Title: Deltaic Depositional Systems
1Deltaic Depositional Systems
Arno River Delta (Med) (a wave dominated and
engineered delta)
2Deltaic 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)
3Importance Of Deltas
- Site of substantial fossil fuel resource
accumulation - Coal, Oil, and Natural Gas
4Importance 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)
5Main Geological Characteristics Of Deltas
- Isopach thick... major stratigraphic component of
(Terrigenous Clastic) sedimentary basin fill
Mississippi Delta
6Main Geological Characteristics Of Deltas
- Regressive - Progradational successions
- Abandonment Transgressive Stage
7Main 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)
8Delta 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)
9Main 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
10Main Delta Sedimentary Facies
- Generic River-Dominated Delta Model
- large rivers
- broad shelf
- low wave energy
- low tidal range
11Main Delta Sedimentary Facies
- Generic River-Dominated Delta Model
- Upper Delta Plain
- above highest high tide
- low gradient/ meandering river systems
- fresh water lakes swamps
12Main Delta Sedimentary Facies
- Generic River-Dominated Delta Model
- Lower delta plain
- between the tides
- Distributary channels
- Inter-distributary bay fill
- levees
13Main Delta Sedimentary Facies
- Generic River-Dominated Delta Model
- Subaqueous Delta (Delta Front)
- below lowest low tide
- distributary mouth bar - bar finger sands
- bays
14Delta Front Progradation
15Main 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
16Generic 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)
17Generic Tide Dominated Delta Model
- 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)
18Transgressive Mississippi Delta Model
19Transgressive Mississippi Delta Model
20Transgressive Mississippi Delta Model
21Environmental 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
22Environmental 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
23Coastal Elevation in Louisiana
24Natures Revenge
- Louisianas vanishing wetlands