Deepwater Carbonate Signals

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Deepwater Carbonate Signals
The Central High Atlas Type Examples
C. G. St. C. Kendall
Department of Geological Sciences, University of
South Carolina
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High Atlas
Study Area
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Outline of Presentation

• Introduction to deepwater sediments of High Atlas
• Geological setting of High Atlas
• Oed Ziz Jurassic carbonates marls
• Generation sequestration of deepwater sediments
  of High Atlas
• Jebel bou Dehar Jurassic carbonates marls
• Amellago Jurassic carbonates marls
• Significance of High Atlas as deepwater play
  model
• Conclusions

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Jurassic Fill of High Atlas
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Hiya
Jurassic High Atlas Middle Atlas
Basins Expanded then Compressed As North
America Moved West in Response to Spreading of
Atlantic Movement East of the Moroccan Meseta
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Sections with Deepwater Jurassic Carbonate
Sediment Sequestered in Basin
Pliensbachian Jebel bou Dehar
Aalenian adjacent to village of Amellago
Sinemurian Oed Ziz Tunnel de Legionaire to Rich
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Rt Lateral Motion of Jurassic Shelf
Atlas Fold Mts
Jurassic Carbonate Sediment Sequestered in Basin
on Shelves Formed in Response to Spreading of
Atlantic
Rt Lateral Motion of Jurassic Shelf
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High Atlas Structure Locals
Rt Lateral Motion of Jurassic Shelf
Atlas Fold Mts
MIDELT
RICH
Oed Ziz
Bou Dahar
Amellago
RASHIDIA
Rt Lateral Motion of Jurassic Shelf
Jurassic Carbonate Sediment Sequestered in Basin
and on Shelves!
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Jurassic High Atlas Basin

• Site of turbidite and other non-cohesive
  density flow carbonate sediments and
  mass-transport deposits (MTD) downslope from
  carbonate margins
• Ages range from
• Sinemurian - Oed Ziz from Tunnel de Legionaire to
  Rich
• Pliensbachian In col formed by Jebel bou Dehar
• Aalenian In col formed by Djebels Tikajoine,
  Bou Iflilou, Tamoussat, Mijdider Tagountsa
• Demonstrably functions of local global controls

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High Atlas Oed Ziz Sections

• Site of turbidite and other non-cohesive
  density flow carbonate sediments and
  mass-transport deposits (MTD) downslope from
  carbonate margins
• Age of basin fill ranges from Sinemurian through
  Bajocian
• Oed Ziz traverse from Tunnel de Legionaire to
  Rich and on to Midelt

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Line of Oed Ziz Section
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Oued Ziz Traverse
Basin
Syn Depositional Folds Old Salt Structures?
Shelf to Basin
Shelf
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Oed Ziz High AtlasBasin looking South
Mountain Ridge Overthrust Northward Triassic
Salt Cores?
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Jurassic Fill of High Atlas
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Shelf/Basin Transition
Basin
Shelf to Basin
Shelf
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Shelf Sediment Contribution

• Shelf carbonate sediments of High Atlas range
  from sand to mud to shale prone
• Sediments differences due to water depth, and
  wave energy to carbonate shelves input of
  clastics from updip continental areas
• Finer carbonate mud sediments comprise at least
  70 of total succession is "mud-rich"
• Closer to margin more "sand-rich" with a high
  net-to-gross ratio of carbonate sand mud
  accumulations thicker than mud-dominated
  successions in the basin

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Barrage de Hassan Addakhil
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Barrage de Hassan Addakhil
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Oed Ziz Jurassic Shelf
Cycles of limestone marls
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Oed Ziz Jurassic Shelf
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Oed Ziz Jurassic Shelf
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Oed Ziz Jurassic Shelf
Cycles of limestone marls
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Oed Ziz Jurassic Shelf
Shallow grain carbonates common
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Jurassic Fill of High Atlas
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Fine Grain Size Contribution

• Deepwater carbonate sediments of High Atlas range
  from sand to mud prone
• Differences due to sediments eroded from adjacent
  carbonate shelves Liassic and older basin
  margin
• Finer carbonate mud sediments comprise at least
  70 of total succession is "mud-rich"
• Closer to margin more "sand-rich" with a high
  net-to-gross ratio of carbonate sand mud
  accumulations thicker than mud-dominated
  successions basin-ward

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Oed Ziz - Tunnel De Legionnaire/Rich

• Sinemurian turbidite and other non-cohesive
  density flow carbonate sediments and
  mass-transport deposits (MTD) accumulate
  downslope from the carbonate margins of the High
  Atlas Basin as functions of local and global
  controls
• Downslope carbonate elements include
• channels sands
• levee sands
• distal overbank supra fan mud sheets
• slumped downslope small-scale soft-sediment
  deformation features
• Tectonic history suggests that local uplift in
  the basin was penecontemporaneous with deposition

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Oed Ziz - Looking SouthShelf Basin Transition
Shelf
Shelf Margin Turbidites
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Oed Ziz - Tunnel De Legionnaire/Rich
Downslope carbonate elements

• channels sands muds
• levee sands muds
• distal overbank supra fan mud sheets
• slumped downslope blocks
• small-scale soft-sediment deformation features

Tectonic history suggests that local uplift in
the basin occurred with deposition
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Tunnel de Legionaire
Channels Levees
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Tunnel de Legionaire
Channels Levees
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Tunnel de Legionaire
Channel
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Oed Ziz - Tunnel De Legionnaire/Rich
Downslope carbonate elements

• channels sands muds
• levee sands muds
• distal overbank supra fan mud sheets
• slumped downslope blocks
• small-scale soft-sediment deformation features

Tectonic history suggests that local uplift in
the basin occurred with deposition
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Tunnel de Legionaire
Levees
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Tunnel de Legionaire
Levee Graded Bed
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Tunnel de Legionaire
Levee Graded Bed
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TunnelDeLegionaire
LeveeGradedBed
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Hiya
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Tunnel de Legionaire
Downslope Channels Lobes
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Downslope Channel Fill
Tunnel de Legionaire
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Oed Ziz - Tunnel De Legionnaire/Rich
Downslope carbonate elements

• channels sands muds
• levee sands muds
• distal overbank supra fan mud sheets
• slumped downslope blocks
• small-scale soft-sediment deformation features

Tectonic history suggests that local uplift in
the basin occurred with deposition
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Hiya
TunnelDeLegionaire
BoumaCycles
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Hiya
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Tunnel de Legionaire
Bouma Cycles
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Hiya
TunnelDeLegionaire
BoumaCycles
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Flute MarksOn Bed Plane
Tunnel de Legionaire
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Oed Ziz - Tunnel De Legionnaire/Rich
Downslope carbonate elements

• channels sands muds
• levee sands muds
• distal overbank supra fan mud sheets
• slumped downslope blocks
• small-scale soft-sediment deformation features

Tectonic history suggests that local uplift in
the basin occurred with deposition
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Tunnel de Legionaire
Downslope Block
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Oed Ziz - Tunnel De Legionnaire/Rich
Downslope carbonate elements

• channels sands muds
• levee sands muds
• distal overbank supra fan mud sheets
• slumped downslope blocks
• small-scale soft-sediment deformation features

Tectonic history suggests that local uplift in
the basin occurred with deposition
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Disturbed Soft Sediment
Tunnel de Legionaire
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Oed Ziz - Tunnel De Legionnaire/Rich
Downslope carbonate elements

• channels sands
• levee sands
• distal overbank supra fan mud sheets
• slumped downslope
• small-scale soft-sediment deformation features

Tectonic history suggests that local uplift in
the basin occurred with deposition
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Hiya
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Conclusion

• Field studies can be used to predict and
  characterize deepwater reservoirs
• These sediments include non-cohesive density flow
  and mass movements debris flows expressed as
• Channel
• Levee
• Distal over bank supra fan-sheets fills

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Hypothesis

• Sediment transport driven by slope, tectonic
  movement sea level change
• Mud bypassing fans to reach outer basin
• Mud overtops structural depressions to reach
  outer basin
• Encloses lithoherms
• Net-to-gross ratio patterns vary across High
  Atlas Basin

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Central Jurassic Basin
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Jurassic Fill of High Atlas
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Liassic to Pliensbachian Basin Axis Fill
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Basinal Liassic Distal Laminae
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Basinal Pliensbachian Lithoherms interbedded with
thin bedded basinal limestones
Basinal Distal Lithoherms
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Hiya
Distal BasinalLimestones Marls
Pliensbachian CyclesReflect Beat ofSea
LevelChange
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INTERPRETATION OF PLIENSBACHIAN LITHOHERM FACIES
OF AXIAL AREA OF FILL OF CENTRAL HIGH ATLAS BASIN
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Pliensbachian Lithoherm Enclosed in Basinal
Sediment
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Jurassic High Atlas Basin

• Site of turbidite and other non-cohesive
  density flow carbonate sediments and
  mass-transport deposits (MTD) downslope from
  carbonate margins
• Pliensbachian aged slope sediments found in col
  formed by Jebel bou Dehar
• Demonstrably functions of local global controls

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Carbonate Ramp - Pleinsbachian (L. Jurassic)
Jebel bou Dahar - High Atlas - Morocco
Line Of Dip Section
Ksar Morhel
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Lower Jurassic of the Jebel bou Dahar High Atlas,
Morocco
Straits of Gibraltar
isolated platform on rift topography shallow
coral patch reefs deep sponge-microbial reef
tongues 2nd-order
transgression platform retrogradation (syn-
post-rift) After - J. Kenter, M. Harris (Chevron
ETC) E. Adams (Shell Intl EP) K. Verwer (Vrije
Univ., ) G. Della Porta, O. Merino ( Cardiff
Univ.) and T Playton (UT).
Jebel bou Dahar
Morocco

image from Google Earth
middle/ upper slope
lower slope
450 m to top outcrop
5m
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Lower Jurassic of the Jebel bou Dahar High Atlas,
Morocco
image from Google Earth
N
margin
upper slope
basin
lower slope
3 km
lower slope GS/gravel lobe complexes
PS marl background
amalgamated GS/gravel axis
GS/PS flanks
5m
oblique view
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Lower Jurassic of the Jebel bou Dahar,
High Atlas, Morocco
lower slope GS/gravel lobe complexes
PS marl background
amalgamated GS/gravel axis
GS/PS flanks
5m
oblique view
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Lower Jurassic of the Jebel bou Dahar,
High Atlas, Morocco
lower slope GS/gravel lobe complexes
PS marl background
amalgamated GS/gravel axis
GS/PS flanks
5m
oblique view
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Slope Variations Observed in Outcrop
Lower Jurassic, Morocco grain shedding-dominated
retrograding
Background
Grainy flow
In situ
Collapse
Platform
After Ted Playton UT
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The Late Toarcian-Aalenian Amellago carbonate
ramp
Line Of Section
Pierre, A, 2006, Un analogue de terrain pour les
rampes oolitiques anciennes. Un affleurement
continu à léchele de la sismique (falaises
jurassiques dAmellago, Haut Atlas, Maroc) PhD.
Thesis, Université de Bourgogne, 232 p.
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The Late Toarcian-Aalenian Amellago carbonate
ramp
Pierre, A, 2006, Un analogue de terrain pour les
rampes oolitiques anciennes. Un affleurement
continu à léchele de la sismique (falaises
jurassiques dAmellago, Haut Atlas, Maroc) PhD.
Thesis, Université de Bourgogne, 232 p.
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The Late Toarcian-Aalenian Amellago carbonate
ramp
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Source of coarse grained turbidites

• Coarse-grained, sand-rich turbidite systems are
  uncommon
• Evidence of sea level change expressed by
  basinwide
• Repeated and cyclic changes in the lithology
• Occurrence of condensed sequences with ammonites
  and organic and/or radioactive shales.
• Condensed layers result of high positions in the
  sea

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Sediment Source Concepts

• It is proposed climatic changes accentuating the
  signal of carbonate versus clastic shale beat,
  though most of basin fill was carbonate
• Carbonate sediment sequestration on upslope
  shelves but local cementation reduced erosion of
  carbonates during sea level lows.

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Evidence

• Significant deepwater carbonate accumulations are
  found in the axis of the High Atlas Basin
• Elsewhere similar sediments are potential
  reservoirs
• The interbedded ancient carbonate muds and marls
  may be a source of significant petroleum
  reserves in the Moroccan region
• The High Atlas Sections are keys to these
  potential reserves

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CONCLUSIONS

• Turbidite other non-cohesive density flow
  carbonate sediments mass-transport deposits
  (MTD) accumulate downslope from carbonate margins
  of Jurassic High Atlas Basin
• The exposure eclectic character make these
  potential analogs to both ancient carbonate
  clastic deepwater provinces
• Moroccan Atlantic margin has carbonate deepwater
  systems that may contain significant petroleum
  reserves
• Jurassic of High Atlas a key to understanding
  other deepwater systems of past!

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A Moroccan Dream!