implementation windows, is based on implementing HFEs in late fall during the period of greatest sediment enrichment, before higher winter releases for hydropower erode the accumulated sand from the riverbed. Low dam releases associated with drought, however, have changed the pattern of sand accumulation and low reservoir elevations have prevented HFE implementation in the defined window. An alternative strategy for HFE planning and implementation was tested opportunistically in April 2023 following lower‐than‐normal winter dam releases. We present findings from this HFE indicating that sand enrichment and sandbar building equaled or exceeded that of HFEs conducted under the established management protocol. These findings show that management goals for sediment under conditions of prolonged drought may be achievable but will likely require substantial changes in dam management strategies.

Investigating the evolution of sand bars and natural channel formation in the Mandovi estuary along the central west coast of India

Coastal formations, such as sandbars, play a vital role in shaping the environment and maintaining local and regional coastal morphology. This study deals with two noteworthy sandbars, namely Aguada and Reis Magos which are in the Mandovi estuary of the Goa region in the central west coast of India. They have attracted great attention because of their dynamics and their role in shaping the adjoining coast. This study employs a comprehensive approach, incorporating in-situ observations and remote sensing methods, to investigate the mechanisms underlying the emergence and dissipation of these sandbars and their linkage with adjoining navigational channels and coastline. During the intense wave conditions of the southwest monsoon (June to September), these sandbars undergo a temporary phase of dispersion. This phenomenon results in the accumulation of sand from both the sandbars and the neighbouring Miramar beach within the navigational channel. As a consequence, it obstructs maritime traffic and forms a unified shallow bar, obstructing maritime navigation in the area. However, following the attenuation of monsoon waves in October to November, the sandbar and beach initiate a gradual replenishment process, aimed at compensating for the sediment loss incurred during the monsoon season. This recurring trend has demonstrated persistent characteristics over an extended period. The presence of the sandbar may pose navigational challenges for large barges, cruise ships, and fishing boats but on the other hand, it serves as an effective barrier against incoming high-energy waves into the inner parts of the Mandovi estuary. Results revealed notable variations in the extent of the sandbar over the study period. The maximum recorded extent of the sandbar was 82.48ha and 32.59ha on May 04, 2021, while the minimum extent was measured at 36.68ha and 7.14ha on February 14, 2019, for Reis Magos and Aguada bar respectively. The sandbar promotes a calm environment along the shoreline and reduces erosion susceptibility by dissipating the wave energy before reaching the riverbanks. The absence of this protective sandbar would have significantly impacted the parts of the Goa region. Notably, the maximum erosion of 107m was observed at the right bank of the estuary, while the maximum accretion of 141m was recorded in the Caranzalem from 1975 to 2023. This study contributes valuable insights into the formation, dissipation, and environmental implications of sandbars within the estuary in Goa. The integration of in-situ observations and remote sensing data affords a comprehensive understanding of sandbar dynamics, highlighting the essential role that they play in coastal protection, navigation and the preservation of the local environment.

Origin of sandy substrates controlling the distribution of open vegetation ecosystems in Amazonia

Understanding the role of open vegetation, particularly in white-sand ecosystems (WSE) and savannas, is crucial for elucidating their role in Amazonian biotic diversification. These ecosystems predominantly develop on sandy terrains, suggesting that the geological substrate significantly influences the vegetation upon it. Therefore, the interaction between landscape changes and biotic diversification is closely tied to the dynamics and resilience of these sandy substrates. Current WSE and savannas in lowland Amazonia colonized fluvial sediments deposited during the past 120 ka, with marked synchronicity over the last 23 ka, as shown by optically stimulated luminescence (OSL) and radiocarbon ages of such sandy substrates. In contrast, sandy substrates supporting open vegetation in highland areas, unsuitable for Quaternary sand accumulation, would have persisted beyond the Quaternary, as ancient sedimentary rocks in these areas are prone to developing sandy soils. The current distribution of open vegetation ecosystems in lowland Amazonia is coupled with the deposition and erosion of sandy sediments by Quaternary fluvial systems, while weathering sandy substrates in highland areas serve as long-term and resilient refugia beyond the Quaternary. The contrasting spatiotemporal dynamics of landscape changes in lowland and highland areas has implications for biodiversification or extinction events leading to current biogeography patterns in Amazonia.

Influence of Terrain on Windblown Sand Flow Field Characteristics around Railway Culverts

Aeolian sand hazards are often a threat to culverts, which are important channels and pieces of infrastructure of the desert railway. In addition to wind speed, wind direction, and culvert structure, terrain may also be an important reason for the formation of culvert sand hazards. However, there are few studies on the effect of terrain on the sediment accumulation characteristics of culverts. This paper established computational fluid dynamics (CFD) models of railway culverts (flat and concave culverts) based on Euler’s two-fluid theory. An analysis of the influence of terrain on the distribution law of the flow fields and sand accumulation around railway culverts was carried out. The results show that the horizontal wind speed curves changes in a “W” shape along the centre axis surface from the forecourt to the rearcourt within a range of 30 m~66.8 m. Low-speed backflow is formed at the inlet and outlet of the culvert, and the minimum wind speed reaches −3.6 m/s and −4.2 m/s, respectively, when the height from the bottom of the culvert is 1.0 m and 1.5 m, resulting in intensified sand sedimentation. In concave culverts, the lower the roadbed height, the easier it is for sand to accumulate at the culvert outlet, the rearcourt, and the track; the sand volume fraction is close to 0.63, affecting the normal operation of the trains. On the contrary, the higher the roadbed, the easier it is for sand to accumulate at the culvert inlet, hindering the passage of engineering vehicles and reducing the function of the culverts. These results reveal that terrain plays a pivotal role in the sand accumulation around culverts and that it should be one of the key considerations for the design of new railway culverts. This work can provide a theoretical basis for preventing and managing sand hazards in railway culverts.

Evaluation of stresses on the surface of production columns equipped with sand filters when downing into a horizontal well

Relevance. The need to estimate the time of formation sand accumulation near the annulus of a horizontal well and the unit length of filter elements in the bottom of production strings and to determine the stresses on the surface of production strings equipped with sand filters when lowering into the well. Aim. Based on a study of the reasons for the continued flow of sand into wells equipped with anti-sand filters, to develop and propose measures related to the need to choose a reduction in the number of filters that provide the design flow rate of a horizontal well or a significant increase in the length of the filtering surface of the filters in order to reduce erosive wear of the wire winding. Objects. We are considering a well with a horizontal section, equipped with sand filters, the same size as the casing strings. It was assumed that the integrity of the surface of the filter elements would be preserved and the conditions for their destruction would be eliminated when lowering into the horizontal shaft. This presupposes the necessary efficient operation of the well throughout the entire operational period. The section of the first set of curvature and the forces arising during this are considered as wellas stability of a pipe string during possible stops. Centralizers are evenly located along the length of the column, then in some sections we will have a multi-span statically indeterminate beam, in each section of which a radial load acts. Methods. When studying the time of formation sand accumulation in the annular space of a horizontal well and a unit length of filter elements in the bottom of production strings, it is necessary at the first stage to determine the stresses on the surface of production strings equipped with sand filters when lowering into the well. Studying the assessment of the existence time of the transition period is of particular interest. This is, in other words, during what operational period there is a complete accumulation of formation sand in the annular space and the transition of formation drainage along the entire length of the horizontal wellbore to drainage of only zones adjacent to the filters. To calculate the fluid flow rate when the annular space of the horizontal well is completely filled with sand, the design values ​​of the AC4.8 formation parameters were used. The maximum value of depressions used in the calculations is assumed to be 1.5 MPa. Results. Consideration of situations that arise when filters are lowered into horizontal wells indicates that the outer surface of the filter elements is not protected from destruction as a result of contact stresses with the walls of the drilled wellbore. To protect against destruction and rubbing open gaps by clay-containing rocks, rigid centralizers should be installed along the edges of the filter elements, the maximum allowable distances between which should not exceed 4.0–4.5 m.

Numerical simulation and field study on predicting wind-blown sand accumulation in sand mitigation measures of the Ganquan railway

The accumulation of sand induced by wind poses a significant challenge to the safety and maintenance of railways in arid and desert regions. Accurate calculation and prediction of sand accumulation are crucial for ensuring continuous railway operation. This research is centered on the region significantly impacted by sand accumulation along the Ganquan Railway. Wind speed, wind direction, and sand carrying capacity data near this section were monitored. Using the collected wind speed, wind direction, and wind-sand flow density data, numerical simulations were conducted using the Computational Fluid Dynamics (CFD) method to predict the amount of sand accumulation within the sand mitigation measures of the Ganquan Railway. Monitoring results indicate that the dominant wind direction in spring and summer is due west, while in autumn and winter it is southwest, with an average wind speed of 12 m/s. A positive correlation was observed between wind-sand flow density and wind speed. The wind-sand flow density above 2 m was nearly zero, indicating that the wind-sand flow structure is concentrated within 2 m from the ground, with an average wind-sand flow density of 3.50×10−5 kg/m3. Through numerical simulation, the characteristics of the wind field and sand accumulation distribution within the calculation domain were determined. A relationship equation between sand accumulation mass and width over time was derived. Initially, the sand accumulation width increases uniformly and then stabilizes, while the sand accumulation mass rises uniformly to a plateau before in-creasing rapidly. From these findings, the optimal period for sand removal was identified as between 350 and 450 days after the sand mitigation measures are put into operation.

Effect of bridge height on airflow and aeolian sand flux near surface along the Qinghai-Tibet Railway, China

In this work, we studied the near-surface flow field structure of railway bridges with different heights through field investigation and wind tunnel simulation experiments. Meanwhile, we simulated the distribution of sand accumulation around a bridge via CFD software based on the sand accumulation around the Basuoqu bridge in the Cuona Lake section of the Qinghai–Tibet Railway. Results show that the sand around this railway bridge is mainly from the lake sediment on the west side of the railway and the weathered detritus on the east side. The height of the railway bridge in the sandy area affects the distribution of the near-surface flow field and the variation in speed on both sides of the bridge. The wind speed trough on both sides of the 6 m high bridge is higher, and the horizontal distance between the wind speed trough and the bridge section is 1.5 times that of the 3 m high bridge. Wind speed attenuates in a certain range on the windward and leeward sides of the bridge, forming an aeolian area; under the beam body, it is affected by the narrow tube effect, forming a wind erosion area. The height of the bridge determines its sand transport capacity. Under certain wind conditions, the overhead area at the bottom of the 3 m high bridge and its two sides do not have the sand transport capacity, so sand accumulates easily. Nevertheless, the sand accumulation phenomenon gradually disappears with the increase in bridge clearance height. The objectives of this study are to reveal the formation mechanism of sand damage for railway bridges, provide theoretical support for the scientific design of railway bridges in sandy areas, and formulate reasonable railway sand prevention measures to ensure the safety of railway running, which have certain theoretical significance and practical value.

Water–salt migration and deformation characteristics in gravelly sulfate saline soil under the effect of localized fine sand accumulation

The water-salt migration law and deformation characteristics of coarse-grained saline soils have been extensively studied and illustrated. However, owing to the influence of the chemical composition and physical properties of the soils, coarse-grained soils are prone to localized soil absorption during mixing and compaction. This type of working condition of the existing localized fine sand accumulation layers is seldom discussed in the literature. In this study, water-salt migration and deformation of natural gradation specimens and specimens with localized fine sand accumulation layers in natural gradation were monitored and detected for the field fill conditions in an airport embankment project using self-designed test equipment based on nine freeze–thaw cycle physical simulation tests at environmental temperatures ranging from −30 °C to 25 °C. Under the freeze–thaw cycle, compared with the natural gradation, the specimens with localized fine sand accumulation layers had a higher influence on water and salt migration, which indicates that the depth range of drastic changes in water and salt increased by 80% and 84%, respectively. The cumulative deformation curves under the effects of natural gradation and localized fine sand accumulation exhibited similar trends. The difference between the deformation of the natural samples and samples with localized fine sand accumulation layers was 16% when the salt content of the upper part of the roadbed was 0.3%. In addition, the cumulative vertical settlement deformation of the specimens decreased with an increase in the salt content of the upper part of the roadbed and gradually transformed into vertical uplift deformation. The results of this study provide a basis for the selection of materials for airport roadbed backfill and their application in construction in seasonally frozen areas.

A predictive formula for determining the clinical significance of colonic sand accumulation in horses

A predictive formula for determining the clinical significance of colonic sand accumulation in horses

High resolution luminescence and radiocarbon dating of Holocene Aeolian silt (loess) in west Greenland

Loess–palaeosol sequences serve as valuable archives of changes in climate and atmospheric mineral dust deposition. However, little work has been conducted on Holocene loess in the Arctic, despite the sensitivity of this region to climate changes. Aeolian silt/loess profiles in the ice-free region of western Greenland near Kangerlussuaq were sampled to develop a robust age framework using both luminescence and bulk organic matter radiocarbon dating. Radiocarbon ages generally show consistent age increases with depth but are likely offset to younger ages due to sediment mixing in the upper 10–20 cm of the profiles. Quartz OSL signals exhibit insensitivity, while low-temperature infrared stimulated luminescence performed at 50 °C (IR50) and the post-IR IRSL at 180 °C (pIRIR180) signals of polymineral fine grain revealed a consistent natural inherited dose of approximately 5 Gy for pIRIR180 and an unbleachable residual of around 2 Gy for IR50, with substantial fading rates in the latter. This led to a notable age overestimation when compared with bulk organic matter radiocarbon ages. To develop an appropriate dating approach, we evaluated the differential bleaching rates of feldspar IR50 and pIRIR180 signals, and corrected for modern inherited doses. Radiocarbon ages measured on the bulk organic carbon oxidised at 400 °C (LT 14C) increased very consistently with depth, allowing calculation of accumulation rates. The presence of the atmospheric radiocarbon bomb signal at depth indicated down-mixing of surface material into the profile, which caused negative (younger) age offsets. The offset-corrected radiocarbon-based age-depth model could be compared to the luminescence results.We show that a combination of LT 14C with polymineral pIRIR180 dating allows the development of age models for these deposits. This multi-chronological approach reveals that loess accumulation in the region was initiated around 4 ka, probably consisting of two main phases of loess accumulation at 4–3 ka and <1 ka. The initial phase matches the proposed onset of aeolian sand activity in the wider region, but post-dates local ice retreat by c. 3 kyr. The more recent phase of accumulation also matches the timing of increased sand accumulation in the region and likely coincides with Neoglacial to Little Ice Age ice advances, or even enhanced dust activity in the last decades.

Archaeological excavations at Sarūq al‐Ḥadīd‐2022–2023 season: stratigraphy and new absolute chronological sequence of Area G

AbstractThe 3‐month excavation conducted in Area G at Sarūq al‐Ḥadīd yielded novel insights into the historical occupation, abandonment and utilisation patterns of the site. The archaeological strata unearthed during our excavation dating span a significant timeframe, ranging from the fourth to the first millennium BC. Employing a stratigraphical approach, we systematically established a relative chronological sequence for the area supported by C14 absolute dating. This methodological framework enabled us to discern the temporal evolution of the site, unveiling pertinent information regarding the nature of occupation, the construction phase of the well and its temporal utilisation and the occurrences of natural phenomena such as climatic disruption, alluvial processes and sand accumulation.

Aeolian sand challenges in desert rail infrastructures, overview of Iran’s experience and advancement

The processes of wind erosion and the movement of dunes have destructive effects on the transportation infrastructure with an emphasis on railway lines. Consequently, the construction and maintenance costs of desert railways will increase under the influence of sand sediment movement. In severe conditions, passing trains can also be affected, compromising their safety and comfort. However, the passage of railway infrastructures through desert areas prone to aeolian sand is inevitable. This research discusses the main challenges encountered by railways in Iran's deserts, including two ultimate and serviceability limit states that affect civil works, track superstructure, rolling stock, and signaling systems. It also examines the mitigating measures implemented in Iran based on the source, transport, or deposition areas of sand dunes. Moreover, the performance of Iran's desert railways has been classified based on wind sand activities. According to the distribution map of Iran's railway network, sand accumulation in the main desert lines has been classified into four levels: very severe, severe, moderate, and low. The research also presents the experience of implementing and monitoring the hump slab track system, which has proven to be a sustainable solution for addressing the dune problem with suitable efficiency over a period of six months.

Dating post-LGM aeolian sedimentation and the Late Palaeolithic in Central Yakutia (northeastern Siberia)

Central Yakutia is a large region in northeastern Siberia characterized by extensive permafrost, large river valleys, mountain glaciers, and large massifs of aeolian sands; the geological history of the region is complex and, at present, poorly constrained. In recent years, it has been shown that aeolian sands cover up to 60% of large parts of Central Yakutia. This paper presents the results of luminescence dating of aeolian sedimentation at the Diring Yuriakh Palaeolithic site located in the middle reaches of the Lena River. Field studies identified several thick units of aeolian sand, which cover an old deflation surface with Late (Duktai culture) and Early Palaeolithic (Diring culture) artefacts. The reliability of the OSL chronology was assessed by comparison of ages based on the optically stimulated luminescence from quartz and the infra-red stimulated luminescence from potassium-rich feldspars; these age pairs are in good agreement, implying that at least the quartz grains were sufficiently bleached before sedimentation. We obtained OSL ages that reflect three periods of accumulation between the LGM and the Holocene: ∼21 ka, 15-14 ka, and 12.5–10 ka. These periods of accumulation broadly coincide with global cooling episodes during the Last Glacial Maximum, the Older Dryas, and the Younger Dryas, with some extension into subsequent warmer intervals, whereas the intervening intervals without preserved sediments are taken to reflect dune stability during warmer periods. The sand on the terraces, sourced from alluvial bars in the river channel, was blown up the valley slope during cold and dry periods when the vegetation cover was sparse. When the climate warmed, the vegetation took some time to spread, and so the accumulation of aeolian sand on the high terraces continued into the warm periods. We also infer periods of deflation (wind erosion) that occurred before 21 ka and between 20 and 15 ka, presumably due to increased aeolian activity and localized remobilization of sediment. The new OSL chronology shows that the younger artefacts located at the cape of Diring Yuriakh, belonging to the Late Palaeolithic Duktai culture, are older than 15 ka. The new ages also show that the post-LGM aeolian sand sequences at Diring Yuriakh are correlated with the regionally developed subaerial Dolkuma Formation.

Machine-learning-assisted seismic prediction of massive (up to 500 m) sands and their geologic meaning: Lower wilcox intraslope basins, south-central Texas, USA

We studied deep (up to 6000 m) Lower Wilcox strata (Guadalupe A) immediately above the Midway shale using a 1000-km2 3D seismic volume and sparse six deep-well, wireline-log data in south-central Texas. Although some of the wells encounter sandstones collectively as thick as 500 m, traditional seismic attributes and seismic inversion are unable to reveal the sign and extent of the massive sand distribution in the intraslope minibasins. A new workflow that incorporates machine learning into seismic lithology and geomorphology was tested for quantitative mapping of sand-content sandstone thickness. The procedure significantly updates current workflows for better geologic and reservoir prediction with higher resolution and accuracy. In addition to good fit to impedance in training wells, results tied gamma-ray and sand-content curves at a blind-test well, ensuring high confidence in stratigraphic and depositional interpretation. The study recognized multiple thick, sandy intraslope minibasins in a 30-km-wide upper slope. Clinoforms on the shelf, erosional channels at the shelf edge, sandy channels, and fans in intraslope minibasins were found to support the interpretation of a unique sediment-disposal system triggered by hyperpycnal flows. Existence of massive sand accumulations in the upper slope zone in the Gulf Coast suggest the existence of another major mechanism of large sand transport during the early Wilcox in a high sea-level stand and possibly a future deep gas play in the area.

Late Pleistocene depositional processes of coastal aeolian deposits and their relationship with environment change on the Changxing Island of Liaodong Peninsula, northeastern China

Coastal aeolian deposits are product of the coupling between aerodynamics and coastal hydrodynamics, which is of great significance for reconstructing aeolian activities and the coastal environmental change. Here, we investigated the coastal aeolian deposits on Changxing Island, northeastern China, using geochemistry and microscopy of the minerals together with the published sedimentological data. The results showed that aeolian deposits are mainly derived from beach sands reworked by wind. Previously published Optically Stimulated Luminescence (OSL) dating results show that the deposition ages of the aeolian deposits are 41 ka, 49 ka, and 67 ka, respectively. The sedimentologic and geochemistry of aeolian deposits are sensitive to climate change. Notably, the micromorphology structure of the surface of quartz sand particles reveals the process of the coastal environment evolution. ∼41 ka, the surface of the grains is characterized by significant subaqueous environments, showing subangular with high relief, large conchoidal fracture, and V-shaped pits. These features correspond to the early sub-interstadial stage of MIS3, characterized by a warm and humid climate and sea level highstand. Under the relative sea level rise, the high rate of sand supply produced by coastal erosion contribute to aeolian deposit formation. In contrast, at 49 ka and 67 ka, the quartz grain exhibits typical aeolian environment features that exhibits subrounded with low relief, upturned plates, and dish-shaped pits, which respond to glacial periods of cold and windy conditions and sea level lowstand. The exposure of abundant sandy material, coupled with lower vegetation cover and strong East Asian winter monsoon (EAWM) contribute to higher sediment availability and sand accumulation. We therefore propose that sediment supply control by sea-level change is the primary reason for coastal aeolian sand deposition under different climatic backgrounds.

Climate-Driven Wave Analysis Reveals Changes in Alongshore Sediment Transport: The Case of the Coastal Zone of a Harbor in Thermaikos Bay (NW Aegean Sea)

The sediment transport along a coastal zone of Thermaikos Bay and the interaction with the coastline were studied in the present research. This study concerns the greater basin of an existing breakwater, for which the sand transport during the time periods 1950–1968 and 2009–2017, before and after the construction of the breakwater, were examined. The breakwater led to sand accumulation behind it, causing the well-known phenomenon of salient. It was revealed that climate change, in terms of wind conditions, significantly affected sediment transport; more specifically, the sand transport during 2009–2017 not only decreased significantly, but also changed its direction, in relation to 1950–1968. Based on the information obtained, technical interventions are proposed for the interception of sediment transport and the consequent accumulation of sand behind the breakwater.