Search

The Stimson formation is a late‐infilling eolian sandstone in Gale crater, Mars that formed from sand accumulation in a dune field analogous to the modern active Bagnold dune field, enabling a unique opportunity to compare the past to the present dune fields on Mars. Previous work suggested that the Stimson has a coarser grain‐size distribution than the active Bagnold dunes based on three images of the Stimson. We analyze grain size in the Naukluft and Emerson plateaus of the Stimson by observing 115 images throughout the formation to classify textures and quantitatively measuring grains in eight representative individual images. Results indicate that the Stimson has a primary grain size mode at <200 μm. In addition, more than 50% of the observed Stimson rock targets display a coarser grain population with a long‐tailed distribution including grains ∼600–1200 μm. The primary grain size mode is similar to that observed in the Bagnold dunes, but the coarse grain size mode was neither observed in the Bagnold dunes nor in ripples adjacent to the dune field. Models for saltation mechanics indicate that the favored grain size for eolian transport on Mars, ∼100–200 μm, is independent of atmospheric density, though atmospheric density affects the wind speeds at which grains can be transported by winds. We conclude that the source of the Stimson dunes was more proximal and coarser than the source of the Bagnold dunes and that the paleoatmosphere was likely not significantly denser than the modern Martian atmosphere. Plain Language Summary: The Curiosity rover on Mars observed ancient cemented sand‐dune deposits called the Stimson formation near the modern and active Bagnold dunes. These observations provide a unique opportunity to compare past and present environments on Mars. Here, we present measurements of the size of sand grains in the Stimson deposits to compare with previously published measurements of the active Bagnold sands. We minimize bias by using observations from two cameras to find proportionate contributions of texture groups and quantify grain sizes for each texture group. We find that more than half of the images of Stimson deposits contain grains that are coarser than the coarsest grains observed near the modern sand dunes. Previous work hypothesized that these coarser grains could imply that the Stimson dunes formed under either a denser or a thinner atmosphere. We use sediment transport theory and observations to show that the atmosphere was likely similar to modern Mars. Instead, the coarse grains reveal that there must have been a supply of coarse grains nearby when the Stimson dunes formed, likely from eroding riverbeds. Cementation of the Stimson dunes required the presence of liquid water and may thus have required a denser atmosphere, possibly indicating cyclic atmospheric changes through time. Key Points: Comparing ancient and modern windblown sediments enables the study of Mars' eolian environments through timeAbout half of the targets in the Stimson sandstone contain a coarse fraction of grains (>500 μm) that is not observed in the modern Bagnold dunesThe presence of coarse grains in the Stimson necessitates a proximal coarse‐grained source [ABSTRACT FROM AUTHOR]

• The CO is one of the thickest tuff beds known for the Santa Cruz Formation. • CO tuff represents aeolian processes. • CO tuff includes a rich and diverse mammal assemblage. • The formation of the assemblage can be linked to a normal attritional model. • Biotic and abiotic processes conditioned the taphonomic history of the remains. The CO tuff is one of the volumetrically largest volcaniclastic events so far recorded in the Early-Middle Miocene Santa Cruz Formation (Patagonian Argentina). It represents aeolian processes, related with westerlies, that reworked and transported enormous quantities of volcanic ash from the Andes into the continental interior that accumulated in fluvial floodplain deposits. This volcanic event generated a major environmental change at ∼17 Ma (Burdigalian) and hostile living conditions for the biota of the area, at least during the time of deposition. We performed here a comprehensive study including taxonomic, sedimentological, and taphonomic aspects of the mammal assemblage recovered from this tuff deposit. The assemblage is constituted by representatives of Microbiotheria, Paucituberculata, Folivora, Cingulata, Rodentia, Notoungulata, and Litopterna, reflecting a wide mammalian diversity. The formation of the assemblage can be linked to a normal attritional model, in which the death of the individuals and subsequent deposition and burial of their remains would have occurred gradually over time, simultaneously with the accumulation of volcanic ash, at the place of death or very close to it. The time between the death and burial would have been relatively short, in accordance with the rapid and continuous influx of volcanic ash to the depositional environment. This multidisciplinary study allows us to interpret and reconstruct the possible taphonomic pathways of the mammal assemblage and to provide novel information on this particular preservation context linked to volcanically-influenced fluvial environments. [ABSTRACT FROM AUTHOR]

This study investigated wind erosion and soil particle distribution at the Sakaka Solar Power Plant in Saudi Arabia, assessing the potential impacts on solar panel efficiency and site management. Soil samples from various locations within the site were analyzed using a sieve-based approach and log-normal function fitting to characterize particle size distributions. The analysis revealed two consistent size modes across all samples: a primary mode centered around 524 μm and a secondary mode at approximately 168 μm, with an additional fine sand population around 100 μm. Wind erosion and soiling events were monitored using big spring number eight (BSNE) sediment samplers strategically placed around the site. Results showed significant spatial and temporal variations in sediment fluxes, with the highest rates observed in the West (149.05 kg/m), Southwest (47.14 kg/m), and Northwest (9.42 kg/m) sectors. The total drift during the study period was 205.61 kg/m, with 66% of the annual total occurring between May and August, aligning with the region's known wind patterns. Detailed analysis of erosion events revealed that the western quadrant of the site consistently experienced the highest erosion fluxes, up to 13 times greater than those in the southern quadrant during peak events. The effectiveness of existing erosion control measures, such as a sand ridge 180 meters upwind of the western boundary, was found to be limited, reducing sand flux by only 58% at the nearest monitoring station. These findings highlight the critical need for targeted erosion mitigation strategies, particularly along the western perimeter of the solar plant. The study underscores the importance of considering soil texture and local wind patterns in the assessment and management of wind erosion risks at solar power installations in arid environments. [ABSTRACT FROM AUTHOR]

This work aimed to investigate the abrasion of quartz grains from beach and dune deposits on the Mediterranean coast of Andalusia. Five sites were established on the coasts of Malaga and Almeria provinces: Genoveses, Monsul, Carraca, Malagueta, and Artola. Grain size and mineral composition were determined for 15 samples taken from beaches (6) and dunes (9). Quartz abrasion was established using the morphoscopic method. Investigated deposits, with two exceptions, are primarily medium-grained and moderate sorting. The share of quartz is relatively small – in aeolian sands, it is on average 38.3% and is higher than in beach sands (average 26.4%). The average proportion of fresh and angular NU grains is significantly higher in aeolian sands (58.9%) than beach sands (43.4%), indicating morphoselection’s important role during wind transport. In beach sands, there are, on average, 32.4% of grains with aeolian abrasion (RM and EM/RM), which is twice as much as in dune sands (15.5%). The multiple predominances of EM/RM grains over RM grains indicate a relatively short aeolian activity.

Coastal regions globally face escalating challenges from climate change, including rising sea levels and intensified storm events. To address these threats, coastal resilience emerges as a critical paradigm advocating the integration of nature‐based solutions with traditional engineering approaches. Coastal dunes, acting as protective barriers, offer a promising avenue. This three‐year study assesses the efficacy of an artificial dune system to address local sand‐related nuisances on the adjacent seawall featuring planted marram grass in Oosteroever, Belgium. The focus is on understanding sediment accumulation, dune morphology and vegetation development. The results demonstrate a significant increase in dune height, reaching up to 2 m in the zones planted with marram grass, surpassing the height of the adjacent seawall. Comprehensive profiles and drone surveys revealed consistent dune growth of 27 m3/m, which contrasted with the substantial erosion in the adjacent unvegetated beach areas of up to 30 m3/m. One storm event caused dune toe erosion of 1.5 m3/m, but the dune demonstrated rapid recovery through natural aeolian processes. Marram grass development was not impacted by the initial planting configuration and density and was more pronounced at the perimeter edges of the dune. This study highlights the success of the 'dune‐in‐front‐of‐a‐dike' approach, offering insights for sustainable coastal resilience strategies. [ABSTRACT FROM AUTHOR]

This article reviews the literature covering the period from 1965 to 2020 dedicated to the issue of artificial beach nourishment along the Polish coast, with a particular focus on the Hel Peninsula. The primary sources used in this work include 34 reports from unpublished case studies and projects implemented by the Department of Maritime Hydrotechnics, Maritime Institute in Gdańsk, between 1971 and 2020. This paper also presents detailed information about the total fill volume in cubic meters of dredged material deposited along the Polish coast and lagoon shores in 1980–2020. During these 40 years, approximately 40.5 million m3 of sediment was deposited along the Polish coast and lagoon shores. Particular consideration was given to beach fills along the Hel Peninsula, which was at actual risk of breaking in its basal and central sections after intense storms at the turn of 1988 and 1989. The survey materials collected enabled the assessment of the coastal morphodynamics of the peninsula under the Coastal Protection Program through the prism of changes in the fill volume along the coastal sections, which were replenished with material coming from submarine deposits. The peninsula's stability was also assessed, taking into account the ongoing climate change. Moreover, this article discusses the proposed rules and terms for protecting the Polish coast by way of artificial nourishment. [ABSTRACT FROM AUTHOR]

Arid and semiarid ecosystems around the world are often prone to both soil salinization and accelerated soil erosion by wind. Soil salinization, the accumulation of salts in the shallow portions of the soil profile, is known for its ability to decreases soil fertility and inhibit plant growth. However, the effect of salts on soil erodibility by wind and the associated dust emissions in the early stages of soil salinization (low salinity conditions) remains poorly understood. Here we use wind tunnel tests to detect the effects of soil salinity on the threshold velocity for wind erosion and dust production in dry soils with different textures treated with salt‐enriched water at different concentrations. We find that the threshold velocity for wind erosion increases with soil salinity. We explain this finding as the result of salt‐induced (physical) aggregation and soil crust formation, and the increasing strength of surface soil crust with increasing soil salinity, depending on soil texture. Even though saline soils showed resistance to wind erosion in the absence of abraders, the salt crusts were readily ruptured by saltating sand grains resulting in comparable or sometimes even higher particulate matter emissions compared to non‐saline soils. Interestingly, the salinity of the emitted dust is found to be significantly higher (5–10 times more) than that of the parent soil, suggesting that soil salts are preferentially emitted, and airborne dust is enriched of salts. Plain Language Summary: In this study we investigated how the use of slightly saline irrigation water may affect soil susceptibility to wind erosion and the dust emission potential of dry soils, and how these processes are affected by the amount of clay in the soil. Results indicated that, even though salinity decreased the susceptibility of soils to wind erosion due to aggregation and crust formation, abrasion by sand particles resulted in the breakdown of saline crusts, leading to emissions comparable or sometimes even higher to those of non‐saline soils. The higher salt concentration found in the dust than in the dust‐emitting soil suggests that the airborne transport of salts may have important implications for contaminant transport and salinization of downwind areas. Key Points: Threshold velocities for wind erosion increase with increasing soil salinity because salts induce the formation of a soil crustCrust formation and aggregation can delay dust emission from soil surfaces even under low salinity conditionsSalts are preferentially emitted and amplified in airborne dust [ABSTRACT FROM AUTHOR]

Coastal dunes are found along the sandy coasts of oceans, seas, and large lakes all around the world. They are dynamic landforms that evolve along complex morphological and biological continua in response to a range on controls linked to climate, sea level, sediment movement, vegetation cover, and land use. By collating research across the full spectrum of processes shaping different types and sizes of dunes and smaller aeolian bedforms, special issues can aid researchers to identify new research directions and methods emerging from the discipline. This editorial summarizes the 25 contributions to the special issue Coastal dunes: links between aeolian processes and landform dynamics. We grouped the contributions into four broad themes: (1) long‐term dune evolution, (2) short‐term aeolian transport, (3) research methods, and (4) coastal dune management. Contributions to the special issue demonstrate that research interest in coastal dunes, and particularly the impacts of human interventions on dunes, continues to grow. It also shows how aeolian research on coastal dunes covers a range of temporal and spatial scales, from ripple dynamics and instantaneous airflow‐transport processes to dune field evolution with rising sea levels and large‐scale dune stage shifts. We highlight potential avenues for future research including vegetation roughness characteristics and their effect on wind flow and sediment transport, the challenges of upscaling short‐ and small‐scale results to larger and longer spatiotemporal scales, and the study of both natural and managed dune landscapes. [ABSTRACT FROM AUTHOR]

This article presents the degree of aeolization of Pleistocene deposits in the foreground of the European sand belt in southern Poland. Ten of the 13 sites were established in the Oświęcim Basin and three in the south part of the Silesian Upland. Attention was focused on four types of deposits formed during three glaciations (Sanian, Odranian, Vistulian): boulder clay, fluvioglacial sands and gravels, end moraine deposits, and aeolian sands. Quartz grain abrasion (for the 0.8–1.0 mm fraction) was examined by mechanical graniformametry and the morphoscopic method. The record of aeolian processes in analyzed deposits is the presence of quartz grains RM (very well-rounded and mat) and EM/RM (moderately rounded and mat). They were found in deposits of various origins and ages but in variable proportions. Considering only the average percentage of grains RM, it should be regarded that abrasion of deposits is low in the case of fluvioglacial deposits, moderate in the case of glacial deposits, and good in the case of aeolian deposits. However, the key factor in determining the degree of abrasion is the share of EM/RM grains, which in the abovementioned deposits are seven, three, and twice as many as RM grains. Therefore, the most noteworthy research result is the very high total share of grains with aeolian abrasion (RM + EM/RM), amounting on average to 84.1% for Odranian fluvioglacial deposits, 86.7% for Sanian glacial deposits and 92.6% for Late Glacial aeolian deposits. It means that in the study area, glacial and fluvioglacial transport included deposits with good aeolian abrasion obtained in the periglacial environment before the transgression of the ice sheets. Probably due to the longer persistence of periglacial conditions in southern Poland, compared to its central and northern parts, the degree of aeolization of fluvioglacial and glacial deposits is better. At the same time, there is a significant differentiation in the aeolization of fluvioglacial deposits within the outwash plain in the foreland of the maximum extent of the Odranian ice sheet. In its proximal part, near the front of the ice sheet, fluvioglacial deposits are characterized by much worse abrasion of quartz grains than in the distal part.

Dust provides an ecologically significant input of nutrients, especially in slowly eroding ecosystems where chemical weathering intensity limits nutrient inputs from underlying bedrock. In addition to nutrient inputs, incoming dust is a vector for dispersing dust-associated microorganisms. While little is known about dust-microbial dispersal, dust deposits may have transformative effects on ecosystems far from where the dust was emitted. Using molecular analyses, we examined spatiotemporal variation in incoming dust microbiomes along an elevational gradient within the Sierra Nevada of California. We sampled throughout two dry seasons and found that dust microbiomes differed by elevation across two summer dry seasons (2014 and 2015), which corresponded to competing droughts in dust source areas. Dust microbial taxa richness decreased with elevation and was inversely proportional to dust heterogeneity. Likewise, dust phosphorus content increased with elevation. At lower elevations, early season dust microbiomes were more diverse than those found later in the year. The relative abundances of microbial groups shifted during the summer dry season. Furthermore, mutualistic fungal diversity increased with elevation, which may have corresponded with the biogeography of their plant hosts. Although dust fungal pathogen diversity was equivalent across elevations, elevation and sampling month interactions for the relative abundance, diversity, and richness of fungal pathogens suggest that these pathogens differed temporally across elevations, with potential implications for humans and wildlife. This study shows that landscape topography and droughts in source locations may alter the composition and diversity of ecologically relevant dust-associated microorganisms.

Crete is located in the collision zone of tectonic plates; therefore, the island coast was often shaped due to tectonic phenomena. In 365 AD, a major earthquake caused the uplift of the coast of western Crete by a few metres. It means that the modern beaches of this part of the island are fragments of the former seabed with its littoral deposits. Some of these deposits are affected by wind activity. The article aims to answer the question, did wind transport lasting more than 1600 years give the marine deposits the features of aeolian deposits? Grain size and mineral composition were determined for samples from seven research sites in western Crete. Deposits representing three sedimentary environments were examined – high-energy beach, aeolian, and beach with permanent or periodic fluvial supply. Quartz abrasion was established using the morphoscopic method. In the 0.8–1.0 mm fraction, less resistant carbonate minerals dominate (on average, 77%), while the content of more resistant quartz is low (on average, 18%). It means most deposits are relatively young and were briefly in the range of aeolian processes. Coastal deposits are dominated by moderately rounded and mat grains EM/RM, on average 79%. The content of very well-rounded and mat grains RM is low, on average 18%. Multiple predominances of EM/RM grains in relation to RM grains indicate short-term aeolian transport. It can be concluded that the degree of aeolisation of coastal deposits by wind activity from 365 AD to the present is weak, at most moderate.

Summary: Shrub encroachment is a common ecological state transition in global drylands and has myriad adverse effects on grasslands and the services they provide. This physiognomic shift is often ascribed to changes in climate (e.g. precipitation) and disturbance regimes (e.g. grazing and fire), but this remains debated. Aeolian processes are known to impact resource distribution in drylands, but their potential role in grassland‐to‐shrubland state changes has received little attention.We quantified the effects of 'sandblasting' (abrasive damage by wind‐blown soil) on the ecophysiology of dryland grass vs shrub functional types using a portable wind tunnel to test the hypothesis that grasses would be more susceptible to sandblasting than shrubs and, thus, reinforce transitions to shrub dominance in wind‐erodible grasslands when climate‐ or disturbance‐induced reductions in ground cover occur.Grasses and shrubs responded differently to sandblasting, wherein water‐use efficiency declined substantially in grasses, but only slightly in shrubs, owing to grasses having greater increases in day/nighttime leaf conductance and transpiration.The differential ecophysiological response to sandblasting exhibited by grass and shrub functional types could consequently alter the vegetation dynamics in dryland grasslands in favour of the xerophytic shrubs. Sandblasting could thus be an overlooked driver of shrub encroachment in wind‐erodible grasslands. [ABSTRACT FROM AUTHOR]

Aeolian sediment transport occurs as a function of, and with feedback to ecosystem changes and disturbances. Many desert grasslands are undergoing rapid changes in vegetation, including the encroachment of woody plants, which alters fire regimes and in turn can change the spatial and temporal patterns of aeolian sediment transport. We investigated aeolian sediment transport and spatial distribution of sediment in the surface soil for 7 years following a prescribed fire using a multiple rare earth element (REE) tracer‐based approach in a shrub‐encroached desert grassland in the northern Chihuahuan desert. Results indicate that even though the aeolian horizontal sediment mass flux increased approximately three‐fold in the first windy season in the burned areas compared to control areas, there were no significant differences after three windy seasons. The soil surface of bare microsites was the major contributor of aeolian sediments in unburned areas (87%), while the shrub microsites contributed the least (<2%) during the observation period. However, after the prescribed fire, the contribution of aeolian sediments from shrub microsites increased considerably (∼40%), indicating post‐fire microsite‐scale sediment redistribution. The findings of this study, which is the first to use multiple REE tracers for multi‐year analysis of the spatial and temporal dynamics of aeolian sediment transport, illustrate how disturbance by prescribed fire can influence aeolian processes and alters dryland soil geomorphology in which distinct soils develop over time at very fine spatial scales of individual plants. Plain Language Summary: In this study, we investigated how soil and nutrients attached to soil particles are transported and redeposited by wind after a prescribed fire using a new tracer method in a desert grassland. Results from this long‐term (7‐years) experiment in a desert grassland in the northern Chihuahuan desert reveal the role of fire in changing the erosional and depositional areas on the soil surface, which in turn determine what vegetation type can dominate the landscape. In a grassland encroached with shrubs, prescribed fire modified soil erosion processes and resulted in a more uniform distribution of nutrients in the landscape, favoring grass recovery. The findings also highlight the role of prescribed fires as an effective grassland management tool. Key Points: First long‐term analysis of post‐fire aeolian sediment transport using multiple rare earth element tracersAeolian transport, fires, and vegetation modify surface processes in which distinct soils develop at very fine spatial scales of individual plantsDemonstrates long‐term changes in the post‐fire shift in aeolian sediment source and sink dynamics in heterogeneous dryland landscapes [ABSTRACT FROM AUTHOR]

The Samalayuca Dunes (SMD) (Médanos de Samalayuca), Chihuahua, México, are one of México's largest and least studied dune fields, now managed as a Protected Area for their ecological characteristics. We present a morphometric characterization of the dune field based on remote sensing and field studies, to advance under standing of its physical environment. SMD's generally-fine sands originate from shoreline deposits of Paleolake Palomas, transported eastward (downwind) along an aeolian corridor, accumulating primarily as echo dunes upwind of the sierras of Samalayuca and Presidio. A complex wind regime, with northerly and southerly winds complementing regionally-prevailing southwesterlies, modified by topographic effects, shapes the SMD's morphology. The sand sea covers ~139.7 km2, with ~113.8 km2 in the main eastern body and ~25.9 km2 in a northwester n subfield. We describe six major dune for ms: north to south straight-crested dunes, east to west straight-crested dunes, star dunes, vegetated parabolic dunes, relict transverse dunes, and "megastar" (draa) dunes. Mean interdune centroid spacing is 76.5 m. The active dunes, previously described as an "aklé" pattern, are predominantly straight-crested dune sets oriented near-perpendicular to each other with general north-south and east-west crest orientations, 4-5 m high, spaced ~67 m apart for north-south trending crests and ~53 m for east-west trending crests, representing a nearly perpendicular interference pattern in some locations. The active dunes are superimposed in a compound and complex arrangement on relict remnants of much larger north-northwest trending transverse dune ridges fanning out from south to north-northwest, spaced approximately ~1 km apart and ~50 m high. The easternmost dune ridge contains an active set of at least 15 active megastar and reversing dunes up to 120 m tall, increasing in size and complexity from south to north. As a protected area with historical and ecological value, additional geologic investigations should be performed at the SMD, to help conserve this remarkable geologic feature. [ABSTRACT FROM AUTHOR]

Grain size affects the rates of aeolian sediment transport on beaches. Sediment in coastal environments typically consists of multiple grain‐size fractions and exhibits spatiotemporal variations. Still, conceptual and numerical aeolian transport models are simplified and often only include a single fraction that is constant over the model domain. It is unclear to what extent this simplification is valid and if the inclusion of multi‐fraction transport and spatial grain‐size variations affects aeolian sediment transport simulations and predictions of coastal dune development. This study applies the numerical aeolian sediment transport model AeoLiS to compare single‐fraction to multi‐fraction approaches for a range of grain‐size distributions and spatial grain‐size scenarios. The results show that on timescales of days to years, single‐fraction simulations with the median grain size, D50, often give similar results to multi‐fraction simulations, provided the wind is able to mobilize all fractions within that time frame. On these timescales, vertical variability in grain size has a limited effect on total transport rates, but it does influence the simulation results on minute timescales. Horizontal grain‐size variability influences both the total transport rates and the downwind bed grain‐size composition. The results provide new insights into the influence of beach sediment composition and spatial variability on total transport rates toward the dunes. The findings of this study can guide the implementation of grain‐size variability in numerical aeolian sediment transport models. Plain Language Summary: The growth of coastal dunes is caused by the wind, which moves sand from the beach to the dunes. The sand grains on the beach have different sizes. For instance, the size of the sand grains can vary from the waterline to the start of the dunes. Small sand grains are more easily picked up by the wind than larger, heavier grains. Thus, the size of sand grains and how they are spread over the beach can impact how much sand is moved by the wind. We use computer simulations to calculate how much sand is moved by the wind under different conditions. We investigate how different assumptions about the grain size on the beach influence these calculations. The results show that the calculations with one single sand size, in most cases, give comparable results to simulations with more complicated sand size variations. The simplified approach is beneficial because it reduces the need for detailed field data of grain sizes for future calculations. Key Points: The effects of multi‐fraction transport and spatial grain‐size variations were examined with the numerical aeolian transport model AeoLiSThe D50 can be used as a representative grain size in aeolian sediment transport modeling on a time scale of days to yearsThe bed surface grain size in the upwind source area might be the most relevant to include in aeolian sediment transport models [ABSTRACT FROM AUTHOR]

This article presents the results of studies on aeolian processes in the Oświęcim Basin in southern Poland. There are only a few large dunes in the western part (Woszczyce area) of the vast area of the Basin (about 1800 km2), and several dozen small forms (1–3 m high) in the central part (Świerczyniec area) All these forms are located on the outwash plain from the Odra Glaciation – dunes in the proximal part of sandur and small forms in the distal part. Grain size indices were determined for all samples taken at 17 sites, and quartz grain abrasion was examined using mechanical graniformametric and morphoscopic methods. The study found that the fluvioglacial deposits are not very diverse in grain size but significantly differentiated in terms of the degree of aeolization. In the proximal part of the outwash plain, deposits are characterized by very poor abrasion of quartz grains, two-three times worse than those from the distal part. Aeolian sands, in terms of grain size, do not differ essentially from fluvioglacial deposits, and in the distal part of sandur, there are no differences in the abrasion of the quartz grains. Conversely, in the proximal part, there was a significant increase in the degree of aeolization of the dune deposits compared to the source fluvioglacial deposits.

Janus is the Roman god of transitions. In many environments, state transitions are an important part of our understanding of ecological change. These transitions are controlled by the interactions between exogenous forcing factors and stabilizing endogenous feedbacks. Forcing factors and feedbacks are typically considered to consist of different processes. We argue that during extreme events, a process that usually forms part of a stabilizing feedback can behave as a forcing factor. And thus, like Janus, a single process can have two faces. The case explored here pertains to state change in drylands where interactions between wind erosion and vegetation form an important feedback that encourages grass‐to‐shrub state transitions. Wind concentrates soil resources in shrub‐centered fertile islands, removes resources through loss of fines to favor deep‐rooted shrubs, and abrades grasses' photosynthetic tissue, thus further favoring the shrub state that, in turn, experiences greater aeolian transport. This feedback is well documented but the potential of wind to act also as a forcing has yet to be examined. Extreme wind events have the potential to act like other drivers of state change, such as drought and grazing, to directly reduce grass cover. This study examines the responses of a grass‐shrub community after two extreme wind events in 2019 caused severe deflation. We measured grass cover and root exposure due to deflation, in addition to shrub height, grass patch size, and grass greenness along 50‐m transects across a wide range of grass cover. Root exposure was concentrated in the direction of erosive winds during the storms and sites with low grass cover were associated with increased root exposure and reduced greenness. We argue that differences between extreme, rare wind events and frequent, small wind events are significant enough to be differences in kind rather than differences in degree allowing extreme winds to behave as endogenous forcings and common winds to participate in an endogenous stabilizing feedback. Several types of state change in other ecological systems in are contextualized within this framework. [ABSTRACT FROM AUTHOR]

The coastal plain of Cabo Frio is located in an area where natural elements coexist (lagoons, restinga vegetation, stationary and transgressive dunes, etc.) with the urban site of the municipality. By investigating the dynamics and behavior of the megaform parabolic, an asymmetry was observed in its displacement over the plain, with different migration rates: 12.2m/year along its central axis, and 7.3m/year on the avalanche face. In terms of area coverage, it experienced a loss of 9.4 ha, resulting in a decrease of 13.6%. In addition to human presence, coastal environments can also be sensitive to environmental changes such as climate change and wave climates, which may lead to a landscape transformation process in this área. [ABSTRACT FROM AUTHOR]

• Propagules of aquatic microinvertebrates dispersed through laboratory wind tunnel. • Propagules embedded in playa soil surfaces bombarded by saltating sand & recovered. • Simulation of the dominant natural process of wind erosion and aeolian transport. • Propagules of all seven taxa tested were viable after wind erosion and transport. • Propagules can successfully disperse short to long distances in air (anemochory). Ephemeral wetland surfaces are preferential locations for wind erosion and repositories for resting stages (propagules) of aquatic invertebrates. Dormant propagules can disperse to new habitats via wind (aeolian transport, or anemochory). Wind transport of invertebrate propagules has been documented at local and regional scales, but prior laboratory wind tunnel tests of propagule anemochory neither replicated the predominant natural processes of wind erosion in drylands, saltation-sandblasting, nor determined the viability of experimentally wind-transported propagules. We used a soil saltation wind tunnel to test aeolian erosion, transport, and subsequent viability of propagules from seven aquatic invertebrate species. A propagule-bearing crusted soil surface was prepared, then abraded by saltating silica sand in the wind tunnel to emit aeolian sand and dust. Sediment was collected from three downstream sections of the wind tunnel, representing different transport distances in the environment, and propagules were quantified for each section by species. The wind-eroded material was rehydrated with sterile media to detect hatching of any propagules which survived the sandblasting. Although survival was much lower than in a control experiment without wind tunnel saltation treatment, and hatching rates were lower than those reported from undisturbed egg banks, viable individuals of all wind-tunnel-tested species were detected after hydration. Larger propagules settled closer to the source of entrainment than smaller propagules, indicating a shorter dispersal distance for larger propagules- although only short-distance anemochory may be necessary for dispersal across drainage basins. These results demonstrate that resting stages of many invertebrates can be wind-bombarded from natural surfaces along with sand and dust, dispersed into and transported through the atmosphere, and remain viable. Future investigations of anemochory of aquatic invertebrates from ephemeral waters should use appropriate wind tunnels to evaluate propagule and surface properties as potential adaptations for wind dispersion. [ABSTRACT FROM AUTHOR]

The current distribution of dune fields and sandy lands in northeastern China is closely related to the hydrological environment with fluvial processes often providing sediments for dune formation. The Keerqin Sandy Land (also known as Horqin) incised by the tributaries of the West Liao River and located at the northern boundary of East Asian summer monsoon (EAM) in northeastern China, is sensitive to monsoon system variability. As such, aeolian-fluvial-paleosol sequences in northeastern China are valuable geological archives for reconstructing river system behavior and palaeoclimate since the Late Quaternary. Here we show from analysis of these archives that fluvial systems were active at ∼11 ka likely due to the occurrence of floods at the end of the last glaciation. This was followed by frequent channel migration within the floodplains around 7∼5 ka associated with mid-Holocene monsoon precipitation fluctuation and higher humidity. Sediments from this active Holocene fluvial system along with a more humid climate produced conditions in the Keerqin Sandy Land that resulted in extensive paleosol formation. These findings are consistent with the timing and development of paleosols in other sandy lands in northeastern China. Former channels and floodplains along with a higher groundwater table aided the early development of agriculture in this region: many of the former flood plains are still intensively cultivated and highly productive. • New aeolian-fluvial-paleosol sequences in the Keerqin Sandy Land are investigated to reconstruct the changes of river system behavior and palaeoclimate. • The chronology is based on both radiocarbon and OSL dating methods, ensuring a high level of reliability. • Two distinct periods of active fluvial systems were identified in the study area, i.e., at ca. 11 ka and during 7–5 ka. [ABSTRACT FROM AUTHOR]

Despite frequent observations of slope streaks and dust devil tracks on the same slopes in various regions on Mars, only a few instances in Arabia Terra have documented slope streaks directly triggered by dust devils. Here we present new observations of dust devil-induced slope streaks in Elysium Planitia and Amazonis Planitia. These observations represent a rare opportunity to study the erosional effects of both dust devils and slope streaks on the martian surface. Since dust devil tracks and the triggered streaks are formed basically simultaneously and are therefore subject to similar alteration processes, e.g., settling dust from the atmosphere, the relative albedo of these features can be determined using high-resolution orbital images. Our relative albedo analyses of twelve dust devil-induced slope streaks revealed that slope streaks appear substantially darker than the respective dust devil tracks. These observations might indicate a stronger erosion of fine-grained material by slope streaks compared to dust devils. • New dust devil-induced slope streaks observed in Elysium Planitia and Amazonis Planitia. • Dust devil-induced slope streaks are significantly darker than dust devil tracks. • Slope streaks might have a stronger erosional effect on martian slopes than dust devils. [ABSTRACT FROM AUTHOR]

On the basis of long-term station-based studies and soil-sedimentary sequences, a reconstruction of the morpholithogenesis of the Onon–Torey Plain in the Holocene has been performed. A rhythmicity of the functioning of geomorphological systems is revealed. It manifests itself in a regular change in the dynamic phases of relief formation. Characteristics of morphological, lithological, and dynamic parameters of each phase are obtained. The sequence of their change in geomorphological cycles at different hierarchical levels is determined. It is shown that the largest cycle, encompassing the entire Holocene on the Onon–Torei plain is most fully represented in sections of the valleys of the Imalka and Onon rivers. In eolian deposits, 1800-year cycles are especially clearly pronounced by periods of pedogenesis. A change in the conditions of aeolian accumulations in dune sections occurs every 260 years. In the mouths of the ravines opening into the basin of Lake Zun-Torei and the valley of the Builesan River, in the proluvial and proluvial-solifluction deposits of the Atlantic and Subatlantic periods, 130-year and intra-secular Brickner cycles are recorded, the duration of which is about 50 years. A regional scheme of alternation in the Holocene of extreme fluvial and arid phases with normal zonal dynamic phases of relief formation has been compiled. The horizons of fluvial genesis comprise the lower part of the sediments of the Holocene macrocycle. A strong manifestation of fluvial processes was noted in the Preboreal and Atlantic periods of the Holocene, as well as in the transitional time from the Atlantic to the Subborial period. The normal zonal phase of matter integration in systems is evidenced by buried humus soil horizons. Soils aged about 8000, 6400, and 1200–1400 calendar years ago received regional formation. A tendency towards a reduction in the area of the lakes and an increase in the role of eolian processes against the background of a general aridization of the climate over the past 10 000 years has been established. According to radiocarbon dating, sedimentation–accumulation rates are obtained. In general, the high dynamism of morpholithogenesis in the steppes of Central Asia is shown, which causes planation. [ABSTRACT FROM AUTHOR]

Vesicular horizons are common on the surface of landforms in arid regions and play an important role in the hydrological properties and pedogenic processes in these areas. Vesicular pores are a characteristic feature of vesicular horizons and include separate pores with spherical to elliptical shapes and dimensions of micrometers to millimeters in diameter (Dietze et al., 2012). The eastern region of Isfahan located in the eastern part of the Zayandehroud River basin is affected by environmental disasters due to severe environmental drought, destructive human activities, and desertification processes. Although vesicular horizons are frequent in the soils and landforms of the eastern region of Isfahan (Bayat et al., 2018), there is no information about the geochemical and mineralogical properties of these horizons. The aim of the present study was to investigate the physical, chemical, geochemical, and mineralogical properties of vesicular horizons at different elevation levels of three landforms in the eastern region of Isfahan. Materials and Methods The study area is located in the center of Iran, east of Isfahan and around Segzi Playa. According to the meteorological stations of the region, the mean annual precipitation and temperature are about 107 mm and roughly 15 ˚C, respectively. Groundwater in piedmonts and plateaus of the region is deep and there are no signs of groundwater activity in the studied soils and landforms. The studied landforms include a remnant paleosurface across the Zayandehroud River (RP), a pediment in Jey industrial city (JP), and an alluvial fan near the Zefreh (ZA). Seven samples of vesicular horizons were taken from vesicular horizons in RP (at altitudes of 1542 and 1552 m), ZA (altitudes of 1623, 1764, and 1901 m), and JP (at altitudes of 1542 and 1557 m) landforms. The samples were described according to Schoenberger (2012) and analyzed regarding standard methods (Soukup et al., 2008; Soil Survey Staff, 2014). Results and Discussion The thickness of the studied vesicular horizons varied in the range of 3-6 cm, and on the alluvial fan, the thickness of the horizon increases with increasing the elevation. The chemical properties of the studied samples indicated very low electrical conductivity and organic carbon content and were similar to vesicular horizons in the Mojave Desert of California (McFadden et al., 1998). The particle size distribution indicated the predominance of sand particles in all samples and all samples were characterized by a bimodal distribution of particle sizes suggesting the contribution of at least two mechanisms in the transfer of particles to the studied vesicular horizons (Karimi et al., 2017; Sweeney et al., 2013). Mineralogical analysis of the samples showed the predominance of quartz and calcite in all samples and varied concerning the presence of mica and fibrous minerals. It seems that quartz is inherited from the parent material while calcite and mica minerals originated from the parent material and were also added by the wind. Fibrous minerals were probably of autogenic origin. The geochemical properties of the samples were consistent with the mineralogical results and showed the abundance of SiO2 and CaO in all samples. Among the trace elements, the highest abundance is observed in the strontium, which is due to the association of this element with carbonates (Ding et al., 2019). A comparison of geochemical properties of vesicular horizons with associated rocks showed the enrichment of SO3 and CaO relative to corresponding parent material indicating the addition of soluble ions, carbonates, and especially gypsum to the surface of the studied landforms. The Zr/Al ratio showed an increasing trend with increasing the silt content which proved the aeolian source of the silt particles as previous studies have shown a very strong correlation between aeolian sediments and the element zirconium (e.g., Waroszewski et al., 2018). Conclusions Increasing the amount of silt and the ratio of fine-grained particles to sand with increasing the elevation indicated the role of aeolian processes in adding fine-grained particles to the surfaces of different landforms of eastern Isfahan. Mineralogical and geochemical evidence also confirms the effect of dust on the formation of these horizons, so that the addition of mica minerals along with silt particles has occurred at higher altitudes. The geochemical study of vesicular horizons and application of Zr/Al ratios show that the composition of past and current dust in eastern Isfahan was the origin of dust for different landforms of the region is the same. Finally, the existence of developed vesicular horizons in the surfaces of the landforms of the region demonstrates long-term processes of wind erosion and dust influx into the soils. These natural processes are probably intensified by anthropogenic activities in recent years. [ABSTRACT FROM AUTHOR]

This paper is a summary of the results of research on the accumulation conditions of the Upper Younger Loess (LMg) in Poland and Bug loess (bg) in Ukraine from the maximum stage (MIS 2) of the Vistulian (Weichselian) Glaciation in central and eastern Europe. These studies included an analysis of the morphological (topographic) situation of the loess cover, its grain size and heavy mineral composition, the preserved structures of loess sedimentation as well as mollusc and pollen analyses of this loess. They revealed that the accumulation of Upper Younger Loess (UYL) might have been more dependent on the prevailing moisture conditions than previously thought. These conditions could have been caused by cold air masses from an ice sheet and warm air masses from the Mediterranean Sea and Atlantic coming together in the Carpathians and the Holy Cross Mountains and favouring the formation of dust storms and precipitation. In this process, a loading of loess dust (formed from local rocks weathering in periglacial conditions) by atmospheric moisture particles was especially significant. The moist substrate not only favoured the periodic development of vegetation and molluscs but also enabled the interception of dust and the accumulation of an increasingly thick loess cover. Westerly and south-westerly winds predominated in the UYL as indicated by the topographic position of loess patches and the mineral composition of the studied loess. Periodically an increased air circulation from the east and northeast occurred. [ABSTRACT FROM AUTHOR]

Aeolian processes have shaped and contributed to the geological record in Gale crater, Mars, long after the fluviolacustrine system existed ∼3 Ga ago. Understanding these aeolian deposits, particularly those which have been lithified and show evidence for aqueous alteration, can help to constrain the environment at their time of deposition and the role of liquid water later in Mars' history. The NASA Curiosity rover investigated a prominent outcrop of aeolian sandstone within the Stimson formation at the Greenheugh pediment as part of its investigation of the Glen Torridon area. In this study, we use geochemical data from ChemCam to constrain the effects of aeolian sedimentary processes, sediment provenance, and diagenesis of the sandstone at the Greenheugh pediment, comparing the Greenheugh data to the results from previous Stimson localities situated 2.5 km north and >200 m lower in elevation. Our results, supported by mineralogical data from CheMin, show that the Stimson formation at the Greenheugh pediment was predominately sourced from an olivine‐rich unit that may be present farther up the slopes of Gale crater's central mound. Our results also suggest that the Greenheugh pediment Stimson formation was cemented by surface water runoff such as that which may have formed Gediz Vallis. The lack of alteration features in the Stimson formation at the Greenheugh pediment relative to those of the Emerson and Naukluft plateaus suggests that groundwater was not as available at this locality compared to the others. However, all sites share diagenesis at the unconformity. Plain Language Summary: We use geochemical data from the Curiosity rover's ChemCam instrument to investigate the geological history of the Greenheugh pediment capping unit. The Greenheugh pediment is a geologic feature that has a gently sloping top, forming a broad plain extending from the base of the valley, Gediz Vallis. The Greenheugh pediment is capped by a unit of broadly uniform thickness which represents the remains of the Stimson dune field that existed <2.5 Ga (mid‐to late‐Hesperian). ChemCam geochemical data shows that the sands deposited at the Greenheugh capping unit were largely sourced from a nearby olivine‐rich unit. Surface waters then cemented the windblown sand deposits, ponding at the unconformity with the underlying mudstone unit, creating concretions toward the base. Episodes of groundwater circulation did not affect the rocks at Greenheugh as much as they did at other Stimson localities, though both sites share evidence of acid‐sulfate alteration along the unconformity. These results suggest that the ancient Stimson dune field was a dynamic environment, incorporating grains from the surrounding geological units on Mt Sharp. Furthermore, liquid water was stable at the surface in the Hesperian and was available for multiple diagenetic events along bedrock weaknesses. Key Points: ChemCam geochemical results support that the Greenheugh pediment capping unit was deposited within the Stimson sand sea in the HesperianThe Greenheugh pediment capping unit was sourced from olivine‐rich sands, potentially recycled from units farther up Mt SharpGreenheugh experienced less interaction with groundwaters than Stimson at the Emerson and Naukluft plateaus, but shared diagenesis at the unconformity [ABSTRACT FROM AUTHOR]

The wind interacts with the surface of Mars, forming aeolian landforms. The orientation of these landforms informs us about the formative wind directions. The observations of the orientation of aeolian landforms on Meridiani Planum between Mars years 26 and 38 indicated that there is a seasonality of formative wind directions in this region. The studied landforms were shaped by a predominant SE wind during summer, while during winter several wind directions played a role in their formation. Throughout the Mars year, the most formative were the NW winds. The presence of dark wind streaks oriented toward the west during winter indicates that E winds occur in this season on Meridiani Planum, as previously predicted by numerical simulations. It was also found that aeolian deflation led to complete erosion of smaller dunes, and that the relatively strong deflation was responsible for the scarcity of fine-grained ripples on Meridiani Planum. In this region, fine-grained ripples were found only in a few locations, and they were mainly small bedforms with wavelengths up to several centimeters. • In situ and orbital data from a period between Mars years 26 and 38 were analyzed. • There is a seasonality of aeolian landforms on Meridiani Planum. • The most formative winds blow from NW, but in summer SE winds dominate. • Numerically predicted modern E winds occur mainly in winter. • Deflation led to complete erosion of three dome dunes in the studied period. [ABSTRACT FROM AUTHOR]

Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the flux of particles in aeolian saltation-the wind-driven transport of sand in hopping trajectories-scales with wind speed, largely because models do not agree on how particle speeds and trajectories change with wind shear velocity. We present comprehensive measurements, from three new field sites and three published studies, showing that characteristic saltation layer heights remain approximately constant with shear velocity, in agreement with recent wind tunnel studies. These results support the assumption of constant particle speeds in recent models predicting linear scaling of saltation flux with shear stress. In contrast, our results refute widely used older models that assume that particle speed increases with shear velocity, thereby predicting nonlinear 3/2 stress-flux scaling. This conclusion is further supported by direct field measurements of saltation flux versus shear stress. Our results thus argue for adoption of linear saltation flux laws and constant saltation trajectories for modeling saltation-driven aeolian processes on Earth, Mars, and other planetary surfaces.

Aeolian processes are a dominant cause of Martian surface modification today. Sand is pervasive, even while the contemporary transport of sand at high-threshold wind speeds implies sand breakdown. Thus, detecting the origin(s) of sand on Mars is an important open question in Mars science. One long-standing hypothesis for an origin of Martian sand is as volcaniclastic sediments, either epiclastic (from the breakdown of effusive volcanic rock) or pyroclastic (from explosive sedimentation). Recent analyses identified the most likely pyroclastic unit on Mars, the Medusae Fossae Formation (MFF) – mapped as the Hesperian and Amazonian-Hesperian transitional units (Tanaka et al., 2014) – as an origin of Martian sand, a genesis consistent with inferences from other work. On these bases, we continued in this work to test for a volcaniclastic origin of Martian sand elsewhere on Mars. We inspected the seven units from the global geologic map of Mars interpreted as possibly/partially volcaniclastic and six geographic terrains ascribed as likely volcanogenic in a more recent analysis. Of these units and geographic terrains, potential sand sources (PSSs) were detected only within two locales: 1) the remaining (central and eastern) extent of the MFF, and 2) Arabia Terra. Arabia Terra shows more numerous PSS, commonly characterized as having proximal dune fields. The explosive volcanic history of the region points towards a pyroclastic origin, though the geologic complexity of the region suggests complexity in the provenance of Arabia Terra PSSs. In contrast to PSS identifications in the western MFF, PSSs in the central and eastern MFF were clustered along the contact of the MFF with lava plains, indicating a potential epiclastic sand origin. Thus, these results indicate both pyroclastic and potentially epiclastic origins for sand on Mars. However, these sand origins as detected by this work are confined to limited locales and (for the MFF) in the amount of sand generated. To further evaluate the amount of sand production in these two study regions from volcanogenic processes, spectroscopic analysis of PSSs in comparison with sand deposits would be a means to test first whether the PSSs were indeed generating sand and secondly if that sand were of volcanic origin. Potential sand flux modeling would be a means to establish the source location(s) of the sand. The origin(s) of the pervasive sand on Mars remain(s) to be better understood, for which the work presented here provides a foundation. • A survey of Martian volcanogenic units identified limited potential sand sources. • Identified sources are confined to Arabia Terra and the Medusae Fossae Formation. • Potential sand sources in Arabia Terra indicate a pyroclastic genesis for the sand. • In the central / eastern MFF, context and distribution allow for epiclastic genesis. • These results indicate volcanogenic sand on Mars but in limited locales and amounts. [ABSTRACT FROM AUTHOR]

Dust provides an ecologically significant input of nutrients, especially in slowly eroding ecosystems where chemical weathering intensity limits nutrient inputs from underlying bedrock. In addition to nutrient inputs, incoming dust is a vector for dispersing dust-associated microorganisms. While little is known about dust-microbial dispersal, dust deposits may have transformative effects on ecosystems far from where the dust was emitted. Using molecular analyses, we examined spatiotemporal variation in incoming dust microbiomes along an elevational gradient within the Sierra Nevada of California. We sampled throughout two dry seasons and found that dust microbiomes differed by elevation across two summer dry seasons (2014 and 2015), which corresponded to competing droughts in dust source areas. Dust microbial taxa richness decreased with elevation and was inversely proportional to dust heterogeneity. Likewise, dust phosphorus content increased with elevation. At lower elevations, early season dust microbiomes were more diverse than those found later in the year. The relative abundances of microbial groups shifted during the summer dry season. Furthermore, mutualistic fungal diversity increased with elevation, which may have corresponded with the biogeography of their plant hosts. Although dust fungal pathogen diversity was equivalent across elevations, elevation and sampling month interactions for the relative abundance, diversity, and richness of fungal pathogens suggest that these pathogens differed temporally across elevations, with potential implications for humans and wildlife. This study shows that landscape topography and droughts in source locations may alter the composition and diversity of ecologically relevant dust-associated microorganisms. [ABSTRACT FROM AUTHOR]

Gale crater, the field site for NASA's Mars Science Laboratory Curiosity rover, contains a diverse and extensive record of aeolian deposition and erosion. This study focuses on a series of regularly spaced, curvilinear, and sometimes branching bedrock ridges that occur within the Glen Torridon region on the lower northwest flank of Aeolis Mons, the central mound within Gale crater. During Curiosity's exploration of Glen Torridon between sols ∼2300–3080, the rover drove through this field of ridges, providing the opportunity for in situ observation of these features. This study uses orbiter and rover data to characterize ridge morphology, spatial distribution, compositional and material properties, and association with other aeolian features in the area. Based on these observations, we find that the Glen Torridon ridges are consistent with an origin as wind‐eroded bedrock ridges, carved during the exhumation of Mount Sharp. Erosional features like the Glen Torridon ridges observed elsewhere on Mars, termed periodic bedrock ridges (PBRs), have been interpreted to form transverse to the dominant wind direction. The size and morphology of the Glen Torridon PBRs are consistent with transverse formative winds, but the orientation of nearby aeolian bedforms and bedrock erosional features raise the possibility of PBR formation by a net northeasterly wind regime. Although several formation models for the Glen Torridon PBRs are still under consideration, and questions persist about the nature of PBR‐forming paleowinds, the presence of PBRs at this site provides important constraints on the depositional and erosional history of Gale crater. Plain Language Summary: Wind has played a major role in sculpting the surface of Mars. Gale crater, the field site for NASA's Mars Science Laboratory Curiosity rover since it landed there in 2012, contains a vast and varied record of deposition and erosion by the wind. This study focuses on a series of regularly spaced, generally straight bedrock ridges that occur within the clay‐bearing Glen Torridon region of Aeolis Mons (informally named Mount Sharp) in Gale crater. During Curiosity's exploration of the Glen Torridon region between sols ∼2300–3080 of the mission, the rover drove through this field of ridges, acquiring images and compositional observations along the way. This study characterizes the Glen Torridon ridges using orbiter and rover data to determine their shape, size, occurrence, and relationship to other wind‐formed features in the area. We find that the Glen Torridon ridges were carved by wind into the bedrock of Mount Sharp. Questions remain about the winds that formed these ridges, but this study provides important information about the history and environment of Gale crater and reports the first rover observations of this type of erosional feature on Mars. Key Points: Decameter‐long, regularly spaced bedrock ridges oriented northeast‐southwest occur throughout the Glen Torridon region of Aeolis MonsGlen Torridon ridges cross‐cut elevation contours and bedding, exhibit bifurcations, and are disrupted by small impact cratersGlen Torridon ridges are erosional periodic bedrock ridges whose formation places erosional and depositional constraints on Aeolis Mons [ABSTRACT FROM AUTHOR]

Several studies have shown that dust emission (vertical flux, F) can be considered a constant fraction (k) of the saltating flux (horizontal flux, Q), that is, F=kQ. This coefficient of proportionality, or dust production efficiency factor, is often called the 'k factor' and is fundamentally related to soil properties especially soil texture. Beyond regional and global modeling applications, a practical utility of k is for air quality regulatory agencies where k can be used to estimate F based on only measurements of Q, which is more easily measured in the field. Only a few studies have directly estimated the k factor from soils within potential dust sources even though dust models that represent the sandblasting process typically utilize k. The goal of this study was to compare two methods to calculate k from sandy sediments and compare those estimates with an empirical method of calculating the k factor. The first method (method 1) used the difference between F calculated from two sets of sediment samplers whereas the second method (method 2) used a set of aerosol monitors to measure F. We found that the range of k values from our study are consistent with soil texture‐based estimates of k and also have the correct order of magnitude. Thus, any of the methods described in our study are appropriate for estimation of k for sandy soils. [ABSTRACT FROM AUTHOR]

The article is based on a long-term study of floodplain soils of the Amur River valley within the north-eastern part of the Middle-Amur Lowland. The results of field work on the soil-geomorphological profile across the Slavyansky Island, located 200 km from Khabarovsk down the Amur River, are discussed. The study analyzes the occurrence of the island's floodplain soils on riolkas[1] and their properties, with an emphasis on morphology and lithological and particle-size composition. The features of soil formation on riolkas of different genesis – alluvial and aeolian – are shown. On sandy and sandy-loam deposits of alluvial riolkas (“meadow-forest” ridges) poorly developed sod gley soils are formed. On heavy loam and clay alluvium of the “meadow“ ridges, annually flooded by river waters, sod-meadow gley soils develop under the woodreed grass stand. Sand deposits of high aeolian riolkas are characterized by a homogeneous fine-grained structure without interlayers, signs of organic matter and with a significant amount of mica. They describe poorly developed sod-forest soils under high-trunk oak forests. The formation of texture-differentiated soils on all types of riolkas was not revealed. When the floodplain reaches the position of the first terrace above the floodplain, the differences in the lithological composition and particle-size distribution, soil texture, height above the water edge and the nature of vegetation on the inherited riolkas provide a multidirectional evolution of soil formation. At the same time, the development is taking place in accordance with the zonal types of soils (sod-forest, brown-earth, texture-differentiated – soil with a bleached horizon (podbel)). The last are mainly formed on clay-loam alluvium, which can overlay not only alluvial, but also some aeolian riolkas. [1]Riolkas are ancient, relatively high sand ridges (extended dunes) with plant cover found in Amur region (Russian Far East).

Dust provides an ecologically significant input of nutrients, especially in slowly eroding ecosystems where chemical weathering intensity limits nutrient inputs from underlying bedrock. In addition to nutrient inputs, incoming dust is a vector for dispersing dust-associated microorganisms. While little is known about dust-microbial dispersal, dust deposits may have transformative effects on ecosystems far from where the dust was emitted. Using molecular analyses, we examined spatiotemporal variation in incoming dust microbiomes along an elevational gradient within the Sierra Nevada of California. We sampled throughout two dry seasons and found that dust microbiomes differed by elevation across two summer dry seasons (2014 and 2015), which corresponded to competing droughts in dust source areas. Dust microbial taxa richness decreased with elevation and was inversely proportional to dust heterogeneity. Likewise, dust phosphorus content increased with elevation. At lower elevations, early season dust microbiomes were more diverse than those found later in the year. The relative abundances of microbial groups shifted during the summer dry season. Furthermore, mutualistic fungal diversity increased with elevation, which may have corresponded with the biogeography of their plant hosts. Although dust fungal pathogen diversity was equivalent across elevations, elevation and sampling month interactions for the relative abundance, diversity, and richness of fungal pathogens suggest that these pathogens differed temporally across elevations, with potential implications for humans and wildlife. This study shows that landscape topography and droughts in source locations may alter the composition and diversity of ecologically relevant dust-associated microorganisms.

The relevance of the research of exogenous processes, including deflation, is caused by both positive and negative impact of the processes on landscape components and economic activity. Besides, features of regional material migration under the action of aeolian processes, the accumulation intensity of deposits, and their material composition are poorly understood. Environmental conditions and anthropogenic impact cause the development of wind erosion and deflation in geosystems of Tomsk region. The main aim of this study is to estimate accumulation intensity of aeolian deposits and determine its material composition for the landscapes in the southeast of Tomsk region. Objects of the research are natural and anthropogenic landscapes of the Tom-Yaya interfluve within the Basandayka river basin (the right tributary of the Tom river). Methods: field measurements with sampling, laboratory analyses, analytical studies. Results of the study have revealed based on long-term observations that aeolian processes in the agricultural landscapes of the southeast of the forest zone in the West Siberia appear annually. The intensity of the processes has a variety from year to year and reaches the maximum values in dry winters. Dust prevails in the grain size distribution of aeolian deposits. Quartz and muscovite are dominant in total mineral composition. Aeolian deposits contain a significant amount of plant nutrients (humus – up to 10 %) in many cases. The authors consider that the bulk of the aeolian deposits within the key area (southeast of the Tomsk region) in the cold season has a local origin. The strong similarity of the grain size distribution, chemical and mineral compositions of deposits with soils of the area are indicative of that.

Here we present new observations of two different interactions between aeolian ridges and boulder fields on Mars that provide insight into past wind conditions. First, an analysis of ridge and boulder interactions at two test sites in Proctor Crater and an additional site 430 km to the northeast shows that ridge geometry can be affected by changes in surface roughness elements generated by boulder fields. Second, a detailed examination of some of the boulder fields found that individual boulders can generate multi-armed 'wakes' that have no clear proxy on Earth. The ridge/boulder dynamics suggest that transverse aeolian ridges acted as roughness during their development, indicating that they formed at a length scale greater than wind ripples. The boulder wakes seem to represent an unusual interaction between flow separation and pre-exiting ridges; why this pattern is not observed on Earth remains uncertain. [ABSTRACT FROM AUTHOR]

Ripples, transverse aeolian ridges (TARs), and dark‐toned sand sheets and dunes are common aeolian bedforms on the Martian surface. They are important for understanding the nature of present‐day Martian sediments and regional aeolian processes. Here we present a case study investigation of ripples, TARs, a dark‐toned sand sheet, and dunes in an unnamed—but well‐covered by remote sensing datasets—crater in Terra Sabaea, Mars, to consider their nature and possible origin scenarios. Repeat high‐spatial resolution images show only minor albedo changes among the dark‐toned sand dunes but no obvious changes in the ripples and TARs. Visible and infrared spectra show that the megaripples and TARs are pyroxene‐bearing, while the dark‐toned sheet and dunes are olivine‐bearing. Thousands of TARs are superimposed on the crater walls, and they have a similar composition as the bedrock exposed around the central pit, suggesting that some percentage of the sediment composing the TARs may be locally derived. Megaripples have a similar composition as TARs, suggesting they may share a similar origin. Dark‐toned sand sheets and sand dunes show a different composition from the substrate of the crater, plus bedform orientations indicative of a dominant, north‐northwest wind, indicating that some of these dark sands might have been blown in from outside of the crater. Alternatively, the sand in the megaripples, TARs, sand sheets, and dunes could share a common source, and some or even all of them could be recycled from the weathering and erosion of the sand‐bearing clastic rocks exposed in the crater walls. Plain Language Summary: Ripples, transverse aeolian ridges (TARs), dark‐toned sand sheets and dunes are widely distributed across the Martian surface. We present a detailed local case study in an unnamed crater in Terra Sabaea to consider the nature, and origin scenarios of the ripples, TARs, dark‐toned sand sheets, dunes, and wind sediment transport processes as a whole. The megaripples and TARs have similar compositions, suggesting that they might share a similar sand source and formation mechanism. Dark‐toned sand sheet and dunes have different compositions from the bedrocks, megaripples and TARs, suggesting that the dark sands might be blown in from out of the crater. Alternatively, all of them might share the same sediment source and the sands were recycled from the weathering and erosion of the sand‐bearing clastic rocks exposed in the crater walls. Key Points: We performed a detailed case study at one of the few places on Mars that have received sufficient Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and repeat High Resolution Imaging Science Experiment coveragesThousands of transverse aeolian ridges (TARs) occur on the crater slopes, which might suggest a local sediment sourceWe show dust‐free spectra of megaripples and TARs in CRISM. They have similar compositions, supporting they might have similar origins [ABSTRACT FROM AUTHOR]

Aims: Grassland-to-shrubland transition is a common form of land degradation in drylands worldwide. It is often attributed to changes in disturbance regimes, particularly overgrazing. A myriad of direct and indirect effects (e.g., accelerated soil erosion) of grazing may favor shrubs over grasses, but their relative importance is unclear. We tested the hypothesis that topsoil "winnowing" by wind erosion would differentially affect grass and shrub seedling establishment to promote shrub recruitment over that of grass. Methods: We monitored germination and seedling growth of contrasting perennial grass (Bouteloua eriopoda, Sporobolus airoides, and Aristida purpurea) and shrub (Prosopis glandulosa, Atriplex canescens, and Larrea tridentata) functional groups on field-collected non-winnowed and winnowed soils under well-watered greenhouse conditions. Results: Non-winnowed soils were finer-textured and had higher nutrient contents than winnowed soils, but based on desorption curves, winnowed soils had more plant-available moisture. Contrary to expectations, seed germination and seedling growth on winnowed and non-winnowed soils were comparable within a given species. The N2-fixing deciduous shrub P. glandulosa was first to emerge and complete germination, and had the greatest biomass accumulation of all species. Conclusions: Germination and early seedling growth of grasses and shrubs on winnowed soils were not adversely nor differentially affected comparing with that observed on non-winnowed soils under well-watered greenhouse conditions. Early germination and rapid growth may give P. glandulosa a competitive advantage over grasses and other shrub species at the establishment stage in grazed grasslands. Field establishment experiments are needed to confirm our findings in these controlled environment trials. [ABSTRACT FROM AUTHOR]

Wind erosion, or the transportation and deposition of sand into desert dunes and aeolian loess, is one of the most important aeolian activities. The progression of aeolian landforms expands arid and barren landscapes, leading to the degradation of adjacent areas. The Gonghe Basin, as a typical plateau with abundant sand sources, is highly sensitive to changes in the local climate conditions. In order to quantify the spatial-temporal variations in the aeolian landforms in the Gonghe Basin, we conducted field surveys and also analyzed twelve remote sensing (Landsat5 TM and Landsat8 OLI) images that sample the Gonghe Basin from 1989 to 2019. In the Gonghe Basin, we identified aeolian landforms such as climbing dunes on the windward slopes of the foothills, checkerboard dunes in the southeastern part of the basin, flat dunes, parabolic dunes and crescent dunes on the east and west sides of Longyangxia Reservoir, shrubby sandbanks on the valley slope in Shazhuyu, Tanggemu, and Indel, and sandy thickets at the bottom of the valley near the Dalian Sea, the Longyangxia Reservoir, and the tributaries of the Yellow River. From 1989 to 2005, the area of the aeolian regions expanded by 816.7 km2, with an annual conversion rate of 0.05%. From 2015 to 2019, the area of the aeolian regions shrunk by 2411.9 km2, with an annual conversion rate of −0.15%. The number and size of the fixed and semi-fixed dunes (e.g. the shrubby sandbanks on the valley slope and the sandy thickets at the bottom of the valley) were more stable than those of the mobile dunes (e.g. the checkerboard dunes, the flat dunes, the crescent dunes, the parabolic dunes, and the climbing dunes). The fixed and semi-fixed dunes were arranged in an irregular ring shape, and the location of the center of gravity of this ring did not change significantly from 1989 to 2019; in this time, the mobile dunes migrated to the northwest. [ABSTRACT FROM AUTHOR]

Mars exhibits diverse surface changes at all latitudes and all seasons. Active processes include impact cratering, aeolian sand and dust transport, a variety of slope processes, changes in polar ices, and diverse effects of seasonal CO2 frost. The extent of surface change has been surprising and indicates that the present climate is capable of reshaping the surface. Activity has important implications for the Amazonian history of Mars: understanding processes is a necessary step before we can understand their implications and variations over time. Plain Language Summary: Many surface processes are active across the surface of Mars, producing changes that can be observed from orbit and by landed missions. The observed changes include new impact craters, sand and dust transported by the wind, a variety of flows on slopes, and many changes to perennial ice deposits. Many changes are driven by seasonal CO2 frost. These changes indicate that surface evolution on Mars is ongoing and not confined to past climate conditions. Key Points: Many different surface processes are actively shaping the geomorphology of Mars todayCurrent surface changes must be understood in order to correctly interpret changing environments over timeSeveral active Martian processes were not predicted and lack a terrestrial analog [ABSTRACT FROM AUTHOR]

We studied a multisequal soil succession (MSS) just south of Torres del Paine National Park (51°S), at the present-day core of the Southern Westerly Winds (SWW). The Río Serrano Section comprises paleosol horizons with associated intervening loess and sandy loess beds formed during the Holocene. Our record suggests strong and stable aeolian activity between ∼9.3–7.2 ka followed by a decline with centennial-scale variations until ∼5 ka. A strengthening commenced at ∼5 ka and culminated in a maximum between ∼2.2–0.5 ka with millennial-scale variations. Subsequent weakening of aeolian activity between ∼0.5 and 0 ka was coeval with the deposition of a ∼40 cm-thick paleosol, after which aeolian activity increased abruptly and reached an unprecedented maximum starting in the mid-20th century. The inferred wind intensity variations from our data bear partial agreement with competing hypotheses of SWW evolution, which postulate minimum SWW influence in SW Patagonia during the early Holocene and maximum influence during the Late Holocene, or vice versa. When analyzed through the lens of vegetation physiognomy/distribution and associated hydrological balance inferences from neighboring sites, our results suggest a primary control by precipitation and wind speeds associated to SWW strength at regional scale, modulated by the position of the forest/steppe ecotone east of the austral Andes. Human activities during the mid-20th century (deforestation, fire-regime shifts, livestock grazing, land use changes) caused an unprecedented increase in aeolian activity through decreased vegetation cover that increased sediment availability for aeolian transport, marking a striking difference with the magnitude of natural processes before the Anthropocene. Our results highlight the importance of climate change and natural/human-driven changes in vegetation cover for deciphering wind intensity histories, particularly in the transition from humid to semiarid environments along the eastern slope of the southern Patagonian Andes. • The Southern Westerly Winds (SWW) play a key role on global climate. • SWW Holocene changes in Southern South America (SSA) are still matter of debate. • Most of SWW reconstructions in SSA are based on indirect proxies of wind intensity. • Vegetation cover is a key factor on wind transport affecting sediment availability. • This is particularly significant in the transition from humid to arid environments. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the environmental factors that influence the orientation of lakes and basins in continuous permafrost of the Yana–Indigirka Lowland, NE Siberia. In this area, 24,782 lakes each with an area of >10,000 m2 were digitized from Google Earth satellite imagery, and four categories of lakes and drained lake basins were identified in two sub-study areas from Sentinel 2 imagery. Regionally, the lakes show a single modal orientation east–west to ESE–WNW, which is broadly parallel to the prevailing wind from 80 to 90° recorded at the nearest meteorological stations during June–October, when the lakes are likely to have been partially or completely ice-free and therefore exposed to wave-induced currents. Regression analysis suggests that lake orientation tends to be strongest in flatter terrain (<1°) that is not formed in silt- and ice-rich yedoma deposits. Locally, however, two sub-study areas show two modes of almost equal size, with lakes and basins aligned ESE–WNW or NNE–SSW, and thus approximately either parallel to or perpendicular to prevailing winds. Local deviation from the ESE–WNW lake alignment in the sub-study areas is attributed to a sandy substrate and topographic control. Sandy substrates appear to favour perpendicular orientations, whereas elongate depressions aligned broadly east–west, and supporting meandering rivers, favour parallel orientations. Overall, therefore, the impact of prevailing summer wind direction on lake and basin orientation is moderated by environmental factors of topography and substrate. • Regionally, lakes tend to be oriented east–west, parallel to prevailing wind. • Such orientation is strongest in flattish terrain not underlain by silty yedoma deposits. • Locally, lakes and basins are aligned parallel or perpendicular to prevailing wind. • Local, perpendicular orientation is favoured by sandy substrates. • Local, parallel orientation occurs along linear, topographic depressions. [ABSTRACT FROM AUTHOR]

The northeastern part of the Ebro Basin (NE Spain) features loess that cover an area of about 40 km2 on the northern slopes of the Serra d'Almenara anticline. The deposits and soils developed from them were mapped, described, and dated by luminescence. Additionally, grain size, percentage of heavy minerals (>2.8 g/cm3), and the mineralogical composition of the heaviest fraction (>3.2 g/cm3) were analysed. The coarse textures of the deposits indicate a very proximal origin. Therefore, potential source areas of the sands and silts were analysed with special attention given to the extensive river floodplains and alluvial fans close by, as well as gypsum-rich rocky outcrops. The mineral signature of the loess shows that it mainly originates from the alluvial plain of the Segre River, located about 10–30 km to the west. In some places, the loess also received particles from the alluvial fans of the Ondara and Corb rivers located south of the Almenara reliefs. In addition, the gypsum present in the loess is apparently derived from Eocene deposits. The loess in the study area was deposited during cold phases of the last two glacial cycles when the topographic obstacle of the Serra d'Almenara blocked the dominant winds from the southwest. Analysis of the almost 4-meter-thick profile of Pilar d'Almenara shows initial but limited accumulation phases in Marine Isotope Stages (MIS) 6, followed by the formation of a red soil during MIS 5e. Accumulation resumed during MIS3, with more energetic and powerful wind transport during the final phase of MIS 3 (ca. 34–30 ka) and early MIS 2, but prior to the Last Glacial Maximum. Our data highlights the prominent role of large rivers and alluvial fans as the sources of particles that are later reworked by the wind. • The most important heavy mineral species as tracers are zircon, staurolite, rutile and inosilicates. • Diiodomethane facilitates the recognition of very heavy minerals in sands. • Luminescence dating, together with the particle size and mineralogical results, allow for the identification of periods of maximum activity and the origin of materials in each era. [ABSTRACT FROM AUTHOR]

Sandy deposits can have a different genesis and form in different sedimentation environments. The example of the tar sands of the Early Permian age of the Republic of Tatarstan (Russia) shows the possibility of their complex and polygenic formation with the cardinal processing of the initial sediments under the influence of superimposed processes. Using paleogeomorphological analysis and mineralogical and lithological studies, the effect of aeolian processes on the formation of a sandy horizon with a two-layer structure has been established. As a result of the short-term sea regression, the coastal-marine sands were partially above the sea level. The upper part of the sandy sediments was subjected to aeolian processes with the blowing of the clay component from the sands, which led to the formation of two benches – the upper sandy and the lower sandy-clayey ones. The boundary between them is the ancient groundwater table (Stokes surface), which can be used as a reference point in the development of geological models.

Active aeolian systems are present across the martian surface, with active dune fields commonly found in depressions such as craters and valleys. There are many dune fields within the equatorial region of Mars, including Valles Marineris, but the effects of topography on wind regimes and consequently dune migration in Valles Marineris is poorly understood. We investigated both the ripple and dune migration in a dune field in Coprates Chasma using High Resolution Science Experiment Images (HiRISE) and Context Camera (CTX) images. Migration rates of dune brinks and ripples were measured over varying time scales, between Earth years 2007–2014. The dunes here are some of the tallest on Mars, with heights of up to 182 m. The dune brinks are migrating eastwards at a rate of 0.1–0.3 m/EY through the valley due to topographical influences on the local winds. Potential sediment sources for the dune field were identified and investigated by studying thermal inertia and mineralogy. The topographic slope‐related katabatic winds travel down the valley walls and converge with the dominant winds traveling through the center of the valley, causing overall eastwards dune migration. Topography is likely the dominant control on the local wind regime; slope winds travel down the sides of the valley walls and are funneled through the center of the valley. These local winds subsequently facilitate the migration of the large dunes in Coprates Chasma, thus expanding our understanding of local winds in the Martian environment. Plain Language Summary: Sand dunes and dune fields are common on Mars. Wind erosion and the formation of dunes and ripples are one of the dominant active surface processes on Mars. Localized winds allow dune movement to occur and measuring how fast the dunes and ripples are moving is important for understanding the martian environment. We can monitor the movement of dunes and ripples by using high resolution (0.25 m/px) and medium resolution (5–6 m/px) satellite images. Measuring the migration of the dunes and ripples in Valles Marineris (the largest canyon in the solar system) allows inferences to be made about present‐day wind regime. We found the valley topography and steep slopes may accelerate the winds traveling eastwards through the valley, which converge with winds traveling down the valley slopes. It is likely that these combined winds facilitate the erosion of several source regions, supplying sand to the dune field enabling the migration of the large dunes and ripples. These results highlight the effects of topography on local winds and the influence a wind regime has on large dunes. Key Points: Dune brink and ripple migration in Coprates Chasma quantified for both short and long time periods for Earth years 2007–2014Potential sources for the dune field evaluated using thermal inertia and mineralogyCanyon topography may influence the local wind regime and thus the activity of bedforms [ABSTRACT FROM AUTHOR]