Connections between sedimentary basins during continental ...
Evolution of Sedimentary Basins
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Transcript of Evolution of Sedimentary Basins
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Evolution of Sedimentary Basins
Sedimentation and Tectonics:
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Evolution of sedimentary basins is spatially relatedto continental evolutionand global tectonicprocesses.
Several studies show a close relationship betweensedimentary pattern and larger structuralelements of the Earth
Continents are formed bydifferent tectonicprocessess and related magmatism.
On the other hand these continents are destroyed
by continuous physical and chemicalweathering/erosion processes.
These sediments have been shifted through masstransport by water, wind and ice to nearest
depression(Basins).
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In order to understand evolution of sedimentary
basins following aspects/factors are considered :
1) Distribution of sediments(Large Scale).
2) Kinds of Sedimentary basins existing during
geological history.
3) Nature and organisation of sedimentary fill.
4) Relationship between sediments and theirsource land(Provenance)
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1) Distribution of Sediments
Sediments are known to occur throughout thegeological history from 4200 m.y to present day.
They are extremly useful and provide crucial
information on the evolution of upper
continental crust, global surface environments,
redox conditions and biological evolution
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During the Achaean era(4200-2500m.y)
sediments spatially associated with volcanism
and chemical alteration processes weredominant over physical breakdown. These
sediments were involved in sedimentation and
metamorphism of varying degrees.
During Proterozoic stable environments
prevailed so sediments was quite extensive and
extensive flat sequences of conglomerates,
sandstone, shales and limestone weredeposited and these sediments were not
affected by deformation and metamorphism.
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During Phanerozoic, sediments were dominated
by volcanoclastic sequences in differentenvironments(shallow to deep waters). These
sedimentary associations contain abundant
biogenic materials such as plant and animal
fossils.
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2) Kinds of sedimentary basins existing
during Geological history
Achaean sedimentary basins are extremelydifficult to characterize in regard of its nature
and geometry as these basins were affected by
several episodes of deformation andmetamorphism and their original geometry and
other characteristics have been erased.
Intracratonic and back arc basins were commonduring middle to late archaean(3200-2600)
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During Proterozoic, globally stable environment
prevailed as continental crust lost huge amountof heat producing elements during late archaean
techtanothermal events.
Most of the Proterozoic sedimentary basins arestable, continental platforms, where detrital
sediments derived from large cratons were filled.
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During Phanerozoic large sedimentary basins
developed along plate margins(back arc andisland arc basins) and also in collisional
environments(Sedimentary fill between two
continents e.g Tethys sea between India andAsian plate).
The sedimentary basins were huge and spatially
associated with orogenic cycle.
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4) Nature and organisation of
sedimentary fill
The Nature and organisation of sedimentary
sequences provide information on sedimentary
environments
It is not easy to characterise the nature and
organisation of sedimentary fill up in the
Archaean sedimentary sequence as they are
affected by deformaton and matamorphism andtheir original and depositional characteristics have
been disrupted.
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The Proterozoic sedimentary sequences globally
comprise abundant flat sequences of
conglomerate-sandstone-shale and carbonateassociationswhich are unmetamorphosed
The Phanerozoic sediments are fossiliferous and
comprise thick associations of conglomerate,sandstone, greywacke-argillite, shale, carbonate
and iron stones. These sediments were deposited
in diverse environments including shallow to
deep marine environments and were derived
from old continental crust as well as young
volcanic arc.
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4) Relationship between sediments
and their source land (Provenance)
In recent years numerous studies focussed on
sedimentologgy particularly to characterise
sediment source(provenance) by using sediment
characteristics, dating of heavy minerals(zircon,
monazite, garnet)and isotope tracers.
These studies show that sediments derived from
mixed sources with contrasting histories.
Combined sedimentological and geochronological
studies of clastic sediments useful to reconstruct
geometry of the source land
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Isotope tracers (Nd, Sr and Pb) provide
information on history of source areas of someclastic and chemical sediments.
O and C isotopes are particularly useful tocharacterize sedimentary environments and
digenetic processes including residence time of
non-clastic sediments in water.
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In summary sedimentary basins known to occur
throughout the earths history and provide
information on the evolution of continents.
They are known to occur in diverse
environments including Intracratonic, passive
margin, backarc, island arc, rift and continental
collisional environments.
Thus Evolution of sedimentary basins is spatially
associated with magmatism and tectonic
processes
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Sediment Supply and climate
The process of transporting/deposition ofsediments from the source area to the
depositional area or basin is known as sediment
supply
Normally sediments are derived through physical
or chemical breakdowns while the Achaean
sediments presents a different scenario as
sediments were derived through volcanism and
chemical alteration processes.
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Climate
Climate play a very crucial and important rule insedimentary formations
The very basic building block i.e sediments were
derived as a result of climatic factors acting ondifferent rocks or materials
Without the influence of climate a lot of
sedimentary formations would not be available.