8/14/2019 Aeolian and Barrier Island System.pptx
1/37
8/14/2019 Aeolian and Barrier Island System.pptx
2/37
Group Members :
Mustahsan ShuaibMohtasim Niazi
Ehsan Haroon
Syed Muhammad Ali Shah
Ahsan Khursheed
Rehamt Ali
*Aeolian and Barrier Island
Depositional System
8/14/2019 Aeolian and Barrier Island System.pptx
3/37
8/14/2019 Aeolian and Barrier Island System.pptx
4/37
*There are various depositional environmentsin which the processes of sedimentationoccurs.
*Here in this presentation two importantdepositional systems Aeolianand BarrierIsland Systems will be discussed.
*Aeolian depositional system is a very diversesystem which includes a lot of geological
features and structures so it will be discussedin detail as compared to Barrier Island system
8/14/2019 Aeolian and Barrier Island System.pptx
5/37
*
*Aeolian sedimentary processes are those
involving transport and deposition of material
by the wind
*The most obvious aeolian environments arethe large sandy deserts in hot dry areas of
continents
*Aeolian sands deposited in desert
environments have distinctive characteristicsthat range from the microscopic grain
morphology to the scale of cross-
stratification
*Aeolian sandstones are good hydrocarbon
reservoirs and aquifers.
Introduction
8/14/2019 Aeolian and Barrier Island System.pptx
6/37
8/14/2019 Aeolian and Barrier Island System.pptx
7/37
8/14/2019 Aeolian and Barrier Island System.pptx
8/37
*
8/14/2019 Aeolian and Barrier Island System.pptx
9/37
8/14/2019 Aeolian and Barrier Island System.pptx
10/37
8/14/2019 Aeolian and Barrier Island System.pptx
11/37
Two forms of wind erosion
Deflation
Removal of material by wind transport
Abrasion
Mechanical weathering of rock by wind
blown sand
Wind Erosion
8/14/2019 Aeolian and Barrier Island System.pptx
12/37
The blowing away ofloose sand, silt, and claysized particles
Larger particlesremain
Only takes place indesert areas, or in theabsence of vegetation
Roots tend to holdsoil in place
8/14/2019 Aeolian and Barrier Island System.pptx
13/37
*
Desert pavement is formed when sand and
silt are blown away
Deflation may excavate depressions in excess
of 50 m
8/14/2019 Aeolian and Barrier Island System.pptx
14/37
8/14/2019 Aeolian and Barrier Island System.pptx
15/37
*
*Natural sandblasting
*Kinetic energy of wind is transferred to wind-driven
particles
*Particles impact rock surfaces & knock off small pieces
8/14/2019 Aeolian and Barrier Island System.pptx
16/37
Abraded and polishedrock surface producedby wind erosion
At least one polishedsurface facing thewind
Prevailing winddirection may bedetermined
Uncommon comparedto stream erosion
8/14/2019 Aeolian and Barrier Island System.pptx
17/37
*Following are the main features and structures
that are present in a typical Aeolian System,
o
Rippleso Dunes
o Cross Beddings
o Mud Cracks
8/14/2019 Aeolian and Barrier Island System.pptx
18/37
*Ripples form perpendicular to wind from saltatinggrains
*Ripples occur at regularly spaced intervals
*Ripples may form on dune surfaces
*Crest to crest distance ranging from a few centimetres
to several metres
*Ripple heights range from less than a centimetre to
more than ten centimetres
8/14/2019 Aeolian and Barrier Island System.pptx
19/37
8/14/2019 Aeolian and Barrier Island System.pptx
20/37
*
A hill or ridge of sand deposited by wind form fromsmall irregularities in the land surface
Air flow is disrupted
A pocket of low wind velocity is formed
Sediment accumulates in the pocket
Growing mound further disrupts air flow
Crest becomes unstable, sand avalanches down the
slip face
8/14/2019 Aeolian and Barrier Island System.pptx
21/37
*
Dune geometry
Asymmetrical shape
Shallow upwind slope,
10-12O
Steep downwind slope,
33-34O, angle of repose
There are many types of
the sand dunes
depending upon thewind patterns and flows.
8/14/2019 Aeolian and Barrier Island System.pptx
22/37
8/14/2019 Aeolian and Barrier Island System.pptx
23/37
*Cross beddings are the features which are
strongly related to the Aeolian system
*Cross-bedding is the bedding in which adjacent
beds may dip in different directions
*Each bed shows the paleo-current of the winds
*In deserts the wind direction is changing
constantly thats why we find alternating beds
dipping in different directions
8/14/2019 Aeolian and Barrier Island System.pptx
24/37
*Cross beddings showing wind flowing pattern
in paleo-environment.
8/14/2019 Aeolian and Barrier Island System.pptx
25/37
* In the deserts temporary lakes are formed known
as Playa lakes which are formed in the rainy
season
*Especially when flash floods occur
*These playa lakes are the dump site for the
minerals deposits and the ores also*Along with the minerals fine sediments like clay
and evaporites also deposit
*These fine grain sediments form a plain covering a
large area
*Mud cracks are produces in these areas when
water evaporates
*Sometimes these cracks are preserved hence can
be used for interpretation of paleo-environment.
8/14/2019 Aeolian and Barrier Island System.pptx
26/37
8/14/2019 Aeolian and Barrier Island System.pptx
27/37
* Lithologiessand and silt only
*Mineralogymainly quartz, with rare examples ofcarbonate or other grains
* Texturewell- to very well-sorted silt to medium sand
* Fossilsrare in desert dune deposits, occasionalvertebrate bones
* Bed geometry sheets or lenses of sand
* Sedimentary structures large-scale dune crossbeddingand parallel stratification in sands
* Palaeocurrents dune orientations reconstructed fromcross-bedding indicate wind direction
* Colouryellow to red due to iron hydroxides and oxides
* Faciesassociations occur with alluvial fans, playa lakes,and lake facies in deserts,
8/14/2019 Aeolian and Barrier Island System.pptx
28/37
8/14/2019 Aeolian and Barrier Island System.pptx
29/37
*
*Mainland beaches are long, narrow accumulationsof sand aligned parallel to the shoreline andattached to land
*Barriers range in size from less than 100m wide toseveral kilometers and their length ranges from afew hundred meters to many tens of kilometers
*They are similar to mainland beaches but areseparated from land by a shallow lagoon, estuary,
or marsh*Barrier-island systems are generated
predominantly by marine processes
Introduction
8/14/2019 Aeolian and Barrier Island System.pptx
30/37
*
*Beach and barrier-island are best developed onwave-dominated coasts with small to moderatetidal range
*Types of coasts with respect to tidal range:
Microtidal (0-2 m tidal range)
Mesotidal (2-4 m tidal range)
Macrotidal (>4 m tidal range)
*Barriers are generally absent on Macrotidal
coasts
8/14/2019 Aeolian and Barrier Island System.pptx
31/37
*The barrier-island setting is not a singleenvironment but a composite of three separate
*environments
*They may be partially attached to the land,forming a beach spit,
*or wholly attached as a welded barrier thatcompletely encloses a lagoon,
*or can be isolated as a barrier island in front ofa lagoon
8/14/2019 Aeolian and Barrier Island System.pptx
32/37
8/14/2019 Aeolian and Barrier Island System.pptx
33/37
*
*Beach deposits form on the beach face or
foreshore, which is the intertidal zone extending
from mean low-tide level to mean high-tide level,
corresponding to the zone of wave swash
*Shore facedepositsform in an environment thatextends from mean low tide level on the beach
down to the lower limit of fair-weather wave base
*Back-barrier sediments are deposited in several
sub environments in the back-barrier lagoon
landward of barrier beaches.
8/14/2019 Aeolian and Barrier Island System.pptx
34/37
8/14/2019 Aeolian and Barrier Island System.pptx
35/37
8/14/2019 Aeolian and Barrier Island System.pptx
36/37
*Lithologysand and conglomerate
*Mineralogymature quartz sands and shelly sands
*Texturewell sorted, well rounded clasts
*Bed geometry elongate lenses
*Sedimentary structures low-angle stratification andwave reworking
*Palaeo currentsmainly wave-formed structures
*Fossils shelly debris
*Colornot diagnostic ( depends on local lithology)
*Facies associations may be associated with coastalplain, lagoonal or shallow-marine facies
8/14/2019 Aeolian and Barrier Island System.pptx
37/37THATS ALL!