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Deepwater Carbonate Signals

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Title: Deepwater Carbonate Signals


1
Deepwater Carbonate Signals
The Central High Atlas Type Examples
C. G. St. C. Kendall
Department of Geological Sciences, University of
South Carolina
2
High Atlas
Study Area
3
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

4
Jurassic Fill of High Atlas
5
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
6
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
7
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
8
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!
9
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

10
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

11
Line of Oed Ziz Section
12
Oued Ziz Traverse
Basin
Syn Depositional Folds Old Salt Structures?
Shelf to Basin
Shelf
13
Oed Ziz High AtlasBasin looking South
Mountain Ridge Overthrust Northward Triassic
Salt Cores?
14
Jurassic Fill of High Atlas
15
Shelf/Basin Transition
Basin
Shelf to Basin
Shelf
16
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

17
Barrage de Hassan Addakhil
18
Barrage de Hassan Addakhil
19
Oed Ziz Jurassic Shelf
Cycles of limestone marls
20
Oed Ziz Jurassic Shelf
21
Oed Ziz Jurassic Shelf
22
Oed Ziz Jurassic Shelf
Cycles of limestone marls
23
Oed Ziz Jurassic Shelf
Shallow grain carbonates common
24
Jurassic Fill of High Atlas
25
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

26
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

27
Oed Ziz - Looking SouthShelf Basin Transition
Shelf
Shelf Margin Turbidites
28
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
29
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30
Tunnel de Legionaire
Channels Levees
31
Tunnel de Legionaire
Channels Levees
32
Tunnel de Legionaire
Channel
33
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
34
Tunnel de Legionaire
Levees
35
Tunnel de Legionaire
Levee Graded Bed
36
Tunnel de Legionaire
Levee Graded Bed
37
TunnelDeLegionaire
LeveeGradedBed
38
Hiya
39
Tunnel de Legionaire
Downslope Channels Lobes
40
Downslope Channel Fill
Tunnel de Legionaire
41
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
42
Hiya
TunnelDeLegionaire
BoumaCycles
43
Hiya
44
Tunnel de Legionaire
Bouma Cycles
45
Hiya
TunnelDeLegionaire
BoumaCycles
46
Flute MarksOn Bed Plane
Tunnel de Legionaire
47
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
48
Tunnel de Legionaire
Downslope Block
49
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
50
Disturbed Soft Sediment
Tunnel de Legionaire
51
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
52
Hiya
53
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

54
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

55
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56
Central Jurassic Basin
57
Jurassic Fill of High Atlas
58
Liassic to Pliensbachian Basin Axis Fill
59
Basinal Liassic Distal Laminae
60
Basinal Pliensbachian Lithoherms interbedded with
thin bedded basinal limestones
Basinal Distal Lithoherms
61
(No Transcript)
62
Hiya
Distal BasinalLimestones Marls
Pliensbachian CyclesReflect Beat ofSea
LevelChange
63
(No Transcript)
64
INTERPRETATION OF PLIENSBACHIAN LITHOHERM FACIES
OF AXIAL AREA OF FILL OF CENTRAL HIGH ATLAS BASIN
65
Pliensbachian Lithoherm Enclosed in Basinal
Sediment
66
(No Transcript)
67
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

68
Carbonate Ramp - Pleinsbachian (L. Jurassic)
Jebel bou Dahar - High Atlas - Morocco
Line Of Dip Section
Ksar Morhel
69
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
70
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
71
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
72
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
73
Slope Variations Observed in Outcrop
Lower Jurassic, Morocco grain shedding-dominated
retrograding
Background
Grainy flow
In situ
Collapse
Platform
After Ted Playton UT
74
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.
75
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.
76
The Late Toarcian-Aalenian Amellago carbonate
ramp
77
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

78
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.

79
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

80
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!

81
A Moroccan Dream!
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