Intersections between wind regimes, topography and sediment supply: Perspectives from aeolian landforms in Central Asia

Fitzsimmons, Kathryn E.; Nowatzki, Maike; Dave, Aditi Krishna; Harder, Hartwig

doi:10.1016/j.palaeo.2019.109531

Cited by 42 publications

(39 citation statements)

References 76 publications

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“…Thus alluvial plains and dry riverbeds with mixed grain-size sediments are a possible source of coarse silt. Such surfaces have been identified as major sources of fine sediment for aeolian transport to desert soils in the Mojave Desert (Sweeney et al, 2013; Cui et al, 2019) and for loess deposits in the Illi basin (Fitzsimmons et al, 2019). In the Sahara and its margins, patchy interdune lacustrine and playa deposits dating to the African humid period are widespread (Lézine et al, 2011) and may be an important source of silt (e.g., Ehrmann et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

“…They also indicate some of the challenges in assessing source areas for the coarse silt component of desert loess, which could be derived from a wide area, with diverse sources. However, modern and paleo-wind direction data from independent sources (e.g., sand dune orientations) can be used to develop pathways for sediment transport in conjunction with back-trajectory modeling, as demonstrated by Fitzsimmons et al (2019).…”

Section: Discussionmentioning

confidence: 99%

“…Loess deposits are widespread in the foothills and piedmonts of the mountains of central Asia, but their source(s) is poorly known (Schaetzl et al, 2018). In the Illi basin of southern Kazakhstan, Fitzsimmons et al (2019) analyzed the relationships between potential sediment sources, wind regimes, and loess deposits and concluded that most of the loess is derived from areas within 50 km of the deposit location. Back-trajectory analyses suggest the main sources for loess in southern Kazakhstan lie in areas where dunes and fine-grained sediments are juxtaposed, as in river source–bordering dune fields and alluvial plains.…”

Section: Sedimentary and Geomorphic Evidence For Desert Loess Provenancementioning

confidence: 99%

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On the formation of desert loess

Lancaster

2020

Quat. res.

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Sequences of quartz-rich coarse (20−63 μm) silt occur in many low- and midlatitude unglaciated arid and semiarid areas and have been termed “desert loess.” The processes by which these deposits are generated have been debated for decades. All hypotheses to explain their origin seek to provide mechanisms for the generation of silt-sized material without glacial grinding, which is the main process involved in the production of coarse silt at high latitudes. Possible mechanisms for the formation of coarse silt in arid regions include derivation from preexisting siltstones, mechanical weathering of silicate rocks, and abrasion of sand grains in active dune environments during intense transport events. Examination of the characteristics of desert loess and field and laboratory experiments to assess the role of dune areas as a source of coarse silt by abrasion and/or resuspension of residual fines suggests that many loess sequences are dominated by locally derived coarse silt. Improvements in the characterization of desert loess particle size, mineralogy, and geochemistry are needed, however, to identify sources and sinks of coarse silt, especially when combined with climatic back-trajectory analysis. Properly scaled experiments and modeling of particle collisions will also help to better quantify the effectiveness of abrasion in the generation of coarse silt in support of field observations.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Sedimentary and Geomorphic Evidence For Desert Loess Provenancementioning

confidence: 99%

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On the formation of desert loess

Lancaster

2020

Quat. res.

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“…The region's longest and most continuous post-Paratethyan archives are predominantly aeolian and have accumulated as thick blankets of loess along the mountain piedmonts. This aeolian dust has been transported by air masses associated with the major climate subsystems of the region, chiefly the westerlies 17 , with additional contributions from northerly transport or local katabatic winds 12,18 . Despite the potential of its widespread aeolian deposits 19 to record palaeoclimatic information [20][21][22][23][24] , paleoclimate datasets generated for ACA thus far are either coarse in timescale 17 or focus on recent, short-term intervals insufficient to inform us about long-term feedbacks 13,25 .…”

Section: Introductionmentioning

confidence: 99%

“…d18 Osw was calculated using the oxygen isotope equilibrium fractionation equation53,54 using pairs of T∆47…”

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confidence: 99%

Central Asian Modulation of Northern Hemisphere Moisture Transfer Over the Late Cenozoic

Prud'homme

Scardia

Vonhof

et al. 2020

Preprint

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Earth’s climatic evolution over the last 5 million years (Myr) is primarily understood from the perspective of marine mechanisms. While changes in ocean circulation go a long way towards explaining the transport of moisture onto the continents, the role of terrestrial feedbacks in the opposite direction remain largely unexplored. Here we reconstruct the last 5 Myr of rainfall variability in Central Eurasia from an 80 m-thick sedimentary succession at Charyn Canyon, Kazakhstan. Charyn Canyon lies at the centre of the world’s largest land mass and at the present-day transition between the mid-latitude westerlies and Siberian high-pressure system. Our record provides the first opportunity to interrogate long-term interactions between mid-latitude westerly and high latitude climate systems over the Eurasian continent. This missing terrestrial link highlights the significance of land-water feedbacks for long-term global climate.

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Investigating palaeodune orientations and contemporary wind regimes in Southeast Kazakhstan using a semi‐automated mapping framework

Nowatzki,

Fitzsimmons,

Harder

et al. 2024

Earth Surf Processes Landf

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The Ili‐Balkhash region in southeastern Kazakhstan hosts morphologically diverse dormant desert dune fields and presents an interesting opportunity for geomorphological and palaeoenvironmental studies. Because the morphology of aeolian dunes is primarily driven by wind dynamics, the dormant dunes in the study area may reflect past wind conditions. We assess their concurrence with modern ERA5 wind data to test whether there has been a change in wind regime since the dunes' last phase of activity. Our approach includes dune mapping, the quantification of dune orientations, the modelling of modern bedform orientations, and optically stimulated luminescence (OSL) dating for temporal context. The centrepiece of our methodological contribution is a novel semi‐automated mapping workflow using geographic object‐based image analysis (GEOBIA) and machine learning (ML) on Sentinel‐2 satellite imagery. Within the scope of a case study, we map dune fields in the Ili‐Balkhash region and quantify dune orientations. We further apply the maximum gross bedform‐normal transport (MGBNT) concept to model bedform orientations matching modern wind regimes for each of the sites. We find that strong winds show better alignment with observed dune orientations than wind regimes comprising all wind speeds. Furthermore, bedform orientations in some of our study sites, namely those that are located in the open plain southeast of Lake Balkhash, do not reflect modern winds. The divergence between dune orientations and wind regime suggests changes in local wind dynamics since the dune fields' last phase of activity.

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Intersections between wind regimes, topography and sediment supply: Perspectives from aeolian landforms in Central Asia

Cited by 42 publications

References 76 publications

On the formation of desert loess

On the formation of desert loess

Central Asian Modulation of Northern Hemisphere Moisture Transfer Over the Late Cenozoic

Investigating palaeodune orientations and contemporary wind regimes in Southeast Kazakhstan using a semi‐automated mapping framework

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