Geologic Evolution of Surface-Piercing Salt Domes in the
Ghaba Salt Basin, Interior Northern Oman: First Results
Johannes Schoenherr, Ansgar Heimann, Lars Reuning,
Janos L. Urai, Ralf Littke, Peter A. Kukla, Marc Holland, Zuwena Rawahi
Petroleum
Development
Oman
Physical properties of Rock Salt
Sandstone
differential stress in MPa
Rock Salt
SALT
1018 Pa·s
1017 Pa·s
Permeability
~ 10-12 m2
~ 10-21 m2
Density
~ 2,6 g · cm-3
~ 2,2 g · cm-3
Conductivity
~ 2.5 W/m x K
Up to 6.5 W/m x K
brittle-ductile
transition
depth in km
Viscosity
Moho @ 30 km
Salt Structures
Active
Reactive
Passive
Sediments
Warren (2006)
SALT
SALT
SALT
Extrusive Salt Structures
Iran: Salt Glaciers
Oman: Salt Domes
-10
13C
Modified after Peters et al. (2003), Amthor et al. (2005), Filbrandt et al. (2006)
Geological setting of the South Oman Salt Basin
+10
Geometry of the South Oman Salt Basin
Anat
om
the
f
o
y
A
pirs
a
i
D
alt
ra S
Aims of study
•
To obtain general data on the salt domes as only very
little is known from literature!
•
Sedimentological and structural correlation of former
intra-salt carbonate stringers in the field
•
What are the implications of the field observations for
the style of salt tectonics in Northern Oman?
Long-term Aim:
Compare data with results from the SOSB
Outline
1.
Geology of the Salt Domes - What is known?
2.
Field Data: Overview of Six Salt Domes
3.
Field Data: Jebel Majayiz and Qarn Nihayda
4.
Summary of Field Data
5.
Lab Data
6.
Interpretation
Modified after Peters et al. (2003), Amthor et al. (2005), Filbrandt et al. (2006)
Geological setting of the Salt Domes
Geometry of the Salt Domes
Richard (1998)
Ghaba Salt Basin
- Salt dome growth
occurred along deeprooted basement
faults, which
developed at Late
Cretaceous times
Filbrandt et al. (2006)
Facies & Lithologies of Salt Domes
salt
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salt
Facies & Lithologies of Salt Domes
Schröder et al. (2005)
Facies & Lithologies of Salt Domes
Rock salt
Rock salt and Cap rock
Deformation Structures - Folds
Deformation Structures - Folds
Deformation Structures - Thrusts
Deformation Structures - Thrusts
Deformation Structures - Cataclasites
Deformation Structures - Zebra rocks
Deformation Structures - Zebra rocks
The ‘Zebra’-fabric is
mostly associated with
a hydrothermal origin
(e.g. Smith et al., 2006)
Microstructures of Zebra Veins
Long side of each micrograph is 4.2 mm
- Multiple episodes of hydrofracturing
Hyrothermal tectonism in Central Oman
1. Diapir growth along pre-existing
deep-rooted fault zone
2. Re-activation of fault zone in Late
Cretaceous times associated with
hydrothermal fluids
Outline
1.
Geology of the Salt Domes - What is known?
2.
Field Data: Overview of Six Salt Domes
3.
Field Data: Jebel Majayiz and Qarn Nihayda
4.
Summary of Field Data
5.
Lab Data
6.
Interpretation
Jebel Majayiz – Geometry and shape
• piercement of surface postdates the formation of drainage
systems in central north Oman
• the interior of salt domes is
characterized by numerous
juxtaposed carbonate ‘stringers’
N
Quickbird Image
1 km
Jebel Majayiz – Geometry
N
500 m
Jebel Majayiz – Field data
S
N
N
Jebel Majayiz – Field data
Qarn Nihayda – Geometry and outcrops
200 m
Qarn Nihayda – Geometry and outcrops
Qarn Nihayda – Geometry and outcrops
Qarn Nihayda – Internal structure
250 m
• a general trend in strike (NW-SE)
• Local chaotic juxtaposition is a result of
overthrusting, strong compartmentalization by
faulting and (near) surface dissolution of salt
between the ‘stringer’ intervals.
Qarn Nihayda – Internal structure
Qarn Nihayda – Geometry
200 m
• Southern part is more
flattened and consists mainly
of anhydrite cap rock
Result of salt dissolution
Summary of Data
Satellite Images
•
JM shows no general orientation of ‘stringers’
•
QN indicates an overall symmetry of the ‘stringer’
configuration
Field Data
•
Facies analysis clearly confirms affinity to the Ara Group
of SOSB
•
Local chaotic juxtaposition of ‘stringers’
•
Carbonate ‘stringers’ are strongly deformed
Thrusts, Folds, Cataclasites, Zebras
Indications for hydrothermal basement-derived(?) fluid
flow during Late Cretaceous tectonism in N Oman
Outline
1.
Geology of the Salt Domes - What is known?
2.
Field Data: Overview of Six Salt Domes
3.
Field Data: Jebel Majayiz and Qarn Nihayda
4.
Summary of Field Data
5.
Lab Data
6.
Interpretation
Lab Data
1.
Differential paleo-stress calculation
to asses deformation in deep and upper part of a salt diapir
2.
Maturity analysis
to assess paleo-temperature(s) and burial depth(s)
3.
Diagenesis & Geochemistry
to assess degree of carbonate alteration
5 mm
1. Differential paleo-stress calculation
Subgrain size piezometry
SOSB
Surface-salt
Subsurface-salt
2. Maturity analysis
sample
Paleo-Temperature estimation
VRr = BRr + 0.2443/1.05
Schoenherr et al. (2007)
Tburial = (ln(VRr) + 1.68)/0.0124
Barker & Pawlewicz (1994)
JM
JM
JM
JM
BRr (%) VRr (%) Burial T (°C)
calculated
max. burial
depth (km)
2
3
6
7
2.54
2.37
1.50
1.93
2.65
2.49
1.66
2.07
214
209
176
194
7.14
6.97
5.87
6.47
QA 2
QA 4.6
3.60
3.85
3.66
3.90
240
245
8.00
8.17
QK1
2.02
0.96
2.07
0.86
0.91
1.88
0.99
1.99
2.03
1.37
2.16
1.15
2.20
1.05
1.10
2.02
1.18
2.13
2.17
1.53
197
147
199
140
143
192
149
196
198
170
6.58
4.88
6.64
4.65
4.77
6.41
4.95
6.55
6.59
5.67
QK3
QK4
Qk5
QK8
Qk10
3. Diagenesis & Geochemistry
Negative 13C excursion at
Pre-Cambrian/Cambrian Boundary
-10
A4C
Some stringers of the Salt Domes can be
geochemically clearly correlated to the A4C interval
of the SOSB!
13C
+10
Outline
1.
Geology of the Salt Domes - What is known?
2.
Field Data: Overview of Six Salt Domes
3.
Field Data: Jebel Majayiz and Qarn Nihayda
4.
Summary of Field Data
5.
Lab Data
6.
Interpretation
Preliminary evolutionary model of Jebel Majayiz
1
- Downbuilding initiates passive
diapir growth
- Oil generation
Preliminary evolutionary model of Jebel Majayiz
1
2
- Downbuilding until grounding of
Haima clastics on pre-Ara strata
Preliminary evolutionary model of Jebel Majayiz
1
2
3
8
- Sedimentation
- Formation of Zebra rocks in Late Cretaceous
times due to hydrothermal tectonism
Preliminary evolutionary model of Jebel Majayiz
1
3
2
4
- Reactive diapirsim along fault zones
- Major deformation structures formed in
the diapir stem
Preliminary evolutionary model of Jebel Majayiz
1
3
2
4
5
- Ara Salt dissolution
- formation of cap rock
- chaotic juxtaposition
of the ‘stringers’
Qarn Nihayda – Paleo-temperature distribution
200 m
• Maturity increases from
the dome centre to the
dome margins.
This suggests that
dome centre was buried
deeper and hence
comprises the
stratigraphically
lowermost carbonate
intervals (e.g. A1C).
200
225
200
240
180
Qarn Nihayda – Diagenesis & Geochemistry
200 m
200
A4C
225
200
240
A4C
180
Preliminary evolutionary model of Qarn Nihayda
1
?
A5
A1
2
A
A3
A4
2
QN most likely shows a symmetric paleo-T
zonation, reflecting the original stratigraphic
configuration
Preliminary evolutionary model of Qarn Nihayda
A5
A1
2
3 A
A
A4
• Field data comparable to
analogue models?
• Prediction of the flow
behaviour
Callot et al. (2006)
Conclusions
• Salt Dome lithologies of the GSB are clearly comparable
to the Ara Group facies of the SOSB
Important outcrop equivalent for SOSB!
• Higher stresses in the diapir stem than in the deep
subsurface stronger deformation of carbonates in GSB
• Late Cretaceous tectonics in Northern Oman was
associated with hydrothermal fluids
• Salt was rising from a depth of c. 8 km
• Original stratigraphy may be preserved during diapir
growth!