1. style and fashion
2. footwear

Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.1 LITHOFACIES AND SOURCE ROCK FACIES
The lithologic log used to characterize the lithofacies of the analyzed
samples at the outcrop locations are shown in the base map (Figure 5.1).
However, due to extensively erosion, only selected outcrops and sampling were
recorded. The informations of Tungku Formation are also included as it
unconformably lies as underburden rocks for the Dent Group sediments, so as to
show the contact of unconformities.
Rocks sampling are based on the sedimentological log and hand specimen
description. These samples were used for the geochemical and petrological
analyses. Four probable reservoir rock samples (e.g. sandstones and limestone)
from Togopi and Ganduman Formations also were analyzed to determine possible
secondary migration through oil-oil correlation.
Selected sedimentological logs are presented in this section to describe the
main
lithofacies.
The
remaining
of
the
sedimentological
logs
including
abbreviations can be found in Appendix 2. Sequence stratigraphy is discussed in
section 5.4 by integrating sedimentology, micropaleontology and palynology.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
N
Legend
Libung Fm
Tungku Fm
Ayer Fm
Sebahat Fm boundary
Ganduman Fm boundary
Dent Heaven
Togopi Fm boundary
Gas Seepage
Coast line
Track
Town
Dip/strike
Sampling
location
5 km
Felda Wilayah Sahabat
Figure 5.1. Location of sedimentological log according to samples locality.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.1.1 LITHOFACIES OF TUNGKU FORMATION
The lithofacies of Tungku Formation comprise volcaniclastics, tuffaceous
sandstone, and conglomerates. This unit unconformably underlies the shaly and
sandy unit of Sebahat Formation. The volcaniclastic and tuffaceous sandstone
occurs in Bagahak Palm Oil Plantation, which is not the map in figure 5.1. The
conglomerate unit of Tungku Formation crops out at the abandon Ladang Sahabat
1 Quarry, at Locality 55 (Figure 5.2) and Ladang Ikhtisas Semporna Quarry (Stop
45).
At Ladang Sahabat 1 Quarry, the excavated hill exposure shows more than
50m of conglomerate. The conglomerate is clast supported. The clasts are
rounded and variable in size ranging from 5cm to 50cm. This conglomeritic unit of
Tungku Formation is interpreted as alluvial deposit. Unfortunately, no clear contact
of unconformity was observed between Sebahat and Tungku Formation at this
locality, although, the Sebahat sediment was found about 50 meters away from the
foothill (Figure 5.3). The presence of structural evidence for right lateral strike-slip
faults is indicated by the dilation surface as shown in Figure 5.2-d. The orientation
of the faults is 230/70 and 280/80. The fault orientation can be correlated to the
major trend fault that trending NE-SW Wrench Fault (Tongkul, 1993) and NW-SE
strike slip fault (Tokuyama and Yoshida, 1974; Figure 2.12).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
a
c
NE-SW
Brecciated
zone
b
d
Fault
plane
Cong
Figure 5.2. Field photographs of Tungku conglomerate unit at Locality 55. a) Steeply dip angle (010/50) trending to the ENE. b)
Close up of the strike-slip fault plane. c) Right lateral movement trending NE-SW. d) Dilation surface showing bidirectional of
wrench faults.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Lithofacies System Tract
SR
37
Conglo
VF SsT
F SsT
M SsT
C SsT
VC SsT
Mud
50 m
Formation
Grain size
Description
ID
GMd
Depositional
Environment
TST
Dark grey mudstone,
Shelf - inner neritic
calcareous concreation
beds
Boulder size clast
40 m
(30cm-50m), clast
30 m
Cong
LST
conglomerate, matrix
Alluvial Channel, incised valley
20 m
Tungku Formation
supported
consist of coarse
10
m
sand grain, reverse
0m
graded bedding
Figure 5.3. Lithological log at Locality 55 which shows a very thick conglomerate
unit (Abbreviation as defined in Appendix 2).
* VF Sst: very fine grained sandstone; F Sst: fine grained sandstone; M Sst: M Sst: moderately fine
grained sandstone; C Sst: coarse grained sandstone; VC Sst: very coarse grained sandstone;
Cong: conglomerate; TST: Trangressive System Tract; LST: Lowstand System Tract.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
An angular unconformity between Sebahat and Tungku Formation was
observed at Ladang Ikhtisas Semporna Quarry at Stop 45 (Figure 5.4). At this
locality, the clast supported conglomerate unit is unconformably overlained by thick
interbedded sandstone and siltstone. This evidence shows the abrupt change in
depositional setting from non-marine conglomerate units to marginal marine
sandstone/siltstone units with a clear erosional contact, which suggests an
unconformity (Figure 5.5). This sandstone-siltstone unit is similar to that found at
Bukit Marua quarry and upstream of Sungai Makua as previously reported by
Ismail Che Mat Zin (1994). This angular unconformity is related to the Mid Miocene
Unconformity (MMU) (Hutchinson, 2008) or Shallow Regional Unconformity (SRU)
(Balaguru, 2006b).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
a
HMS
Cong
b
Sebahat
Formation
Erosional unconformity
Tungku
Formation
Figure 5.4. Field photograph of Tungku conglomerate unit at Stop 45 at Ladang Ikhtisas Semporna Quarry. a) Outcrops of
conglomerate unit overlain by sandstone unit. b) Close up view showing an angular unconformity that separate the basal sandy
unit of Sebahat Formation and conglomeritic unit of Tungku Formation as shown by erosional surface.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Lithofacies
Conglo
VF SsT
F SsT
M SsT
C SsT
VC SsT
Grain size
Mud
Formation
20 m
System
Depositional
Description
ID
Tract
Coarse grain sandstone,
Environment
Distributary
with clay matrix, fining
ChSSt
upwards with cross bedding
and cross bedding
Thick sandstone
TST
R35
channel
interbedding with thin
mudstone, parallel bedding,
rare bioturbations,disperse
HMS
plants fragments, erosional
surface (angular
10 m
unconformity SRU,
Flood plain or levee?
SEBAHAT
15 m
5m
TUNGKU
supported conglomerate,
matrix consist of coarse
Conglo
LST
sand grain, Coarsening
upwards, Bed load structure,
0m
Alluvial channel, incised valley
Balaguru, 2006)
Clast size (30cm-50m), clast
high energy deposition
Figure 5.5. Lithological log at Stop 45 outcrop at Ladang Ikhtisas Semporna Quarry
(Abbreviation as defined in Appendix 2).
* VF Sst: very fine grained sandstone; F Sst: fine grained sandstone; M Sst: M Sst: moderately fine
grained sandstone; C Sst: coarse grained sandstone; VC Sst: very coarse grained sandstone;
Cong: conglomerate; HMS; heterolithic mudstone and sandstone; ChSSt: channelized sandstone;
TST: Trangressive System Tract; LST: Lowstand System Tract.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.1.2 LITHOFACIES OF SEBAHAT FORMATION
Outcrop exposures of the Sebahat Formation are very rare due to extensive
weathering and erosion of the low resistance mudstones. The thickest outcrop
(Locality 56) is 7m, which comprises dominantly of shelf sediment. Seismic section
indicates the Sebahat Formation thickens in an offshore direction (Ismail, Che Mat
Zin, 1994). Noad (1998) calculated the maximum thickness of the Sebahat
sediments as 2500m thick.
The lithofacies of the Sebahat Formation consist predominantly grey silty
mudstone, with some interbedded thin siltstone and fine-grained sandstone. The
lowest part of the Sebahat Formation is characterized by thin, coarse to fine grain
sandstone units (Figure 5.4). The dark grey silty mudstone (GMd) with thin
calcareous siltstone bed overlies this sandstone unit which can be found at Locality
56 (Figure 5.6 and Figure 5.8). The calcareous siltstones bed indicates marine
environment. Most of the samples selected for source rock evaluation are grey
mudstones or GMd facies of Sebahat Formation. There is not much variation in
lithology towards the east which is still dominated by grey mudstone; however, the
degree of bioturbation increases (Figure 5.7 and Figure 5.9). The upper most unit
of the Sebahat Formation dominated by sandstone (Figure 5.10 and Figure 5.11)
which indicate a transition from marine to coastal areas.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
B
A
GMd
Calcareous
concreation
C
GMd
Figure 5.6. Field photograph of Sebahat Formation outcrop at Locality 56. a) Picture showing dark grey silty mudstone
interbedded with thin siltstone. b) The siltstone beds often form as calcareous lenses. c) Examples of the dark grey silty
mudstone (GMd) which was sampled for analyses.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
a
GMd
b
GMd
Figure 5.7. Field photograph of Sebahat Formation outcrop at Locality 6. a)
Outcrop of highly bioturbated grey silty shale. b) Close up view shows the trace
fossil possibly Ophiomorpha?, which indicates shallow marine sediments.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Lithofacies
System
Depositional
Description
ID
Tract
Environment
Dark grey
5m
SEBAHAT
mudstone,
calcareous
SR
37
GMd
TST
concreation beds,
disperse organic
matter
0m
Shelf - Holomarine inner neritic
VF SsT
F SsT
M SsT
C SsT
VC SsT
Mud
Formation
Grain size
VF SsT
F SsT
M SsT
C SsT
VC SsT
Grain size
Mud
Formation
Figure 5.8. Lithological log of Locality 56, Ladang Sebahat 1 Quarry (foothill, 50 m
away from vey thick conglomerate unit of Figure 5.2) (Abbreviation as defined in
Appendix 2).
Lithofacies
System
Depositional
Description
ID
Tract
Environment
Dark grey
5m
SEBAHAT
mudstone, consist
of fossils
GMd
SR 2
TST
shallow shelf
brachiopods,
molluscs,
0m
gastropods
Figure 5.9. Lithological log of Locality 6, nearby Telecomunication Tower at
Chenderawasih town (Abbreviation as defined in Appendix 2).
* VF Sst: very fine grained sandstone; F Sst: fine grained sandstone; M Sst: M Sst: moderately fine
grained sandstone; CSst: coarse grained sandstone; VC Sst: very coarse grained sandstone;
GMd: grey mudstone; TST: Trangressive System Tract.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Sandy facies of Lower
Ganduman Formation
Onlapping sequence
Muddy facies of Sebahat
Formation
Figure 5.10. Field photograph of Sebahat Formation outcrop at Locality 11. The sandy facies of Ganduman Formation was
onlapped on the muddy facies of Sebahat formation.
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Lithofacies
VC SsT
VF SsT
F SsT
M SsT
C SsT
Grain size
Mud
Formation
Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
System
Depositional
Description
ID
Tract
10 m
LOWER GANDUMAN
Silty sandstone, low
Environment
Estuarine
angle cross
SLSt
lamination of the
Early HST siltstone
Lower dip agle (200)
channel
Estuarine-tidal
bedding, heterolithic
SR 9
HMS
sandstone and
mudstone, consist
coaly fragments
flat
Higher dip agle (350) Estuarine-tidal
5m
bedding, heterolithic
SR 8
HMS
Late TST sandstone and
mudstone, consist
0m
coaly fragments
flat
Figure 5.11. Lithological log of outcrop at Locality 11, Ladang Felda Sahabat 36
pass by (Abbreviation as defined in Appendix 2).
* VF Sst: very fine grained sandstone; F Sst: fine grained sandstone; M Sst: M Sst: moderately fine
grained sandstone; C Sst: coarse grained sandstone; VC Sst: very coarse grained sandstone;
Cong: conglomerate; HMS; heterolithic mudstone and sandstone; SlSt: silty sanstone; TST:
Trangressive System Tract; LST: Lowstand System Tract.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.1.3 LITHOFACIES OF GANDUMAN FORMATION
Pliocene Ganduman was deposited in a fluvio-marine environment (Haile
and Wong, 1965). The unit is sub-divided into lower and upper parts based on
sand content (Ismail Che Mat Zin, 1994). The Lower Ganduman Formation
sediments contain greater sand content whereas the Upper Ganduman Formation
greater has greater mud content.
Lithofacies of Lower Ganduman are described in general here because
Khalid Ali (2004) has previously done an extensive sedimentological study of these
sediments, and described all facies associations. The sandy sediment of Lower
Ganduman Formation conformably overlies the coastal plain sandstone facies of
Sebahat Formation. At Stop 68, stacked channelized sandstones overlying
interdistributary mudstone and flood-plain coal was observed (Figure 5.12 and
Figure 5.13). The thick cross-bedded channelised sandstones are interpreted to
represent the distributary channels. This facies comprises of channelized
sandstone with fining upward sequences. Primary structures such as trough crossbedded and cross-bedding are common. The abundant of Ophiomorpha trace
fossils in this sandstone facies indicates coastal plain environments. The coal
seam occurring below the sandstone sequence has been interpreted as flood plain
marsh or peat swamp deposits. The thickness of this coal seam is about 30cm
thick.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Following this sediment succession, the stacked channelized sandstone that
indicates the coastal plain sediment is observed at Locality 3 (Figure 5.14 and
Figure 5.15). This sandstone was interpreted to be deposited in a distributary
fluvial channel. Through cross bedding and cross bedding is commonly found in
this outcrop. Ophiomorpha trace fossils are commonly observed.
Towards the east of the Sebahat Formation, the sediments are comprised of
shorefaces sediments. At locality 26, the upper shoreface sediments were
observed to be comprised of fine to medium grained thin lamination sandstone,
with mud drapes within the bottom of layers (Figure 5.16 and Figure 5.17). The
bioturbations are abundant with Ophiomorpha and Planolities which indicate near
shoreline environment.
The upper shoreface deposits that represent estuarine environment can be
observed at Locality 15 (Figure 5.18). The thin interbedded siltstone and fine
grained sandstone (GSMd) which indicate the estuarine tidal flat were capped by
two thin coal seams of approximately 20cm to 50cm thick. The shoreface
sediments change to a more marine as shown by thick shelf mudstone beds. This
sequence indicates distal facies of lower shoreface deposits.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
At Locality 48, the lower shoreface sediment was observed (Figure 5.20).
The sediments comprise of thick shelf mudstone (GMd), interbedded with thin
siltstone and fine grain sandstone (GSMd) sequence. The bioturbations are
abundant within GSMd facies which are associated with a lot of reworked amber
and coal clasts. The GSMd facies was capped by coal seam which indicates the
flooding plain area of probable mangroves swamp. In other localities, the GSMd
facies contains abundant benthonic gastropods and mollusks fossils (Figure
5.21.1) that varies in size. The presence of benthic fossils is an indication of
shallow marine environment with water depth less than 50 m.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
CHSSt
SdCo
GMd
Figure 5.12. Field photograph of outcrop at Stop 68 shows stacked channelised sandy units (CHSSt) associated with
interdistributary lagoonal mudstone (GMd) and flood plain coal seams (SdCo). The thick, cross-bedded channelised sandstones
are interpreted to represent distributary channels of prograding deltas.
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Depositional
Conglo
VF SsT
F SsT
M SsT
C SsT
VC SsT
Grain size
Mud
Formation
Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Lithofacies ID
System Tract
Description
Environment
Stack channelized
20 m
sandstone, fining upward
ChSSt
Early HST
cross bedding, through
Distributary channel
LOWER GANDUMAN
15 m
sequence, common with
cross lamination, abundant
bioturbation common wirh
10 m
Ophiomorpha
Laminated mudstone with
Lagoonal mud
embayment
5m
SEBAHAT
GMd
ChSSt
C
R57
SdCo
disperse plant fragments
sand channel
Late TST
Thin laminated coal
Flood plain mud
Marsh
GMd
ChSSt
0m
Distributary
channel
sand channel
Distributary
channel
Figure 5.13. Lithological log of outcrop at Stop 68 shows the maximum flooding
surface, indicated by coal seam (Abbreviation as defined in Appendix 2).
* VF Sst: very fine grained sandstone; F Sst: fine grained sandstone; M Sst: M Sst: moderately fine
grained sandstone; C Sst: coarse grained sandstone; VC Sst: very coarse grained sandstone;
Cong: conglomerate; ChSSt; channelized sandstone; GMd: grey mudstone; SdCo: Sandy coal;
HST: Highstand System Tract; TST: Trangressive System Tract.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
A
ChSSt
B
C
D
Figure 5.14. Field photograph of outcrop of stacked channelised sandstone (ChSSt) at Locality 3. a) Vertical burrows of
Ophiomorpha. b) Cross bedding sandstone. c) Through cross bedding sandstone.
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Lithofacies
VC SsT
VF SsT
F SsT
M SsT
C SsT
Grain size
Mud
23 m
Formation
Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
System
Depositional
Description
ID
Tract
Environment
parallel bedding of
sandstone, bioturbation
LmSSt
by Ophiomorpha
20 m
common
Stack chanelize
sandstone, fining-upward
sequence, medium to
20 m
coarse grained, cross
bedded and through
cross bedded are
HST
RS
4
common, bioturbation by
Ophiomorpha common,
10 m
Distributary channel
15 m
LOWER GANDUMAN
ChSSt
pebbel clast observed at
the bottom channel
parallel bedding of
LmSSt
5m
0m
sandstone, bioturbation
by Ophiomorpha
Cross lamination of
ChSSt
sandstone, bioturbation
LmSSt
by Ophiomorpha
parallel bedding of
sandstone, bioturbation
by Ophiomorpha
common
parallel bedding of
ChSSt
sandstone, bioturbation
by Ophiomorpha
Figure 5.15. Lithological log of multi-storey stack channelized sandstones at
Locality 3 (Abbreviation as defined in Appendix 2).
* VF Sst: very fine grained sandstone; F Sst: fine grained sandstone; M Sst: M Sst: moderately fine grained sandstone; C
Sst: coarse grained sandstone; VC Sst: very coarse grained sandstone; Cong: conglomerate; ChSSt; channelized
sandstone; LmSSt: laminated sandstone; HST: Highstand System Tract.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
a
ChSSt
LmSSt
b
Figure 5.16. a) Field photograph of outcrop at Locality 26 which shows the upper shoreface sediments. b) Thin laminated very
fine grained sandstone and siltstone (LmSSt) with commonly observed mud drapes and Planolites and Ophiomorpha.
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Depositional
VC SsT
Mud
Grain size
VF SsT
F SsT
M SsT
C SsT
30 m
Formation
Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Lithofacies ID
Description
Parallel bedding of
HMS
Environment
Lower Shoreface
heterolithic sandstonemudstone, bioturbation by
Ophiomorpha common
Medium to coarse
sandstone, fining-upward
LmSSt
25 m
sequence, cross bedded,
through cross
bedded,Ophiomorpha
burrows
Parallel laminated sst,
Upper Shoreface
intercalating with thin layers
of siltstone.Bioturbation is
20 m
abundant, common with
LmSSt
Ophiomorpha and
15 m
LOWER GANDUMAN
Planolites. Mud drapes are
common indicates tidal
influence
parallel bedding of
LmSSt
Lower Shoreface
sandstone, bioturbation of
Ophiomorpha
10 m
GMd
lower shoreface delta plain
mud
Parallel bedding of
heterolithic sandstone-
HMS
mudstone, common
bioturbation of
Ophiomorpha
Parallel laminated sst,
Upper Shoreface
intercalating with thin layers
5m
of siltstone.Bioturbation is
abundant, common with
LmSSt
Ophiomorpha and
Planolites. Mud drapes are
common indicates tidal
0m
influence
Figure 5.17. Lithological log of outcrop at Locality 26.
* GMd: Grey mudstone; LmSSt: laminated sandstone; HST: Highstand System Tract.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
a
Co
GSMd
b
Co
Paleo Soil
Co
Figure 5.18. a) Outcrop at Locality 15 shows the heterolithic mudstones and very
fine grained sandstone lithofacies (HMS) that capped by thin coal seam (Co). b)
Close up view that shows the two layers of coal seam.
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VF SsT
F SsT
M SsT
C SsT
VC SsT
Grain size
Mud
Formation
Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
15 m
C
SR
13
Lithofacies
System
Depositional
Description
ID
Tract
SLSt
HST
Co
MFS
PS
Environment
Top soil,
Fine to medium grain
silty sandstone
Massive coal seam
weathered
Swamp
Flood plain mud
Green paleosoil
Flood plain mud
GMd
Grey silty mudstone
UPPER GANDUMAN
MFS
10 m
C
C
PS
GMd
paleosoil,
Swamp
plant Flood plain mud
Grey silty mudstone
Flood plain mud
Estuarine tidal
5m
GSMd
0m
Massive coal seam
Green
rootlet
Thin
interbedded
and
HST (PS 1) mudstone
sandstone, abundant
of reworked coal and
amber,
high
bioturbation
flat (Upper
shoreface)
Figure 5.19. Lithological log of outcrop at Locality 15 (Abbreviation as defined in
Appendix 2).
* VF Sst: very fine grained sandstone; F Sst: fine grained sandstone; M Sst: M Sst: moderately fine grained sandstone; C
Sst: coarse grained sandstone; VC Sst: very coarse grained sandstone; SlSt: silty sandstone ; Co: coal; PS: paleosoil;
GMd: Grey mudstone; GSMd: grey silty mudstone; MFS: maximum flooding surface; HST: Highstand System Tract.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
PS6
PS5
PS4
PS3
GMd
Book as
scale
PS2
PS1
GSMd
Figure 5.20. The interbedded sandstone and grey silty mudstone with grey mudstone indicates lower shoreface deposits at
Locality 48. This sediment indicates six set of parasequences (PS1-PS6). The Ophiomorpha burrows are common within the
GSMd facies.
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Lithofacies ID
VF SsT
F SsT
M SsT
C SsT
VC SsT
Grain size
Mud
20 m
Formation
Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
System
Description
Tract
Dark brown massive fine grain
ChSSt
C
SR
32
Co
PS
Depositional
Environment
Distributary
HST
sandstone
coal seam
MFS
green paleosoil
channel
Swamp
Flood plain
Thin interbedded mudstone and
GSMd
HST (PS6)
coal and amber, high bioturbation
Dark grey shelf mudstone
GMd
GSMd
10 m
UPPER GANDUMAN
GMd
sandstone, abundant of reworked
HST (PS 5) Dark grey shelf mudstone
GSMd
GMd
HST (PS4) Dark grey shelf mudstone
GSMd
Dark grey shelf mudstone
GMd
HST (PS 3)
Thin interbedded mudstone and
GSMd
sandstone, abundant of reworked
HST (PS2)
5m
GMd
Lower shoreface
15 m
coal and amber, high bioturbation
Dark grey shelf mudstone
Thin interbedded mudstone and
GSMd
sandstone, abundant of reworked
coal and amber, high bioturbation
HST (PS 1) Dark grey shelf mudstone
GMd
0m
Figure 5.21. Lithological log of outcrop at Locality 48 (Abbreviation as defined in
Appendix 2).
* VF Sst: very fine grained sandstone; F Sst: fine grained sandstone; M Sst: M Sst: moderately fine grained sandstone; C
Sst: coarse grained sandstone; VC Sst: very coarse grained sandstone; SlSt: silty sandstone ; Co: coal; PS: paleosoil;
GMd: Grey mudstone; GSMd: grey silty mudstone; MFS: maximum flooding surface; HST: Highstand System Tract.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
a
b
c
Oyster
Figure 5.21.1. Fossil assemblages of benthic faunas within the GSMd facies of
Upper Ganduman Formation which indicate shallow marine environment,
particularly shoreface; (a) Smaller brachiopods and gastropods fossil; (b) Larger
brachiopod? (c). Oyster fossils.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.1.4 LITHOFACIES OF TOGOPI FORMATION
The outcrops of Togopi Formation are mainly distributed along the most
eastern part of the Dent Peninsula coastline. The age of the Togopi Formation
ranges from Pliocene to Pleistocene (Walker, 1993). The outcrop exposures of this
formation generally made up of transported limestone that consists of nodular
clasts and fossil fragments supported by clay matrix. The fragments are made up
of skeletal components, mainly of benthonic foraminifera, mollusk fragments,
echinoderms and coral fragments. The facies is semi-consolidated and was
interpreted by Ismail Che Mat Zin (1994) as transported limestone. At Locality 52
inside the Sahabat 47 limestone quarry, thick allochthonous limestone (8 meters)
overlies fossiliferous consolidated marl (Figure 5.22 and Figure 5.24). The marl
bed also is exposed at Locality 20, unconformably overlying the mudstone facies of
the Upper Ganduman Formation (Figure 5.23 and Figure 5.25). The grey silty
sandstone facies (GSMd) contains abundant mollusk and brachiopods fossils
(Figure 5.24). This contact between the two formations is marked as Late Pliocene
Unconformity (Balaguru, 2006b).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
a
UCLSt
b
c
d
CLSt
UCLSt
UCLSt
Figure 5.22. a) The lithofacies of the excavated Togopi Limestone outcrop at Locality 52 in the Sahabat 24 limestone quarry; b)
The upper part shows the consolidated marl (CLSt); c) Coral fragments inside the unconsolidated limestone (UCLSt); d) The
nodular unconsolidated limestone.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Togopi Limestone
CLSt
Sequence boundary
Upper Ganduman
Mudstone
GMd
Figure 5.23. Transitional contact surface between the Togopi Formation and Upper Ganduman Formation at Locality 20
indicates a possible unconformity.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Lithofacies
Formation
Grain size
System
Depositional
M SsT
C SsT
VC SsT
VF SsT
F SsT
Limestone
Description
ID
Tract
CLSt
10 m
Environment
consolidated
limestone
Unconsolidated
UCLst
UCLst
TOGOPI
5m
Shallow marine
limestone
Unconsolidated
TST
CLSt
limestone
consolidated
limestone
Unconsolidated
UCLst
limestone
Unconsolidated
UCLst
limestone
0m
Figure 5.24. Lithological log of outcrop at Locality 52 (Abbreviation as defined in
Appendix 2).
0m
To
Lithofacies ID
System
Depositional
VF SsT
F SsT
M SsT
C SsT
VC SsT
Description
Tract
CLSt
UPPER GANDUMAN
5m
Limestone
Formation
Grain size
TST
Environment
consolidated limestone
Dark grey mudstone,
shallow marine
Lower Delta
consist of fossils
GMd
HST
brachiopods, molluscs,
gastropods
Plain
Figure 5.25. Lithological log of outcrop at Locality 20 (Abbreviation as defined in
Appendix 2).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.1.5 SOURCE ROCK FACIES
Six source rocks facies are identified based on the sedimentologic analyses
and hand specimen description. Samples belonging to these facies were further
analyzed to determine the source rock quality. The source rock facies are shown in
Table 5.1 which are correlatable with depositional environments and System Tract.
The main source rocks interval is within the Highstand System Tract (HST) and
Trangressive System Tract (TST). The hand specimens photo of the source rock
facies are as shown in Figure 5.26.
Most of the analysed samples were taken from GMd facies. This facies is
massive grey to dark grey mudstone, associated with very fine-grained organic
particles which were interpreted to have been deposited during TST or late HST
periods in the delta plains discussed in section 5.4.1. The grey silty sandstone
facies (GSMd) is coarser grained and contain a lot of plant debris, coals fragments
and amber clasts. These GSMd facies is sediments of heterolithic sandstone and
mudstone association which were deposited in lower shoreface environment during
HST periods. This facies is found in most of the Upper Ganduman sediments. The
sandy coal (SdCo) facies is dull black coal associated with fine grained sands. This
facies was deposited during HST as levee deposits in distributary lower shoreface
channel. The coaly sandstone (CoSSt) facies on the other hand is a coastal plain
sediment with some coal laminations. The coals (Co) facies shows a bright black
colour, whereas the brown coal (BCo) facies is slightly brown in colour and
intimately associated with some unlithified woody materials.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Among the source rocks facies, two possible reservoir facies have also been
analyzed (Figure 5.27). These samples are sandstones which were taken from the
Lower Ganduman Formation and unconsolidated shallow marine limestone of
Togopi Formation. These reservoir rocks are analyzed to determine the possible
presence of migrated hydrocarbons.
Table 5.1. Six source rocks facies and two reservoir rocks identified based on
sedimentological description.
No
Source Rocks Facies
Facies ID
Environment of
Deposition
1
Grey mudstone
GMd
Delta Plain
2
Grey Silty sandstone
GSMd
Shoreface
3
Sandy coal
SdCo
Levee
4
Coaly sandstone
CoSSt
Coastal plain
5
Coal
Co
Swamp
6
Brown Coal
BCo
Swamp
7
Sandstone
SSt
Fluvial
8
Limestone
LSt
Allochtonuous
TST= Trangressive System Tract; HST= High Stand System Tract.
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System
Tract
TST/HST
HST
HST
HST
HST
HST
HST
TST/HST
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Amb
GMd
GSMd
GMd
Figure 5.26. Collected samples representing source rock facies for analyses. Amb: Amber clast, taken within grey silty
sandstone facies (GSMd); GSMd: Facies of grey silty sandstone comprises coaly fragments and amber clast; GMd: Facies of
grey silty mudstone.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
SdCo
BCo
Co
SSt
Figure 5.26 (cont.). Collected samples representing source rock and reservoir rock facies for analyses. SdCo: Sandy coal
(carbagilite); BCo: Brown coal or lignites; Co: Bright-black coal; SSt: Medium grain white silty sandstone.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
CLst
SSt
ULst
CLst
Figure 5.27. Collected samples representing reservoir rock facies for analyses. CLSt: Consolidated limestone; SSt: Brown
coarse grain bioturbated sandstone; ULSt: Unconsolidated silty limestone with vuggy porosity; CLSt: Consolidated fossiliferous
limestone.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.2 PALYNOLOGICAL ANALYSES
Ten mudstone and siltstone samples from Sebahat and Ganduman
formations were analyzed for pollen. The palynological analyses were used to
determine type of vegetation in specific environments which could determine the
source of the pollens that were transported by the river system. In addition, the
likely depositional environments of the source rocks and probable condition of
deposition could be determined. The palynomorph count data are in Appendix 6.
The results of pollen counts for each sample are shown in Figure 5.28.
The palynomorph data show significant amounts of mangrove pollen that
were dominated by Rhizoporacea sp, Bruguera sp, with small numbers of
Avicennia sp in both the Sebahat and Ganduman Formations (Figure 5.29). The
significant abundant of mangrove pollen strongly suggest the contribution of
mangrove swamp plants, thus indicates mangrove environment (Figure 5.30). The
pollens can be transported from mangrove downward to the basin. Spores were
also abundant with mangroves grass species as shown by monolete smooth
spores, thus indicates most likely a constantly wet swamp. Rare numbers of the
Dipterocarpaceae sp pollens were also preserved which could potentially influence
indicate higher terrestrial plant input nearby.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
SR37 Sebahat Formation
SR35 Sebahat Formation
Abundance (%)
0
5
10
15
20
25
Abundance (%)
30
35
40
45
Rhizophor a
Br ugeir a
Avicennia f r r
Sonner at ia alba
Sonner at ia caseolar is
Sonner at ia levipoli
Excoecar ia agal.
Nypa
Br ownlowia
Oncosper ma
Celt is
Calamus 90
Calamus 215
Calamus 346
Canar ium
Caesalpiniaceae
Dillenia
Dipt er ocar pus
Macar anga
Mor aceae
Blumeodendr on
Calophyllum
Cephalomappa 20
Cephalomappa 86
Dur io t p
Sapot aceae
St emonur us
Cant hium dicoc t p
Myr t aceae
Pandanus
Pomet ia
Composit ae t ub
Gr amineae
Lit hocar pus
Consent r icyst es cir s
Randia
Magnoliaceae
Palmae
Lyt hr aceae
Juglandaceae
Quer qus
Acr ost hicum aur eum
Acr ost hicum spec
Lygodium scandens
Monolet e smoot h
Monolet e ver r ucat e
Lycopodium phlegmar ia
Pt er is ver r ucat e
St enochlaena palust r is
St enochlaena usmensis
Cyclophor us
Ilex
For am t est lining
Car ya
Bar r ingt onia
0
5
10
15
25
30
35
GD1 Upper Ganduman Formation
SR3 Sebahat Formation
Abundance (%)
Abundance (%)
0
Rhizophor a
Br ugeir a
Avicennia f r r
Sonner at ia alba
Sonner at ia caseolar is
Sonner at ia levipoli
Excoecar ia agal.
Nypa
Br ownlowia
Oncosper ma
Celt is
Calamus 90
Calamus 215
Calamus 346
Canar ium
Caesalpiniaceae
Dillenia
Dipt er ocar pus
Macar anga
Mor aceae
Blumeodendr on
Calophyllum
Cephalomappa 20
Cephalomappa 86
Dur io t p
Sapot aceae
St emonur us
Cant hium dicoc t p
Myr t aceae
Pandanus
Pomet ia
Composit ae t ub
Gr amineae
Lit hocar pus
Consent r icyst es cir s
Randia
Magnoliaceae
Palmae
Lyt hr aceae
Juglandaceae
Quer qus
Acr ost hicum aur eum
Acr ost hicum spec
Lygodium scandens
Monolet e smoot h
Monolet e ver r ucat e
Lycopodium phlegmar ia
Pt er is ver r ucat e
St enochlaena palust r is
St enochlaena usmensis
Cyclophor us
Ilex
For am t est lining
Car ya
Bar r ingt onia
20
Rhizophora
Brugeira
Avicennia f r r
Sonnerat ia alba
Sonnerat ia caseolaris
Sonnerat ia levipoli
Excoecaria agal.
Nypa
Brownlowia
Oncosperma
Celt is
Calamus 90
Calamus 215
Calamus 346
Canarium
Caesalpiniaceae
Dillenia
Dipt erocarpus
Macaranga
Moraceae
Blumeodendron
Calophyllum
Cephalomappa 20
Cephalomappa 86
Durio t p
Sapot aceae
St emonurus
Cant hium dicoc t p
Myrt aceae
Pandanus
Pomet ia
Composit ae t ub
Gramineae
Lit hocarpus
Consent ricyst es cirs
Randia
Magnoliaceae
Palmae
Lyt hraceae
Juglandaceae
Querqus
Acrost hicum aureum
Acrost hicum spec
Lygodium scandens
Monolet e smoot h
Monolet e verrucat e
Lycopodium phlegmaria
Pt eris verrucat e
St enochlaena palust ris
St enochlaena usmensis
Cyclophorus
Ilex
Foram t est lining
Carya
Barringt onia
5
10
15
20
25
0
30
5
10
15
20
25
30
35
40
Rhizophora
Brugeira
Avicennia f r r
Sonnerat ia alba
Sonnerat ia caseolaris
Sonnerat ia levipoli
Excoecaria agal.
Nypa
Brownlowia
Oncosperma
Celt is
Calamus 90
Calamus 215
Calamus 346
Canarium
Caesalpiniaceae
Dillenia
Dipt erocarpus
Macaranga
Moraceae
Blumeodendron
Calophyllum
Cephalomappa 20
Cephalomappa 86
Durio t p
Sapot aceae
St emonurus
Cant hium dicoc t p
Myrt aceae
Pandanus
Pomet ia
Composit ae t ub
Gramineae
Lit hocarpus
Consent ricyst es cirs
Randia
Magnoliaceae
Palmae
Lyt hraceae
Juglandaceae
Querqus
Acrost hicum aureum
Acrost hicum spec
Lygodium scandens
Monolet e smoot h
Monolet e verrucat e
Lycopodium phlegmaria
Pt eris verrucat e
St enochlaena palust ris
St enochlaena usmensis
Cyclophorus
Ilex
Foram t est lining
Carya
Barringt onia
Figure 5.28. The distribution of palynomorph of the respective samples.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
R26A Sebahat Formation
R26B Sebahat Formation
Abundance (%)
0
5
10
15
20
Abundance (%)
25
30
35
40
Rhi zophor a
Br ugei r a
Avi cenni a f r r
Sonner ati a al ba
Sonner ati a caseol ar i s
Sonner ati a l evi pol i
Excoecar i a agal .
Nypa
Br ownl owi a
Oncosper ma
Cel ti s
Cal amus 90
Cal amus 215
Cal amus 346
Canar i um
Caesal pi ni aceae
Di l l eni a
Di pter ocar pus
Macar anga
Mor aceae
Bl umeodendr on
Cal ophyl l um
Cephal omappa 20
Cephal omappa 86
Dur i o tp
Sapotaceae
Stemonur us
Canthi umdi coc tp
Myr taceae
Pandanus
Pometi a
Composi tae tub
Gr ami neae
Li thocar pus
Consentr i cystes ci r s
Randi a
Magnol i aceae
Pal mae
Lythr aceae
Jugl andaceae
Quer qus
Acr osthi cumaur eum
Acr osthi cumspec
Lygodi umscandens
Monol ete smooth
Monol ete ver r ucate
Lycopodi umphl egmar i a
Pter i s ver r ucate
Stenochl aena pal ustr i s
Stenochl aena usmensi s
Cycl ophor us
Il ex
For amtest l i ni ng
Car ya
Bar r i ngtoni a
0
5
10
15
20
25
30
35
Rhi zophor a
Br ugei r a
Avi cenni a f r r
Sonner ati a al ba
Sonner ati a caseol ar i s
Sonner ati a l evi pol i
Excoecar i a agal .
Nypa
Br ownl owi a
Oncosper ma
Cel ti s
Cal amus 90
Cal amus 215
Cal amus 346
Canar i um
Caesal pi ni aceae
Di l l eni a
Di pter ocar pus
Macar anga
Mor aceae
Bl umeodendr on
Cal ophyl l um
Cephal omappa 20
Cephal omappa 86
Dur i o tp
Sapotaceae
Stemonur us
Canthi umdi coc tp
Myr taceae
Pandanus
Pometi a
Composi tae tub
Gr ami neae
Li thocar pus
Consentr i cystes ci r s
Randi a
Magnol i aceae
Pal mae
Lythr aceae
Jugl andaceae
Quer qus
Acr osthi cumaur eum
Acr osthi cumspec
Lygodi umscandens
Monol ete smooth
Monol ete ver r ucate
Lycopodi umphl egmar i a
Pter i s ver r ucate
Stenochl aena pal ustr i s
Stenochl aena usmensi s
Cycl ophor us
Il ex
For amtest l i ni ng
Car ya
Bar r i ngtoni a
SR17 Upper Ganduman Formation
SR12 Upper Ganduman Formation
Abundance (%)
Abundance (%)
0
5
Rhi zophor a
Br ugei r a
Avi cenni a f r r
Sonner ati a al ba
Sonner ati a caseol ar i s
Sonner ati a l evi pol i
Excoecar i a agal .
Nypa
Br ownl owi a
Oncosper ma
Cel ti s
Cal amus 90
Cal amus 215
Cal amus 346
Canar i um
Caesal pi ni aceae
Di l l eni a
Di pter ocar pus
Macar anga
Mor aceae
Bl umeodendr on
Cal ophyl l um
Cephal omappa 20
Cephal omappa 86
Dur i o tp
Sapotaceae
Stemonur us
Canthi umdi coc tp
Myr taceae
Pandanus
Pometi a
Composi tae tub
Gr ami neae
Li thocar pus
Consentr i cystes ci r s
Randi a
Magnol i aceae
Pal mae
Lythr aceae
Jugl andaceae
Quer qus
Acr osthi cumaur eum
Acr osthi cumspec
Lygodi umscandens
Monol ete smooth
Monol ete ver r ucate
Lycopodi umphl egmar i a
Pter i s ver r ucate
Stenochl aena pal ustr i s
Stenochl aena usmensi s
Cycl ophor us
Il ex
For amtest l i ni ng
Car ya
Bar r i ngtoni a
10
15
20
25
30
0
35
5
10
15
20
25
30
35
40
Rhi zophor a
Br ugei r a
Avi cenni a f r r
Sonner ati a al ba
Sonner ati a caseol ar i s
Sonner ati a l evi pol i
Excoecar i a agal .
Nypa
Br ownl owi a
Oncosper ma
Cel ti s
Cal amus 90
Cal amus 215
Cal amus 346
Canar i um
Caesal pi ni aceae
Di l l eni a
Di pter ocar pus
Macar anga
Mor aceae
Bl umeodendr on
Cal ophyl l um
Cephal omappa 20
Cephal omappa 86
Dur i o tp
Sapotaceae
Stemonur us
Canthi umdi coc tp
Myr taceae
Pandanus
Pometi a
Composi tae tub
Gr ami neae
Li thocar pus
Consentr i cystes ci r s
Randi a
Magnol i aceae
Pal mae
Lythr aceae
Jugl andaceae
Quer qus
Acr osthi cumaur eum
Acr osthi cumspec
Lygodi umscandens
Monol ete smooth
Monol ete ver r ucate
Lycopodi umphl egmar i a
Pter i s ver r ucate
Stenochl aena pal ustr i s
Stenochl aena usmensi s
Cycl ophor us
Il ex
For amtest l i ni ng
Car ya
Bar r i ngtoni a
Figure 5.28 (cont.).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
c
b
a
e
d
f
h
g
a: Avicennia sp; b: Rhizophoracaea sp; c: Sonneratia
caseolaris; d: Psilasporaceae; e: Lithocarpus; f:
Sonneratia alba; g:Malvaceae sp; h: Dipterocarpacea
sp
Figure 5.29. Photomicrograph of variaties of pollens that indicates different plant
species and significantly dominated by mangrove plants.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Specifics to each of the formation, the Upper Ganduman Formation most
likely was deposited in a more proximal part of mangrove swamps as recorded by
abundant of Rhizophoracea sp and Bruguera sp (personal communication, Azmi,
2008). The Sebahat Formation however is more distal parts which received lesser
amount of mangrove pollens. Palynological analysis are compatible with the
previous study of Ismail Che Mat Zin (1994) that interpreted the Sebahat and
Ganduman Formations as a complete sequence of fluvio-deltaic environments (see
section 5.4.1).
However, the palynological interpretation is influenced by a wide range
depositional environment where pollens were transported. Thus, by using the
depositional model of Mazlan et al. (1999), a general interpreted depositional
environment has been suggested that ranging from back mangroves to the shelf or
beyond to the continental slope (as highlighted in red circle in Figure 5.32).
Therefore, the foraminifera data is needed to establish how far the sediments were
deposited in the shelf and the relative water depth.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Distribution of Palynomorph in different depositional environments
250
200
Abundance
SR17
SR12
150
GD1
SR3
R26B
R26A
100
SR35
SR37
Mangrove
Riparian
Seasonal
Montane
Spore
Carya
Barringtonia
Ilex
Foram test lining
Cyclophorus
Stenochlaena usmensis
Pteris verrucate
Stenochlaena palustris
Lycopodium phlegmaria
Monolete smooth
Monolete verrucate
Acrosthicum spec
Other
Lygodium scandens
Querqus
Acrosthicum aureum
Juglandaceae
Palmae
Lythraceae
Randia
Magnoliaceae
Consentricystes cirs
Gramineae
Lithocarpus
Pometia
Compositae tub
Pandanus
Myrtaceae
Stemonurus
Canthium dicoc tp
Durio tp
Peat sw amp
Sapotaceae
Cephalomappa 86
Calophyllum
Cephalomappa 20
Moraceae
Blumeodendron
Macaranga
Dillenia
Rainforest varia
Dipterocarpus
Canarium
Caesalpiniaceae
Calamus 346
Calamus 215
Celtis
Calamus 90
Oncosperma
Nypa
Brownlowia
Excoecaria agal.
Sonneratia levipoli
Sonneratia alba
Sonneratia caseolaris
Brugeira
Avicennia fr r
0
Rhizophora
50
RiparianOtherCoastal
Plant species in specific environment
Figure 5.30. Stacked bar graph shows the distribution of different species of pollens in different depositional environments.
Relatively, the pollens and spores are dominated by mangrove plant species.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.3 MICROPAEONTOLOGY
A micropaleontological study was carried out on 8 samples (5 samples from
the Sebahat Formation; 3 samples from the Ganduman Formation). The
foraminiferal assemblages are dominated by benthonic microfossils with significant
numbers of planktonic microfossils were recorded (see Table 5.2). The
foraminiferal assemblages were used to interpret the depositional environment and
relative water depth. All the recovered microfossils were moderately preserved.
The number of recovery assemblages could also be affected by the degree of
weathering of samples.
The samples from Sebahat Formation are relatively abundant of benthonic
forams with Trochamina sp being the highest. The high numbers of agglutinated
forams suggest the depositional environment is shallow water benthic zones,
probably nearby brackish mangroves which received clastic sediments. The
presence of floating microfossils such as Globigerina sp and Orbulina sp indicate
the open sea area with water depth less than 50 m. Therefore, the marine
environment was limited to an inner neritic zone. The rare numbers of benthonic
foram in the Ganduman Formation sediment suggests the water level was slightly
shallower than Sebahat Formation. This evidence is supported by the presence of
macrofossils of benthic faunas. On the other hand, the significant number of
planktonic foram of Orbulina sp (Figure 5.31) in the GD 1 samples indicates a
deeper water depth. Therefore, the depositional environment possibly ranges from
coastal plain to inner neritic (Figure 5.32).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Table 5.2. The assemblages of benthonic and planktonic foraminifera correspond with environments and water depth (after
Phleger, 1960).
Indeterminite benthic
Diatom
Ammonia sp
Loxostomum sp
2
5
2
1
4
-
-
Sebahat
-
2
-
-
-
-
-
-
Mudstone
Sebahat
6
-
-
-
-
-
8
R 26 A
Mudstone
Sebahat
4
1
-
1
-
-
R 26 B
Mudstone
Sebahat
5
-
-
-
-
6
GD 1
Coaly
siltstone
-
2
-
-
7
SR 12
Siltstone
1
8
-
8
SR 17
Siltstone
Upper
Ganduman
Upper
Ganduman
Upper
Ganduman
2
5
-
1
SR 37
2
SR 25
3
SR 3
4
5
Lithology
Silty
mudstone
Coaly
siltstone
Environment
Water
Depth (m)
Preservation
Bathysiphon sp
20
Sample
ID
Orbulina sp
Indeterminite arenaceous
Sebahat
No
Interpretations
Globigerinoides sp
Formation
Ammodiscus sp
Planktonic
Trochamina sp
Benthonic
9
3
Inner Neritic
< 50m
Mod
-
1
Inner Neritic
< 50m
Mod
6
1
-
Inner Neritic
< 50m
Mod
6
6
2
-
Inner Neritic
< 50m
Mod
-
-
4
-
2
Inner Neritic
< 50m
Mod
-
-
-
-
-
7
Inner neritic
< 50m
Mod
-
-
-
-
-
3
-
Inner neritic
< 50m
Mod
-
-
-
-
-
2
-
Inner neritic
< 50m
Mod
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Figure 5.31. Image of Orbulina sp.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Figure 5.32. Characterization of depositional environments in Malaysian Basin using foraminiferas and palynomorph (after
Mazlan et. al., 1999).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.4 DISCUSSION
5.4.1 RECONSTRUCTION OF PALEO DEPOSITIONAL ENVIRONMENT AS
RESPONSE TO RELATIVE SEA LEVEL CHANGES.
A depositional sequence is defined as a relatively conformable
succession of genetically related strata bounded by unconformities or their
correlative conformities (Vail, et al., 1977) which represent the record of one
cycle of relative sea level. Figure 5.33 shows the reconstructed model of
depositional environments of the Dent Group sediments as responsed to the
relative sea level fluctuation.
The reconstructed model is used to understand the source rock condition
during deposition, especially in the Sebahat and Ganduman Formations. A
global sea level curve of Haq et al., (1987) was used to correlate between the
sediment deposition and relative sea level fluctuation. The model has also
integrated with sequence stratigraphic concept, adopted from Posamentier and
Allen (1999) to determine the depositional cycles and sequences, targeting to
the source rocks facies description. The complete sequence and depositional
environments are manifested in the proposed composite lithostratigraphic log
(Figure 5.34). In vertical succession, all depositional sequences are composed
of sequence boundary, lowstand systems tract, transgressive systems tract,
highstand systems tract, and the following sequence boundary.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
As reported by Ismail Che Mat Zin (1994), the sediments of Sebahat
and Ganduman Formations were deposited in a complete unit of deltaic
sequence which represents the distal facies of the Sebahat Formation and the
proximal facies of the Ganduman Formation, whereas the Togopi sediments
were deposited in a shallow marine shelf as transported carbonates. Two
complete depositional sequences are proposed that develop the Dent Group
sediment. The first sequence was characterized by complete sequence of
sandtone-mudstone deposition of fluvial-deltaic system of Sebahat and
Ganduman Formations. The second cycles is completed by depositional of
shallow marine Togopi formation sediments. The proposed depositional
environment model to characterize the source rock facies of Sebahat and
Ganduman formations from early Middle Miocene to middle Pliocene is
displayed in Figure 5.35.
5.4.1.1 FIRST SEQUENCE
A. Lowstand System Tract (LST)
The first sequence begins with lowstand system tract (LST), a relative
sea level fall where active erosion and deposition occurred. Referring to the
model in Figure 5.33-A, the conglomerate of the Tungku Formation was
deposited in an incised valley of alluvial channel during the early sea level drop
period. During this period, active erosion processes have eroded the
conglomerates unit of Tungku Formation. Ismail Che Mat Zin, (1994) previously
reported the erosion occurrences in the early Miocene of this sediment which
was a result of major phase of uplifting. The erosional surface was later
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
unconformably overlained by thin coastal plain sandstone facies of Sebahat
Formation in early tranggressive periods as shown in Figure 5.4. This field
evidence clearly shows erosional contact between the conglomerate unit and
the onlap sandstone unit on top of conglomerate as observed at Ladang
Ikhtisas Semporna Quarry (Stop 45).
The conglomerate unit was deposited as an alluvial deposit under high
energy condition whereas the coarse-medium grained sandstone and mudstone
units of the Sebahat Formation are relatively shallow marine sediments which
lower energy condition. Microfossils study of a mudstone samples from
Sebahat-1 Quarry reveal marine environment as shown by the presence of
planktonic foraminifera such as Golobigerina sp and Orbulina sp. The abrupt
change of depositional setting from high energy to low energy has suggested a
possible sequence boundary or unconformity. This angular unconformity was
previously interpreted as regional unconformity (MMU) that divided the Segama
Group and Dent Group which occurred as a result of a major sea level fall
during middle Miocene period (Balaguru, 2006b). Subsequently, the plants
development during Neogene period that mainly distributed in coastal to coastal
plain environments (Mazlan et al., 1999) has been eroded together with clastic
sediments and deposited apparently in the fluvio-deltaic environment.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
B. Transgressive System Tract (TST).
The transgressive systems tract consists of a retrogradational set of
sequences. The lowest part of the first sequence is characterized by thin
sandstone facies of Sebahat Formation. A relative sea level rise in the middle
Miocene, probably started at 15.5 Ma (Haq et al, 1987) was thought to provide a
major retrogradational event (landward movement) of deltaic mud from offshore.
This period interpreted as Trangressive System Tract (TST) is typically
characterized by the onlapping sequence of shelf mudstone (GMd Facies) of
the Sebahat Formation to the conglomeritic unit or sandstone unit. The
continual erosion of uplifted Segama Group sediments fed the shallow marine
zones by the clastic sediments and a lot of organic debris from inland. As a
result, the organic rich layer such coaly sandstone (CoSSt) was deposited in
coastal plain environment. The retrogradational mudstone facies (GMd facies)
at the same time was deposited in the offshore or transitional environment
(Figure 5.33-B). This evidence is supported by the bimodal curved in the GCMS
peaks (Figure 6.30) and Pr/nC17 Vs Ph/nC18 crossplot diagram (Figure 6.32)
which significantly related to the transitional zone. The presence of planktonic
foraminiferas such as Globigerinoides sp. and Orbulina sp. in the Gmd facies
suggests the middle neritic environment with maximum water depth less than
50m (personal communication, Azmi 2008).
The calculated Pr/Ph ratios range from 0.5 to 2.5 indicates the sediments
were deposited under oxic to sub-oxic condition. Thus, the oxic to sub-oxic
condition is thought not a suitable condition for the organic matter preservation
where the biodegradation by bacteria actively occurred. However, rapid
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
sedimentation 300-1000 m/Ma (Noor Azim Ibrahim, 1994) could suggest the
organic matter was well preserved. The varieties of plant input mainly
terrigineous origin could potentially be a good organic sources for this source
rock facies. Palynological analyses indicate the mangroves plant types are
abundantly present which could contribute to Type II/III kerogen for oil or gas
generation as reported in Mahakam Delta (Peters et al, 2000).
Towards the land, the facies change to a mixed sand-mud facies which is
related to the coastal plain environments. The thick channelized sandstones are
interpreted to represent distributary channels. On top of this sandstone facies,
thin coal seam (SdCo) of about 30cm thick was observed and interpreted as
flood plain marsh or peat swamp lower coastal plain deposit. This coal layer
characterized the flooding surface of the TST period. This is partly explained by
petrographic analysis which reveals the coal facies accumulated within a
mangrove peat swamp (see Figure 6.4 in section 6.0.1.2). The maximum
flooding surface is characterized by the presence of calcareous concretion
which marks the time of maximum flooding or transgression of the shelf and
separates the TST and HST (e.g. Helland-Hansen and Martinsen, 1996; and
Nummedal et al., 1993). Most of the eroded sediments that associated with
organic matter were sourced from marsh and mangrove swamps were
transported into delta plain environments.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
C. Highstand System Tract (TST)
The highstand systems tract consists of an aggradational set
sequences (Figure 5.33-C). The trangression mud of Sebahat Formation was
thought to cease when sediment accumulation rates exceed sea level rise and
increase volume of sediment. These caused the inland sediment to prograde
toward the nearshore-coastal plain environment. This prograding sediments is
typically charecterized by the Lower Ganduman Formation sediments. The
Lower Ganduman sediments contain greater sand content that represent
proximal coastal plain facies whilst the Upper Ganduman sediments comprises
muddy facies that represent distal part. Within this prograding sediments,
several heterogeneities of facies were recorded such as channelized sandstone
(ChSSt), silty sandstone (SlSt) and laminated sandstone (LmSt). However, this
facies is not discuss in detail as the discussion is focussed on source rocks
depositional setting.
Abundant bioturbation within the sandstone facieses of the Lower
Ganduman indicates it has been deposited in a coastal plain environment.
Commonly, the burrow of Ophiomorpha sp. is found in both Upper Ganduman
and Lower Ganduman Formation, while Planolites sp. found in Lower
Ganduman.
The sandstone facies composed of several sub-facies which are silty
sandstones (SlSt), channelized sandstone with trough cross bedding and cross
bedding (ChSSt) and laminated sandstone (LmSSt). As was mentioned above,
this
discussions
focuses
on
the
source
rock
facies;
therefore,
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
heterogeneities of the sandstone facies were group into sandstone (SSt). The
distributary channel sandstone and interdistributary mudstone with flood plain
coal seam (Co facies) found at Locality 37 and Locality 3 are typical examples
of lower delta plain succession. The distributary channel sandstone that shows
fining upward successions with cross bedding and through cross bedding
(ChSSt) is common. The coal seam was a peat swamp deposit and indicates
the flooding surface. Coal facies description of the Upper Ganduman coals
confirmed the development of paleomire was in a marsh and mangrove swamp
environments (see Figure 6.4 in section 6.0.1.2). This is supported with the
cross plot of Pr/nC17 Vs Ph/nC18 which indicates a transitional environment (see
Figure 6.32), and this will be discussed further in chapter 6.
The shoreface sediments were deposited in the eastern part in Dent
Peninsula. The upper shoreface deposits are characterized by thin parallel
laminated sandstone intercalating with thin layers of mudstone as observed at
Locality 26. The trace fossils are abundant with Ophiomorpha and Planolites.
The mud drapes were commonly preserved which indicates tidal influence.
Further to the east, the proximal lower shoreface facies can be found. This
facies comprises of interbedded heterolithic mudstone and sandstone (HMS)
and facies of grey mudstones which is an example of a parasequence set in
distal lower shoreface deposits. These parasequences were deposited in the
late HST period, which provides a lot of amber and coal clasts to be deposited
in the lower shoreface. The HMS facies has also been considered as potential
source rock beds as it is rich in amber and coal clasts.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.4.1.2 SECOND SEQUENCE
D. Lowstand System Tract (LST)
The second sequence is not discussed in details because the sediments
are limited to the limestone and calcareous sandstone facies. Thus, these
sediments are not of interest for source rocks evaluation, however they may act
as good reservoir rocks. As these sediments were identified as reservoir rocks,
some samples were analysed using GCMS to investigate if migrated
hydrocarbons are present thus indicate migration could have occurred.
The second sequence was developed during the Lowstand System Tract
(LST) when the relative sea level falls during the late Pliocene tectonic event
(Figure 5.33-D). A major uplift and erosion during this period caused the
calcareous sandstone older than the Togopi Formation being eroded and
deposited in a braided channel deposit (Balaguru, 2006a). This deposit was
believed to be a remnant of incised valley fills fluvial system. Active erosion
during this period caused most of the LST sediments being eroded.
E. Transgressive System Tract (TST) to Highstand System Tract (TST)
Relative sea level rise during this period provides an accommodation
space for the shallow marine sediments to be deposited (Figure 5.33-E). The
trangressive to highstand sedimentary packages consist of calcareous silty
limestone with vuggy pores. This limestone is semi-consolidated and associated
with abundant fossils and very loose. The limestone of Togopi Formation has
previously been interpreted by Ismail Che Mat Zin (1994) as transported
sediments, deposited in shallow marine environments.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
A. Lowstand System Tract (LST) : Progradational sequence
Cong
Cong
B. Trangressive System Tract (TST) : Retrogradational sequence
GMd
Figure 5.33. The reconstructed model of depositional environments of the Dent
Group sediments as responsed to the relative sea level fluctuation (modified
after Noad, 1998 and ISIS, 2005).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
C. Highstand System Tract (HST): Aggraditional sequence
SSt
D. Lowstand System Tract (LST) : Progradational sequence
Figure 5.33. (continue).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
E. Trangressive System Tract (TST) to Highstand System Tract (HST)
: Retrogradational to Aggraditional sequences.
Figure 5.33. (continue).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Legend
HST
Coastal
plain
sandstone
C
HST
Coastal plain
sand and peat
swamp coals
S
e
b
a
h
a
t
TST
Calcareous
concreation
Missing section
Angular
Unconformity
U
p
p
e
r
Maximum Flooding
Surface
Flooding Surface
G
a
n
d
u
m
a
n
Shelf
Mudstones
C
Middle HST
Lower
shoreface
heterolithic
sandstone and
mudstone
Late HST
T
o
g
o
p
i
L
o
w
e
r
Early HST
TST
T
u
n
g
k
u
G
a
n
d
u
m
a
n
Upper
Shoreface
sandstone
TST
Eroded
LST
Late HST
LST
Figure 5.34. Composite lithostratigraphic logs in the Dent Peninsula (not to the
scale).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Inland
Estuarine
Coastal Plain
Shoreface
Inner Shelf
Cong
HMS
Outer Shelf
Slope
Co
SSt
Cong
GSMd
SSt
GMd
Range of Sebahat
sediments
Range Ganduman
sediments
Back Inland
Upper Delta Plain
Coastal Plain sand
Back mangrove/ Upper Estuarine
Lower Delta Plain
Shelf mud
Front mangrove/ Lower Estuarine
Distributary Mouth Bar
Distributary channel
Silty-Muddy sand/prodelta
Figure 5.35. The proposed depositional environment model to characterize the
source rock facies within Sebahat and Ganduman formations from early Middle
Miocene to middle Pliocene (modified after Noad, 1998 and ISIS, 2005).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
5.4.2 PALEO VEGETATION AND ORGANIC MATTER INPUT
The varieties of terrestrial plant type that grew throughout the Neogene
developed mostly in coastal plains and lagoonal areas e.g. interchannel peat
swamp and back mangroves swamps (Mazlan et al., 1999). A humid, ever-wet
tropical climate ensured high terrigenous productivity during the deposition of
the middle Miocene to Pliocene period. Based on the present day vegetation,
the type of vegetation would be dominated by mangroves plants, since the
spores and pollen preserved in these sediments are significantly comparable
based on the palynological analyses. This terrigenous organic matter could be a
potential organic source for the petroleum source rock facies.
As discussed earlier, the reconstructed paleodepositional environment
model indicates most of the source inputs to the deltaic system were originated
from terrestrial plants organic matter. The marsh and mangrove of wet forest
swamps have been suggested as the major source for the organic matter
accumulation. This was revealed by the high abundant of plant pollens that
originated from mangrove swamp such as Bruguira sp. and Rhizophora sp. with
lesser pollen from rain forest plants, peat swamp, and coastal area. The
erosional process occurred during early Miocene (Balaguru, 2006b) was
thought to become the important agent draining the sediments together with
these organic matter to delta plains.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Similar evidence has been observed in Py-GC traces. Higher terrestrial
plant organic matter is indicated by the presence of cadinane in coals (see
Figure 5.36-a). Cadinane is a product of depolymerization and subsequent
hydrogenation of polycadinene, a compound found in angiosperm dammar resin
and in all the Dipterocarpaceae family plants that inhabit Southeast Asia (van
Aarssen et al., 1992). The presence of Dipterocarpaceae plant type that is
related to the cadinane compound also is supported by pollen analyses (Figure
5.36-b). Thus, the presence of Dipterocarpaceae pollen strongly suggests the
paleo vegetation was also populated by angiosperm plant species.
The TIC chromatograms of the deltaic sediments, mostly mudstone
(GMd facies), show the abundance of higher molecular weight compounds
(>nC25) especially the nC30 which typically related to the terrestrial organic
matter (Figure 5.37). This nC30 compound originated from higher land plant
(Hunt, 1995). Further investigations on the biomarker compositions within this
nC30 region significantly show high abundance of Oleanane or Ursane (Figure
5.38). The presence of these terrestrial angiosperm plant markers suggest the
palaeo vegetation was formed from Cretaceous flowering plant (Hunt, 1995).
Another terrestrial higher plant compound is indicated by
lup-20(29)-ene-
3-one. This compound is a progenitor of Lupane that contain in Tertiary brown
coals, as previously was reported by Wang and Simoneit (1990).
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Reworked amber clasts are embedded within the heterolithic mudstone
and sandstone (GSMd) facies of the Ganduman and the Sebahat Formation.
These amber clasts which are thought to originate from higher plant were
further analyzed with FTIR to predict plant type. The FTIR spectrum of this
transported amber indicates an angiosperm plant type as suggested by the
similar spectrum of prime dammar resin from manila (Senftle and Larter, 1988).
The spectrum shows a strong bond of CH2CH3 and CH3 aliphatic bending with
relatively low olefinic bond (Figure 5.39), a typical characteristic for the
angiosperm type resin.
Response_
S ig n a l: S R 2 5 -1 S T . D \ F I D 1 A . C H
1.3e+07
1.25e+07
1.2e+07
b
a
1.15e+07
1.1e+07
1.05e+07
1e+07
9500000
9000000
8500000
8000000
7500000
7000000
Pr
Xy
6500000
6000000
5500000
5000000
3500000
3000000
C10 C11
C8
Phe
4000000
C12
C17
C14
Cad
4500000
C18
Ph
C28
C20
C32
C24
2500000
2000000
1500000
1000000
500000
10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 55.00 60.00 65.00 70.00 75.00
Time
Figure 5.36. a) A Py-GC pyrogram of a coal clast within coaly sandstone shows
the presence of cadinane (Cad); b) Dipterocarpacea pollen found within the
coaly sandstone sample.
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
Abundanc e
T IC: R38_MdSt-Sb.D\ data.ms
Terrestrial
signal
5500000
5000000
4500000
4000000
3500000
3000000
nC30
nC24
Ph
Pr
1500000
nC20
2000000
nC18
nC17
2500000
1000000
500000
25.00
30.00
35.00
40.00
45.00
50.00
55.00
60.00
65.00
T ime-->
Figure 5.37. Total Ion Chromatogram significantly preserved terrestrial
compound as indicates by extreme high nC30.
Abundanc e
Ion 191.00 (190.70 to 191.70): R32_MdSt-Sb.D\ DAT A.MS
17000
16000
15000
Olean-12-ene
14000
Hopane
Oleanane
18000
13000
12000
11000
10000
5000
4000
Lupane
Mo
C31R
6000
C33S
C33R
7000
C32R
C31S
8000
C32S
9000
3000
2000
1000
48.00
50.00
52.00
54.00
56.00
58.00
60.00
62.00
64.00
T ime-->
Figure 5.38. Mass fragmentogram of ion 191 shows the Oleanane and Lupane
peaks as a terrestrial signals. Also shown is oleanane molecular compound.
Petroleum Source Rock Evaluation and Basin Modelling of the Tertiary Dent Group, Dent Peninsula, East Sabah …………………………………………………………………………………………………………….
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Chapter 5: Result and Discussion: Outcrop, Source Rock Facies and Depositional Environment
97.5
97
Amber
sample
96
93
92
91
90
88
87
86
85
84
CH2CH3 Bending
CH3 Bending
Aliphatic band
89
%T
Ester
Carbonyl band
94
83
82
81
79.7
4000.0
3600
3200
Vinylidene
95
2800
2400
2000
1800
cm-1
1600
1400
1200
1000
800
650.0
Figure 5.39. FTIR spectrum obtained from reworking amber typically shows an angiosperm plant type as indicated by relative high
CH2CH3 and CH3 Bending peaks and low vinylidene peak.
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