Stratigraphy, structure and petroleum potential of

Stratigraphy, structure and petroleum potential of the Lady Franklin and
Maniitsoq Basins, offshore southern West Greenland
Aage Bach Sørensen
Bureau of Minerals and Petroleum, Postboks 930, DK-3900 Nuuk, Greenland (e-mail: [email protected], [email protected])
(Previous address: Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350 Copenhagen K, Denmark)
ABSTRACT: The Lady Franklin Basin, which contains a thick succession of
Cretaceous and Cenozoic sediments, constitutes the western part of the southern
West Greenland offshore area. In the Davis Strait and Labrador Sea region rifting
was initiated in the earliest Cretaceous and a number of basins formed. In time these
basins deepened, although subsidence was interrupted by two main phases of uplift
and erosion that took place in middle and late Cretaceous time, resulting in two
hiatuses in the succession. Sediments with source or reservoir potential were
deposited in the basins. Source rocks are known to occur in the marine Cretaceous
successions of onshore northern Canada and central West Greenland and also
offshore eastern Canada, and can therefore be expected to occur in the Lady
Franklin and Maniitsoq basins.
In the Lady Franklin area Paleocene volcanism associated with further tectonism
caused the eruption of flood basalts and hyaloclastites on top of the Cretaceous
mudstone and sandstone succession. A Lower Palaeogene sediment succession,
which may contain both source and reservoir rocks, was then deposited on top of
the basalts, as seen in the nearby Canadian Hekja O-71 well. Around the Ypresian to
Lutetian transition a regression took place. The regression gave rise to an
unconformity and a hiatus spanning a few million years throughout the entire West
Greenland shelf. New deposition followed and, after a long period, major compression set in and a regression occurred across the whole shelf in Late Oligocene time.
Erosion set in and was deep on the southern shelf, resulting in a hiatus spanning
about 39 Ma. To the north the hiatus is only about 19 Ma.
In early Middle Miocene time the tectonic regime in the Davis Strait area changed.
Subsidence and deposition resumed offshore West Greenland. These events may
have created conditions for generation of hydrocarbons in the potential source-rock
sequences in the Cretaceous succession. Therefore, although hydrocarbon exploration has been limited in this region and had little success, it is thought that conditions
are favourable for the discovery of significant oil and gas accumulations.
KEYWORDS: offshore West Greenland, stratigraphy, structure, petroleum system, Cretaceous,
Palaeogene, Neogene
INTRODUCTION
The Lady Franklin and Maniitsoq basins are located offshore
West Greenland at the boundary of Canadian waters. The
basins were established during Early Cretaceous rifting and are
separated by a number of highs. The basins contain a
Cretaceous–Cenozoic succession of sediments. The stratigraphy of the West Greenland Shelf is similar in many ways to the
stratigraphy of the basins on the Canadian Labrador Shelf.
Petroleum exploration offshore West Greenland has so far
been concentrated further north and on the Fylla Platform to
the east, where the most recent well, Qulleq-1, was drilled in
2000 (Fig. 1). Further southwest in Canadian territory a
prospective petroleum basin, the Saglek Basin, has been proved
by the Hekja gas/condensate discovery (Klose et al. 1982). The
Lady Franklin and Maniitsoq basins, which are among the
Petroleum Geoscience, Vol. 12 2006, pp. 221–234
deepest basins offshore West Greenland, seem to have a similar
structural setting.
In recent years modern seismic acquisition and processing
technology have improved significantly the quality of seismic
data in areas where basalts are interlayered in the sedimentary
succession. A flood basalt formation, erupted during the
mid-Paleocene rifting phase in the Labrador Sea region,
separates the Cenozoic from the Cretaceous clastic sequences
in part of the investigated area. The presence of this Paleocene
basalt was proved in the only well, Gjoa G-37, drilled in
the study area. Flood basalt eruption centres, such as the
Hecla–Maniitsoq centres, are located around the Lady Franklin
Basin.
Seismic data used for the present study consist of a set of
seismic lines acquired in 1997–2003 by TGS–Nopec and
Nunaoil A/S. The lines are of good quality and have a line
1354-0793/06/$15.00 2006 EAGE/Geological Society of London
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A. B. Sørensen
Fig. 1. Cretaceous basins, regional structural elements and extent of flood basalts around the Lady Franklin Basin and the Hecla–Maniitsoq
volcanic centres, offshore southern West Greenland. Basalt limits shown in stipple are based on interpretations by Chalmers & Pulvertaft (2001)
and Skaarup et al. (2006).
spacing of c. 15 km, except in the area to the south of the Lady
Franklin Basin where the line spacing is 30–60 km. Lines from
older surveys were used as a supplement. Well data from
Qulleq-1, Nukik-1 and 2, Kangâmiut-1 and the Canadian
wells Gjoa G-37, Ralegh N-18 and Hekja O-71 were available
for seismic calibration. In addition, an interpretation of the
wells drilled on the West Greenland shelf was carried out for
the purpose of well ties and interpretation of major unconformities. As a result of this work important revisions of
previous interpretations by Chalmers & Pulvertaft (2001) and
Sønderholm et al. (2003) on the Cenozoic tectonic and stratigraphic development of the West Greenland shelf area are
proposed.
In this study the following horizons were identified on
seismic sections and form the basis of interpretations: 1, Top
Miocene; 2, Top Palaeogene (near Top Lower Eocene); 3, Intra
Lower Eocene 1; 4, Intra Lower Eocene 2; 5, Near Top
Paleocene (Thanetian); 6, Top (Selandian) Basalt; 7, Base Basalt;
8, Top Cretaceous; 9, Intra Upper Cretaceous unconformity;
10, Top Fylla (Santonian) Sandstone equivalent; 11, Base Fylla
Sandstone; 12, Intra Upper Cretaceous (only in Maniitsoq
Basin); 13, Top Lower Cretaceous (Appat); 14, Intra Lower
Cretaceous (only in Maniitsoq Basin); 15, Top Pre-Cretaceous.
On the West Greenland shelf exploration wells document
the presence of a Cretaceous–Cenozoic succession corresponding to that found in the Hopedale and Saglek basins off eastern
Canada. The structural style of the West Greenland shelf
also resembles that of these Canadian basins. Chalmers et al.
(1993), Chalmers & Laursen (1995) and Chalmers & Pulvertaft
(2001) have described the geological development of the West
Greenland shelf and have suggested a stratigraphic subdivision
that corresponds to the stratigraphy of the Canadian shelf
published by McWhae et al. (1980) and Balkwill (1987). North
of the present study area, in the Nuussuaq Basin of central
West Greenland (Fig. 1), there are extensive outcrops of
Cretaceous–Paleocene sediments and Paleocene–Lower
Eocene flood basalts that correspond to successions of the
same age offshore (Bojesen-Koefoed et al. 1999; Chalmers et al.
1999). The onshore succession includes both source-rock
and reservoir lithologies. The numerous oil seeps that have
been found in this area suggest the existence of at least
five distinct source rocks, including marine sources of
SW Greenland stratigraphy and petroleum potential
possible Early–Middle Cretaceous or even Late Jurassic age
(Bojesen-Koefoed et al. 2004).
REGIONAL GEOLOGICAL SETTING
The Lady Franklin Basin is the westernmost basin in West
Greenland waters. The basin is bounded to the west by the
Ungava strike-slip fault zone, which consists of three large fault
sets (Fig. 1). Further to the west and southwest, the Saglek and
Hopedale basins are located on the Labrador Shelf. Both these
basins have been explored extensively for hydrocarbons and a
number of exploration wells have been drilled. Examination of
seismic data and wells in these basins indicates that rifting
between Canada and Greenland started in the Labrador Sea
region in Early Cretaceous (Berriasian) time (McWhae et al.
1980; Balkwill 1987). No evidence of Jurassic or Triassic
sediments was found in the Saglek and Hopedale basins (Bell
1989). These basins are located north of the Cartwright Arch
where the Charlie Gibbs fracture zone in the Atlantic Ocean
approaches the Newfoundland coast. A comprehensive stratigraphic subdivision of the Cretaceous and Cenozoic successions in the Hopedale and the Saglek basins was published
by McWhae et al. (1980). Five major unconformities were
demonstrated: at the base and top of the Lower Cretaceous;
at the Cretaceous–Paleocene boundary; and at Upper Eocene
and Upper Miocene levels (cf. Fig. 2). Several rift phases,
accompanied by volcanic activity, uplift and creation of unconformities, have affected the geological evolution of the area
greatly and have influenced possible petroleum systems in the
basins strongly.
In the northern and central part of the Hopedale Basin
significant hydrocarbon discoveries have been made in the
Snorri J-90, S. Hopedale E-33, Gudrid H-55 and Bjarni H-81
wells (Bell 1989). In the Saglek Basin a gas/condensate discovery was made in the Hekja O-71 well, not far from Greenland
territory (Fig. 1).
PRE-CRETACEOUS–LOWER PALEOCENE OF THE
LADY FRANKLIN AND MANIITSOQ BASINS
Pre-Cretaceous
Until now no Mesozoic sediments older than Cretaceous age
have been found in the area between Greenland and Canada.
It has generally been assumed that the Lady Franklin and
Maniitsoq Basin areas, together with large parts of the present
area between Greenland and Canada, were land areas during
the Late Palaeozoic until the start of the Cretaceous period
(Balkwill 1987; Bell & Howie 1990). However, some
re-deposited Late Jurassic palynomorphs have been identified
recently by palynological investigations in Cretaceous sediments offshore southern West Greenland (Piasecki 2003; H.
Nøhr-Hansen pers. comm. 2004). These palynomorphs could
have been transported into the area from the more elevated
areas to the northeast. They could also have been derived from
Jurassic sediments that had previously been deposited in a Late
Jurassic rift system, extending from the south of the Charlie
Gibbs Fracture Zone northwards along the Southwest
Greenland coast. New seismic data indicate that previously
unreported basins are present in these areas.
Offshore southern West Greenland the formation of a series
of basins and highs (Figs 1, 3) was initiated at the start of the
Cretaceous along a main system of NNW–SSE-trending
faults formed as a result of rifting. The Hecla High complex on
the east side of the Lady Franklin Basin is thought to consist
of Precambrian to Early Palaeozoic rocks and Paleocene
extrusives. Precambrian basement was encountered in the
223
Kangâmiut-1 and Nukik-1 wells offshore West Greenland. The
Lady Franklin Basin is bounded to the west by the Gjoa
Paleocene volcanic complex and the Ungava transform fault
zone (Fig. 1). The base of this basin can only be seen on a few
of the seismic lines. In some of the Canadian offshore wells
the Precambrian crystalline basement complex is overlain by
Ordovician limestones (Bell 1989), and it is possible that similar
limestones underlie the Cretaceous sediments offshore West
Greenland.
A seismic line (Fig. 4) running eastwards from the Gjoa
volcanic centre shows a succession of Cretaceous sediments
which underlie Paleocene volcanics and which rest on an
anticipated Precambrian basement block. This area is part of
the southwest flank of the Lady Franklin Basin.
Palaeozoic sediments, if present, are not expected to be
prospective for hydrocarbon exploration. However, Palaeozoic
source rocks may be present, because bituminous beds with
possible source-rock potential occur within Ordovician strata in
northeast mainland Canada (Sanford & Grant 1990). Hydrocarbons generated from such source rocks might have accumulated in traps associated with Precambrian fault blocks where
Lower Cretaceous or younger reservoir lithologies reach
closures or form stratigraphic traps.
Cretaceous
In the Canadian area the lowermost Cretaceous rocks are the
Alexis Formation volcanics (Umpleby 1979; Balkwill 1987);
these have been dated to 122–118 Ma in the upper part and
139 Ma near the base. The latter date corresponds very well to
dates reported by Larsen et al. (1999) on dykes in a coastparallel dyke swarm in Southwest Greenland. Corresponding
volcanics may underlie Cretaceous sediments in basins offshore
West Greenland.
Cretaceous sediments have been interpreted throughout
most of the study area. These can be divided into two
successions separated by an unconformity of presumed midCretaceous age (Top Lower Cretaceous reflection; Figs 2, 3,
4, 5). The lower succession, which is likely to consist of
interbedded sandstones and mudstones, is interpreted as being
of Early Cretaceous age (cf. Chalmers et al. 1993). The Lower
Cretaceous sediments can, in places, have the appearance of a
series of fans which build out into the interpreted syn-rift
basins, as seen for example in the Maniitsoq Basin (Fig. 3). At
the interpreted Lower to Upper Cretaceous boundary a thin
unit (Intra Lower to Top Lower Cretaceous) bounded by
unconformities can be seen in the Maniitsoq Basin (Fig. 3).
In the Lady Franklin Basin only an unconformity is present
(Figs 4, 5).
In the Lady Franklin Basin the mid-Cretaceous unconformity is overlain by a mudstone unit or a laterally extensive unit
interpreted as consisting mainly of sandstones, the Fylla sandstone unit, which in the northern and central part of the basin
is up to about 200 m thick (Fig. 5). This sandstone unit is
presumed to be equivalent to the marine Santonian sandstone
unit underlying the Kangeq Sequence in the Qulleq-1 well, the
oldest sediment dated so far in wells offshore West Greenland
(Christiansen et al. 2001). The Fylla sandstone unit seems to
extend over wide areas offshore southern West Greenland, as it
is found in the Lady Franklin, Maniitsoq and Nuuk basins, as
well as on the Fylla platform. This sandstone unit is thought to
be the most important reservoir unit in the basins offshore
southern West Greenland (Figs 1, 2). The sandstone is interpreted from seismic evidence to be a lowstand facies and is
bounded at the top by an unconformity that may have been
caused by a new, early Campanian, tectonic pulse (cf. Dam et al.
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A. B. Sørensen
Fig. 2. West Greenland and Labrador Shelf stratigraphic correlation diagram including known and presumed source-rock units. Canadian
stratigraphy based on McWhae et al. (1980), Balkwill (1987) and Bell (1989). Possible source-rock units known from the Canadian Labrador shelf
and presumed source-rock units in the West Greenland shelf suggested by oil seeps on Nuussuaq and in the Kangâmiut-1 well numbered as
follows. 1, Rut H-11, Hekja O-71?; 2, Herjof M-92; 3, South Hopedale L-39; 4, Herjolf M-92, Skolp E-7, Hekja O-71?; 5, North Leif I-01; 6,
Nuussuaq peninsula (Marrat oil); 7, Nuussuaq peninsula (Niagornaarsuk oil); 8, Nuussuaq peninsula (Kuugannguaq oil); 9, Nuussuaq peninsula
(Itilli oil) and Ellesmere Island, Kanguk Fm.; 10, Kangâmiut-1 ?.
2000) which initiated new rifting and subsidence in the West
Greenland basins.
Overlying this unconformity a thick seismically rather transparent interval consisting primarily of mudstone was deposited.
This interval has been interpreted to be a deep-water deposit,
the Kangeq Sequence (Chalmers et al. 1993). The Kangeq
sediments are generally very homogeneous but an internal
erosional unconformity thought to be of Campanian age can be
seen in the central and northern part of the Lady Franklin Basin
(Figs 2, 5). Small fans or turbidite units are also present in the
Kangeq Sequence. The Upper Cretaceous sediments in the
Qulleq-1 well were described by Christiansen et al. (2001). In
the study area the Upper Cretaceous succession is terminated
by a regional erosional unconformity (Figs 2, 3, 5).
Correlation The Lady Franklin and Maniitsoq basins were
probably initiated at the same time as other basins offshore
eastern Canada and West Greenland (McWhae et al. 1980;
Balkwill 1987; Chalmers et al. 1993). The maximum age of
sediments in the Canadian basins is fixed by the youngest age
obtained from volcanics in the Alexis Formation that underlie
the Cretaceous sediments in many places, i.e. 122–118 Ma
SW Greenland stratigraphy and petroleum potential
225
Fig. 3. Section through the northern part of the Lady Franklin Basin area, the South Maniitsoq High and Maniitsoq Basin, with presumed
strike-slip faults of Late Cretaceous age cutting through the Cretaceous succession and pre-Cretaceous basement. Late Cretaceous basin inversion
and erosion can also be seen. For profile location see Figure 7 (courtesy of Nunaoil A/S).
(Barremian–Aptian). The oldest sediments in these basins
have been termed the Bjarni Formation. This has been
divided into a lower, predominantly continental, member and
an upper, partly marine member. Basal beds in the Lower
Bjarni Member are not older than Barremian, while the top
of the formation is generally not younger than middle Albian
(Fig. 2; Balkwill 1987). The oldest sediments in the Lady
Franklin and Maniitsoq basins are expected to correspond to
the lower and upper members of the Bjarni Formation and
to be correlatives of the Kitsissut and Appat sequences
identified by Chalmers et al. (1993) in Greenland waters
further north. Chalmers et al. (1993, p. 925) correlated these
sequences with the lower and upper members of the
Bjarni Formation, respectively. Recently Nøhr-Hansen (in
Sønderholm et al. 2003) dated sediments in the Ogmund E-72
well located further southwest in the northern part of the
Canadian Hopedale Basin as Aptian–Albian (Upper Bjarni
Member). Seismic interpretation of the area further north
around the Kangâmiut-1 and Ikermiut-1 wells (Fig. 1) indicates that sequences below the Kitsissut Sequence are present
in this part of the West Greenland shelf (Chalmers et al.
1995). Such sediments may also have been deposited in the
Lady Franklin Basin.
The mid- and Late Cretaceous unconformities identified in
the Lady Franklin Basin (Figs 2, 3) are believed to be timeequivalent to the Canadian mid-Cretaceous Avalon and the
Cretaceous–Paleocene Bylot unconformities, respectively
(McWhae et al. 1980; Chalmers et al. 1993), both of which are
present in the Ogmund E-72 well (Sønderholm et al. 2003). The
mid-Cretaceous Avalon unconformity, which truncates the
Upper Bjarni Member, is an important feature of tectonic origin
on the Canadian shelf. The precise stratigraphic level of the
unconformity and the time span of the hiatus are not known on
the West Greenland shelf. In the Canadian Ogmund E-72 well,
Nøhr-Hansen (in Sønderholm et al. 2003) found a hiatus
spanning the interval Turonian–mid-Campanian. In this well
another hiatus related to the younger Bylot unconformity spans
most of the Late Maastrichtian (Sønderholm et al. 2003). Similar
ages are envisaged for unconformities in the Lady Franklin
Basin.
Lower Paleocene
The Cretaceous–Paleocene boundary offshore southern West
Greenland is represented by a major unconformity (Chalmers
et al. 1993; Chalmers & Pulvertaft 2001). Figure 3 shows a
profile through the South Maniitsoq High and Basin where a
strike-slip fault of Late Cretaceous–Early Paleocene age can
also be seen. The erosion of the Upper Cretaceous Kangeq
Sequence is very variable, judging from the thickness variations
of the Cretaceous succession. Seismic interpretation of this
profile (Fig. 3) also indicates that only a thin layer of Lower
Paleocene clastics may be present.
In most of the area around the Lady Franklin Basin the
boundary between the Cretaceous and Palaeogene sequences is
placed at the Late Cretaceous unconformity, or at the base of
the basalts if no unconformity can be seen (Figs 2, 5). The
Cretaceous–Palaeogene hiatus in wells offshore southern
West Greenland has been documented by Nøhr-Hansen (in
Sønderholm et al. 2003). In the Ikermiut-1 well a major
unconformity separates the Lower Campanian from the Upper
Paleocene, and in the Qulliq-1 well a hiatus spans the same
interval. The time span of the corresponding hiatus seen on the
seismic sections in the Lady Franklin area could not, however,
be established. Sediments of Early Paleocene (Danian) age are
not present in wells offshore West Greenland, apart from
Nukik-2. It therefore appears that most of the Maastrichtian–
Danian interval is not represented over large areas offshore
southern West Greenland (Fig. 2). Just west of the Lady
Franklin Basin the Canadian well Gjoa G-37 reached Danian
sediments at TD (Nøhr-Hansen 2003). Figure 6 shows that a
thin clastic unit of Selandian (P4) age (60.9–57.9 Ma) is present
in the three northern wells, in Nukik-2 and in Gjoa G-37.
PALEOCENE BASALTS
Flood basalts occur in two areas bordering the Lady Franklin
Basin: around the Hecla–Maniitsoq eruption centres, where a
seismically transparent thin flood basalt succession was erupted;
and in the southern part of the Lady Franklin Basin, where a
much thicker basalt sequence is present (Fig. 4). In the latter
area, which formerly constituted an island, here named
226
A. B. Sørensen
Fig. 4. Seismic section showing the flood basalt of ‘Escarpment Island’ with a transpressed strike-slip fault (initially the Gjoa Eruption Centre),
which is developed as a more normal strike-slip fault northwards. The escarpment (up to 700 m high) is seen to the east. Layers of flood basalt
deposited under water extend from the escarpment eastwards to the boundary (at the marked strike-slip fault) of a Cretaceous basin. Below Base
Basalt a sequence of Cretaceous sediments overlying Palaeozoic or Precambrian basement has been interpreted. For legend see Figure 2; for
profile location see Figure 7 (courtesy of TGS).
‘Escarpment Island’, at least two eruption centres seem to have
been located (Figs 1, 4). Along the northeast coast of the island
an escarpment (up to 700 m high), first observed by Chalmers
& Laursen (1995), was formed; this may be considered as the
southwestern boundary of the Cretaceous basins of the southern West Greenland shelf. The basalts below the escarpment
are slightly transparent to virtually opaque. On a seismic line
extending eastwards from Gjoa G-37 (Fig. 4), a presumed
Cretaceous section can be seen on top of a basement faultblock located below the basalt escarpment. What can be
identified as a former flood basalt island on the new seismic
lines, with a pronounced escarpment along its northeast margin
and an up-thrusted volcanic edifice, called here the Gjoa
Eruption Centre (Fig. 4), was considered previously to be a
subaqueously erupted basalt body around the Gjoa G-37 well
combined with later mafic intrusions (Balkwill 1987). Based on
the interpretation of magnetic anomalies and on anomalies
along seismic lines, the area was presumed previously to be
underlain by oceanic crust extending from the central part of
the Labrador Sea (Roest & Srivastava 1989; Srivastava & Keen
1995). However, in the Gjoa G-37 well sediments originally
dated to be of Maastrichtian age, but now considered to be
Danian (Nøhr-Hansen 2003), are present below the basalt
(Klose et al. 1982; Chalmers & Pulvertaft 2001, p. 89; Fig. 2).
The present interpretation suggests that no oceanic crust is
present in the area with basalts around the Gjoa well and
Escarpment Island. The boundary between continental crust
and the area with oceanic crust in the middle of the Labrador
Sea area must be moved further south. The basalt surface of
Escarpment Island dips gently southwards and the subaerial
basalt flows change with increasing depth into submarine
hyaloclastites. Seismic data indicate that the basalts of the
western part of the former island are connected with the
Canadian basalt province around the Davis Strait High (Fig. 1).
The Gjoa Eruption Centre is a domal elevation of the basalt
surface centred about 32 km east of the Gjoa well. It is
c. 12.5 km wide and rises about 1500 m above the surrounding
basalt surface. It is also expressed as a strong positive gravity
anomaly (Fig. 7). The Near Top Paleocene marker onlaps the
western flank of the structure; this feature suggests that the
Gjoa Eruption Centre had primary relief. Indications that the
structure had primary relief as a volcanic centre are also seen on
the eastern flank, where it appears that lavas flowed down the
slope and thickened as they accumulated on the flat-lying area
to the east. The greater part of the relief must, however, be
attributed to compressional forces. Unconformities at the base
SW Greenland stratigraphy and petroleum potential
227
Fig. 5. Seismic section through the Lady Franklin Basin with the Central Ridge showing Fylla sandstone underlain by Early and Late Cretaceous
(Turonian?) mudstone and sandstone successions. A few basalt sills can also be seen. The Cretaceous basin is in an upthrown position relative
to Top Basalt southwest of the interpreted strike-slip fault system. For legend see Figure 2. For profile location see Figure 7 (courtesy of TGS).
Fig. 6. Well-correlation diagram for West Greenland wells and the Canadian Gjoa G-37 well. Redrawn from Nøhr-Hansen (2003). Time-scale
and zonation after Berggren et al. (1995) and Mudge & Bujak (2001).
of the Intra Lower Eocene and Top Palaeogene markers and
thinning of the Eocene units on the flank of the dome show
that the compression and uplift took place primarily during the
Early Eocene.
Structures seen in the two NE–SW seismic lines north of the
Gjoa Volcanic Centre indicate that a NNW–SSE strike-slip
fault crosses these lines. Extrapolated southwards this fault
runs into the Gjoa Volcanic Centre. It is therefore concluded
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A. B. Sørensen
Fig. 7. Bouguer gravity anomaly map (based on unpublished 100 km high pass filtered data by J. A. Chalmers, GEUS) with fault map overlay
showing the Ungava transform fault zone and structures offshore southern West Greenland shelf. 1, Davis Strait High; 2, Hecla High; 3, South
Hecla High; 4, Lady Franklin Basin; 5, Fylla Platform; 6, Maniitsoq High; 7, Maniitsoq Basin; 8, South Maniitsoq High; 9, Kangâmiut Ridge; 10,
Gjoa Eruption Centre; 11, ‘Escarpment Island’; 12, Atammik High; 13, Nukik Platform; 14, Nuuk Basin; 15, Ungava transform fault zone.
that the folding and thrusting that gave rise to the elevated
feature was due to transpression along this fault. Further east
another strike-slip fault has been interpreted at the boundary of
the proposed Cretaceous (Lady Franklin) basin (Fig. 4). The
boundary between the Lady Franklin Basin and the western
basalt-covered area also seems to lie along a set of strike-slip
faults (Figs 1, 5, 7). The basalts extend further north and cover
a large part of the Ungava Fault Zone area (Chalmers &
Pulvertaft 2001; Skaarup et al. 2006).
The base of the basalts has been mapped where possible
around the Hecla–Maniitsoq eruption centres. The basalts are
estimated to be up to 200–300 m thick, except over the central
parts of the Hecla and Maniitsoq highs where they are
somewhat thicker and opaque. In the area between the two
eruption centres, in particular, only a very thin and seismically
transparent basalt layer is present (Fig. 1). Along the eastern
boundary of the basalt area two small but characteristic
escarpments indicate that water depths at the time of basalt
eruption were up to 100 m. The flood basalts of the Hecla and
Maniitsoq highs are expected to be underlain by basement
blocks and Cretaceous sediments which are cut by NW–SEtrending strike-slip faults along which feeder dykes to the
eruption centres may be located (Figs 1, 3).
The basalts in the Lady Franklin area are of mid-Paleocene
age, as two basalt samples in the Gjoa G-37 well have been
dated by the CO2 laser argon method at 59.51.0 Ma and
59.31.8 Ma, respectively (Williamson et al. 2003). These
volcanics can be correlated with the two lower formations
in the volcanic succession in the Nuussuaq area in central
West Greenland. In this area the lowest formation (Vaigat
Formation) and the lower part of the overlying Maligât
Formation have yielded 40Ar/39Ar ages between 60.70.4 Ma
and 59.40.5 Ma (latest Danian–earliest Selandian), while the
uppermost lavas (Kanísut Member) yielded an age of
52.50.2 Ma (Early Eocene) (Storey et al. 1998). Other basalts,
such as the Late Paleocene alkali basalt dyke swarm in the
Maniitsoq region, were dated by Larsen et al. (1999) to
55.21.2 Ma (40Ar/39Ar ages). Williamson et al. (2003)
obtained an age of 57.71.2 Ma for the basalts in the
Hellefisk-1 well.
SW Greenland stratigraphy and petroleum potential
Williamson et al. (2003) reported CO2 laser argon ages of
62.92.5 Ma and 55.12.3 Ma for basalts off Cape Dyer and
in central Davis Strait. These ages are, within error, the same as
those obtained from eruptives in the central West Greenland
volcanic province. Williamson et al. (2003) concluded that there
were two major phases of volcanism in the region that took
place at c. 60 Ma and 55 Ma, respectively. The dates obtained
on the Gjoa basalts (Williamson et al. 2003; Fig. 3) show that
the volcanism in the Lady Franklin area belonged to the first of
these two volcanic phases. The tectonic activity, synsedimentary faulting of Thanetian sediments at the Hekja O-71
well, and the strike-slip faulting in the Escarpment Island area
(Fig. 4), are time-equivalent to the latest volcanic episode
c. 55 Ma, reported by Williamson et al. (2003) and Larsen et al.
(1999) and, hence, contemporaneous with the initiation of
seafloor spreading in the North Atlantic and the reorientation
of the spreading axis in the Labrador Sea (Srivastava 1978;
Chalmers & Pulvertaft 2001).
Basalt intrusions
Sills and dykes, presumably of basalt, are very common in
the Cretaceous succession. In the Lady Franklin Basin the
intrusions are especially common in the southern part of
the basin and further east along the northern boundary of
Escarpment Island (Fig. 4). Also to the east of the Hecla High,
in the southern part of the Nuuk Basin, many dykes and sills are
present. The intrusions are almost confined to the lower part
of the Cretaceous succession, that is below or within the
interpreted Fylla sandstone interval. It is presumed that the
intrusions are of Paleocene age. Some dykes, however, could be
of mid-Cretaceous age and be related to volcanism associated
with tectonic activity responsible for the regional midCretaceous uplift phase, either the event that caused uplift and
formation of the Avalon unconformity or a later Santonian
event. Sills and dykes of presumed Paleocene age are also found
in the Kangâmiut Basin (Fig. 1). Since these intrusions appear
almost exclusively in the interpreted Lower Cretaceous Appat
Sequence, some of them may be of Early–mid-Cretaceous age.
Seismic interpretation in the Maniitsoq Basin area indicates that
no or only few basalt dykes occur in this basin.
POST VOLCANIC DEVELOPMENT
Late Paleocene–Eocene
After eruption of flood basalts offshore southern West
Greenland at around 59 Ma (Williamson et al. 2003), renewed
subsidence and deposition of the first post-basalt clastic sediments started around the Selandian–Thanetian transition
(Figs 2, 4, 6). During Late Paleocene and Early Eocene four
sequences were deposited (Figs 4 (lower part), 5). The lowest
two sequences are aggradational in character, the upper two
clearly progradational. When the first sequence was deposited,
both Escarpment Island (Figs 1, 4) and the Hecla and Maniitsoq basalt areas were islands. This sequence is more than 400 m
thick in the Hekja and Gjoa wells and seems to be distributed
throughout the Lady Franklin, Maniitsoq and Nuuk basins.
Dalhoff et al. (2003) reported that this sequence (sequence
3500) is one of the most extensive sequences on the West
Greenland shelf. A pronounced unconformity (Near Top
Paleocene, green reflection), which developed on top of it, is
overlain by a sequence of almost similar thickness (Fig. 4, lower
part of figure). This sequence is of Early Eocene age. The
pattern of layering of the two sequences shows that the time
during which they were deposited was tectonically very active.
The Gjoa Eruption Centre (Fig. 4) was faulted upwards and
229
syn-sedimentary faults formed at the Hekja O-71 well. Figure 4
also demonstrates how the sequences onlap the escarpment and
thin against the Gjoa Eruption Centre, the two sequences
having been deposited as the structure was folded upwards.
The two overlying progradational Lower Eocene sequences
(between the green stippled and red reflections on Figs 4, 5)
were deposited from the northwest and show clear downlapping relationships. The uppermost sequence consists of several
sub-sequences. The layers are often strongly progradational and
appear to have a varying sandy–clayey lithology.
The Lower Eocene succession is truncated by the most
pronounced unconformity on the West Greenland shelf (red
reflection Figs 3, 4, 5). This unconformity represents a hiatus
which offshore southern West Greenland spans a time from the
beginning of Middle Eocene until Middle Miocene (Fig. 2
Nøhr-Hansen 2003; Piasecki 2003; Sønderholm et al. 2003). It is
thought that this unconformity represents two hiatuses, one of
Middle Eocene and one of Oligocene age (Fig. 2). The first was
presumably caused by a major eustatic sea-level fall (Haq et al.
1987, 1988). An unconformity of this age is found throughout
the North Atlantic region and is related to erosion near the
beginning of Middle Eocene time. In the southern Labrador
Sea at ODP sites 112 and 647 (Fig. 1), investigations by
Kaminski et al. (1989) and Baldauf et al. (1989) showed that an
interval with a special foraminiferal Glomospira fauna referred to
NP 14 is present at this level. According to Nøhr-Hansen
(2003), hiatuses of the same age (early Lutetian) are present in
the Kangâmiut-1, Ikermiut-1 and Hellefisk-1 wells on the West
Greenland shelf (Figs 2, 6). The second (Oligocene) hiatus
includes half of the uppermost Eocene zone E8b in the
Hellefisk-1 well (Fig. 6). The Kangâmiut Formation cannot be
interpreted with confidence in the Lady Franklin area because
of lack of good well tie; it seems, however, that the formation
is missing here. To the south, in the Nukik-1, -2 and Qulleq-1
wells, mid-Miocene sediments overlie Early or early midEocene layers directly. In the Canadian well Gjoa G-37 the
lowermost Lutetian is preserved (Nøhr-Hansen in Sønderholm
et al. 2003; Fig. 6). It is, however, not known if a mid–Late
Eocene succession was originally deposited in the southern
areas of the West Greenland Shelf.
Oligocene
As just described, the Palaeogene–Neogene hiatus in the wells
on the West Greenland shelf spans, as a minimum, the time
interval latest Eocene to mid-Miocene (Hellefisk-1 well). However, at ODP sites 112 and 647, situated over oceanic crust in
the southern Labrador Sea, Oligocene sediments are present,
and the hiatus here occurs at the boundary between Early
Oligocene and mid-Miocene successions (Laughton et al. 1972a;
Baldauf et al. 1989). This hiatus, together with the presence of
alkali basalts at Avatarpaat (west of Disko) that have been
40
Ar/39Ar dated at 27.40.6 Ma and a dyke swarm on
Ubekendt Ejland dated to 34.10.2 Ma (Storey et al. 1998),
indicates that tectonic activity accompanied by volcanism took
place in the area west and southwest of Greenland during
Oligocene time. Laughton et al. (1972b, p. 266) indicated that a
major unconformity also occurs between Oligocene and
Miocene strata at ODP site 113 in the southern Labrador Sea.
The tectonic regime in the region seems to have changed
from general subsidence and N–S sinistral displacement along
the Ungava Fault zone in Early–Middle Eocene to a period
(Late Eocene–Oligocene) with uplift, SE–NW-directed compression and strike-slip faulting in the Lady Franklin area. The
Ungava Fault Zone (Figs 1, 7) was probably segmented during
this tectonic event. An alternative explanation for the segmen-
230
A. B. Sørensen
tation may be that changes in the stress directions in Late
Eocene–Oligocene time caused changes in the strike-slip movements and concomitant offsets along the Ungava Fault system
and the formation of pull-apart basins along the faults (J. A.
Chalmers pers. comm.; cf. Klose et al. 1982, fig. 7). The
cessation of lateral movements along the Ungava Fault system
could have been caused by the collision of Northwest
Greenland and southeast Ellesmere Island with northernmost
Canada along the Eurekan orogenic belt (De Paor et al. 1989).
A number of thrust faults on the southeastern part of Ellesmere
Island may be related to such an episode. The most important
consequence of the changed tectonic regime was that there was
uplift and erosion of the West Greenland shelf and transport
of large amounts of sediment towards the south into the
Labrador Sea area. Oligocene sediments have, for example,
been found in the wells at ODP sites 112 and 647, both of
which are situated in an area underlain by oceanic crust
(Baldauf et al. 1989; Kaminski et al. 1989; Fig. 1). The
biostratigraphy of wells in this area indicates that the
Palaeogene–Neogene unconformity spans a shorter time interval (Late Oligocene to near early Middle Miocene times)
than in the wells on the West Greenland shelf further north.
At site 112 located in the middle of the Labrador Sea a c.
160 m thick Oligocene section is present. Regression on the
West Greenland shelf during Late Oligocene may have been
related to both local compressional uplift and to a fall in
sea-level that could have been caused by major structural
changes in the North Atlantic. In this region spreading
shifted from the Aegir Ridge to the Kolbeinsey Ridge during
Oligocene time (Nunns 1983; Mosar et al. 2002). Late Oligocene sea-level fluctuations have also been observed in the
North Atlantic area (Martinsen et al. 1999; Sørensen 2003).
The period of uplift and erosion lasted until early midMiocene time, after which the tectonic regime changed and
subsidence of the whole Davis Strait and the Labrador Sea
area began.
Neogene
On the West Greenland shelf there is an unconformity between
sediments of mid-Miocene and Palaeogene age (Fig. 2
Nøhr-Hansen 2003; Piasecki 2003; S. Piasecki pers. comm.
2004). The unconformity truncates the Palaeogene sequences
and, in the Lady Franklin and Maniitsoq basins, it is presumed
that it represents a hiatus of about 35 Ma (Fig. 2). The Neogene
succession in the Lady Franklin Basin is up to c. 600 m thick
and is clearly transgressive from SE to NW. The Neogene
succession directly overlies the basalts on top of the Hecla and
Maniitsoq highs. Any Eocene strata deposited here could have
been eroded during the Oligocene uplift before deposition of
Neogene sediments started. No detailed studies have been
carried out on the Neogene succession in the nearby Gjoa G-37
well. Nøhr-Hansen (in Sønderholm et al. 2003) investigated the
Palaeogene succession in this well and found that it was
impossible to define the exact position of the Palaeogene–
Neogene boundary, as only a few samples were available for
analysis.
During the Neogene there were two depocentres offshore
southern West Greenland: the Nuuk Basin to the northeast and
the Labrador Sea Basin located south of the Lady Franklin
Basin and Fylla Platform, where up to 1600 m and 1000 m
sediments, respectively, were deposited. The amount of
Neogene subsidence increased from the north around the
Hellefisk-1 well southwards into the Labrador Sea. The base of
the Neogene drops from 640 m below sea-level in the
Hellefisk-1 well, to about 1800 m below sea-level in the Nukik
and Qulleq-1 wells, and it reaches around 2500 m below
sea-level in the Lady Franklin Basin. Further south, in the
southern Labrador Sea where the underlying crust is oceanic,
the base Neogene is as deep as 3897 m below sea-level at ODP
site 112 (Laughton et al. 1972a).
The Miocene sequence alone is around 225 m thick in the
Hellefisk-1 well and increases to about 525 m in the depocentre
near Nukik-2 (S. Piasecki pers. comm.). It is difficult to map the
Miocene succession with confidence in the Lady Franklin Basin
as there are no well ties. The sequence is topped by an
unconformity (Figs 3, 4, 5) that may represent a time span of
most of Late Miocene time. In the wells on the West Greenland
shelf an unconformity spanning about 2 Ma, comprising the
latest Miocene (Messinian) interval, is found (S. Piasecki pers.
comm. 2004; Fig. 2). At ODP Sites 112 and 647 in the southern
Labrador Sea a somewhat longer hiatus spanning from 11 Ma
to 4 Ma at Site 112 is present (Laughton et al. 1972a; Baldauf
et al. 1989). The hiatus may primarily be a result of a glacially
induced sea-level fall during early Pliocene (Davies 1972). A
Plio-Pleistocene succession consisting of contourites, prograding sequences and slumps tops the Neogene succession in the
Lady Franklin Basin.
TECTONIC SUMMARY
The possible existence of a petroleum system in the Lady
Franklin and Maniitsoq basins is related closely to the development of the complicated tectonic regime in the Davis Strait
area. Cretaceous and Paleocene rifting interrupted by phases of
uplift were followed here during the Eocene by northward
drifting of Greenland. Major Oligocene uplift and phases of
Neogene subsidence and the formation of the deep Labrador
Sea as it is known to day, finalized this development, and
created the conditions for the formation of a petroleum system.
+ The first recorded rifting phase in the Davis Strait and
Labrador Sea took place in Berriasian–Valanginian times,
with the formation of half-graben related to movements on
coast-parallel to sub-parallel extensional faults (McWhae
et al. 1980; Balkwill 1987). Subsequently, continental and
marine clastic syn-rift sediments of the Lower and Upper
Bjarni members were deposited in the graben. Chalmers et al.
(1993) have shown that corresponding rift-related Lower
Cretaceous units named the Kitsissut and Appat sequences
are present offshore West Greenland and, presumably, also
in the Lady Franklin Basin.
+ In the Lady Franklin and Maniitsoq basins a period of major
uplift and the formation of a regional unconformity took
place in mid-Cretaceous time.
+ In the southern basins offshore southern West Greenland
early Late Cretaceous erosion was followed by deposition of
a sandstone unit, the Fylla sandstone, in the Santonian.
Renewed rifting and extension caused deepening (probably
in the early Campanian) along rotational NW–NNW-striking
faults in the old, Lower Cretaceous basins of the shelf.
Deposition of the Kangeq mudstone sequence followed.
In the Lady Franklin Basin an intraformational (?Late
Campanian) unconformity can be mapped in the Kangeq
Sequence.
+ At the end of Cretaceous time the extensional tectonic
regime changed into a compressional regime resulting in
uplift accompanied by NNW–SSE-orientated strike-slip
faulting (Fig. 3). On the Fylla Platform a set of NE–SWtrending faults formed.
+ A period of uplift followed, caused by activity related to an
arriving plume (cf. Dam et al. 1998). Sedimentation was
231
SW Greenland stratigraphy and petroleum potential
Fig. 8. Seismic section from the
northern part of the Lady Franklin
Basin showing a geological setting
similar to the Qulleq-1 area on the Fylla
Platform, where the Fylla sandstone is
found at the bottom in small basins or
pinching out against basement blocks as
shown on this figure (courtesy of TGS).
+
+
+
+
sparse and lasted until late Danian or early Selandian times.
Afterwards intense volcanic activity started around the Lady
Franklin Basin and further north off southeast Baffin Island
and in coastal central West Greenland. The volcanism is
thought to have lasted until near the end of the Selandian.
In Thanetian time a new tectonic phase accompanied by
volcanic activity was initiated and continued into the Early
Eocene; this is particularly well documented in the West
Greenland volcanic province. This phase was related to the
onset of seafloor spreading in the North Atlantic area.
Sinistral N–S-orientated displacement along the newly established Ungava Fault system took place in the old Cretaceous
basins (Figs 1, 7). Early Eocene N–S-trending faults are also
present to the north and east, in areas around the
Kangâmiut-1 and Ikermiut-1 wells and on the Fylla Platform
where the Fylla West Boundary Fault was also active at this
time.
Major subsidence of the West Greenland offshore area also
started in the Thanetian and lasted until a new period of
sea-level fall occurred in earliest Lutetian time, resulting in
a regional unconformity being formed over the West
Greenland shelf and the northern part of the Labrador Sea.
Shortly after the mid-Eocene event renewed subsidence
resulted in deposition of a succession of Middle–Late
Eocene, and presumably also Early Oligocene, sediments in
the northern part of the southern West Greenland offshore.
A major change in tectonic style occurred in the Oligocene
when compression, volcanism and uplift caused erosion of
the West Greenland shelf area as well as large areas in the
Labrador Sea. An interplay between sea-level fall (Haq et al.
1988) and cessation of the left-lateral strike-slip movements
along the Ungava Fault system, probably caused by the
collision of the Greenland plate with northernmost Canada,
may be an explanation for the Oligocene uplift offshore
West Greenland.
The period of uplift and erosion ended in mid-Miocene
time, when renewed subsidence of the shelf began. The
subsidence accelerated southwards and affected the area of
the Labrador Sea strongly (Davies 1972), which today
reaches a water depth of more than 3000 m and a depth to
base Neogene of 3987 m at ODP site 112 in the south.
Sedimentation lasted until Late Miocene, when the last short
phase of uplift of the shelf occurred. A final phase of
subsidence started in early Pliocene time. Around Qulleq-1
more than 1500 m of subsidence took place during Neogene
time.
PETROLEUM POTENTIAL
Potential reservoir successions
This study has shown that hydrocarbon reservoirs in the area of
the Lady Franklin and Maniitsoq basins are likely to be located
primarily within the Cretaceous and secondarily in the Palaeogene successions. Sandstone sequences appear to be present in
both the Lower Cretaceous (Appat and Kitsissut sequences)
and Upper Cretaceous (Fig. 2). In the Upper Cretaceous the
primary reservoir unit is the Santonian Fylla sandstone,
deposited in a shallow-water depositional setting after the
mid-Cretaceous hiatus. This sandstone unit was drilled in the
Qulleq-1 well (Christiansen et al. 2001). The present study
suggests that it is present not only in the Fylla Platform but also
in the Nuuk and Lady Franklin basins (Figs 5, 8). In the Lady
Franklin area the Santonian sandstone and the underlying
Appat Sequence are situated at depths of c. 3000–5000 m and
are sealed by the thick Kangeq mudstone. Other possible
reservoirs are shallow-water deposits related to unconformities
in the Kangeq Sequence which can be mapped at least in the
Lady Franklin Basin (Fig. 5).
Depending upon depth of burial the Appat and Kitsissut
sequences (Fig. 5) are expected to have promising reservoir
properties like the Bjarni Formation of the Canadian Hopedale
and Saglek basins (Bell 1989). The Appat Sequence is thought
to consist of varying amounts of mudstone and sandstone,
which may have been transported into the Lady Franklin and
Maniitsoq basins from coastal areas of both West Greenland
and Canada. The Kitsissut Sequence is difficult to define in the
Lady Franklin Basin. The sequence, if present, is not separated
clearly from the Appat Sequence by an unconformity. The
Lower Cretaceous sediments in the Maniitsoq Basin are interpreted to be syn-rift deposits like the Canadian Lower Bjarni
Member (Fig. 3; Balkwill 1987). These consist of erosional
products and fans from the local ‘basement’ blocks that acted
as islands in a shallow sea. Good reservoir sands in the Early
Cretaceous could therefore be present around such ‘basement’
blocks in the Lady Franklin area.
Interpretation of the new seismic lines has shown that some
of the ‘basement’ blocks mapped in the offshore area of
southern West Greenland may partly consist of sediments that
could be of Palaeozoic to mid-Mesozoic age (Fig. 9b). Chalmers
et al. (1995) suggested that the Deep Sequence, defined further
north, could be of Palaeozoic age. These sediments are not
likely to contain reservoir-quality sandstones and carbonates
because porosities and permeabilities would be too low. How-
232
A. B. Sørensen
Fig. 9. (a) Fylla sandstone prospect in the Lady Franklin Basin. The flat-spot and gas chimney strongly suggest that a Cretaceous hydrocarbon
system exists here (courtesy of TGS). (b) Detail from Figure 2 (SW flank of Maniitsoq Basin) showing truncated, folded, presumed Palaeozoic
rocks with possible Ordovician source-rock beds (courtesy of Nunaoil A/S). For legend see Figures 2, 3.
ever, they could contain source-rock sequences such as those
known in northeast Canada (Sanford & Grant 1990).
Source rocks and a possible live petroleum system
A Cretaceous petroleum system has been proven in the
Canadian Hopedale and Saglek basins located southwest and
west of the Lady Franklin Basin (Klose et al. 1982; Bell 1989).
Biostratigraphic and kerogen maturation studies were carried
out on possible source intervals in a number of wells located in
these two Canadian basins (Bujak et al. 1987). New stratigraphic
investigations by Nøhr-Hansen (in Sønderholm et al. 2003) and
the present interpretation of the Lady Franklin Basin indicates
that the development of these three basins may be similar.
Bojesen-Koefoed et al. (1999) have shown that Cretaceous
source rocks are also present in the Nuussuaq Basin area
further north (Fig. 1). It is reasonable to expect that sourcerock sequences and a petroleum system corresponding to what
is found in these basins further north and south are also present
in the basins offshore southern West Greenland (Figs 1, 9a, b).
To the southwest of the Lady Franklin Basin a gas/
condensate discovery was made in the Hekja O-71 well (Klose
et al. 1982). The gas is found in a 76 m sand/shale succession of
latest Paleocene age. Reserves are estimated to be a minimum
of 2.31012 SCF gas. The average porosity is 16% and
permeability is 10 mD. The reservoir succession is underlain by
shale. The organic carbon content of this shale is 1.6% and
vitrinite reflectance is 0.5%. Resinite is present in a 300 m thick
layer in the shale and an average hydrogen index of up to 400
has been determined in some intervals. The shale can therefore
be considered as a possible source for oil, when mature, but not
for gas (Sønderholm et al. 2003). Consequently the Hekja gas
may be sourced from a Cretaceous or older interval underlying
the basalts. Further south, in the Hopedale Basin, drilling has
revealed Lower Cretaceous marine shale and continental coal
beds of the Bjarni Formation that could be possible sources for
the gas/condensate in the Hekja discovery (e.g. Herjolf M-92
and Skolp E-07, Fig. 2; Bell 1989).
Lower–mid-Cretaceous source rocks are presumed to have
generated two of the oil types found in seeps on the Nuussuaq
peninsula further north – the Itilli and the Kuugannguak oil
types (Fig. 2; Bojesen-Koefoed et al. 1999). The former is
presumed to have been generated from an early mature to
mature marine source rock having a composition similar to
that of the organic-rich shales of the Cenomanian–Turonian
Kanguk Formation on Ellesmere Island (Núñez-Betulu et al.
1993) or possibly even from Upper Jurassic source rocks
as known in the Jeanne d’Arc Basin (Bojesen-Koefoed et al.
2004). The Kuugannguak type may be sourced from coals or
carbonaceous shales of Albian–Coniacian age. Santonian–
Campanian shallow-marine source rocks of the Markland
Formation are present in the Herjof M-92 well (Bell 1989). A
corresponding source may have generated the Niagornaarsuk
type oil found on Nuussuaq (Fig. 2; Bojesen-Koefoed et al.
1999).
A source rock such as the organic-rich shales of the Kanguk
Formation on Ellesmere Island may be present in the lower
part of the Kangeq Sequence in the Lady Franklin Basin or in
the upper part of a predominantly Lower Cretaceous succession below, dependent upon the exact stratigraphic location of
the mid-Cretaceous hiatus (Fig. 2). Seismic data have shown
that the mid-Cretaceous unconformity is situated at a depth of
about 3500–4500 m in the Lady Franklin and Maniitsoq basins.
It is therefore probable that lower–mid-Cretaceous source
rocks, if present in these basins, are at a mature stage.
Paleocene source rocks (Fig. 2) may have generated the
Marrat oil, a typical wax-rich deltaic oil that is dominant in
seeps on Nuussuaq, Disko and Hareøen (Bojesen-Koefoed
et al. 1999). This oil is also present in the basalts and
hyaloclastites in the GANW-1, GANE-1 and GANK-1 slim
core wells drilled on the Nuussuaq peninsula. The oil may have
leaked from a larger accumulation located below the basalts
west of Disko and Nuussuaq. As already mentioned, west of
the Lady Franklin Basin Late Paleocene source rocks are
present in the Hekja O-71 well. These were presumably also
deposited in the Lady Franklin and Maniitsoq basins but are
expected to be early mature, having therefore a limited potential. Further southwest an Early Eocene marine source rock was
found in the Rut H-1 well in the southern part of the Saglek
Basin (Bell 1989).
In conclusion, the presence of source rocks of similar age or
type on Nuussuaq and in northern Canada and offshore in the
Hopedale and Saglek basins indicates that similar source rocks
should be present in the Cretaceous–Paleocene successions in
basins offshore West Greenland (Fig. 2). A gas show in the
233
SW Greenland stratigraphy and petroleum potential
Kangâmiut-1 well (Chalmers et al. 1995) also confirms this
prediction. Maturation of the source rocks is favourable in the
somewhat deeper Lady Franklin, Maniitsoq, Nuuk and other
West Greenland basins as compared to the Canadian Hopedale
and Saglek basins.
Palaeozoic carbonate rocks have been encountered in wells
located in the southern part of the Hopedale Basin, in outcrops
on the southern part of Baffin Island and also in Cumberland
Sound (Jenkins 1984; Fig. 1). Lower Cretaceous gasprone Bjarni Formation source rocks or bituminous beds in
Ordovician limestones (Bell & Howie 1990) must be considered to be the most probable sources for the gas/condensate
discovery in the Hekja O-71 well. Similar source rocks may also
be present in the Lady Franklin and other basins offshore
southern West Greenland. Seismic data from the Fylla
Platform area indicate that a Palaeozoic succession may overlie
Precambrian basement in that area. Consequently, a petroleum
system based on either Cretaceous or Palaeozoic source rocks
and Lower–mid-Cretaceous or Paleocene reservoir sequences
can be expected to be present in basins offshore West
Greenland (Figs 9a, b). The Itilli oil type from onshore central
West Greenland may be the most interesting oil type to be
found in the southern West Greenland basins; as already
mentioned it indicates the presence of a source rock of
similar age to that in the Canadian Arctic Kanguk Formation
(Bojesen-Koefoed et al. 2004).
Possible Cretaceous source rocks located at a depth of
c. 4000 m below sea-level in the Lady Franklin Basin are
expected to have reached maturity for oil generation in Late
Neogene time when subsidence of more than 2000 m and
deposition of up to 700 m thick sediments took place.
CONCLUSIONS
The Lady Franklin and Maniitsoq basins and surrounding areas
seem to have the potential to be a new West Greenland
petroleum province. During the Cretaceous period source- and
reservoir-rock sequences have been deposited in the basins.
Marine source-rock sequences identified or thought to exist on
Nuussuaq and in the Canadian Hopedale and Saglek basins may
extend into the basins offshore southern West Greenland
including the Lady Franklin and Maniitsoq basins. The Lady
Franklin Basin subsided in more than one pulse and the
proposed source-rock sequences of mid- and Early Cretaceous
age are now situated at depths of main petroleum generation.
A reservoir unit believed to correspond to the Santonian
Fylla sandstone interval drilled in the Qulleq-1 well is situated
just above possible source-rock sequences. Furthermore, a
Paleocene gas/condensate-bearing reservoir succession was
drilled in the Hekja O-71 well not far west of the Lady Franklin
Basin, where flat-spots have also been observed in Cretaceous
structures.
The Neogene subsidence of the area may have favoured late
oil generation. Therefore, the Lady Franklin Basin and its
surroundings may constitute a prospective area containing a live
petroleum system.
The author would like to thank TGS and Nunaoil A/S for
permission to reproduce and publish the seismic sections in this
paper. Special thanks are owed to the Bureau of Mineral and
Petroleum and the Geological Survey of Denmark and Greenland
(GEUS) for support and funding of the project, which was carried
out as part of the preparation for the West Greenland Licensing
round 2004. The author would also like to thank T. C. R. Pulvertaft
and J. A. Chalmers at GEUS, and Ioannis C. Baartman, DONG, for
discussions of the scientific ideas presented here and for improving
the English text. The paper is published with the permission of the
Geological Survey of Denmark and Greenland.
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Received 10 October 2005; revised typescript accepted 25 April 2006.