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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 terrigenous clastic sediment accumulation where fluvial dispersal systems encounter standing water

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deltaic depositional systems

Deltaic Depositional Systems

Modern and

Ancient

Arno River Delta (Med)

(a wave dominated and engineered delta)

deltaic depositional systems2
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)

importance of deltas
Importance Of Deltas
  • Site of substantial fossil fuel resource accumulation
    • Coal, Oil, and Natural Gas
importance of deltas4
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)

main geological characteristics of deltas
Main Geological Characteristics Of Deltas
  • Isopach thick... major stratigraphic component of (Terrigenous Clastic) sedimentary basin fill

Mississippi Delta

main geological characteristics of deltas6
Main Geological Characteristics Of Deltas
  • Regressive - Progradational successions
  • Abandonment – Transgressive Stage
main geological characteristics of deltas7
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)
delta types
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)
main processes influencing delta depositional systems
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
main delta sedimentary facies
Main Delta Sedimentary Facies
  • Generic River-Dominated Delta Model
    • large rivers
    • broad shelf
    • low wave energy
    • low tidal range
main delta sedimentary facies11
Generic River-Dominated Delta Model

Upper Delta Plain

above highest high tide

low gradient/ meandering river systems

fresh water lakes & swamps

Main Delta Sedimentary Facies
main delta sedimentary facies12
Generic River-Dominated Delta Model

Lower delta plain

between the tides

Distributary channels

Inter-distributary bay fill

levees

Main Delta Sedimentary Facies
main delta sedimentary facies13
Generic River-Dominated Delta Model

Subaqueous Delta (Delta Front)

below lowest low tide

distributary mouth bar - bar finger sands

bays

Main Delta Sedimentary Facies
main delta sedimentary facies15
Generic River-Dominated Delta Model

Prodelta

Offshore transitional to open marine

Normal Marine Shelf

High biological productivity

Abundant slumps and syndepositional deformation

Main Delta Sedimentary Facies
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

Generic Wave Dominated Delta Model

Rhone River Delta (Med)

(a wave dominated delta)

generic tide dominated delta model
High Tidal Range

Extensive lower delta plain/tidal mudflats

Shore perpendicular, elongate sand dominated facies, tidal channel deposits

Generic Tide Dominated Delta Model

Ganges - Brahmaputra River Delta (Indian Ocean)

(a tide dominated delta)

environmental issues in modern deltas
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
environmental issues in modern deltas22
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 nation’s oil and natural gas supplies through the state
nature s revenge
Nature’s Revenge
  • Louisiana’s vanishing wetlands