Geological Survey of Denmark and Greenland Bulletin 13, 2007
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Review of Survey activities 2006, 29-32 |
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29
The extensive and very deep ?Jurassic/Cretaceous-Palaeogene
sedimentary basins offshore West Greenland have a signifi-
cant petroleum exploration potential. This is particularly true
for the offshore region west of Disko and Nuussuaq where a
live petroleum system has been documented for many years.
At present, stratigraphic knowledge in this area is almost non-
existent and analogue studies from onshore areas and offshore
exploration wells to the south are therefore crucial to under-
standing the distribution and quality of possible reservoir rocks
in the Disko-Nuussuaq offshore area.
sedimentary basins offshore West Greenland have a signifi-
cant petroleum exploration potential. This is particularly true
for the offshore region west of Disko and Nuussuaq where a
live petroleum system has been documented for many years.
At present, stratigraphic knowledge in this area is almost non-
existent and analogue studies from onshore areas and offshore
exploration wells to the south are therefore crucial to under-
standing the distribution and quality of possible reservoir rocks
in the Disko-Nuussuaq offshore area.
One of the main risk parameters in
petroleum exploration in this region is the
presence of an adequate reservoir rock.
Tectonostratigraphic considerations sug-
gest that several sand-prone stratigraphic
levels are probably present, but their pro v -
enance and reservoir quality are at present
poorly known both onshore and offshore.
presence of an adequate reservoir rock.
Tectonostratigraphic considerations sug-
gest that several sand-prone stratigraphic
levels are probably present, but their pro v -
enance and reservoir quality are at present
poorly known both onshore and offshore.
A sediment provenance study including
zircon provenance U-Pb dating and whole-
rock geochemical analysis was therefore
initiated by the Geological Survey of Den -
mark and Greenland (GEUS) in prepara-
tion for the Disko West Licensing Round
2006 (Scherstén et al . 2007). The main
aims of this study were to:
rock geochemical analysis was therefore
initiated by the Geological Survey of Den -
mark and Greenland (GEUS) in prepara-
tion for the Disko West Licensing Round
2006 (Scherstén et al . 2007). The main
aims of this study were to:
1. Characterise the source areas and dispersal patterns for the
various sandstone units of Cretaceous-Paleocene age in
the Nuussuaq Basin and compare these with sandstone
units in selected West Greenland offshore exploration wells
(Figs 1, 2), employing advanced zircon provenance U-Pb
dating using laser ablation inductively coupled plasma
mass spectrometry (LA-ICP-MS; cf. Frei et al . 2006).
the Nuussuaq Basin and compare these with sandstone
units in selected West Greenland offshore exploration wells
(Figs 1, 2), employing advanced zircon provenance U-Pb
dating using laser ablation inductively coupled plasma
mass spectrometry (LA-ICP-MS; cf. Frei et al . 2006).
2. Detect possible changes in sediment source with time, e.g.
local versus regional sources.
Provenance of Cretaceous and Paleocene sandstones in
the West Greenland basins based on detrital zircon dating
the West Greenland basins based on detrital zircon dating
Anders Scherstén and Martin Sønderholm
© GEUS, 2007.
Geological Survey of Denmark and Greenland Bulletin
13, 29-32. Available at:
www.geus.dk/publications/bull
Fig. 1. Simplified geological map of eastern
Canada and Greenland (modified from Escher &
Pulvertaft 1995 and St-Onge
et al
. 2006). Green -
land is shown in a Paleocene pre-drift position
(from Oakey 2005, p. 222). Arrows indicate
possible source of Grenvillian age components in
West Greenland zircon samples. Inset shows samp -
led localities in the Nuussuaq Basin;
1
, Itsaku on
Svartenhuk Halvø (
SH
);
2
, Upernivik Ø;
3
,
Ikorfat;
4
, Paatuut;
5
, Kingittoq;
6
, Atanikerluk;
7
, Pingu and
8
, Grønne Ejland. Sampled wells are
GRO#3 (
G
), Hellefisk-1 and Qulleq-1.
30
Zircon as a provenance tool is receiving increasing atten-
tion and has proven to be a powerful indicator of clastic sedi -
ment sources, a tracer of the Earth's oldest materials, and a
tracer of continental crust-forming processes (Froude et al .
1983; Williams & Claesson 1987; Dodson et al . 1988; Fedo
et al . 2003; Hawkesworth & Kemp 2006). Zircon is common
in continental rocks and it is assumed that its distribution in
sediments will normally represent the source rocks. Although
there are several complications, the sediment zircon U-Pb age
frequency should in general terms mirror the relative propor-
tions of different source materials. This as sump tion is partic-
ularly important if exotic components can be identified, as
their frequency will provide an estimate of the exotic influx:
it may also be essential in tra cing sediment paths that affect
the detrital compositions and subsequent diagenetic history
of possible hydrocarbon reservoir rocks.
ment sources, a tracer of the Earth's oldest materials, and a
tracer of continental crust-forming processes (Froude et al .
1983; Williams & Claesson 1987; Dodson et al . 1988; Fedo
et al . 2003; Hawkesworth & Kemp 2006). Zircon is common
in continental rocks and it is assumed that its distribution in
sediments will normally represent the source rocks. Although
there are several complications, the sediment zircon U-Pb age
frequency should in general terms mirror the relative propor-
tions of different source materials. This as sump tion is partic-
ularly important if exotic components can be identified, as
their frequency will provide an estimate of the exotic influx:
it may also be essential in tra cing sediment paths that affect
the detrital compositions and subsequent diagenetic history
of possible hydrocarbon reservoir rocks.
Cretaceous sediment provenance
It is assumed that the age structure of the North Atlantic cra-
tons surrounding the study area is well enough known to
constrain the origin of the source components that con-
tributed to the sediments. Archaean gneisses that range from
3850 to 2600 Ma (Hollis et al . 2006) dominate southern
West Greenland. Important peaks occur at 3600, 3100, 2900
and 2700 Ma. Farther north, the Archaean basement was
reworked during the Nagssugtoqidian/Rinkian orogeny,
which adds an age peak centred at 1900-1750 Ma (Figs 1, 3;
Connelly et al . 2000).
tons surrounding the study area is well enough known to
constrain the origin of the source components that con-
tributed to the sediments. Archaean gneisses that range from
3850 to 2600 Ma (Hollis et al . 2006) dominate southern
West Greenland. Important peaks occur at 3600, 3100, 2900
and 2700 Ma. Farther north, the Archaean basement was
reworked during the Nagssugtoqidian/Rinkian orogeny,
which adds an age peak centred at 1900-1750 Ma (Figs 1, 3;
Connelly et al . 2000).
As part of this study, 4262 grains were dated from 65 sed-
iment samples from eight localities in the Nuussuaq Basin
and three exploration wells (Fig. 1; Scherstén et al . 2007).
Data that are> 10% discordant were filtered out as they are
more likely to be disturbed by common Pb contamination,
ancient Pb-loss and mixed domains. The remaining 2735
grains display a relative age distribution that is dominated by
age peaks between ~2500-3200 Ma (Fig. 3). There is also a
peak at ~3600 Ma, which constitutes several samples sug-
gesting that 3600 Ma age components are perhaps more
abun dant than those from the well-known Godthåbsfjord
area (Friend & Nutman 2005; Hollis et al . 2006). A ~1900
and three exploration wells (Fig. 1; Scherstén et al . 2007).
Data that are> 10% discordant were filtered out as they are
more likely to be disturbed by common Pb contamination,
ancient Pb-loss and mixed domains. The remaining 2735
grains display a relative age distribution that is dominated by
age peaks between ~2500-3200 Ma (Fig. 3). There is also a
peak at ~3600 Ma, which constitutes several samples sug-
gesting that 3600 Ma age components are perhaps more
abun dant than those from the well-known Godthåbsfjord
area (Friend & Nutman 2005; Hollis et al . 2006). A ~1900
Fig. 2. Simplified stratigraphic scheme of the Nuussuaq Basin and West
Green land offshore region showing stratigraphic distribution of ana
-
lysed samples.
Fig. 3. Relative
207
Pb/
206
Pb age distribution of 2735
<10% discordant zir-
con grains from the Cretaceous-Palaeogene sediments in this study (red
curve). The relative probability reflects the likelihood of finding any
given age, although the ~1900 Ma peak is overrepresented due to sam-
pling bias. Zircon ages from the Qulleq-1 well show small but signifi-
cant peaks at ~1600-1700 and ~1100 Ma (n is the number of grains that
are within error of 1600 and 1100 Ma, respectively). These appear to be
coupled and may have been either derived from East Greenland or the
Canadian Shield. See text for further discussion.
Ma peak is also distinct, but is probably overrepresented due
to sampling bias through the many samples taken at Itsaku
where this age component is strongly represented in compa -
rison to the sediments farther south (see discussion below).
The 1900 Ma peak is slightly asymmetric with a tail towards
younger ages and an age component around 1600-1700 Ma.
The overall age distribution is in excellent agreement with a
source from the West Greenland crystalline basement; and
the zircon data support the existing depositional models indi-
cating that a major deltaic system drained into the Nuussuaq
Basin from the east-south-east during Cretaceous-Paleocene
time (Pedersen & Pulvertaft 1992).
to sampling bias through the many samples taken at Itsaku
where this age component is strongly represented in compa -
rison to the sediments farther south (see discussion below).
The 1900 Ma peak is slightly asymmetric with a tail towards
younger ages and an age component around 1600-1700 Ma.
The overall age distribution is in excellent agreement with a
source from the West Greenland crystalline basement; and
the zircon data support the existing depositional models indi-
cating that a major deltaic system drained into the Nuussuaq
Basin from the east-south-east during Cretaceous-Paleocene
time (Pedersen & Pulvertaft 1992).
A small but significant peak at ~1100 Ma suggests a distal
component that is not readily explained by derivation from
the West Greenland crystalline basement as described above.
This component seems to be associated with the 1600-1700
Ma occurrence noted above (Fig. 3). Two possible sources can
explain the dual peaks: from East Greenland or Labrador
(Fig. 1). If an East Greenland origin is favoured, it would be
anticipated that this signature would also be associated with
Caledonian ages between 380 and 480 Ma, which have not
yet been identified (Figs 1, 3). Given the large number of
grains analysed, it would be expected that even a very small
contribution would have been detected suggesting Labrador
as the most likely source for the 1100 Ma peak. A southern,
Labrador source for the 1100 Ma component in the Qulleq-1
well is corroborated by the absence of the 1900 Ma peak that
is ubiquitous in the Nuussuaq Basin to the north (Fig. 4). The
samples from the Qulleq-1 well are domi nated by Archaean
ages without contributions from rocks reworked during the
Nagssugtoqidian/Rinkian orogenic event.
the West Greenland crystalline basement as described above.
This component seems to be associated with the 1600-1700
Ma occurrence noted above (Fig. 3). Two possible sources can
explain the dual peaks: from East Greenland or Labrador
(Fig. 1). If an East Greenland origin is favoured, it would be
anticipated that this signature would also be associated with
Caledonian ages between 380 and 480 Ma, which have not
yet been identified (Figs 1, 3). Given the large number of
grains analysed, it would be expected that even a very small
contribution would have been detected suggesting Labrador
as the most likely source for the 1100 Ma peak. A southern,
Labrador source for the 1100 Ma component in the Qulleq-1
well is corroborated by the absence of the 1900 Ma peak that
is ubiquitous in the Nuussuaq Basin to the north (Fig. 4). The
samples from the Qulleq-1 well are domi nated by Archaean
ages without contributions from rocks reworked during the
Nagssugtoqidian/Rinkian orogenic event.
In the Nuussuaq Basin the 1100 Ma component is very
rare in the onshore, deltaic facies and occurs almost exclu-
sively in the deep-water deposits in accordance with a long-
shore transport component from the south as the source of
this component. However, current data from turbidite chan-
nel units on western Nuussuaq show transport directions
towards the south (Dam & Sønderholm 1994). It is not pos-
sible to explain this apparent discrepancy based on the pre-
sent database. More data including the other offshore wells
will be needed to elucidate the possible interconnections and
transport paths in the West Greenland offshore basins.
sively in the deep-water deposits in accordance with a long-
shore transport component from the south as the source of
this component. However, current data from turbidite chan-
nel units on western Nuussuaq show transport directions
towards the south (Dam & Sønderholm 1994). It is not pos-
sible to explain this apparent discrepancy based on the pre-
sent database. More data including the other offshore wells
will be needed to elucidate the possible interconnections and
transport paths in the West Greenland offshore basins.
Paleocene point source provenance
on Svartenhuk Halvø
on Svartenhuk Halvø
A set of samples was collected on Itsaku on Svartenhuk Halvø
where a major hiatus separates an Upper Albian to Lower Ceno -
manian deltaic succession from an Upper Campanian to Paleo -
cene marine turbidite succession. The detrital zircon age
where a major hiatus separates an Upper Albian to Lower Ceno -
manian deltaic succession from an Upper Campanian to Paleo -
cene marine turbidite succession. The detrital zircon age
distribution in the deltaic succession is typical for the
Nuussuaq Basin and dominated by a distinct peak at ~2800
Ma; this is flanked by scattered peaks between 2400 and
3200 Ma (Fig. 4), as well as significant peaks at 3600-3800
Ma representing Eoarchaean components. A 1900 Ma peak is
another typical feature of the Nuussuaq Basin sedi ments,
whereas the occurrences of 1100 and 1600-1700 Ma peaks
are more intermittent (see above). The overall pattern is in
good agreement with that of the general West Greenland
Cretaceous population and deltaic deposition from the east-
south-east.
Nuussuaq Basin and dominated by a distinct peak at ~2800
Ma; this is flanked by scattered peaks between 2400 and
3200 Ma (Fig. 4), as well as significant peaks at 3600-3800
Ma representing Eoarchaean components. A 1900 Ma peak is
another typical feature of the Nuussuaq Basin sedi ments,
whereas the occurrences of 1100 and 1600-1700 Ma peaks
are more intermittent (see above). The overall pattern is in
good agreement with that of the general West Greenland
Cretaceous population and deltaic deposition from the east-
south-east.
The zircon age distribution of the overlying turbidite suc-
cession is in stark contrast to the lower section (Fig. 4). Here,
the zircon population forms a single, well-defined ~1900 Ma
peak with an apparent normal distribution indicative of a
single point source with respect to zircon. The only known
source that fits this distribution is the 1869 ± 9 Ma Prøven
igneous complex (Fig. 1; Thrane et al. 2005). Assuming the
Prøven igneous complex forms a single source to the upper
part of the succession, a Tukey's biweight mean of 1872 ± 4
Ma (n = 275) can be calculated, which is in excellent agree-
ment with the Prøven igneous complex. A few grains scatter
towards 2700 Ma, which likely reflects inherited compo-
nents, in accordance with its derivation from lower conti-
nental crust (Thrane et al. 2005).
the zircon population forms a single, well-defined ~1900 Ma
peak with an apparent normal distribution indicative of a
single point source with respect to zircon. The only known
source that fits this distribution is the 1869 ± 9 Ma Prøven
igneous complex (Fig. 1; Thrane et al. 2005). Assuming the
Prøven igneous complex forms a single source to the upper
part of the succession, a Tukey's biweight mean of 1872 ± 4
Ma (n = 275) can be calculated, which is in excellent agree-
ment with the Prøven igneous complex. A few grains scatter
towards 2700 Ma, which likely reflects inherited compo-
nents, in accordance with its derivation from lower conti-
nental crust (Thrane et al. 2005).
Trace element systematics in zircon may provide further
constraints on zircon origin in provenance studies (Hoskin &
Ireland 2000). However, several hurdles need to be overcome.
For instance, many features are shared intimately between
zircon that are derived from widely different sources (Hoskin
& Ireland 2000), and in a detrital population each grain has
Ireland 2000). However, several hurdles need to be overcome.
For instance, many features are shared intimately between
zircon that are derived from widely different sources (Hoskin
& Ireland 2000), and in a detrital population each grain has
31
Fig. 4. Relative probability diagram for
207
Pb/
206
Pb ages for zircon from
Upper Albian - Cenomanian deltaic sediments (red) and Upper Cam -
panian/Maastrichtian - Paleocene marine sediments (blue) on Itsaku,
Svartenhuk Halvø. The deltaic deposits display a pattern that is typical
for the sediments in the Nuussuaq Basin, whereas the constrained pat-
tern of the overlying marine deposits is unique and seems to require a
single point source.
32
to be treated separately, as a common age does not necessarily
imply the same source rock, and by inference, the same cry -
stallisation processes or conditions. Nevertheless, it is as -
sumed here that zircon from the upper part of the section
represents one population that was derived from the Prøven
igneous complex. Trace element abundances were deter-
mined for 138 zircon grains from this part of the section and
contrasted against Archaean (n = 424) zircon grains from
other stratigraphic levels. As expected, there are no systematic
variations with age, which would require an age dependent
systematic change in zircon crystallisation processes. Tita n -
ium in zircon thermometry (Watson et al. 2006) enables cal-
culation of zircon crystallisation temperatures. The upper
zircon population yields a mean temperature of 845 ± 19°C
(± 2
imply the same source rock, and by inference, the same cry -
stallisation processes or conditions. Nevertheless, it is as -
sumed here that zircon from the upper part of the section
represents one population that was derived from the Prøven
igneous complex. Trace element abundances were deter-
mined for 138 zircon grains from this part of the section and
contrasted against Archaean (n = 424) zircon grains from
other stratigraphic levels. As expected, there are no systematic
variations with age, which would require an age dependent
systematic change in zircon crystallisation processes. Tita n -
ium in zircon thermometry (Watson et al. 2006) enables cal-
culation of zircon crystallisation temperatures. The upper
zircon population yields a mean temperature of 845 ± 19°C
(± 2
mean
; n = 93; GJ-1 standard reproducibility 668 ± 30°C
2
n = 17), which is similar to zircon saturation temperatures
of 790- 880°C (n = 4) calculated from bulk rock data and the
independently estimated intrusion temperature of the Prøven
igneous complex (Thrane et al. 2005). The Prøven igneous
complex is inferred to have been derived from a lower conti-
nental crust source as reflected by significantly negative Eu-
anomalies from a plagioclase residue (Eu/Eu* ~0.45; Thrane
et al. 2005). This appears to be reflected by the zircon popu-
lation, which has a mean of 0.23 ± 0.03 (± 2
independently estimated intrusion temperature of the Prøven
igneous complex (Thrane et al. 2005). The Prøven igneous
complex is inferred to have been derived from a lower conti-
nental crust source as reflected by significantly negative Eu-
anomalies from a plagioclase residue (Eu/Eu* ~0.45; Thrane
et al. 2005). This appears to be reflected by the zircon popu-
lation, which has a mean of 0.23 ± 0.03 (± 2
mean
; n = 93;
GJ-1 standard reproducibility 0.96 ± 0.06 2
n = 23). The
values contrast with the average Archaean population
(Eu/Eu* = 0.49 ± 0.03 2
(Eu/Eu* = 0.49 ± 0.03 2
mean
; n = 257), which is assumed to
be dominated by rocks such as tonalite-trondhjemite-grano -
diorite (TTG) suites that have Eu/Eu* ~1.0. Thus, the zircon
population of the Upper Campanian to Paleocene marine tur-
bidite succession seems tOForm a single population that is in
accordance with derivation from the Prøven igneous com-
plex. This implies a major change in depositional transport
direction compared to the underlying Lower Cretaceous
deltaic deposits from a south-eastern and eastern source to a
northern source.
diorite (TTG) suites that have Eu/Eu* ~1.0. Thus, the zircon
population of the Upper Campanian to Paleocene marine tur-
bidite succession seems tOForm a single population that is in
accordance with derivation from the Prøven igneous com-
plex. This implies a major change in depositional transport
direction compared to the underlying Lower Cretaceous
deltaic deposits from a south-eastern and eastern source to a
northern source.
Acknowledgement
The project was supported by the Bureau of Minerals and Petroleum,
Government of Greenland.
Government of Greenland.
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Authors' address
Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
E-mail:
asch@geus.dk
