llc marginal marine depositional environments core...
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Marginal Marine Depositional Environments Core
Deltas and Deltaic Deposits
Processes and examples from modern and ancient environments with oil field examples
Subaerial– Alluvial fan– Fluvial braided and meandering– Aeolian – wind and desert
Marine– Offshore Bars– Submarine fan – channel-levee complex, Bouma sequence– Carbonates – limestone, dolomite
• Reef, platform, pinnacle, pelagic• Diagenesis
Marginal Marine– Delta – river, wave, tide dominated, fan delta, braid delta– Beach and barrier island
Processes and examples from modern and ancient environments with oil field examples
Subaerial– Alluvial fan– Fluvial braided and meandering– Aeolian – wind and desert
Marine– Offshore Bars– Submarine fan – channel-levee complex, Bouma sequence– Carbonates – limestone, dolomite
• Reef, platform, pinnacle, pelagic• Diagenesis
Marginal Marine– Delta – river, wave, tide dominated, fan delta, braid delta– Beach and barrier island
Depositional Environments
Marginal Marine Depositional Environments Core
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Learning Objectives
By the end of this lesson, you will be able to:
Define what a ‘Delta’ is
Understand the processes which result in the formation of distributary channels, distributary mouth bars, bar fingers and crevasse splays
Relate delta morphology to the slope of the shelf
Describe what controls reservoir shape, size and orientation of deltaic deposits by sediment input, wave energy, and tidal range
Explain variations in delta type as it relates to sediment input environments: Alluvial Fan, Braided Rivers, and common deltas
Selected Major Deltas in the World
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What is a “Delta”?
A River Delta is a landform that is created by deposition of
sediment carried by a river as the flow leaves its mouth and
enters slower-moving or standing water.
This occurs where a river enters an ocean, sea, estuary, lake,
reservoir, or (more rarely) another river that cannot transport
away the supplied sediment.
A Delta Forming in a Mountain Lake
Marginal Marine Depositional Environments Core
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End Members of Delta Types
The Mississippi Delta Over the Last 7–8,000 Years
Over the past ~7000–8000 years there havebeen seven delta lobes ofthe Mississippi
Delta switching every~1000 years or so.
Bed load of Mississippionly about 5%. Mostsediment is suspended.
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Delta Mouth Deposition
An Example:
60 foot (18.2 m) channel depth
50 foot (14.2 m) thick distributary mouth bar
Aerial View of Mississippi Delta Mouth Deposition
A breach in the levee during flood can result in a sub-delta or “crevasse splay”
Marginal Marine Depositional Environments Core
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Aerial View of Delta Mouth Deposition
West Bay —A short-lived Crevasse Splay
Development of a Crevasse Splay
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West Bay Crevasse Splay in Late 1980s
Crevasse splay ismostly submerged
Example of a Productive Crevasse Splay
Admire 650 sandstone –25+ foot (~8m) sands with up to 24% porosity and 1500 millidarcies
400+ mmbor
15x9 mile (24x15 km) near Wichita, Kansas
In 1915, it represented10% of world production
Marginal Marine Depositional Environments Core
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End Members of Delta Types
Profiles of Shelves Off Seven Deltas
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Nile Delta: Wave Dominated
Nile Delta: Wave Dominated
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Niger Delta: Wave and Tidal Dominated
Niger Delta: Wave Dominated Portion
Smooth NigerDelta coastlineEscravos, Nigeria
Would you know you were on a delta?
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NNE–SSW Cross Section Through the Niger Delta
End Members of Delta Types
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Tidal Delta Features
Fly River Delta: Tide Dominated
Fly River Delta, Paupua New Guinea
Tidal delta 5–6 m tides
Good reservoir potential
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Deltaic Structural Styles
SW Iceland: 50 miles wide, 30 mile long braid plain (80x48km)
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Close-up of Vertical Section of Braid Delta
Braid/Fan Delta, Peyto Lake, Alberta, Canada
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Fan Delta Prograding into Indian Ocean, Betty’s Bay, South Africa
Concave upwardprofile of alluvial fan
Fan Delta, Atlantic Ocean Side Capetown South Africa
Notice the effect of relatively high energy wave action on poorly sorted alluvial fan sediments
Potentially good reservoir rock
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Brae Field, North Sea: Productive Example of a Fan Delta
Brae Field, North Sea: Structure Map
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Brae Field, North Sea: Geologic Cross Section
Brae Field, North Sea: Stratigraphic Column
Marginal Marine Depositional Environments Core
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Brae Field, North Sea: Geologic Model
Fan Delta, Modern Day Analogue for Brae Field
Laguna Salida, NWMexico
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Learning Objectives
By the end of this lesson, you will be able to:
Define what a ‘Delta’ is
Understand the processes which result in the formation of distributary channels, distributary mouth bars, bar fingers and crevasse splays
Relate delta morphology to the slope of the shelf
Describe what controls reservoir shape, size and orientation of deltaic deposits by sediment input, wave energy, and tidal range
Explain variations in delta type as it relates to sediment input environments: Alluvial Fan, Braided Rivers, and common deltas
You now can:
Marginal Marine Depositional Environments Core
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