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Deltaic Depositional Systems

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Presentation on theme: "Deltaic Depositional Systems"— Presentation transcript:

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 Destructional 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 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

23 Coastal Elevation in Louisiana

24 Nature’s Revenge Louisiana’s vanishing wetlands

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