Geological Survey of Denmark and Greenland Bulletin
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Nr. 4, Review of Survey activities 2003, pp. 49-52 |
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49
For many years the existence of an oil-prone source rock off
West Greenland was challenged by industry. But since 1992
when active oil seeps were found onshore West Greenland on
the Nuussuaq peninsula (Fig. 1; Christiansen et al. 1996;
Bojesen-Koefoed et al. 1999), the question has changed focus
to the age, distribution and potential of the source rock. Five
different oils each with their own characteristics have
been reported by the Geological Survey of Denmark and
Greenland (GEUS). One of these, a typical marine shale-
derived oil with a possible regional distribution, is known as
the Itilli oil. Geochemical analysis suggests that it may have
been generated from CenomanianTuronian age marine
shales, equivalent to prolific source rocks known from
Ellesmere Island, Nunavut, Canada. Three of the other oils
were generated from deltaic source rocks of Albian,
Campanian and Paleocene ages, while one is of unknown ori-
gin (Bojesen-Koefoed et al. 1999).
West Greenland was challenged by industry. But since 1992
when active oil seeps were found onshore West Greenland on
the Nuussuaq peninsula (Fig. 1; Christiansen et al. 1996;
Bojesen-Koefoed et al. 1999), the question has changed focus
to the age, distribution and potential of the source rock. Five
different oils each with their own characteristics have
been reported by the Geological Survey of Denmark and
Greenland (GEUS). One of these, a typical marine shale-
derived oil with a possible regional distribution, is known as
the Itilli oil. Geochemical analysis suggests that it may have
been generated from CenomanianTuronian age marine
shales, equivalent to prolific source rocks known from
Ellesmere Island, Nunavut, Canada. Three of the other oils
were generated from deltaic source rocks of Albian,
Campanian and Paleocene ages, while one is of unknown ori-
gin (Bojesen-Koefoed et al. 1999).
The presence of a regional marine source rock is impor-
tant to petroleum exploration; GEUS has therefore investi-
gated the possible existence of Mesozoic, in particular
CenomanianTuronian, petroleum source rocks in West
Greenland offshore areas. Since sediments older than the
Santonian are not known from any of the six wells drilled off-
shore West Greenland (Fig. 1), assessment of oil-prone source
rocks in older sedimentary successions must rely on circum-
stantial evidence offered by oil chemistry data and analogy
studies. Petroleum in quantities amenable to chemical analy-
sis has so far not been recovered from offshore. However, oil-
bearing fluid inclusions are known from the Ikermiut-1 well
(unpublished data 2001, Phillips Petroleum and GEUS), a
gas-kick was recorded during drilling of the Kangâmiut-1
well (Bate 1997), and seismic data indicate hydrocarbons in
many areas (cross-cutting reflectors, bright spots, smearing of
seismic).
gated the possible existence of Mesozoic, in particular
CenomanianTuronian, petroleum source rocks in West
Greenland offshore areas. Since sediments older than the
Santonian are not known from any of the six wells drilled off-
shore West Greenland (Fig. 1), assessment of oil-prone source
rocks in older sedimentary successions must rely on circum-
stantial evidence offered by oil chemistry data and analogy
studies. Petroleum in quantities amenable to chemical analy-
sis has so far not been recovered from offshore. However, oil-
bearing fluid inclusions are known from the Ikermiut-1 well
(unpublished data 2001, Phillips Petroleum and GEUS), a
gas-kick was recorded during drilling of the Kangâmiut-1
well (Bate 1997), and seismic data indicate hydrocarbons in
many areas (cross-cutting reflectors, bright spots, smearing of
seismic).
Petroleum exploration offshore West Greenland suffered
for many years under the misconception that oceanic crust
covered vast areas, rendering the region unattractive. How-
ever, the presence of thick sedimentary successions and
rotated fault blocks in Cretaceous basins have been demon-
strated to be present in areas previously believed to be under-
lain by CretaceousTertiary oceanic crust (cf. Chalmers &
Pulvertaft 2001). New high-quality seismic data, acquired by
the seismic company TGS-NOPEC over recent years, com-
covered vast areas, rendering the region unattractive. How-
ever, the presence of thick sedimentary successions and
rotated fault blocks in Cretaceous basins have been demon-
strated to be present in areas previously believed to be under-
lain by CretaceousTertiary oceanic crust (cf. Chalmers &
Pulvertaft 2001). New high-quality seismic data, acquired by
the seismic company TGS-NOPEC over recent years, com-
bined with gravimetric data, have further demonstrated the
presence of deep basins containing thick sedimentary succes-
sions in other areas (e.g. Christiansen et al. 2002). Despite
the progress made over the past few years, the geological evo-
lution of the Davis Strait region in general remains poorly
understood, but new data on oil chemistry may shed some
light on the history of this region.
presence of deep basins containing thick sedimentary succes-
sions in other areas (e.g. Christiansen et al. 2002). Despite
the progress made over the past few years, the geological evo-
lution of the Davis Strait region in general remains poorly
understood, but new data on oil chemistry may shed some
light on the history of this region.
The Itilli oil type
Based on its chemical characteristics, the Itilli oil type is pre-
sumed to have been generated from marine shales of
CenomanianTuronian age, but no known source rocks are
sumed to have been generated from marine shales of
CenomanianTuronian age, but no known source rocks are
Fig. 1. Map showing location of wells drilled offshore West Greenland.
The onshore oil seepage area in the DiskoNuussuaqSvartenhuk Halvø
region is framed and includes the onshore exploration well GRO#3.
Age of oils in West Greenland: was there a Mesozoic
seaway between Greenland and Canada?
seaway between Greenland and Canada?
Jørgen A. Bojesen-Koefoed, Hans Peter Nytoft and Flemming G. Christiansen
Geological Survey of Denmark and Greenland Bulletin 4, 4952 (2004) © GEUS, 2004
exposed or have been drilled in West Greenland. However,
on Ellesmere Island, the lower part of the Kanguk Formation
comprises excellent, highly oil-prone marine shale source
rocks of presumed CenomanianTuronian age (Núñez-
Betelu 1993). The deposits are, however, thermally immature
and cannot be directly compared to the Itilli oil from onshore
West Greenland more than 1000 km to the south. However,
artificial maturation by hydrous pyrolysis of samples of the
Kanguk Formation generates bitumen that shares a number
of important characteristics with the Itilli oil type. These
characteristics include: light-end skewed n-alkane distribu-
tion, pristane/phytane ratio less than 2, abundant tricyclic
triterpanes, abundant 28,30-bisnorhopane and diasteranes,
plus a predominance of C
on Ellesmere Island, the lower part of the Kanguk Formation
comprises excellent, highly oil-prone marine shale source
rocks of presumed CenomanianTuronian age (Núñez-
Betelu 1993). The deposits are, however, thermally immature
and cannot be directly compared to the Itilli oil from onshore
West Greenland more than 1000 km to the south. However,
artificial maturation by hydrous pyrolysis of samples of the
Kanguk Formation generates bitumen that shares a number
of important characteristics with the Itilli oil type. These
characteristics include: light-end skewed n-alkane distribu-
tion, pristane/phytane ratio less than 2, abundant tricyclic
triterpanes, abundant 28,30-bisnorhopane and diasteranes,
plus a predominance of C
27
steranes while maintaining rela-
tively high proportions of C
28
steranes (Fig. 2).
A Mesozoic seaway between Greenland
and Canada?
and Canada?
The recent demonstration of more or less continuous deep
sedimentary basins offshore West Greenland (Christiansen et
al. 2002), the occurrence of reworked marine Upper Jurassic
palynomorphs in the Qulleq-1 well (Christiansen et al. 2001)
together with the apparent relationship between the Itilli oil
and pyrolysates of the lower Kanguk Formation, open possi-
sedimentary basins offshore West Greenland (Christiansen et
al. 2002), the occurrence of reworked marine Upper Jurassic
palynomorphs in the Qulleq-1 well (Christiansen et al. 2001)
together with the apparent relationship between the Itilli oil
and pyrolysates of the lower Kanguk Formation, open possi-
bilities for the existence of regional Mesozoic marine source
rocks in the offshore areas. This implies the existence of a sea-
way between Greenland and Canada during the Mesozoic,
connecting the proto-Atlantic to the proto-Arctic Ocean a
palaeo-Davis Strait, partly analogous to the `Cretaceous
Western Interior Seaway' (CWIS) of North America
(Caldwell & Kauffman 1993; Dean & Arthur 1998). The
CWIS developed as a foreland basin east of the rising
Cordillera along the western margin of the North American
continent, whereas the Davis Strait is a product of rifting and
strike-slip movements, albeit without sea-floor spreading.
This is noteworthy since many published palaeogeographic
maps feature a spreading ridge along the axial part of the
Davis Strait. Despite the differences in origin, the morpho-
logical analogy between a palaeo-Davis Strait and the CWIS
is clear and the potential for deposition of similar types of
sediments in both settings exists. The evolution of the CWIS
is relatively well constrained, and petroleum accumulations,
derived from CenomanianTuronian age marine source
rocks, are known more or less throughout the entire extent of
the seaway from the southern part of the USA to the
Canadian Arctic. A series of marine oils of Ceno-
manianTuronian age from the CWIS, plus a number of
other oils (Table 1), have been collected and analysed to serve
as a reference for comparison with Itilli oils from West
rocks in the offshore areas. This implies the existence of a sea-
way between Greenland and Canada during the Mesozoic,
connecting the proto-Atlantic to the proto-Arctic Ocean a
palaeo-Davis Strait, partly analogous to the `Cretaceous
Western Interior Seaway' (CWIS) of North America
(Caldwell & Kauffman 1993; Dean & Arthur 1998). The
CWIS developed as a foreland basin east of the rising
Cordillera along the western margin of the North American
continent, whereas the Davis Strait is a product of rifting and
strike-slip movements, albeit without sea-floor spreading.
This is noteworthy since many published palaeogeographic
maps feature a spreading ridge along the axial part of the
Davis Strait. Despite the differences in origin, the morpho-
logical analogy between a palaeo-Davis Strait and the CWIS
is clear and the potential for deposition of similar types of
sediments in both settings exists. The evolution of the CWIS
is relatively well constrained, and petroleum accumulations,
derived from CenomanianTuronian age marine source
rocks, are known more or less throughout the entire extent of
the seaway from the southern part of the USA to the
Canadian Arctic. A series of marine oils of Ceno-
manianTuronian age from the CWIS, plus a number of
other oils (Table 1), have been collected and analysed to serve
as a reference for comparison with Itilli oils from West
50
Fig. 2. Characteristics of the Itilli oil type
(modified from Bojesen-Koefoed et al.
1999). Gas chromatogram shows light-end
skewed n-alkane distribution and pri-
stane/phytane
<2 (numbers: n-alkane
carbon number, a: pristane, b: phytane).
Triterpanes monitored by the m/z 191
fragmentogram show abundant tricyclics
(T23: C
23
tricyclic triterpane) and notable
proportions of 28,30-bisnorhopane (H28).
Ts: trisnorneohopane; Tm: trisnorhopane;
H29: norhopane; H30: hopane; H33:
trishomohopane. Steranes monitored by
the m/z 217 and m/z 218 fragmentograms
show a high abundance of diasteranes
(D27) at moderate levels of thermal
maturity indicated by C
29
sterane S/(S+R)
epimerisation ratio of approximately 0.50
(C
29
sterane: S29; S: 20S epimer; R: 20R
epimer), and a relatively high abundance
of C
28
steranes (S28) compared to C
27
(S27), C
29
(S29) and C
30
(S30) steranes.
Greenland. In addition to CenomanianTuronian derived
marine oils from the CWIS, the reference sample database
includes oils generated from Upper Jurassic source rocks in
the Jeanne d'Arc Basin (Newfoundland, eastern Canada) and
in the North Sea, the Cretaceous age Heron H-73 oil from
offshore eastern Canada, and the Cambro-Ordovician Shoal
Point crude from western Newfoundland (Fig. 3).
marine oils from the CWIS, the reference sample database
includes oils generated from Upper Jurassic source rocks in
the Jeanne d'Arc Basin (Newfoundland, eastern Canada) and
in the North Sea, the Cretaceous age Heron H-73 oil from
offshore eastern Canada, and the Cambro-Ordovician Shoal
Point crude from western Newfoundland (Fig. 3).
The distribution of a series of diatom-derived oil con-
stituents known as 24-norcholestanes has proven to be age-
diagnostic, and a standard plot for assessment of oil source
rock maximum age has been devised by Holba et al. (1998).
Using this plot, the reference samples show an NS trend
among the CWIS oils of CenomanianTuronian age (Fig. 4).
The single Cretaceous oil from offshore eastern Canada plots
between the Denver and Alberta Basin oils, as expected from
its geographical position. Upper Jurassic oils from the Jeanne
d'Arc Basin and the North Sea groups occur in a narrow band
at the expected position, whereas the Cambro-Ordovician oil
yields a `Palaeozoic' age. Superimposing data from West
Greenland Itilli oils onto the reference oil plot shows that
samples in which admixture of oil from other sources can be
recognised all yield rather young ages, whereas pure Itilli oil
samples show Cretaceous or even Late Jurassic source rock
ages (Fig. 4). Hence, age-diagnostic biological marker data
support the existence of a regional Cretaceous age marine
petroleum source rock, in addition perhaps to an Upper
Jurassic source rock. A characteristic feature of Cenoman-
ianTuronian age oils from the Canadian Arctic is a relatively
high abundance of C
diagnostic, and a standard plot for assessment of oil source
rock maximum age has been devised by Holba et al. (1998).
Using this plot, the reference samples show an NS trend
among the CWIS oils of CenomanianTuronian age (Fig. 4).
The single Cretaceous oil from offshore eastern Canada plots
between the Denver and Alberta Basin oils, as expected from
its geographical position. Upper Jurassic oils from the Jeanne
d'Arc Basin and the North Sea groups occur in a narrow band
at the expected position, whereas the Cambro-Ordovician oil
yields a `Palaeozoic' age. Superimposing data from West
Greenland Itilli oils onto the reference oil plot shows that
samples in which admixture of oil from other sources can be
recognised all yield rather young ages, whereas pure Itilli oil
samples show Cretaceous or even Late Jurassic source rock
ages (Fig. 4). Hence, age-diagnostic biological marker data
support the existence of a regional Cretaceous age marine
petroleum source rock, in addition perhaps to an Upper
Jurassic source rock. A characteristic feature of Cenoman-
ianTuronian age oils from the Canadian Arctic is a relatively
high abundance of C
28
regular steranes, compared to C
27
and
C
29
regular steranes, whereas Upper Jurassic oils generally
show a rather low abundance of C
28
regular steranes. Some
Itilli oils from West Greenland show sterane distributions
very similar to CenomanianTuronian age oils from the
Canadian Arctic, others may show distributions rather simi-
lar to Upper Jurassic oils, and some may show intermediate
distributions. Hence, regular sterane data further support the
notion of a Cretaceous plus perhaps an additional Upper
very similar to CenomanianTuronian age oils from the
Canadian Arctic, others may show distributions rather simi-
lar to Upper Jurassic oils, and some may show intermediate
distributions. Hence, regular sterane data further support the
notion of a Cretaceous plus perhaps an additional Upper
Jurassic marine petroleum source rock in the Davis Strait
region, and thus the existence of a Mesozoic seaway between
Greenland and Canada.
region, and thus the existence of a Mesozoic seaway between
Greenland and Canada.
Conclusions
The Itilli oil type from onshore central West Greenland is an
oil derived from marine shale, and shows clear similarities to
pyrolysates of immature CenomanianTuronian age oil-
prone source rocks from the Canadian Arctic.
oil derived from marine shale, and shows clear similarities to
pyrolysates of immature CenomanianTuronian age oil-
prone source rocks from the Canadian Arctic.
Analysis of age-diagnostic biological markers and the dis-
tribution of regular steranes indicate a source rock age simi-
lar to that of CenomanianTuronian age oils from the
Canadian Arctic or of older Upper Jurassic oils from the
Jeanne d'Arc Basin.
lar to that of CenomanianTuronian age oils from the
Canadian Arctic or of older Upper Jurassic oils from the
Jeanne d'Arc Basin.
Geochemical data, combined with other indications of
petroleum in West Greenland offshore areas, support the
existence of one or more Mesozoic marine petroleum source
rocks in the larger Davis Strait area, and hence the notion of
a Mesozoic seaway between Greenland and Canada.
existence of one or more Mesozoic marine petroleum source
rocks in the larger Davis Strait area, and hence the notion of
a Mesozoic seaway between Greenland and Canada.
Acknowledgements
Analyses of samples were financed by the Bureau of Minerals and
Petroleum, Government of Greenland (CENTUR Project, grant no.
69.41.06). Samples provided by the United States Geological Survey
(Denver), the Geological Survey of Canada (Calgary and Halifax), and
the Canadian New-foundland Offshore Petroleum Board (St. John's) are
gratefully acknowledged.
Petroleum, Government of Greenland (CENTUR Project, grant no.
69.41.06). Samples provided by the United States Geological Survey
(Denver), the Geological Survey of Canada (Calgary and Halifax), and
the Canadian New-foundland Offshore Petroleum Board (St. John's) are
gratefully acknowledged.
51
Fig. 3. Cretaceous Western Interior Seaway (CWIS) of North America and
the North Atlantic. Red dots: approximate positions of analysed oil sam-
ples.
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52
Fig. 4. Standard diagram for assessment
of oil source rock maximum age using
the nordiacholestane ratio (modified from
Holba et al. 1998). Note NS trend among
CenomanianTuronian from the Cretaceous
Western Interior Sea-way. Mixed oils yield
young source rock ages whereas pure Itilli
oils show Cretaceous or even Jurassic source
rock ages. WCSB: Western Canadian Sedi-
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Authors' address
Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: jbk@geus.dk
Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: jbk@geus.dk
