This document discusses aeolian depositional features and landforms formed by wind erosion and deposition. It begins by introducing aeolian processes and the different environments where they are common. It then describes how wind deposits sediment through sedimentation, accretion, and encroachment. Major landforms formed include sand dunes like barchans, seifs, parabolic, and star dunes. Sand sheets, loess, and sand ridges are also discussed. The document provides detailed descriptions of the formation and characteristics of these different aeolian features and landforms.

1. Department of Applied Geology
Dr. HariSingh Gour Vishwavidyalaya
Sagar, Madhya Pradesh
Depositional Features of Aeolian Cycle
Abhishek Kumar
M.Tech 1st Sem
Reg. No. Y22251018
Under Guidance of:
Prof. P.K. Kathal
Seminar

2. Contents
 Introduction
 Aeolian Environments of Deposition
 Deposition
 Landforms
• Sand Dunes
• Sheets of Sand
• Loess

3. Introduction
 Wind, an important agent causes
erosion & deposition.
 Features formed by wind called
‘aeolian features’.
 It has a widespread effect.
 Effective in areas without vegetation.
 During transport, material forms
two types of deposits
• accumulations of sand
• deposits of silt and clay known as
loess. https://en.wikipedia.org/wiki/Dune#/media/File:D%C3%BCn
e_S-Schlag_Sossusvlei.JPG

4. Environments
 Non-desertic:
(a) along shore lines
(b) along stream courses in semi-arid regions
(c) areas with poorly consolidated sediments (sand grains)
(d) areas of glacial outwash.
 Arid, semi-arid & sub-humid regions show best development
 Such regions generally occur in central & western regions of
continents in northern hemisphere.

5. .
Distribution of aeolian environments in the world. Source: Thomas (1989)

6. Wind Deposition
 On reduction in velocity due to obstruction, wind’s transporting
power reduces.
 Deposition takes place in 3 ways (Bagnold ,1941) :
1. Sedimentation,
2. Accretion, and
3. Encroachment

7. Depositional Landforms
 May occur as sheets of sand/loess/dunes.
 Bagnold (1941 ):two classes based on scale.

8. Sand Dunes
 Hills/mounds of sand.
 “mobile heap of sand with independent
existence, either ground form/fixed wind
obstruction”.
https://en.wikipedia.org/wiki/Dune#/media/File:Rub_al_Khali_00
2.JPG
https://en.wikipedia.org/wiki/Dune#/med
ia/File:Cadiz_Wilderness_and_Valley.jp
g

9. Dune formation
 On obstruction, wind leaves some of
the transported sand
 Gradually adds height to the evolving
dune
 On windward sand moves up &
leeward side slumps where wind
eddies remove particles.
 These simultaneous processes shape
the dune. https://i0.wp.com/academistan.com/wp-
content/uploads/2022/12/Sand-Dune-
Formation.png?w=564&ssl=1

10.  At critical height, particles begin to slip forward & leeward slope slumps
 These processes on windward and leeward sides continue, and gradually
the dunes move towards the slip-face side
Dune movement

11. Barchans
 Crescentic-shaped dunes.
 Tips extending to leeward, make this side
concave & windward side convex.
 Migrates in the downwind direction
 Height ranges 0.5 to 100 m.
 Width ranges 30 to 300 m.
 Forms in limited sand supply &
unidirectional winds.
 Several barchans join their horns to form
transverse dunes, across wind direction.
https://en.wikipedia.org/wiki/Barchan#/media/File:Barchan.jpg
https://en.wikipedia.org/wiki/Dune#/media/File:Tranverse_dune.jpg

12. Seif (Longitudinal Dunes)
 A linear dune, resulting from
bidirectional converging winds.
 Axis aligned parallel to resultant
direction.
 When barchan moves into
bidirectional regime, one horn
elongates.
https://media.springernature.com/lw685/springer-static/image/prt%3A978-1-4614-3134
3%2F12/MediaObjects/978-1-4614-3134-3_12_Part_Fig1-460_HTML.gif
https://i0.wp.com/academistan.com/wp-content/uploads/2022/12/Seif-
Formation.jpg?w=625&ssl=1

13. Parabolic Dunes
 An inversion of barchans
 Horns point windwards
 Typical in moist regions
 Elongated arms held in place by
vegetation
 Formed from blowout dunes
where the erosion of vegetated
sand leads to a U-shaped
depression.
https://upload.wikimedia.org/wikipedia/commons/0/09/P
arabolic_dune.jpg

14. Star Dunes
 Sand mounds with slip faces on 3/more arms
 Radiate from high center of the mound
 Formed in multi-directional wind regime
 Grow upward rather than laterally
 Fixed at one site for years
Sand Ripples
 Small scale, regular, wave-like undulations
 Perpendicular to wind direction
 1 to 30 cm high & few cm to some m apart
 Shape changes very quickly Sand ripples
Star dunes
https://en.wikipedia.org/wiki/Ripple_marks#/me
dia/File:1969_Afghanistan_(Sistan)_wind_rippl
Adapted from McKee (1979)

15.  Long, undulating features
 Saltation is main process of their formation.
 Particles on leeward side protected from wind
impact
 Crest receives grains faster than it loses them
 Depressions lose grains faster than they receive &
hence get hollowed
Whalebacks
 Flat-topped sand ridge extending parallel to wind
 Bagnold: residue from the series of dune chains
downwind
 larger dimensions, may be 100 miles long, 2 miles
wide, & 150 feet high.
Sand Ridges
Sand ridge
https://i0.wp.com/academistan.com/wp-content/uploads/2022/12/
ridge.png?w=469&ssl=1

16. Dunefields
Accumulations of sand
Occupying areas < 30,000 km2 with at least 10 dunes spaced
at distances exceeding dune wavelength
Contain small and simple dunes.
Chains of transverse & seif dunes, barchans & other features
develop on whalebacks to make dune fields.
Sand seas
 Differ from dunefields in areas >30,000 km2
 Bears more complex & bigger dunes.
 Ridges or mounds repeated in rows, giving wavy appearance.
 About 60% of sand seas are dune-covered,
 others may be dune-free and comprise low sand sheets, with
some vegetation
https://geography.name/wp-
content/uploads/2015/09/1-camel-caravan-in-the-
erg-chebbi-southern-morocco-ralph-ledergerber-
640x319.jpg
https://i0.wp.com/academistan.com/wp-
content/uploads/2022/12/Dunefield.jpg?re
size=304%2C228&ssl=1

17. Sand sheet
Sand area marked by flat surface
No topographic relief other than small
ripples.
Sand Shadow
Formed due to obstacle in path of wind.
Flow velocity dips in the lee of obstacle than
surrounding.
Thus sand collect on leeward side &form
the Sand Shadow close to obstacle in its
shelter
Selima sand sheet, Libyan desert
https://i0.wp.com/academistan.com/wp-
content/uploads/2022/12/Sand-

18. Sand Drift
Related to wind blowing as
channelized stream through gaps in
landforms
All the accumulating sand moves
forward through the gap
Close to the gap, no deposition because
the channelized wind is strong.
Farther from the gap, loses its force, &
drops the sand in the line of the gap, a
mound builds up.
 Later this mound forces the wind to
slow down and deposit more sand here.
https://i0.wp.com/academistan.com/wp-content/uploads/2022/12/Sa
Drift.png?w=468&ssl=1

19. Loess
Deposit of wind-blown silt and clay
Composed of angular grains of quartz,
feldspar, & other minerals weakly cemented
by calcite
Has high porosity, nearly 60% & lacks
layering
Wind can carry silt for hundreds or even
thousands of km and then deposit it as loess.
Due to interlocking of silt particles, forms
vertical cliffs and bluffs.
Areas with thick deposits of loess are very
valuable for farming crops.
https://en.wikipedia.org/wiki/Loess#/media/File:LoessVicksbur
Loess in Vicksburg, Mississippi, United States

20. World distribution of loess
Source: Adapted from Livingstone and Warren (1996, 58)

21. References
https://academistan.com/geography/geomorphology/aeolian-landforms-erosional-and-
depositional/
https://courses.lumenlearning.com/earthscienceck12/chapter/wind-erosion-and-deposition/
https://en.wikipedia.org/wiki/Aeolian_processes
Huggett, R.J. (2011). Fundamentals of Geomorphology 3rd Edition. London & New York:
Routledge, Taylor & Francis Group
Plummer, Charles C., Carlson, Diane H. & Hammersley, Lisa (2016). Physical Geology. Mc
Graw Hill Education
Summerfield, M. A. (2013). Global Geomorphology. London & New York: Routledge, Taylor
& Francis Group
Thornbury, W. D. (1954). Principles of Geomorphology. New York: John Wiley & Sons, Inc.,
London: Chapman & Hall, Ltd.

22. Thank you