Windblown Sediment Research Articles

Discovery of Holocene millennial climate cycles in the Asian continental interior: Has the sun been governing the continental climate?

We conducted a high-resolution study of a unique Holocene sequence of wind-blown sediments and buried soils in Southern Siberia, far from marine environment influences. This was accomplished in order to assess the difference between North Atlantic marine and in-land climate variations. Relative wind strength was determined by grain size analyses of different stratigraphic units. Petromagnetic measurements were performed to provide a proxy for the relative extent of pedogenesis. An age model for the sections was built using the radiocarbon dating method. The windy periods are associated with the absence of soil formation and relatively low values of frequency dependence of magnetic susceptibility (FD), which appeared to be a valuable quantitative marker of pedogenic activity. These events correspond to colder intervals which registered reduced solar modulation and sun spot number. Events, where wind strength was lower, are characterized by soil formation with high FD values. Spectral analysis of our results demonstrates periodic changes of 1500, 1000 and 500years of relatively warm and cold intervals during the Holocene of Siberia. We presume that the 1000 and 500year climatic cycles are driven by increased solar insolation reaching the Earth surface and amplified by other still controversial mechanisms. The 1500year cycle associated with the North Atlantic circulation appears only in the Late Holocene. Three time periods — 8400–9300years BP, 3600–5100years BP, and the last ~250years BP — correspond to both the highest sun spot number and the most developed soil horizons in the studied sections.

Airflow reversal and alternating corkscrew vortices in foredune wake zones during perpendicular and oblique offshore winds

On all sandy coastlines fringed by dunes, understanding localised air flow allows us to examine the potential sand transfer between the beach and dunes by wind-blown (Aeolian) action. Traditional thinking into this phenomenon had previously included only onshore winds as effective drivers of this transfer. Recent research by the authors, however, has shown that offshore air-flow too can contribute significantly, through lee-side back eddies, to the overall windblown sediment budget to coastal dunes. Under rising sea levels and increased erosion scenarios, this is an important process in any post-storm recovery of sandy beaches. Until now though, full visualisation in 3D of this newly recognised mechanism in offshore flows has not been achieved. Here, we show for the first time, this return flow eddy system using 3D computational fluid dynamics modelling, and reveal the presence of complex corkscrew vortices and other phenomena. The work highlights the importance of relatively small surface undulations in the dune crest which act to induce the spatial patterns of airflow (and transport) found on the adjacent beach.

Contribution of aeolian sand to backbarrier marsh sedimentation

The frequency of island overwash is commonly assumed to be the main factor regulating sand flux to backbarrier marshes; however, aeolian transport of sand across a barrier has received little attention in saltmarsh research. The contribution of aeolian sand to backbarrier marshes is examined here with marsh cores and measurements of wind-blown sediment transport across transgressive and regressive parts of a barrier island. Backbarrier marshes fronted by a wide washover fan or a high-elevation dune ridge were supplied with aeolian sand that significantly contributed to vertical accretion, especially near the marsh – barrier island edge. The percent volume of the marsh originating from aeolian sand, based on the upper 1 cm of marsh sediment, decreased by an order of magnitude only ∼20 m from the dune – marsh boundary. Sandy beds sampled in every marsh core at depth are composed of aeolian sand and were likely emplaced over time after storms deposited a sandy washover fan near the marsh and/or reduced vegetation cover across the island. Sand beds preserved within backbarrier marsh deposits are commonly thought to have been emplaced rapidly during a storm; however, post-storm aeolian transport should also be considered as an important mechanism for forming sand beds over a longer period of time within saltmarsh strata. The contribution of aeolian sand to backbarrier marsh accretion should increase as sea level continues to rise causing many barrier islands to narrow thereby reducing transport distances between the dune and marsh. Along developed coastlines, however, anthropogenic factors associated with increased development largely decrease the connectivity between the dunes and backbarrier marsh.

Late-Pleistocene paleohydrography, eolian activity and frozen ground, New Jersey Pine Barrens, eastern USA

AbstractThe Late Pleistocene surface paleohydrography of the New Jersey Pine Barrens consisted of a series of broad braided alluvial surfaces with meandering paleochannels. This drainage is best explained in terms of impermeable (i.e. frozen) substrate, high sediment load, variable or decreasing discharge, and eolian sedimentary dynamics. Evidence for eolian activity is provided by wind-abraded sand grains, coversand, dunes, ventifacts, deflation hollows and wind-polished boulders. In several places stream avulsion occurred due to channel infilling by locally-derived wind-blown sediment. The braided and meandering river systems that characterise the tundra and polar semi-desert lowlands of the Western Canadian Arctic are described as modern analogs.

Depositional processes beneath coastal multi‐year sea ice

AbstractThe extent of multi‐year sea ice impacts climate processes worldwide, such as ocean–atmosphere carbon dioxide exchange and deep ocean current formation. Reconstructing these processes in the past, and assessing the distribution of ecologically and climatically significant features, such as polynas, requires recognition of sediments deposited under multi‐year sea ice, but little is known about their characteristics. Textural analysis of subaerial and sea floor sediment in Explorers Cove, McMurdo Sound, at the mouth of Taylor Valley, Antarctica, augmented with observations of sedimentary structures and faunal components, elucidates how sediment is transported to the sea floor and allows characterization of the deposits. Comparison of grain‐size characteristics of subaerial (moraine, delta and sea‐ice surface) sediment and sea floor sediment from short cores taken at depths of 7 to 25 m indicates that the likely source of the moderately to poorly sorted sea floor sand is deltaic sediment; small glacial meltwater streams have built deltas since Taylor Valley became ice‐freeca7000 years ago. Windblown sediment accumulating on the multi‐year sea ice close to the coast typically is coarser grained than sediment on the sea floor; this suggests that the transport of sediment through the ice to the sea floor is not the predominant mode of sediment transfer. However, supra‐sea‐ice sediment does move to the sea floor through local fractures. The rate of sedimentation under multi‐year sea ice is low because of limited stream flow and biogenic sedimentation; the ice cover inhibits primary productivity and dampens waves, precluding physical re‐suspension. The upper centimetres of sea floor sediment are churned by epifaunal scallops and brittle stars that leave no telltale biogenic structures and whose calcite ossicles and shells may be poorly preserved. The resulting deposits under multi‐year sea ice are poorly sorted, massive sand that provides little evidence of the bioturbators that have masked the indicators of the original physical depositional processes.

Wind erosion and PM10 emission affected by tillage systems in the world's driest rainfed wheat region

The Horse Heaven Hills of south-central Washington is the driest rainfed wheat growing region in the world. Low precipitation, high winds, poorly aggregated soils, sparse residue cover, and a tillage-based winter wheat (Triticum aestivum L.) – summer fallow (WW-SF) cropping system often combine to create soil surfaces which are susceptible to wind erosion. No-tillage summer fallow (NTF) and conservation tillage fallow (CTF) with an undercutter sweep implement were examined as alternative practices to traditional tillage fallow (TTF) with a tandem disk implement for reducing wind erosion and PM10 (particulate matter ≤10μm in aerodynamic diameter) emissions during the fallow phase of the WW-SF rotation. Wind erosion and PM10 emissions were assessed with a wind tunnel after primary spring tillage in mid-to-late April and after sowing winter wheat in August. Sediment loss and PM10 vertical flux and loss were generally less for NTF than with TTF, likely due to retention of surface residue and maintaining a soil crust in NTF. Sediment and PM10 loss increased after sowing wheat in both the TTF and CTF treatments. Although NTF abated the loss of sediment and PM0 compared with TTF, NTF is not yet an economical option for most growers in the region. Conservation tillage fallow using the undercutter sweep is an economically viable alternative to TTF for reducing windblown sediment and PM10 loss from agricultural soils in the Horse Heaven Hills.

Aeolian construction and alluvial dismantling of a fault‐bounded intracontinental aeolian dune field (Teruel Basin, Spain); a continental perspective on Late Pliocene climate change and variability

AbstractAn aeolian dune field migrating to the east encroached on the toes of alluvial fans in the Teruel Basin (eastern Spain) during a short interval in the Late Pliocene (ca 2·9 to 2·6 Ma), when Northern Hemisphere glaciation and strong glacial–interglacial cycles began. Preservation of the dune field was controlled by syn‐sedimentary activity of a normal fault. Ephemeral water discharge eroded aeolian sands and formed V‐shaped channels in which aeolian sandstone blocks accumulated. The incorporation of loose aeolian sand in wadi waters modified the sediment/water ratio, changing the physical properties of the flows as they penetrated the aeolian dune field. The erosion and cover of aeolian dune foresets by sheetflood deposits suggest that dune‐damming caused the intermittent ponding of water behind the dunes and its flashy release. The arid climate in the Late Pliocene western Mediterranean realm favoured the transport of windblown sediments from northern Africa and western Mediterranean land masses into the Mediterranean. The formation of the studied aeolian dune field (2·9 to 2·6 Ma) and possibly others (for example, the Atacama, Namib and Sahara deserts) correlates with a strong increase of the influence of obliquity, which can be attributed to the combination of a regional expression related to the reduced effect of precession due to a minimum in the long‐period (2·3 Ma) eccentricity cycle and a remote expression of the onset of the Northern Hemisphere glaciation.

Geochemical and magnetic characteristics of fine-grained surface sediments in potential dust source areas: Implications for tracing the provenance of aeolian deposits and associated palaeoclimatic change in East Asia

We investigated the geochemical and magnetic characteristics of fine-grained surface sediments (fractions <63μm) of 182 samples collected at 20 sites in potential dust source areas of arid China (along the southern border of Mongolia). We found coefficients of variation ranging from 2.8 to 35.2% for the four magnetic parameters (χlf, ARM, SIRM, and the S-ratio) in these samples, and this variation may have great significance for interpreting the magnetic characteristics of aeolian deposits far from their source regions. In addition, the results also show that chemical weathering in the potential dust source areas did not play a major role in pedogenesis and evolution of the characteristics of the fine-grained surface sediments because there were variations of only 5% in the values of the chemical index of alteration, which is usually considered to indicate the intensity of chemical weathering, versus variations of 14% in the Rb/Sr ratio. In addition, there was no significant positive correlation between the magnetic susceptibility and the Rb/Sr ratio, which shows that in the source areas, weathering caused little magnetic enhancement in the fine-grained surface sediments. Therefore, in addition to pedogenesis effects on the windblown sediments deposited far from their source regions, the geochemical and magnetic characteristics of fine-grained surface sediments in source areas exhibited complicated patterns.

First evidence of Pleistocene rock art in North Africa: securing the age of the Qurta petroglyphs (Egypt) through OSL dating

Long doubted, the existence of Pleistocene rock art in North Africa is here proven through the dating of petroglyph panels displaying aurochs and other animals at Qurta in the Upper Egyptian Nile Valley. The method used was optically stimulated luminescence (OSL) applied to deposits of wind-blown sediment covering the images. This gave a minimum age of ~15 000 calendar years making the rock engravings at Qurta the oldest so far found in North Africa.

Controls on marine–erg margin cycle variability: aeolian–marine interaction in the mid‐Cretaceous Iberian Desert System, Spain

AbstractThe interaction between aeolian dunes of the Iberian erg and Tethys waters during the mid‐Cretaceous led to a variety of sedimentary facies associations such as subtidal deposits, aeolian dunes, playa lakes, coastal lakes with tidal creeks, and marshes and lagoonal embayments with tide‐influenced delta deposits. Facies associations are organized in several stacked cycles. Every cycle is defined by a sand‐drift surface separating playa lake deposits below from aeolian dune deposits above, followed by a transgressive surface separating aeolian deposits below from shallow marine deposits above. The latter are covered by playa lake deposits and finally topped by the next sand‐drift surface. Similar marine–erg margin cycles have been explained previously in terms of high‐order relative sea‐level variations (normally controlled by glacioeustasy). The studied erg margin developed during the mid‐Cretaceous which is considered to be the archetypal example of a polar ice‐free greenhouse period. This manuscript presents an alternative explanation for the cycles as caused by climate‐induced variations in the aeolian sediment supply. In this scenario, orbitally induced latitudinal shifts of the boundary between climate belts led to alternating periods of increased and decreased precipitation in the highland catchments of the back‐erg system (Variscan Iberian Massif). When climate belts shifted to lower latitudes, back‐erg highlands were under the influence of the Northern Warm Humid Belt. While arid conditions prevailed in the lowland central‐erg, increased precipitation in the highlands and the consequent recharge of ground water led to a rise of the phreatic level in the erg system; that diminished wind erosion and windblown sediment input to the fore‐erg, so that the desert margin contracted. With ongoing basin subsidence this favoured the transgression. The increased desert‐ground water flux favoured permanent coastal lakes in the fore‐erg margin and the local development of vegetation. In places where such lakes (lagoons) were connected to the sea, tidal channels were active, as seen nowadays along the desert coast of Qatar (Persian Gulf). When climate belts moved to higher latitudes, the catchment areas in the back‐erg Iberian Massif were under the influence of the Northern Hot Arid belt and a decrease of precipitation led to a drop of the phreatic level, allowing deflation of dunes and exposed wadi channel floors, and the formation of desert pavements and deflation lags in the back‐erg area; this favoured the import of large volumes of windblown sand and dust, forcing progradation of the erg and consequently a retreat of the coastline. The sand fraction accumulated in climbing aeolian dunes and dust was trapped in extensive playa lake systems. Another long‐term allocyclic control is formed by active extensional tectonics that enhanced the creation of accommodation space, especially in the first cycle. A high ground water table sustained by subsurface water supply from the Variscan Iberian Massif generated coastal fresh/brackish lakes in which tide‐influenced meandering channels and salt marshes developed. Erg margin cycles thin upward in response to a decrease of the rate of basin subsidence, suggesting that transgressions led to deep erosion of the underlying aeolian dune sands.

Size Distribution of Windblown Sediment Emitted from Agricultural Fields in the Columbia Plateau

Windblown sediment resulting from erosion of agricultural land has impaired visibility and threatened human health in the U.S. Inland Pacific Northwest. There is, however, a lack of information on the size distribution of windblown sediment originating from these lands. Passive collectors were used to trap windblown sediment from heights of 0 to 1.5 m above eroding agricultural fields. Sediment collected during one high-wind event in each of 7 yr was separated into ≤10-, 11- to 32-, 33- to 45-, 46- to 100-, and >100-μm-diameter size fractions. Windblown sediment trapped nearer the soil surface was more characteristic of the erodible portion of the in situ parent soil. Vertical size gradation of windblown sediment was evidenced by a decrease in mass of the 46- to 100- and > 100-μm size fractions and increase in mass of the ≤10- and 11- to 32-μm size fractions with height from the soil surface. Trends in the sediment size distribution with height suggested that sediment ≤32 μm in diameter was transported primarily by suspension, sediment 33 to 45 μm in diameter was transported by saltation and suspension, and sediment >45 μm in diameter was transported primarily by creep and saltation. In addition, the size of windblown sediment observed at all heights above the soil surface was found to increase with increasing wind velocity. A large fraction of windblown sediment was comprised of suspension-sized aggregates and particles, thus mitigation strategies to control wind erosion in the Columbia Plateau must promote aggregation of the suspension component (≤32-μm diameter) of the parent soil or shelter the suspension component at the soil surface from high winds.

Field analog studies of the distribution of windblown sediments at Amboy Crater, California, with application to Mars

Many shallow craters in the Spirit Mars Exploration Rover site contain asymmetric distributions of windblown sediments, which could indicate the predominant local wind direction at the time of their deposition or redistribution. Terrestrial analog field work at the Amboy lava field, Mojave Desert, California, included real-time wind measurements and assessments of active sediment deposition in four small (<100m) craters. Preliminary results indicate that reverse flow or stagnant wind flow likely occurs in craters with depth-to-diameter (d/D) ratios of ≥0.05. Measurements taken within a crater of d/D of ∼0.02 do not indicate reverse flow; therefore, reverse flow is expected to cease within a d/D ranging from 0.02 to 0.05, resulting in wind movement directly over the crater floor in the downwind direction. Craters with asymmetric eolian deposits near the Mars Spirit landing site have d/D from 0.034 to 0.076, suggesting that reverse flow occurs in these craters. Thus, the position of windblown sediments in the small craters on the northwest part of the floor would indicate prevailing winds from the northwest to the southeast at the time of deposition or redistribution.

Modelling wind-blown sediment transport around single vegetation elements

Wind erosion is an important soil erosion and hence a soil degradation problem in the Sahelian zone of West Africa. Potentially, the characteristic dryland vegetation with scattered trees and shrubs can provide for soil erosion protection from wind erosion, but so far adequate quantification of vegetation impacts is lacking. The aim of this study was to develop a model of wind-blown soil erosion and sediment transport around a single shrub-type vegetation element. Starting with the selection of a suitable transport equation from four possible sediment transport equations, the effects of a single vegetation element on wind speed were parameterized. The modified wind speed was then applied to a sediment transport equation to model the change in sediment mass flux around a shrub. The model was tested with field data on wind speed and sediment transport measured around isolated shrubs in a farmer's field in the north of Burkina Faso. The simple empirical equation of Radok (Journal of Glaciology 19: 123–129, 1977) performed best in modelling soil erosion and sediment transport, both for the entire event duration and for each minute within an event. Universal values for the empirical constants in the sediment transport equation could not be obtained because of the large variability in soil and roughness characteristics. The pattern of wind speed, soil erosion and sediment transport behind a shrub and on either side of it was modelled. The wind speed changed in the lee of the vegetation element depending on its porosity, height and downwind position. Wind speed was recovered to the upstream speed at a downwind distance of 7·5 times the height of the shrub. The variability in wind direction created a ‘rotating’ area of influence around the shrub. Compared to field measurements the model predicted an 8% larger reduction in sediment transport in the lee of the vegetation element, and a 22% larger increase beside the vegetation element. Copyright © 2011 John Wiley & Sons, Ltd.

Degradation of mud brick houses in an arid environment: a geoarchaeological model

A common assumption in Near Eastern tell archaeology is that the majority of sediments originate from degraded mud bricks. Little is known about the mechanism of mud brick wall degradation. Here we present a detailed macro- and microscopic ethnoarchaeological study of the degradation of a mud brick house and propose a comprehensive mechanism for tell formation processes in arid environments. The study took place in southern Israel by trenching a ca. 60 year old abandoned mud brick house, followed by extensive sediment sampling. Macroscopic observations showed that mud brick walls degrade by collapse of single bricks and/or collapse of intact wall parts, either inwards or outwards. In addition, infill sediments within the house and outside it, in close proximity to its walls, form alternating sedimentary layers of various colors and textures. The degraded mud brick material lost its distinctive macroscopic structure, which makes it impossible to accurately identify this material by field observations alone. Mineralogical and elemental analyses established the sources of the house infill sediments, namely mud bricks and wind blown sediments. Alternating layers mostly originate from mixing between degraded mud brick material and wind blown sediments. Micromorphological observations revealed microscopic mechanisms of mud brick degradation and include processes of mud slurry gravity flows, sediment coatings and infillings, wind abrasion of walls, small-scale puddling, and bioturbation. This study provides a working scheme for site formation of abandoned mud brick structures in arid environments. It provides a set of criteria by which it is possible to differentiate floors from post-abandonment sedimentary features and thus improves the reliability of activity area research.

Climbing and falling dunes in Valles Marineris, Mars

Multiple occurrences of “wall dunes” are found several kilometers above the Valles Marineris canyon floor. Dune slip face orientation and bed form morphologies indicate transport direction and whether the wall dunes are climbing dunes or falling dunes. On Earth, these types of dunes form in a unidirectional wind regime and are strongly controlled by the local topography. Newly acquired Mars Reconnaissance Orbiter (MRO) images and topography of the walls of Valles Marineris show similar sand dune morphologies, as wind blown sediment has interacted with local and regional topography. Primarily found in Melas and Coprates Chasmata, these climbing and falling dunes are relevant for understanding aeolian sediment flux, sediment sources, and wind directions. Falling dunes show photogeologic and thermophysical evidence of their sand being provided by adjacent outcrops.

Effect of attachment configuration on the trapping efficiency of Vaseline-coated slide catchers for windblown particles

There are various types of the windblown sediment traps developed for wind tunnel and field studies. One of the main supports expected from these traps is in measuring surface dust concentrations to appropriately derive flux equations. The measurement performance and accuracy of a trap is very important and depends strictly upon the physical characteristics and the behaviors of dust grains with air flows. This paper presents the measurement results of static pressure distribution (SPD) of wind flow around Vaseline-coated slide (VCS) catchers with an aim of finding out whether or not particle trapping efficiency (η) of the VCS is related to the SPD. The SPD was evaluated by a wind reduction coefficient (Rc) in a series of wind tunnel experiments with different VCS settings which have different attachment configurations on a pole. Three VCS configurations were considered: a configuration on a circular plastic pole (CPP) and two configurations on wooden square poles (WSP1 and WSP2, respectively). Thus, the primary contribution of this work was to experimentally analyze the effect of the different attachment configurations on the SPD, and the secondary objective was to determine the effect of the SPD on the η. It was shown that spatial correlation and spatial pattern of the Rc were different in the surrounding area of each configuration, and ANOVA and DUNCAN tests indicated that η(s) of WSP1, WSP2, and CPP were different at the significant level of P ≤ 0.05 with the mean of 0.94 ± 0.09, 0.63 ± 0.14, and 1.13 ± 0.07, respectively. Additionally, the amount of PM20, PM40, PM60, PM80, and PM100 trapped by the configurations of WSP1, WSP2, and CPP considerably varied depending upon the particular aerodynamic circumstances associated with every configuration.

The ablation zone in northeast Greenland: ice types, albedos and impurities

AbstractIce types, albedos and impurity content are characterized for the ablation zone of the Greenland ice sheet in Kronprinz Christians Land (80° N, 24° W). Along this ice margin the width of the ablation zone is only about 8 km. The emergence and melting of old ice in the ablation zone creates a surface layer of dust that was originally deposited with snowfall high on the ice sheet. This debris cover is augmented by locally derived wind-blown sediment. Subsequently, the surface dust particles often aggregate together to form centimetre-scale clumps that melt into the ice, creating cryoconite holes. The debris in the cryoconite holes becomes hidden from sunlight, raising the area-averaged albedo relative to surfaces with uniform debris cover. Spectral and broadband albedos were obtained for snow, ice hummocks, debris-covered ice, cryoconite-studded ice and barren tundra surfaces. Broadband ice albedos varied from 0.2 (for ice with heavy loading of uniform debris) to 0.6 (for ice hummocks with cryoconite holes). The cryoconite material itself has albedo 0.1 when wet. Areal distribution of the major surface types was estimated visually from a transect video as a function of distance from the ice edge (330 m a.s.l.). Ablation rates were measured along a transect from the ice margin to the slush zone 8 km from the margin (550 m a.s.l.), traversing both Pleistocene and Holocene ice. Ablation rates in early August averaged 2 cm d−1. Impurity concentrations were typically 4.3 mg L−1 in the subsurface ice. Surface concentrations were about 16 g m−2 on surfaces with low impurity loading, and heavily loaded surfaces had concentrations as high as 1.4 kg m−2. The mineralogical composition of the cryoconite material is comparable with that of the surrounding soils and with dust on a snowdrift in front of the ice margin, implying that much of the material is derived from local sources. A fine mode (clay) is present in the oldest ice but not in the nearby soil, suggesting that its origin is from wind deposition during Pleistocene glaciation.

Rain and Dust: Magnetic Records of Climate and Pollution

Two contrasting examples of the application of mineral magnetism to environmental problems are discussed. Magnetic susceptibility measurements of sediments from the Chinese loess Plateau - the biggest accumulation of windblown sediments on earth - reveal one of the best records of continental climate change available. these records provide a detailed picture of glacial and interglacial cycles and variations in the east asian summer monsoon stretching back more than 2 million years. in the case of anthropogenic airborne particles, the spread of particulate pollutants can be robustly traced throughout a city environment by measuring the magnetic properties of leaves, which trap magnetic particles released from vehicle exhausts and/or industry emissions.

A late Pleistocene record of aeolian sedimentation in Blanche Cave, Naracoorte, South Australia

We provide geochemical analyses and grain size data for a clearly layered, 80 cm thick sedimentary deposit close to a roof collapse in Blanche Cave near Naracoorte in SE South Australia. This deposit contains aeolian material deposited between ∼40 ka and 14 ka cal BP and which yields airborne sediments spanning the Last Glacial Maximum, a period of time with little information for the Australian continent. The deposit also contains abundant vertebrate fossil material derived from owl pellets, accumulation and pitfall entrapment. Below the studied profile, large vertebrate remains are found but are not discussed here. No Holocene sedimentation occurred at the site examined in the cave, and the top of the sequence is capped with a layer that has been anthropologically disturbed and contains exotic Pinus pollen. Chronologies of the deposit were obtained using two dating techniques: single stage accelerator mass spectrometer (SSAMS) 14C analysis of 23 charcoal samples and optically stimulated luminescence (OSL) dating of quartz from 6 sediment samples. The 14C chronology is preferred to describe the history of the deposits since the OSL chronology, which consistently overestimates the associated radiocarbon dates, may be inaccurate due to complexities in calculating dose rates, and may in addition represent the timing of sediment deposition through the cave opening rather than sediment transport to the deposit site. Morphological analysis of single quartz grains and grain size analysis indicate different provenance that is confirmed through the geochemical analyses of bulk sediment. Major elements were measured by X-ray Fluorescence (XRF), trace and rare earth elements by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA ICP-MS), and Neodymium isotopic ratios were obtained using a Thermal Ionisation Mass Spectrometer (TIMS). Our results indicate that the aeolian material deposited in Blanche Cave over the 40–14 ka cal BP period originated from different sources across South Australia, although Nd isotopes clearly indicate a close association with sediments of the Kanmantoo Group outcropping along the eastern portion of the Mount Lofty Ranges and the Padthaway Ridge further south, both being located to the NW and NNW of the cave. During the latter part of Marine Isotope Stage 3, conditions were wetter and windblown sediment came from the coastal region just north and south of the Coorong Lagoon, with winds originating from the north-northwest. At that time, woody taxa appear to have vegetated the landscape. During the drier phases, especially the Last Glacial Maximum, sediment came from further inland, thus suggesting a different predominant wind direction, more from the northwest. The deglaciation saw material originating from a more northerly direction.

Effects of enhanced wind erosion on surface soil texture and characteristics of windblown sediments

It is well documented that wind redistributes and transports soil resources in semiarid ecosystems. However, fewer studies have quantitatively linked wind erosion to detailed grain‐size fractions and associated nutrient content in surface soil and windblown sediment. In this study, we examined (1) the effects of enhanced wind erosion on surface soil particle‐size distribution and (2) carbon (C) and nitrogen (N) characteristics of windblown sediments in a typical desert grassland of southern New Mexico. Our results show that surface soil has become noticeably coarser over a 2‐year period. In particular, content of soil particles in the category of 250–500 μm increased significantly, but soil particles in the fractions of 50–125 μm and &lt;50 μm were significantly depleted. In addition to the enrichment of C and N in the windblown sediments, our results reveal that fine particles (e.g., D &lt; 50 μm) were enriched to a much higher degree at height than C and N. Significantly, our results reveal that nearly 12% of total organic carbon (TOC) and 9% of total nitrogen (TN) were found in the particles with diameter &lt;50 μm, which account for only 1–2% of the mass of windblown sediments. In this wind susceptible environment, our findings suggest that (1) significant soil texture change (e.g., the loss of soil fines) driven by wind erosion could happen rapidly and soil fine particles (e.g., silt and clay) may be depleted within a few years and (2) the loss of even a small fraction of fine particles may indicate a substantial depletion of soil C and N.