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Deltaic Depositional Systems

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Deltaic Depositional Systems Modern and Ancient Arno River Delta (Med) (a wave dominated and engineered delta) * * Deltaic Depositional Systems Locus of voluminous ... – PowerPoint PPT presentation

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Title: Deltaic Depositional Systems


1
Deltaic Depositional Systems
  • Modern and
  • Ancient

Arno River Delta (Med) (a wave dominated and
engineered delta)
2
Deltaic Depositional Systems
  • Locus of voluminous terrigenous clastic sediment
    accumulation where fluvial dispersal systems
    encounter standing water
  • Most common in subsiding basin-settings (passive
    continental margins) where major river systems
    transport large volumes of sediment.

Modern Gulf of Mexico And the Mississippi River
Delta (a river dominated delta)
3
Importance Of Deltas
  • Site of substantial fossil fuel resource
    accumulation
  • Coal, Oil, and Natural Gas

4
Importance Of Deltas
  • Diverse and prolific ecosystems
  • Common site of large human population centers

Nile River Delta (Med Sea) (an engineered,
wave/river dominated delta)
Tigris Euphrates River Delta (Persian Gulf)
5
Main Geological Characteristics Of Deltas
  • Isopach thick... major stratigraphic component of
    (Terrigenous Clastic) sedimentary basin fill

Mississippi Delta
6
Main Geological Characteristics Of Deltas
  • Regressive - Progradational successions
  • Abandonment Transgressive Stage

7
Main Geological Characteristics Of Deltas
  • Contemporaneous non-marine - marginal marine - to
    basinal depositional systems
  • Numerous sub-environments (each of a scale
    similar to that of most other depo systems)

8
Delta Types
  • Constructional Deltas
  • Dominated by the fluvial system
  • strongly progradational/regressive
  • Lobate Elongate
  • Destructional Deltas
  • Dominated by marine processes
  • common marine reworking with transgressive
    intervals
  • Cuspate (transitional to interdeltaic systems)

9
Main Processes Influencing Delta Depositional
Systems
  • Climate
  • Relief
  • Fluvial Discharge (water volume and time
    variation)
  • Sediment load and type
  • River mouth processes
  • Tidal Processes
  • Wave energy

10
Main Delta Sedimentary Facies
  • Generic River-Dominated Delta Model
  • large rivers
  • broad shelf
  • low wave energy
  • low tidal range

11
Main Delta Sedimentary Facies
  • Generic River-Dominated Delta Model
  • Upper Delta Plain
  • above highest high tide
  • low gradient/ meandering river systems
  • fresh water lakes swamps

12
Main Delta Sedimentary Facies
  • Generic River-Dominated Delta Model
  • Lower delta plain
  • between the tides
  • Distributary channels
  • Inter-distributary bay fill
  • levees

13
Main Delta Sedimentary Facies
  • Generic River-Dominated Delta Model
  • Subaqueous Delta (Delta Front)
  • below lowest low tide
  • distributary mouth bar - bar finger sands
  • bays

14
Delta Front Progradation

15
Main Delta Sedimentary Facies
  • Generic River-Dominated Delta Model
  • Prodelta
  • Offshore transitional to open marine
  • Normal Marine Shelf
  • High biological productivity
  • Abundant slumps and syndepositional deformation

16
Generic Wave Dominated Delta Model
  • High wave energy, open coasts, strong longshore
    currents
  • Non-marine, swamp to Eolian dune
  • Arcuate to strand-parallel sand dominated facies,
    barrier island sequences

Rhone River Delta (Med) (a wave dominated delta)
17
Generic Tide Dominated Delta Model
  • High Tidal Range
  • Extensive lower delta plain/tidal mudflats
  • Shore perpendicular, elongate sand dominated
    facies, tidal channel deposits

Ganges - Brahmaputra River Delta (Indian
Ocean) (a tide dominated delta)
18
Transgressive Mississippi Delta Model

19
Transgressive Mississippi Delta Model

20
Transgressive Mississippi Delta Model

21
Environmental Issues in Modern Deltas
  • Damming, Dredging, Diverting
  • Coastal Land loss (erosion/subsidence)
  • Coastal Pollution
  • Nutrient loading,
  • anoxic events
  • Petroleum contamination
  • Habitat Destruction
  • land loss,
  • contamination, and
  • development

22
Environmental Issues in Modern Deltas
  • Mississippi Delta Coastal Land loss
  • Louisiana's coastal wetlands, a national resource
    supporting 30 of the nation's fisheries and most
    of the wintering ducks in the Mississippi Flyway,
    are at risk from the annual conversion of an
    estimated 35-45 mi2 of wetlands to open water.
  • Louisiana's wetland loss rate is the highest of
    any state in the nation. The processes causing
    wetland loss in coastal Louisiana are complex and
    varied.
  • Huge energy infrastructure
  • Louisiana roads, pipelines, and transmission and
    distribution systems transport more than 30
    percent of the nations oil and natural gas
    supplies through the state

23
Coastal Elevation in Louisiana
24
Natures Revenge
  • Louisianas vanishing wetlands
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