Phanerozoic Passive Margins, Cratonic Basins and Global Tectonic

11 Labrador Sea, Davis Strait, and Baffin Bay James A. Chalmers Geological Survey of Denmark and Greenland, Copenhagen K, Denmark

The Labrador Sea is a small oceanic basin about 900 km wide between Greenland and North America that opens to the southeast into the North Atlantic Ocean. To the north, it shallows and passes into the Davis Strait, a 300 km wide seaway leading into Baffin Bay (Fig. 11.1). These seaways are flanked by typical Arctic continental shelves with banks 8 km/sec

The nature of the area between the Hudson and Ungava Fracture Zones is unclear, but Chalmers and Pulvertaft (2001) noted that the spreading-center gravity low crosses the Hudson Fracture Zone (HFZ) and reaches the Ungava Fracture Zone (UFZ), named by Kerr (1967). The age of the oceanic crust between the Hudson and Ungava Fracture Zones is, however, unclear. If both Eocene and Paleocene crust are present, then the Gjoa G-37 borehole lies on oceanic crust of Paleocene age. If, however, they are surrounding this borehole consists of transitional crust, then the spreading center must be flanked by crust of Paleocene age (Chalmers and Pulvertaft, 2001). Kerr (1967) first interpreted a transform fault parallel to the southeast coast of Baffin Island and named it the Ungava Fracture Zone (Kerr, 1967, p. 286). Later workers, for example, Klose et al. (1982), Rice and Shade (1982), Menzies (1982), and Chalmers and Pulvertaft (2001), interpreted this zone as part of a transform system linking seafloor spreading in the Labrador Sea with spreading in Baffin Bay, and this interpretation is shown in Fig. 11.5.

Baffin Bay Despite the absence of magnetic lineaments, oceanic crust was also interpreted in Baffin Bay (Fig. 11.1) using evidence from refraction seismic lines that show that the crust underlying the deeper part of Baffin Bay is very thin, the Moho 389

Phanerozoic Passive Margins, Cratonic Basins and Global Tectonic Maps

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Figure 11.4 Cartoons of crosssections across the southern West Greenland transition zone (A), (B), (C), (D), and the Labrador transition zone (E). The interpretations in (A), (B), (C), and (D) were published in Chalmers (1997) and Chalmers and Pulvertaft (2001) and are along multichannel seismic lines BGR-6, BGR-12, BGR21, and BGR-17, respectively, published by Chalmers and Laursen (1995). The deep structure is on the basis of the wide-angle reflection/refraction line 88 R2 published by Chian and Louden (1994) and shown in Fig. 11.3C. The interpretation in (E) is along multichannel seismic line BGR-17 as shown in Chalmers and Laursen (1995). The deep structure is based on the wideangle reflection/ refraction line 90R1 published by Louden and Chian (1999) and shown in Fig. 11.3B.

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Palaeogene basalts 'Baffin Bay crust' oceanic crust or serpentinised peridotites Transition zone 'Gjoa zone' and its conjugate oceanic crust or transition zone Serpentinite ridge

1A

.2

C ig Ba ar e dy F si n y L a ne n A in 0 1.2 as ig. 1 B 1 .1

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Y B as o r k in

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Figure 11.5 (See legend next page)

391


Figure 11.5 Geological map over Labrador Sea, Davis Strait, and Baffin Bay but showing only Cenozoic ocean crust after Chalmers (1991) and Chalmers and Laursen (1995) in the Labrador Sea. Other data from Balkwill (1987), Jackson et al. (1992), Chalmers et al. (1993), Chalmers et al. (1995), Wheeler et al. (1996), Whittaker et al. (1997), Chalmers et al. (1999), Jackson et al. (1992), Reid and Jackson (1997), Skaarup et al. (2005), and Wheeler et al. (1996). The locations of reflection seismic and composite profiles shown in other figures are marked in red and the locations of P-wave velocity profiles are shown in orange. CB, Cumberland Basin; CD, Cape Dyer; DSH, Davis Strait High; FSC, Fylla Structural Complex; GR, Gjoa Rise; G-37, Gjoa G-37 borehole; HB, Hopedale Basin; HFZ, Hudson Fracture Zone; HR, Hecla Rise; H-1, Hellefisk-1 borehole; Ik-1, Ikermiut-1 borehole; Ka-1, Kangaˆmiut-1 borehole; N-1 and N-2, Nukik-1 and Nukik-2 boreholes; LFA, Lady Franklin Arch; NP, Nukik Platform; NB, Nuussuaq Basin; SaB, Saglek Basin; SFZ, Snorri Fracture Zone; SiB, Sisimiut Basin; UFZ, Ungava Fault Zone. Wells G-3, GRO-3; H-1, Hellefisk-1; I-1, Ikermiut-1; K-1, Kangamiut-1; N-1, Nukik-1; N-2, Nukik-2; Q-1, Qulleq-1; G-37, Gjoa G-37; N-18, Ralegh N-18; O-71, Hecla O-71. Redrawn from Chalmers and Pulvertaft (2001, fig. 11.2) and extended to the north.

392

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Miocene

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?volcano?

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Two-way time (sec)

Figure 11.6 Part of seismic lines AGC90-1 and AGC90-2 across the spreading graben in middle of the Labrador Sea. Note that this display is greatly contracted horizontally. The graben resembles other block-faulted, probably serpentinised, and peridotitic terrains that are typical of very slow-spreading oceanic crust (e.g., Michael et al., 2003; Mutter and Karson, 1992; Ranero and Banda, 1997; Jokat et al., 2003). Structures can be seen that may be individual volcanoes, similar to those reported from the Gakkel Ridge by Michael et al. (2003).

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7

Central Graben 8

8

lying at a depth of 8–9 km below sea bed in the deeper parts of the Bay at latitude 72! N, where the average thickness of sediments is about 4 km (Keen and Barrett, 1972; Keen et al., 1974). In this area, Keen and Barrett (1972) identified a layer with velocities of 5.0–6.3 km/s which they interpreted as oceanic layer 2, and a layer with velocities of 6.5–6.9 km/s interpreted as oceanic layer 3. Later Srivastava et al. (1981) and Balkwill et al. (1990) grouped velocities between 5.7 and 6.8 km/s in central Baffin Bay into a single layer interpreted as problematic oceanic layers 2 and 3. In the absence of any agreed pattern of linear magnetic anomalies in Baffin Bay, only the position of an extinct spreading axis and possible transform faults in the basin have been determined from gravity and magnetic anomaly maps. Whittaker et al. (1997) first pointed out that in northern Baffin Bay there is a WNW–SSE-trending gravity anomaly that closely resembles the negative anomaly in the position of the extinct spreading axis in the Labrador Sea (compare


Figure 11.7 Free air gravity over (A) Baffin Bay and the Davis Strait, and (B) the Labrador Sea and the Davis Strait. Map (A) is north of, and overlaps with map (B). A linear gravity low (B) marks the location of the extinct spreading center in the Labrador Sea, which continues northwest of the Hudson Fracture Zone (HFZ) to terminate at the Ungava Fault Zone (UFZ). Chalmers and Pulvertaft (2001) interpreted the linear gravity lows in (A) in Baffin Bay to mark the presence of extinct spreading centers there too. “D” is the irregular line of gravity highs along the Davis Strait High, west of which is a line of lows indicating the presence of sedimentary basins, probably on continental crust. See text for discussion. The gravity data are from Sandwell and Smith (1992) south of 72! N and from Laxon and McAdoo (1998) north of 72! N. Reproduced from Chalmers and Pulvertaft (2001).

85W

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mgal

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Fig. 11.7B with Fig. 11.7A). Whittaker et al. (1997) interpreted this anomaly as arising from an extinct spreading axis in Baffin Bay and Chalmers and Pulvertaft (2001) showed that there is a corresponding linear anomaly in southern Baffin Bay whose ESE end terminates against the extended Ungava Fracture Zone (Fig. 11.7B). The two linear anomalies are offset about 300 km relative to each other along a distinct magnetic and gravity anomaly trending approximately N–S along 64! W and interpreted by Chalmers and Pulvertaft (2001) as a transform fault. This feature was interpreted as the site of the extinct spreading axis by both Jackson et al. (1979) and Rice and Shade (1982), although Jackson et al. (1979) also considered the possibility that it is the site of a fracture zone. Chalmers and Pulvertaft (2001) named this feature the 64! W fracture zone.

Davis Strait One of the most important differences between the maps in Figs. 11.1 and 11.5 concerns the nature of the crust in the Davis Strait. Seismic refraction measurements in the central part of the Davis Strait (Keen and Barrett, 1972) showed that the depth to the Moho is 22 km. The lowest crustal layer is 18 km thick and has a velocity of 6.2 km/s, which is consistent with both continental fragments such as the Seychelles or Rockall Plateau and with Icelandic-type oceanic crust (Keen and Barrett, 1972; Keen et al., 1974). The presence of plume-derived volcanic rocks at both Cape Dyer on Baffin Island (Clarke, 1970) and in West Greenland (Clarke and Pedersen, 1976) reinforced this interpretation and led Keen et al. (1974) to suggest that a mixture of continental

393


crust and plume-related volcanic rocks might underlie Davis Strait. Srivastava et al. (1982) and Srivastava (1983) argued that the Davis Strait High, an elevated basement feature in the central part of the strait, is most likely continental, while the crust underlying the sedimentary basins that flank the high to the east and west is oceanic. Figure 11.1 summarizes the “traditional” interpretation of the geology of the area. Chalmers and Pulvertaft (2001) pointed out that the Ikermiut-1 commercial well, situated ca. 30 km east of the Davis Strait High, penetrated Turonian and possibly Cenomanian mudstones (N!hr-Hansen, 1998), an observation inconsistent with Srivastava et al.’s (1982) and Srivastava’s (1983) hypothesis that oceanic crust of Campanian or younger age underlies this area. A seismic sequence containing these rocks and two seismic sequences underlying it can be traced westward on reflection seismic lines to where they overlie the eastern flank of the Davis Strait High (Chalmers et al., 1995) (Fig. 11.8) (see below). It must therefore be concluded that both the Davis Strait High and the crust underlying the sedimentary basin to the east are continental. The nature of the crust to the west of the Davis Strait High is less clear. Skaarup et al. (2005) interpreted two groups of seaward dipping reflections (SDRs) in this area (Fig. 11.9); however, the features could also be interpreted as fault blocks, possibly within a series of pull-apart basins on continental crust. However, Funck (personal communication) has interpreted oceanic crust where one of the NUGGET refraction/wide-angle reflection lines acquired in 2003 crosses the southernmost part of the linear gravity anomaly and a plate tectonic reconstruction by Oakey (2005) shows that the area indicated by the linear gravity low closes during the Paleocene. The balance of current evidence suggests that the basins in the western Davis Strait, west of the Davis Strait High are underlain by oceanic crust of Paleocene age and this interpretation is shown on Fig. 11.5.

11.2 Sedimentary Basins on continental crust Basement rocks on Labrador, Greenland, and Baffin Island consist of high-grade gneisses of Archaean and Proterozoic age.

Nuussuaq Basin (onshore central West Greenland) Cretaceous and Palaeogene sediments and Palaeogene volcanic rocks are exposed on the island of Disko and the peninsulas of Nuussuaq and Svartenhuk (69! –72! N) in West Greenland (the Nuussuaq Basin) and near Cape Dyer (67! N) in southeast Baffin Island (Fig. 11.4) (Burden and Langille, 1990; Chalmers et al., 1999). Their stratigraphy is shown in Fig. 11.10, and surface geology and interpreted subsurface structure are shown in Fig. 11.11; Figure 11.12 shows an interpreted composite cross-section along the line of the Vaigat channel between Disko and Nuussuaq and extending offshore to the west.

394


S. P. No . 0

7000

Ik -1

6000

NE

SW 10 k m

Eo

K

Ap

Eo

a

2

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Dav i s St r ai t H i g h

Pc

Ap

Two-way time (sec)

1

Ka

3 Co n t i n en t al c r u s t 4

5

Ap Un g av a Fr ac t u r e Z o n e

‘ d eep ’ s eq u en c e

Figure 11.8 Seismic section from the Sisimiut Basin through the Ikermiut-1 borehole and onto the Davis Strait High. See Fig. 11.5 for location. The flower structure is the Ikermiut Fault, part of the strike-slip Ungava Fault Zone (UFZ, Fig. 11.5). The Ikermiut-1 well (Rolle, 1985) drilled through Cenozoic sediments and into Upper Cretaceous sediments of the Kangeq Sequence (Ka). N!hr-Hansen’s (1998) redating of this well shows upper Paleocene sediments lying unconformably on lower Santonian–Turonian (85–93.5 Ma) sediments of the Kangeq Sequence (Ka). The borehole’s maximum depth was in sediments possibly as old as Cenomanian (93.5–99 Ma). The seismically transparent Kangeq Sequence (Ka) can be traced across folds in the UFZ and south-westward above the eastern flank of the Davis Strait High. Below the Kangeq Sequence, two older sequences can be seen, identified as the Appat (Ap) and “deep” Sequences. Both of these must be older than the oldest sediments identified in Ikermiut-1, of Turonian–early Santonian age. The Appat Sequence can be traced through the faults of the flower structure and onto the flank of the Davis Strait High. These observations mean that the basement of the Davis Strait High must be older than Turonian (89–93.5 Ma) and probably older than Aptian (112.2–121 Ma). As the start of seafloor spreading in the Labrador Sea is dated as either Campanian (magnetochron 33, "75–80 Ma) (Roest and Srivastava, 1989) or mid-Palaeocene (magnetochron 27, 61 Ma) (Chalmers and Laursen, 1995), this must mean that the crust of the Davis Strait High cannot be oceanic. We interpret the Davis Strait High to be a ridge of continental basement within the Ungava Fracture Zone that has been uplifted to sea bed, probably by local transpressional forces. Redrawn from Chalmers and Pulvertaft (2001).

395


Redrawn from Skaarup et al. (2005, fig. 11.7).

0

E

COB 20 km

Inner SDR TWTT (sec)

Figure 11.9 Seismic section 200/75 showing reflections interpreted as seaward dipping reflections (SDRs) by Skaarup et al. (2005, fig. 11.7). The location is shown in Fig. 11.5. Two sets of SDRs appear to be separated by a basement high at 3 s two-way time and 40 km range.

high

Seismic Line 200/75 Outer SDR

2

4

Chalmers et al. (1999) used reflection seismic and gravity data to show that Mesozoic sediments at least 6 km and possibly up to 10 km thick lie under western Nuussuaq in a rift basin dominated by N–S faults. It is not known when rifting took place, but it must have been before the Cenomanian, because Cenomanian sediments belonging to the post-rift sequences are exposed. Sediment thicknesses under Disko, Disko Bay, and eastern Nuussuaq (the eastern area) are much less and faults trend both N–S and WNW–SSE, the latter parallel to shear zones in the adjoining basement area. Oil in surface seeps and in shallow boreholes occurs almost exclusively in the early rift basin. The eastern area may be the remains of a Late Cretaceous thermal subsidence basin in which a delta system was deposited that fanned out to the west and northwest from a point east of Disko island (Pedersen and Pulvertaft, 1992). In the southeast and east of the outcrop area, the sediments consist of fluvialdeltaic sandstones, mudstones, and coal seams of Albian-early Campanian age which constitute the Atane Formation. The fluvio-deltaic sediments pass northwestward into marine mudstones alternating with up to 50 m thick turbidite channel sandstones that were deposited on a submarine slope, the Itilli succession (Dam and S!nderholm, 1994). The present-day eastern boundary of Cretaceous outcrops is a system of major faults. In northern Upernivik " (an island just north of the northern limit of Fig. 11.11), the occurrence of very coarse conglomerate in Cenomanian sediments adjacent to one of the faults indicates active faulting at that time (Rosenkrantz and Pulvertaft, 1969), but farther south, Upper Albian-Cenomanian fluvial sands and shales are cut off by the boundary fault without any evidence of the proximity of syn-sedimentary fault scarps, suggesting that fault movement here was post-Cenomanian (Pulvertaft, 1979, 1989). The oldest Cretaceous sediments are exposed on the north side of Nuussuaq near the boundary fault system. These are of Late Albian age (H. N!hr-Hansen, personal communication, 1996) and consist of conglomerates,

396

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Neogene

60

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Upper Cretaceous Palaeogen e

C10 C19

Sag l ek Formation

Eo c en e

Pal aeo c en e Maas t r i c h t . Cam p an i an San t o n i an Co n i ac i a n Tu r o n i an

Cen o m an i an 100 A l b i an A p t i an

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Val an g i n i an

B er r i as i an

140

Manitsoq Formation

Mi d -o c ean rifting

K an g am i u t Fm .

K en am u Fo r m at i o n

Sea-f l o o r s p r ead i n g

Nu k i k Fo r m at i o n

Ik er m i u t Formation

Car t w r i g h t Fm .

v o l c an i s m Ri f t i n g Th e r m a l s u b s i d en c e/ Fo r m at i o n o f t r an s i t i o n a l crust

vvvvvvvvv v v v v v v v v v v v V+M v v v

Q

s ed i m e n t s

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A t an e Fo r m at i o n

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Qu i k av s ak Fm .

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K an g eq Sequence (i n f er r ed )

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Nu u s s u aq B as i n

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40

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w er Ear l y r i f t / Fo r m B jar n i ati o n A l ex s ag is

Fm .

Or d o v i c i an

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?

A p t i an Kome Cen o m an i an Fo r m at i o n p l u s d eep er s ed i m en t s

unknown s ed i m en t s

Kitsissut

Sequence

(i n f er r ed ) v v v v v v v v v Dy k e s v v v v v v v v v v v

B as em en t

B

C

D

Figure 11.10 Stratigraphic columns from (A) the Labrador (Hopedale and Saglek) Basins, (B) southern West Greenland basins offshore, (C) Cape Dyer, the easternmost point of Baffin Island, and (D) the Nuussuaq Basin onshore central West Greenland (see Fig. 11.5). The time scales are taken from Berggren et al. (1995) for the Cenozoic and Gradstein et al. (1995) for the Mesozoic. Stratigraphy redrawn from Balkwill (1987) for the Labrador Basins, Rolle (1985) for the Cenozoic, Burden and Langille (1990) for Cape Dyer, Chalmers et al. (1993) for the Mesozoic of the southern West Greenland basins offshore, and Dam et al. (1999) for the Nuussuaq Basin. Redrawn from Chalmers and

397

Pulvertaft (2001).


20

C1 - C9

Mi o c en e

Magn etochrons

Age Ma

Pl i o c en e

s o u t h er n Wes t Gr een l an d offshore

L ab r ad or Basins

Tec t o n i c ev en t s


Svartenhuk Halvø

53W

Ice Intrusion Eocene and younger sediments Basalt (on/offshore)

Ubekendt Ejland

Cretaceous-Paleocene sediments (on/offshore) Basement (on/offshore)

71N

Fault Shear zone Areas with numerous intrusions

Fig. 11.12

Nu

us

Va

iga

su

t

aq

70N

70N

Disko

Figure 11.11 Geological map over the Nuussuaq Basin, parts of which are exposed on the island of Disko and the peninsulas of Svartenhuk and Nuussuaq. See text for discussion. The data shown on the composite profile on Fig. 11.12 are located within about 20 km of the dashed line labeled “Fig. 11.12.”

Disko Bugt 69N

69N

40 km

54W

53W

52W

51W

sandstones, heteroliths, and mudstones of fluvio-deltaic origin that are overlain by inner shelf mudstones. These sediments collectively constitute the Kome Formation that Midtgaard (1996) suggested was deposited in an active half-graben with its bounding fault to the west. A low-angle unconformity separates these sediments from the overlying sediments of the Atane Formation (Midtgaard, 1996).

398


3 Offshore west of Disko

2

Distance (km) above or below sea level

Figure 11.12 Interpreted composite crosssection from west of Disko along southern Nuussuaq and Vaigat. See Figs. 11.5 and 11.11 for location. The section above the dashed line has been interpreted from outcrop and reflection seismic data. Below the dashed line, the interpretation is based on gravity modeling. See Chalmers et al. (1999) for details. Chalmers et al. (1999) modeled the gravity high west of the Itilli (It) fault as very thick basalts, but a geologically more realistic interpretation is that the basalts are 2–2.5 km thick and the gravity high is caused by a dense cluster of sill intrusions as shown here. This interpretation is, however, conjectural.

Onshore south Nuussuaq

Offshore in Vaigat

1 Sea level

0 -1

P

It

-2 -3 -4 -5 -6

K-Q

?

? ?

? ?

?

Cretaceous (and older?) sediment of unknown thickness probably present

-7 -8

50 km

-9 Eocene-Recent sediment

Basement

Palaeogene basaltt

Dyke complex

Cretaceous and Danian sediment Lower limit of outcrop and seismic evidence

Important faulting started in the mid-Campanian and was resumed in the midMaastrichtian (Dam and S!nderholm, 1994; Dam et al., 2000). These movements resulted in both rotation and uplift of the Atane Formation sediments in fault blocks (Chalmers et al., 1999), and were followed by the incision of a series of large, deep channels which were filled by transgressive successions of coarse conglomerates and turbidites or by fluvial sandstones (Dam and S!nderholm, 1994, 1998; Dam et al., 1998). An angular unconformity separates upper Campanian-Paleocene sediments from the underlying Atane Formation in many parts of the area. Palaeogene volcanism began in the Nuussuaq Basin with the eruption of the high-temperature, plume-related picrites of the Vaigat Formation (Clarke and Pedersen, 1976; see also Gill et al., 1992; Holm et al., 1993; and Graham et al., 1998), which is generally 8 km (Fig. 11.17A). Dalhoff et al. (2003) showed that sedimentation in the Sisimiut Basin in Paleocene and Eocene times was in a delta whose sediment input was to the north. More than 2 km of sediment accumulated between 61 Ma and ca. 43 Ma. The Ikermiut-1 well was drilled into a line of structures called the Ikermiut Fault Zone (Figs. 11.16 and 11.17A) along the western margin of the Sisimiut Basin. These structures were interpreted by Henderson et al. (1981) as shale diapirs, but Chalmers and Pulvertaft (1993, 2001) have suggested that they may be caused by compression related to strike-slip faulting that was active during the early to middle Eocene (Dalhoff et al., 2003). The folded and faulted Palaeogene and Upper Cretaceous sediments were penetrated by Ikermiut-1, and older, deeper seismic sequences can be traced westward from the well to crop out at seabed on the eastern flank of the Davis Strait High (Figs. 11.8 and 11.17A). Until recently, this feature had been interpreted as continental basement at seabed (Chalmers and Pulvertaft, 2001) but recent seismic data show reflections from presumed sediment within this structure that must be older than Cretaceous. The southern margin of the Sisimiut Basin is an east-west striking fault zone which may have formed extensions of linear shear zones within the Nagssugtoqidian orogen onshore (Wilson et al., 2008). South of the faults is the Nukik Platform whose western margin was drilled by the wells Nukik-1 and Nukik-2. Both wells penetrated between 2300 and 2500 m of Cenozoic sediments.

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Lower-mid-Cretaceous sediments and sills

Basement

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Figure 11.17 Interpreted seismic sections and geo-seismic sections across the basins offshore southern West Greenland. See Figs. 11.5 and 11.16 for locations. (A) Seismic line GGU/90-6 runs from the Davis Strait High in the west across the Ikermiut Fault Zone (drilled by the Ikermiut-1 well) and the Sisimiut Basin. Figure 11.8 shows the western part of this line in more detail. Folding along the Ikermiut Fault zone ceased in mid-Eocene time and Chalmers and Pulvertaft (2001) interpreted this structure to be a “flower structure” caused by left-stepping offset along sinistral strike-slip faults. The westward tilt of the section in the Sisimiut Basin was probably caused by uplift of the Greenland mainland by several kilometers during the Miocene and Plio-Pleistocene (Chalmers, 2000; Japsen et al., 2005). (Continued)

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Figure 11.17 Cont’d (B) Seismic line GGU/90-7 runs from the east flank of the Davis Strait High, across the Kangamiut Ridge to the Nukik Platform. The Kangamiut-1 well encountered Cenozoic sediments (Rolle, 1985) above an overpressured sandstone that may be either of Paleocene or Santonian age (Bate, 1997; N!hr-Hansen, 2003) and it appears to have contained hydrocarbon gas and possibly liquids (Bate, 1997). (Continued)

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Figure 11.17 Cont’d (C) Seismic line GGU/90-8 crosses the Maniitsoq High, the Nuuk Basin, and the Nukik Platform. The Maniitsoq High consists of a Paleocene-age lava dome above an elevated basement area. Unmodeled gravity data suggest the presence of a dense body that could be a gabbroic central complex. The Nukik-1 well encountered Pre-Cambrian basement below Cenozoic sediments (Rolle, 1985), whereas the Nukik-2 well, some 10 km to the north, encountered Paleocene hyaloclastites (Hald and Larsen, 1987) below similar Cenozoic sediments. (Continued)

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Figure 11.17 Cont’d (D) Seismic line GGU/90-9 crosses block faulted terrains between the Maniitsoq and Hecla Highs, the Nuuk Basin, and the Atammik Structural Complex. (Continued)

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Figure 11.17 Cont’d (E) Seismic line HGS/HS90A-8 from the Lady Franklin Basin (LF) in the west, across the Hecla High, the Nuuk Basin, and the Fylla Structural Complex. The Hecla High is a lava dome with elevated basement below which it is difficult to map because of energy loss in the basalts. Gravity data, similar to those on the Maniitsoq High, indicate the possible presence of a central complex. (Continued)

Nukik-1 terminated in Precambrian crystalline basement and Nukik-2 terminated in Paleocene basalts (Hald and Larsen, 1987; Rolle, 1985) that seismic data show to be limited to a series of half grabens on the platform (Chalmers et al., 1993) and to prograde across the faults that bound the platform to the west (Fig. 11.17C). The Kangaˆmiut Ridge is a north-south-trending ridge to the west of the Nukik Platform and separated from it by a graben, the northernmost extension of the Nuuk Basin. The Ridge was formed by movements on N–S-trending faults

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25 km

Middle Eocene to Recent sediments Lower Eocene sediments Lower Eocene basalts Paleocene sediments Paleocene basalts Upper Cretaceous sediments Lower-mid-Cretaceous sediments and sills Basement

Figure 11.17 Cont’d (F) Composite seismic section from the Lady Franklin Basin in the west, across the Hecla High, the Nuuk Basin, the Fylla Structural Complex, and onto the basin margin platform in the east. The Qulleq1 well was drilled into the Fylla Structural Complex in 2000. See Fig. 11.15 for more details.

probably in latest Cretaceous and early Paleocene times. The Kangaˆmiut-1 well was drilled on the west flank of this ridge (Fig. 11.17B). The Kangaˆmiut Ridge is cut by NW–SE faults to the south of the Kangaˆmiut-1 well. The faults continue west of the Ridge into the Kangaˆmiut Basin where they can be seen to be of those that were active during deposition of the Appat Sequence. It is thus possible that Appat Sequence or older sediments may be present on the southern Kangaˆmiut Ridge. Reflections from the base of Cretaceous sediments come from nearly 6 s TWT in the Kangaˆmiut Basin equivalent to >7 km. To the east and southeast of the Nukik Platform are the Atammik and Fylla Structural Complexes (Aram, 1999; Bate et al., 1994; Christiansen et al., 2001; Isaacson and Neff, 1999; Pegrum et al., 2001), both consisting of block-faulted areas. The structural complexes are defined by an extensional and faulting event that rotated Upper Cretaceous sediments in fault blocks (Christiansen et al., 2001) (Fig. 11.17D and E). The crests of the fault blocks have been eroded by a number of unconformities. At Qulleq-1, Paleocene sediments above the lowest unconformity lie directly on rotated Campanian mudstones. The very thin (8 m) Paleocene sediments are separated from 25 m of Eocene sediments by a second

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unconformity above which lie Miocene sediments. Qulleq-1 penetrated through the Campanian mudstones and reached terminal depth in sandstones of Santonian age (Christiansen et al., 2001). Another unconformity can be interpreted on seismic data below the well (Fig. 11.15) on which rest the Santonian sandstones. Beneath this unconformity are sediments in rotated fault blocks that resemble those of the Appat Sequence farther north. The faults bounding these older half-grabens run NW–SE in the Fylla area, parallel to those that cut the Kangaˆmiut Ridge, a quite different direction to the NNE–SSW trend of the Campanian–Paleocene faults that define the later episode of block-faulting. The Nuuk Basin is an N–S-trending graben to the east of the Kangaˆmiut Ridge and a half-graben west of the Atammik and Fylla Structural Complexes. Base Cretaceous lies deeper than 8 km in places in the Nuuk Basin. It is bounded on its west by the Maniitsoq and Hecla Highs, both of which appear to be areas of relatively shallow basement capped by basalt domes (Figs. 11.17C, D, and 11.16E). Correlation using dated seismic sequences (Dalhoff et al., 2003) shows that most of the basalts are of Paleocene age, although younger basalts may be present near the crest of the domes where the mid-Eocene unconformity laps onto the basalts. The Hecla High was formerly known as the Hecla Rise (Tucholke and Fry, 1985) when it was thought to lie on oceanic crust. To the west of both the Maniitsoq and Hecla Rises, large fault blocks step down westward into the Maniitsoq and Lady Franklin Basins, respectively (Fig. 11.17E), that extend into Canadian waters. Most of the fault-blocks are separated stratigraphically from the Paleocene basalts by a relatively unfaulted interval (Fig. 11.17E). It is therefore reasonable to conjecture that the unfaulted interval is equivalent to the Upper Cretaceous Kangeq Sequence and the block-faulted sediments below are equivalent to the Appat and older sequences. There is some evidence of faulting that reaches the base of the basalts along the western margin of the Hecla Rise that presumably took place in latest Cretaceous to early Paleocene time. The geology of the continental margin south of the Fylla Structural Complex, Hecla Rise, and Lady Franklin Basin was poorly known until recently because of lack of data. Recent confidential industry data are beginning to clarify the structure of this area and one result has been to show that the block-faults of the Lady Franklin Basin extend farther seaward than conjectured by Chalmers and Pulvertaft (2001) (compare Fig. 11.5 with their Fig. 11.2). Both the old and new seismic data show the presence of extensive volcanic rocks (Chalmers and Laursen, 1995; Chalmers and Pulvertaft, 2001) that extend to the Gjoa Rise which was drilled in Canadian waters by the well Gjoa G-37 (Klose et al., 1982). Chalmers and Pulvertaft (2001) speculated whether the Gjoa Rise is oceanic, continental, or transitional. Confidential industry data available since then tend to suggest that the area is of highly-extended continental or transitional crust overlain by the Paleocene basalts and Cenozoic sediments drilled by the well (Klose et al., 1982).

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Rotated block-fault structures can be seen on the only publicly-available seismic line under deep water near 63! N, 53! W (Chalmers and Laursen, 1995) (Fig. 11.2). A series of narrow half-grabens separated by basement ridges exist under the shallow shelf and slope south of about 63! N.

Offshore central West Greenland The basalts exposed on Disko and Nuussuaq continue offshore and are exposed at the sea-bed for some 25 km west of the coast (Fig. 11.11). From there, the reflection from the top of the basalts can be seen to dip westward at about 1–2! reaching depths of >3 km to ca. 100 km west of the coast (Skaarup, 2001) (Fig. 11.12). The basalts are covered by a wedge of sediment that thickens westward and is truncated by a shallow unconformity or at the seabed. Reflections within most of the sedimentary pile also dip westward sub-parallel to the top of the basalts and Chalmers (2000) suggested that the entire sequence had been tilted to the west during uplift of the Nuussuaq basin. Japsen et al. (2005) has dated this uplift to two phases, one that started at about 10–11 Ma and the other that started between 2 and 5 Ma. The westerly dip of the basalts is interrupted by N–S-trending faults that form a horst and graben system that Chalmers et al. (1999) suggested may be a splay of the Ungava system (Fig. 11.5). Skaarup et al. (2000) showed the presence of amplitude-versus-offset (AVO) anomalies on part of the horst that may indicate the presence of hydrocarbons. The basalts extend southward to just south of 68! N (Fig. 11.5) where they were drilled by the Hellefisk-1 well (Hald and Larsen, 1987; Rolle, 1985) near their southern edge. They can be traced northward to about 73! N (Whittaker et al., 1997) where they probably overlie the southern part of the Melville Bay Basin (see below). Skaarup (2001) divided the offshore basalts into five seismo-stratigraphic units. The basalts penetrated by the Hellefisk-1 well have been dated (40Ar/39Ar) as 57.7 # 1.2! Ma by Williamson et al. (2001). As they are reversely magnetised, they must have been erupted during either Chron 25r or 26r and biostratigraphic dating by N!hr-Hansen (2003) places them in the older Chron. They can be correlated with Skaarup’s (2001) second shallowest unit (B). It and the older units are therefore of Paleocene age, as are the Vaigat and Maligaˆt Formations onshore, while the youngest unit, which is positively magnetised, must be of C26n or younger age, possibly of C24n (Eocene) age similar to the Kanisut Member in western Nuussuaq. Pre-Cenozoic sediments must underlie the basalts west of the Disko Gneiss Ridge, as inclusions of sandstones with chert pebbles, very similar to some of the Atane Formation sandstones exposed in east Disko, occur in both lavas and volcanic necks in this area. Furthermore, contaminated dykes and lavas containing

418


iron, sulfides, and numerous inclusions of dark, fissile mudstone occur throughout western Disko (Pedersen, 1977a,b,c, 1985; Ulff-M!ller, 1977).

Melville Bay Potential field (Hood and Bower, 1973; Ross, 1973; Ross and Henderson, 1973) and refraction seismic (Keen and Barrett, 1972) data suggested the existence of a basin with >8 km of sediments (Ross and Henderson, 1973) under Melville Bay. These interpretations were confirmed by seismic reflection data (Whittaker et al., 1997) which interpreted a linked series of basins formed on the hanging-wall of a major fault between ca. 73! N and 76! N. Total throw on this fault is of the order of 10 km (Fig. 11.18B) and pre- and syn-rift sediments are overlain by a post-rift sequence that has been eroded along its inner margin. The crest of this very large fault-block forms the Melville Bay Ridge, west of which another SWW-throwing extensional fault bounds the Kiviok Basin. The Melville Bay and Kiviok Basins are separated from the Kap York Basin by a structurally complex zone, a “low relief accommodation zone” in the sense of Rosendahl (1987, p. 469) (Whittaker et al., 1997), and the northern parts of both the Melville Bay and Kiviok Basins have been folded at some time later than the main rift event (Fig. 11.18A). The ages of the sediments and events in these basins are not known as they have never been drilled or sampled. However, it is likely that the folding was due to compression at the same time as the Eocene Eurekan orogeny on Ellesmere Island. If so, it took place during the Eocene. Thickness variations within the sedimentary packages suggest that there may have been two episodes of extension (Whittaker et al., 1997). Extensional episodes in the Nuussuaq Basin and farther south offshore southern West Greenland (see below) took place during the Campanian to Danian. An earlier episode in both these areas may have been contemporaneous with the Aptian–Albian extension offshore Labrador.

North-east Baffin Shelf Jackson et al. (1992) published an interpretation of this area on the basis of multi-channel reflection seismic data that revealed coast-parallel grabens containing flat-lying sedimentary sections that are interpreted to be of Cretaceous to Cenozoic age (Fig. 11.19). Faulted Cretaceous sediments are interpreted to be overlain by unfaulted Cenozoic sediments. However, the only drill hole in the area (ODP 645; Srivastava et al., 1987) penetrated only to the Miocene, so these indentifications must be regarded as tentative. Cretaceous (Campanian) sediments have been sampled at the sea-bed off the NE coast of Baffin Island (MacLean et al., 1981) and oil has been reported as seeping from similar sediments at a different locality (MacLean et al., 1981).

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Basement

Figure 11.18 Geo-seismic sections across the basins in Melville Bay, offshore northern West Greenland. Redrawn from Whittaker et al. (1997). See Fig. 11.5 for locations. The basins have never been drilled nor seabed outcrop samples taken, so the ages assigned to the sedimentary units are hypothetical, but thought to be reasonable on the basis of regional considerations. The Melville N section shows evidence of folding, probably caused by compression as Greenland collided with Ellesmere Island during the Eocene causing the Eurekan orogony (Harrison et al., 1999).


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Figure 11.19 Geo-seismic sections redrawn from seismic sections published by Jackson et al. (1992) across the basins in western Baffin Bay offshore Baffin Island. See Fig. 11.5 for locations. ODP 645 is the only well drilled in the area. It reached Miocene sediments. Samples at seabed outcrop offshore Baffin Island show the presence of Cretaceous sediments (e.g.,

2 3 4 5

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Maclean et al., 1981, fig. 11.9), so the

Northern Baffin Bay

hypothetical attribution of the syn/pre-rift sedimentary units to the Mesozoic and the post-rift units to the Cenozoic is reasonable on regional grounds. Compare with Fig. 11.18. The presence of transitional crust is based on regional considerations shown in Fig. 11.5.

An arc of sedimentary basins on continental crust have been interpreted south of Ellesmere Island and Greenland’s Cape York Peninsula: the Lady Anne, North Water, Cary, and Kap York Basins (Jackson et al., 1992; Whittaker et al., 1997) (Fig. 11.5). The Lady Anne Basin is similar to the basins off north-east Baffin Island with an unfaulted cover on block-faulted sediments (Fig. 11.20). Folding on the hanging-walls of many of the faults is evidence of a period of compression or transpression before the unfaulted cover was deposited. The sediments in North Water Basin appear to have been extensively folded and are difficult to interpret on the available reflection data, which are of relatively poor quality. The Cary Basin is ca. 50-km long and oriented N–S. Sediments increase in thickness westward and its western margin is a 10-km wide “flower structure” (Jackson et al., 1992), indicating the presence of a strike-slip or transpressional regime. Recent reflection seismic data (Neben et al., 2003) suggest that MesoProterozoic Thule Group sediments may lie under the Cenozoic cover in the eastern part of this area. The Kap York Basin (Whittaker et al., 1997) is a narrow, half-graben with its bounding fault on the SW side. Pre-rift and syn-rift sediments can be seen in the deeper parts of the basin. Along the southern part of the basin, up to 50% of the shallower section appears to have been removed following inversion and the remaining thickness of sediment is >5 km in places.

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Figure 11.20 Geo-seismic section across the Lady Anne Basin based on a seismic line shown in Jackson et al. (1992). See Fig. 11.5 for location. The basin has never been drilled nor seabed outcrop samples taken, so the ages assigned to the sedimentary units are hypothetical, but thought to be reasonable on the basis of regional considerations. The section shows evidence of a large regional-scale fold, probably caused by compression as Greenland collided with Ellesmere Island during the Eocene causing the Eurekan orogony (Harrison et al., 1999).

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Refraction lines (Jackson and Reid, 1994; Reid and Jackson, 1997) indicate that all these basins lie on continental crust. Moho depths vary from 40 km indicating substantial extension. One line (Fig. 11.21) crossed the COB, though Reid and Jackson (1997) consider that the crust under the deeper part of Baffin Bay may consist of serpentinised mantle peridotites rather than basaltic crust.

11.3 Geological development Pre-Cretaceous The geology of the area is poorly known for the period between the various Proterozoic orogenies that are exposed onshore in both Canada and Greenland and the mid-Cretaceous. Limestones of Ordovician age crop out widely over northeastern Canada (Wheeler et al., 1996) and have also been encountered in wells on the Labrador Shelf (Balkwill, 1987). The presence of a fault breccia of the same age in West Greenland (Stouge and Peel, 1979) suggests that the Ordovician limestone platform extended as far as there. The “deep sequence” offshore southern West Greenland may be evidence for the presence of such sediments offshore. Carboniferous dolomites were reported from the Gudrid H-55 in the Hopedale Basin (Bell, 1989). However, Balkwill (1987) has raised doubt about this dating, and considers that the reported Carboniferous spores may be contamination. It is also possible that previously unknown Mesozoic sediments may underlie the known Cretaceous basins.

Early Cretaceous (possibly Late Jurassic) Extension and subsidence without significant faulting (sagging) began offshore Labrador during the Early Cretaceous (or possibly Late Jurassic) and the Lower Bjarni formation was deposited into the accommodation space so formed. The extension was accompanied by eruption of the Alexis formation volcanics.

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Figure 11.21 Velocity profiles from the Lady Anne to the Cary Basins (North Baffin 1) and southeastward from the Lady Anne Basin (North Baffin 4). See Fig. 11.5 for locations. The sections are redrawn from Reid and Jackson (1997). Black diamonds along the tops show the OBS locations. North Baffin 1 appears to show the presence of (thinned) continental crust along its entire length, whereas North Baffin 4 appears to cross from continental crust at its northern end to transitional

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A similar episode seems to have happened off southern West Greenland leading to deposition of the Kitsissut sequence. Dykes were intruded into the presentday onshore southern West Greenland between 138 and 133 Ma (Valanginian, magnetochron M-12) (Larsen et al., 1999).

Mid-Cretaceous Faulting and fault-block rotation took place during the Aptian and Albian (115–100 Ma) time on the Labrador shelf and the Upper Bjarni Member was deposited in the hanging-walls of the fault-blocks. A similar episode off southern West Greenland that resulted in deposition of the Appat Sequence is presumed also to have taken place during the Aptian and Albian, although this conjecture is not confirmed. Off southern West Greenland, the faulting during this episode trends NW–SE, parallel to the future COB. On north-eastern Nuussuaq, the Kuuk

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Formation is also of Albian age and may have been deposited in a syn-tectonic environment (Midtgaard, 1996). Faulting of unknown age (but possibly midCretaceous) in the Nuussuaq Basin formed deep half-grabens under western Nuussuaq (Chalmers et al., 1999).

Late Cretaceous On the Labrador Shelf, faulting appears to have ceased by the Cenomanian and post-rift thermal subsidence from Cenomanian to Danian (100–62 Ma) created accommodation space into which the Markland Formation was deposited (Balkwill, 1987). In the Nuussuaq Basin, the accommodation space was filled by sediments in a large delta (the Atane Formation of Cenomanian to Campanian age) from a river that fanned out to the west and northwest from a point east of Disko island (Pedersen and Pulvertaft, 1992). There is no evidence of syn-depositional tectonics before the Campanian and the delta was probably deposited into a basin undergoing post-rift thermal subsidence (Chalmers et al., 1999). The timing of the cessation of faulting offshore southern West Greenland is not so well constrained, but on seismic sections, the Kangeq Sequence resembles the Markland Formation and shows no evidence of faulting previous to the Santonian to the Campanian. These units appear to be composed predominantly of marine mudstones, but sands (the Freydis Member) were deposited around the margins of the Labrador Basins and farther into the basins possibly during periods of lower sea-level (Balkwill, 1987). The Fylla Sandstone, of Santonian age, may be evidence of an equivalent depositional episode offshore southern West Greenland. The extent and depositional environment of these sandstones are poorly known at present. Seismic evidence suggests that they may be present in many other parts of the southern West Greenland Basins, but that they are not present everywhere. ˜ ez-Betelu, During the Cenomanian and Turonian, a rich oil source rock (Nuń 1993) was deposited in the Kanguk Formation in the Sverdrup Basin on Ellesmere Island, north of Baffin Bay. Artificial maturation by hydrous pyrolysis of samples of the Kanguk Formation (Bojesen-Koefoed et al., 2004) generates bitumen that shares a number of important characteristics with the Itilli oil type discovered in seeps on west Nuussuaq (Bojesen-Koefoed et al., 1999), suggesting that source rocks of that age extend at least as far south as the Nuussuaq Basin. Whether they extend into offshore southern West Greenland is unknown, though a pressure kick in the Kangaˆmiut-1 well produced very wet gas suggesting the presence of oil in the reservoir (Bate, 1997). While there is little evidence of continued extension and crustal thinning during the Late Cretaceous in the intra-cratonic basins around the Labrador Sea, extension and crustal thinning may have continued throughout Late Cretaceous time between the Greenland and Canadian cratons. The transitional crust between continental and oceanic crust in the Labrador Sea was formed either by very

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slow seafloor spreading or by extension that thinned the continental crust to only a few km (Chian and Louden, 1994). The extension certainly happened prior to the onset of seafloor spreading at 62 Ma and happened too slowly for volcanism to have occurred as a result of adiabatic decompression of mantle rocks (Chalmers, 1997). For this to have occurred, extension must have been slow and have taken between a minimum of 30 Ma (Bown and White, 1995) and a maximum of 55 Ma (Chalmers, 1997). The details of what happened are unclear, but it seems that the wide-spread extension that took place during the Aptian and Albian became focused into a much narrower zone in which slow extension continued, possibly during the entire Late Cretaceous, that thinned the continental crust to 3 km thickness or less.

Latest Cretaceous to Danian Extension and fault-block rotation took place in the Nuussuaq Basin onshore and offshore in the Fylla, Kangamiut Ridge, Lady Franklin Basin areas, and possibly elsewhere in the West Greenland basins in latest Campanian to early Paleocene time (80–63 Ma). In the Nuussuaq Basin, large submarine channels formed along the crests of the fault-blocks that were later filled by transgressive marine sediments (Dam and S!nderholm, 1994). This episode seems not to have affected the area offshore Labrador (Balkwill, 1987).

Mid-Paleocene Uplift and erosion caused by the impact of the Iceland plume (63–62 Ma) produced a second episode of channeling in the Nuussuaq Basin, but this time the channels were sub-aerial and were the result of major river erosion into the uplifting landscape. Offshore southern West Greenland, the erosion was so extensive that mid-Paleocene sediments lie directly on Santonian sediments in the Ikermiut-1 well (N!hr-Hansen, 2003) and on Campanian sediments in the Qulleq-1 well (Piasecki, 2003) and there is no evidence on seismic data for the presence of Maastrichtian or lower Danian sediments elsewhere in the basins (Dalhoff et al., 2003). An unconformity of middle Paleocene age in the Hopedale and Saglek Basins was followed by transgressive deposition of the Cartwright Formation on the Markland Formation and older rocks. Cartwright Formation facies is similar to that of the Markland formation, dominated by fine-grained sediments in the center of the basins with marginal sands (the Gudrid sandstone). It is likely that the tectonic episode that produced the major fault blocks around Baffin Bay happened at this time. Volcanism took place at 61 Ma (Storey et al., 1998) producing the ultrabasic picrites of the Vaigat and the tholeitic basalts of the Maligat Formations in the

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Nuussuaq Basin (Clarke and Pedersen, 1976). These volcanic rocks can be traced offshore on seismic data and extend from just south of 68! N, where they were penetrated by the Hellefisk-1 well to 71! N. Other centers of volcanism at this time were the Hecla and Maniitsoq Rises and a smaller area on the western Nukik Platform. Subsidence was rapid during the volcanism. The early volcanism in the Nuussuaq Basin produced sub-aquatic hyaloclastite Surtseyan-type structures that built rapidly to above sea-level in western Nuussuaq (the Anaanaa Member) (Pedersen et al., 2002). Sub-aerial lava flows reached the contemporary coastline to the east and prograded eastward as a hyaloclastite Gilbert-delta (Pedersen et al., 1993) into 700 m-deep water, a measure of the amount of subsidence that had taken place. Subsidence continued after the lava system became subaerial, for over a several-hundred meter thick interval, and each lava flow is hyaloclastite at its base and sub-aerial at its top, showing that subsidence was just keeping pace with volcanism. Offshore southern West Greenland, subsidence and sedimentation restarted at the same time as volcanism. The sediments were deposited in a predominantly extensional tectonic environment (Dalhoff et al., 2003). Sediment input to the basins was predominantly from the north, and Dalhoff et al. (2003) have conjectured that these sediments came from the same river system that deposited the Upper Cretaceous Atane Formation in the Nuussuaq Basin and had eroded the Maastrichtian and Danian channels described by Dam and S!nderholm (1998). Lesser amounts of sediment came from east over the Nukik-Platform and from the west as syn-tectonic wedges. The thickness of total sediment decreases substantially from north to south. The sediments were deposited in environments that ranged from fresh-water/marginal marine to upper bathyal. Proximal environments are probably generally sand-prone, but distal environments probably contain larger amounts of mud, some of which could contain a mature source rock for oil such as the Paleocene source rock on Nuussuaq known to have generated the Marraat oil found in seeps there (Bojesen-Koefoed et al., 1999). Basin-floor fans, syn-tectonic wedges, and turbidite channel complexes that could act as hydrocarbon reservoirs sealed by surrounding muds have been identified in many of the seismic sequences. Volcanism also took place on the Hecla and Maniitsoq Rises and in a limited area on western Nukik Platform. This volcanism may have started sub-aquatically, but rapidly built upward so that sub-aerial flows reached a local coastline and prograded as into the water as Gilbert-type deltas. These foresets are typically 100–200 m high, much less than those in the Nuussuaq Basin. Seafloor spreading started in the Labrador Sea and Baffin Bay at the same time as volcanism started onshore (Magnetochron 27n) (Chalmers and Laursen, 1995; Chalmers and Pulvertaft, 2001), the two areas being connected by an area of seafloor spreading in Davis Strait that may have resembled the

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present-day Gulf of California, where short spreading centers are connected by long-offset transform faults. Widespread volcanism affected the continental– ocean transition areas in the Cartwright and Saglek Basins, the northern part of the transition zone on the Greenland side of Labrador Sea, and southern Baffin Bay. The SDRs observed in the latter two areas suggest that the volcanism was of high temperature. Volcanism did not, however affect the Greenland margin south of about 62! N, where the (presumed) Upper Cretaceous transition zone is preserved without a cover of basalt, nor the Hopedale Basin except in its distal part near oceanic crust.

Early to middle Eocene The commencement of seafloor spreading in the northern North Atlantic at the beginning of the Eocene changed spreading from a two-plate system (North America and Greenland þ Europe) to a three plate system in which Greenland moved away from both North America to the west and Europe to its southeast. This could be achieved only by Greenland moving northward and that meant a change in spreading direction in the Labrador Sea from SW–NE to N–S. Strikeslip motion along the Ungava system also changed and one of the obvious consequences was the change in the Ikermiut Ridge area from extension during the Paleocene to compression during the Eocene (Dalhoff et al., 2003). Chalmers and Pulvertaft (2001) interpreted this compression as resulting from a left-lateral step-over on a sinistral strike-slip fault system. Folding in this compressional system lasted until the middle Eocene and ceased at the same time as spreading in the Labrador Sea slowed after Chron 21 (ca. 49 Ma). This change in spreading direction changed movement between Greenland and Ellesmere Island from being predominantly strike-slip along northeastern Nares Strait during the Paleocene to entirely compressional during the Eocene, resulting in the Eurekan orogeny. Total shortening appears to be of the order of 100– 150 km (De Paor et al., 1989). Compressional movements affected the basins around northern Baffin Bay, probably at the same time, and there may have been an episode of northward-directed strike-slip movement along the western margin of the Cary Basin. Tectonism along the Ikermiut Fault Zone, the western margin of the Sisimiut Basin, changed from extensional to transpressional and a flower structure developed while it otherwise continued in a similar pattern to that during the late Paleocene. The Sisimiut delta continued to prograde from the north, and smaller deltas built out over the Nukik Platform from the east while deposition in the basin center was fine-grained (Dalhoff et al., 2003). Renewed volcanism affected western Nuussuaq (Storey et al., 1998), and the Palaeogene basalts west of Disko and Nuussuaq appear to have remained sub-aerial during the early part of the Eocene and were finally transgressed shortly before the formation of the mid-Eocene Unconformity. Analysis of apatite fission-track

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and vitrinite reflectance data suggest that this transgression covered western Nuussuaq, but did not reach as far as inner Disko Bay (Japsen et al., 2005). In the Labrador Basins, the Paleocene Cartwright Formation was succeeded and overstepped by the Eocene Kanamu Formation, but sedimentation continued in a similar pattern of fine-grained clastic sediments in the basin centers and coarser-grained sedimentation around the margins.

11.4 Late Eocene to Neogene The rate of sea-floor spreading in the Labrador Sea, and presumably also in Baffin Bay, slowed abruptly during the mid-Eocene and magnetic anomalies younger than 20r are not visible. Evidence that extension continued, however, is given at the triple junction with the northern North Atlantic, south of Greenland. Readily visible North Atlantic magnetic anomalies are disturbed by a zone colinear with the spreading graben in the Labrador Sea and this zone of disturbance extends to anomaly 13, showing that extension in the Labrador Sea continued to Chron 13 (end-Eocene/start Oligocene) (Srivastava, 1978). Tectonic activity in the Eurekan orogen also declined after the mid-Eocene (Harrison et al., 1999), consistent with the plate-tectonic evidence, and compression along the Ikermiut fault zone off southern West Greenland ceased in the mid-Eocene as the rate of plate separation slowed (Chalmers and Pulvertaft, 2001). Off Labrador, a basin-wide unconformity of late Eocene age separates sediments of the Kenamu and Mokami Formations and an episode of faulting took place during the early phases of deposition of the latter Formation. The history of offshore West Greenland area has not been studied in detail from the mid-Eocene until the Pleistocene. Some information is known, but its causes and consequences are poorly understood. Deltaic sedimentation continued in the Sisimiut Basin during the Late Eocene, but Oligocene sediments equivalent in age to the Mokami Formation appear to be entirely missing (N!hr-Hansen, 2003). This unconformity may be coeval with the formation of a peneplain, today preserved at altitudes of ca. 2000 m onshore (Bonow et al. 2006). Sedimentation resumed offshore in the mid-Miocene, equivalent in age to the Saglek formation off Labrador. Two other regional Neogene unconformities are known of early Pliocene and Plio-Pleistocene age. These unconformities have been identified with two phases of uplift of the coastal area of West Greenland starting at about 10 Ma and at ca. 4 Ma (Japsen et al., 2005). During the late Miocene, sedimentation patterns were complex, caused presumably by the interaction of varying shelf-margin currents, sea level, and sediment supply. The sediments in the Sisimiut Basin and west of Disko and Nuussuaq were tilted upward to the east during the Plio-Pleistocene, probably starting at around 4 Ma (Japsen et al., 2005), and

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were eroded either by a shallow unconformity or at sea bed. This tilting/uplift event produced the present-day coastal mountains that acted as a source of glaciers during the climate deterioration of the late Pliocene that then grew into the Greenland icecap. Major wedges of sediment prograded seaward from the uplifting landmass to form the present-day continental shelf. Its abrupt margins are in many places the limit of the latest progradation episode.

References Aram, R.B., 1999. West Greenland versus V!ring Basin: comparison of two deepwater frontier plays. In: Fleet, A.J., Boldy, S.A.R. (Eds.), Petroleum Geology of Northwest Europe: Proceedings of the 5th Conference. Geological Society, London, pp. 315–324. Balkwill, H.R., 1987. Labrador Basin: structural and stratigraphic style. In: Beaumont, C., Tankard, A.J. (Eds.), Sedimentary Basins and Basin-Forming Mechanisms, Can. Soc. Petrol. Geol. Memoirs 12, pp. 17–43. Balkwill, H.R., McMillan, N.J., MacLean, B., Williams, G.L., Srivastava, S.P., 1990. Geology of the Labrador Shelf, Baffin Bay and Davis Strait. In: Keen, M.J., Williams, G.L. (Eds.), Geology of the Continental Margins of Eastern Canada, Geol. Can. 2, pp. 293–348. Bate, K.J., 1997. Interpretation of the basal section of well Kangaˆmiut-1, offshore southern West Greenland. Geological Survey of Denmark and Greenland Report, 1997/76, p. 24. Bate, K.J., Whittaker, R.C., Chalmers, J.A., Dahl-Jensen, T., 1994. Fylla complex – possible very large gas reserves off S.W. Greenland. Oil Gas J. 92, 79–82. Bell, J.S., 1989. East Coast Basin Atlas Series, Labrador Sea. Atlantic Geoscience Centre, Dartmouth, Nova Scotia. Bell, J.S., Howie, R.D., 1990. Paleozoic geology. In: Keen, M.J., Williams, G.L. (Eds.), Geology of the Continental Margin of Eastern Canada. Geology of Canada. Geological Survey of Canada, pp. 141–165. Berggren, W.A., Kent, D.V., Swisher, C.C., III, Aubry, M.-P., 1995. A revised Cenozoic geochronology and chronostratigraphy. In: Berggren, W.A., Kent, D.V., Aubry, M.-P., Hardenbol, J. (Eds.), Geochronology, time scales and global stratigraphic correlation, Soc. Econ. Paleontol. Mineral. Sp. Pub. 54, pp. 129–212. Bojesen-Koefoed, J.A., Christiansen, F.G., Nytoft, H.P., Pedersen, A.K., 1999. Oil seepage onshore West Greenland: evidence of multiple source rocks and oil mixing. In: Fleet, A.J., Boldy, S.A.R. (Eds.), Petroleum Geology of Northwest Europe: Proceedings of the 5th Conference. Geological Society, London, pp. 305–314. Bojesen-Koefoed, J.A., Nytoft, H.P., Christiansen, F.G., 2004. Age of oils in West Greenland: was there a Mesozoic seaway between Greenland and Canada? Geol. Surv. Denmark Greenland Bull. 4, 49–52. Bonow, J.M., Japsen, P., Lidmar-Bergstro ¨ m, K., Chalmers, J.A., Pedersen, A.K., 2006. Cenozoic uplift of Nuussuaq and Disko, West Greenland – elevated erosion surfaces as uplift markers of a passive margin. Geomorphology. Bown, J.W., White, R.S., 1995. Effect of finite extension rate on melt generation at rifted continental margins. J. Geophys. Res. 100, 18011–18027. Burden, E.T., Langille, A.B., 1990. Stratigraphy and sedimentology of Cretaceous and Paleocene strata in half-grabens on the southeast coast of Baffin Island, Northwest Territories. Bull. Can. Petrol. Geol. 38, 185–195. Chalmers, J.A., 1991. New evidence on the structure of the Labrador Sea/Greenland continental margin. J. Geol. Soc. Lond. 148, 899–908. Chalmers, J.A., 1997. The continental margin off southern Greenland: along-strike transition from an amagmatic to a volcanic margin. J. Geol. Soc. Lond. 154, 571–576.

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Chalmers, J.A., 2000. Offshore evidence for Neogene uplift in central West Greenland. Glob. Planet. Change 24, 311–318. Chalmers, J.A., Laursen, K.H., 1995. Labrador Sea: the extent of continental and oceanic crust and the timing of the onset of seafloor spreading. Marine Petrol. Geol. 12, 205–217. Chalmers, J.A., Pulvertaft, T.C.R., 1993. The southern West Greenland continental shelf – was petroleum exploration abandoned prematurely? In: Vorren, T.O. et al., (Eds.), Arctic Geology and Petroleum Potential. Norwegian Petroleum Society, Special Publications, 2, Elsevier, Amsterdam, pp. 55–66. Chalmers, J.A., Pulvertaft, T.C.R., 2001. Development of the continental margins of the Labrador Sea: a review. In: Wilson, R.C.L., Whitmarsh, R.B., Taulor, B., Froitzheim, N. (Eds.), Non-volcanic Rifting of Continental Margins: A Comparison of Evidence from Land and Sea, Geological Society (London) Special Publication, 187, pp. 79–107. Chalmers, J.A., Christiansen, F.G., S!nderholm, M., Olsen, J.C., Myklebust, R., Sch!nwandt, H.K., 2001. Geological information base growing on North Atlantic rift basins? Offshore 61, 87–89. Chalmers, J.A., Dahl-Jensen, T., Bate, K.J., Whittaker, R.C., 1995. Geology and petroleum prospectivity of the region offshore southern West Greenland – a summary. Rapport Gr!nlands Geologiske Unders!gelse 165, 13–21. Chalmers, J.A., Pulvertaft, T.C.R., Christiansen, F.G., Larsen, H.C., Laursen, K.H., Ottesen, T.G., 1993. The southern West Greenland continental margin: rifting history, basin development, and petroleum potential. In: Parker, J.R. (Ed.), Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference. Geological Society, London, pp. 915–931. Chalmers, J.A., Pulvertaft, T.C.R., Marcussen, C., Pedersen, A.K., 1999. New insight into structure of the Nuussuaq Basin, central West Greenland. Marine Petrol. Geol. 16, 197–224. Chian, D., Louden, K.E., 1994. The continent-ocean crustal transition across the southwest Greenland margin. J. Geophys. Res. 99, 9117–9135. Chian, D., Keen, C., Reid, I., 1995. Crustal structure of the Labrador Sea conjugate margin and implications for the formation of nonvolcanic continental margins. J. Geophys. Res. 100, 24239–24253. Christiansen, F.G., Bojesen-Koefoed, J.A., Chalmers, J.A., Dalhoff, F., Mathiesen, A., S!nderholm, M., et al., 2001. Petroleum geological activities in West Greenland in 2000. Geol. Greenland Surv. Bull. 189, 24–33. Christiansen, F.G., Bojesen-Koefoed, J.A., Chalmers, J.A., Dalhoff, F., Marcussen, C., Nielsen, T., et al., 2002. Petroleum geological activities in West Greenland in 2001. Geol. Greenland Surv. Bull. 191, 84–89. Clarke, D.B., 1970. Tertiary basalts of Baffin Bay: possible primary magma from the mantle. Contrib. Mineral. Petrol. 25, 203–224. Clarke, D.B., Pedersen, A.K., 1976. Tertiary volcanic province of West Greenland. In: Escher, A., Watt, W.S. (Eds.), Geology of Greenland. Geological Survey of Greenland, Copenhagen, pp. 365–385. Clarke, D.B., Upton, B.G.J., 1971. Tertiary basalts of Baffin Island: field relations and tectonic setting. Can. J. Earth Sci. 8, 248–258. Dalhoff, F., Chalmers, J.A., Gregersen, U., N!hr-Hansen, H., Rasmussen, J.A., Sheldon, E., 2003. Mapping and facies analysis of Paleocene–Mid-Eocene seismic sequences, offshore southern West Greenland Labrador Sea: the extent of continental and oceanic crust and the timing of the onset of seafloor spreading. Marine Petrol. Geol. 20, 935–986. Dam, G., S!nderholm, M., 1994. Lowstand slope channels of the Itilli succession (Maastrichtian–Lower Paleocene), Nuussuaq, West Greenland. Sediment. Geol. 94, 49–71. Dam, G., S!nderholm, M., 1998. Sedimentological evolution of a fault-controlled Early Paleocene incised-valley system, Nuussuaq Basin, West Greenland. In: Shanley, K.W., McCabe, P.J. (Eds.), Relative Role of Eustasy, Climate, and Tectonism in Continental Rocks, Society of Economic Paleontologists and Mineralogists Special Publication, 59, pp. 109–121.

430


Dam, G., Larsen, M., S!nderholm, M., 1998. Sedimentary response to mantle plumes: implications from Paleocene onshore successions, West and East Greenland. Geology 26, 207–210. Dam, G., N!hr-Hansen, H., Pedersen, G.K., S!nderholm, M., 2000. Sedimentary and structural evidence of a new early Campanian rift phase in the Nuussuaq Basin, West Greenland. Cretaceous Res. 21, 127–154. De Paor, D.G., Bradley, D.C., Eisenstadt, G., Phillips, S.M., 1989. The Arctic Eurekan Orogen; a most unusual fold-and-thrust belt. Geol. Surv. Am. Bull. 101, 952–967. Funck, T., Louden, K.E., 1999. Wide-angle seismic transect across the Torngat Orogen, northern Labrador: evidence for a Proterozoic crustal root. J. Geophys. Res. 104 (B4), 7463–7480. Geoffroy, L., Gelard, J.P., Leprievier, C., Olivier, P., 1998. The coastal flexure of Disko (West Greenland), onshore expression of the ‘oblique reflectors.’ J. Geol. Soc. Lond. 155, 463–473. Geoffroy, L., Callot, J.-P., Scaillet, S., Skuce, A., Gelard, J.P., Ravilly, M., et al., 2001. Southeast Baffin volcanic margin and the North American-Greenland plate separation. Tectonics 20, 566–584. Gill, R.C.O., Pedersen, A.K., Larsen, J.G., 1992. Tertiary picrites in West Greenland: melting at the periphery of a plume? In: Storey, B.C., Alabaster, T., Pankhurst, R.J. (Eds.), Magmatism and the Causes of Continental Break-up, Geological Society (London) Special Publication, 68, pp. 335–348. Graham, D.W., Larsen, L.M., Hanan, B.B., Storey, M., Pedersen, A.K., Lupton, J.E., 1998. Helium isotope composition of the early Iceland mantle plume inferred from the Tertiary picrites of West Greenland. Earth Planet. Sci. Lett 160, 241–255. Gradstein, F.M., Agterberg, F.P., Ogg, J.G., Hardenbol, J., Van Veen, P., Thierry, J., et al., 1995. A Triassic, Jurassic and Cretaceous time scale. In: Berggren, W.A., Kent, D.V., Aubry, M.-P., Hardenbol, J. (Eds.), Geochronology, Time Scales and Global Stratigraphic Correlation, Soc. Econ. Paleontol. Mineral. Sp. Pub. 54, pp. 95–126. Hald, N., Larsen, J.G., 1987. Early Tertiary, low-potassium tholeiites from exploration wells on the West Greenland shelf. Geol. Surv. Greenland Rep. 136, 25. Hald, N., Pedersen, A.K., 1975. Lithostratigraphy of the Early Tertiary volcanic rocks of central West Greenland. Gr!nlands Geologiske Unders!gelse Rapport 69, 17–24. Harrison, J.C., Mayr, U., McNeil, D.H., Sweet, A.R., McIntyre, D.J., Eberle, J.J., et al., 1999. Correlation of Cenozoic sequences of the Canadian Arctic region and Greenland; implications for the tectonic history of northern North America. Bull. Can. Petrol. Geol. 47, 223–254. Henderson, G., Schiener, E.J., Risum, J.B., Croxton, C.A., Andersen, B.B., 1981. The West Greenland basin. In: Kerr, J.W., Fergusson, A.J., Machan, L.C. (Eds.), Geology of the North Atlantic Borderlands 7, Can. Soc. Petrol. Geol., Calgary, pp. 399–428. Hinz, K., Schlueter, H.U., Grant, A., Srivastava, S.P., Umpleby, D., Woodside, J., 1979. Geophysical transects of the Labrador Sea; Labrador to Southwest Greenland. In: Keen, C.E. (Ed.), Crustal Properties Across Passive Margins, Tectonophysics, vol. 59. pp. 151–183. Holm, P.M., Gill, R.C.O., Pedersen, A.K., Larsen, J.G., Hald, N., Nielsen, T.F.D., et al., 1993. The Tertiary picrites of West Greenland; contributions from “Icelandic” and other sources. Earth Planet. Sci. Lett. 115, 27–244. Hood, P.J., Bower, M.E., 1973. Low-level aeromagnetic surveys of the continental shelves bordering Baffin Bay and the Labrador Sea. In: Hood, P.J. (Ed.), Earth Science Symposium on Offshore Eastern Canada, Geol. Surv. Can. Paper 71-23, pp. 573–598. Isaacson, E.S., Neff, D.B., 1999. A, B AVO cross-plotting and its application to Greenland and the Barents Sea. In: Fleet, A.J., Boldy, S.A.R. (Eds.), Petroleum Geology of Northwest Europe: Proceedings of the 5th Conference. Geological Society, London, pp. 1289–1298. Jackson, H.R., Reid, I., 1994. Crustal thickness variations between the Greenland and Ellesmere Island margins determined from seismic refraction. Can. J. Earth Sci. 31, 1407–1418. Jackson, H.R., Dickie, K., Marillier, F., 1992. A seismic reflection study of northern Baffin Bay: implication for tectonic evolution. Can. J. Earth Sci. 29, 2353–2369.

431


Jackson, H.R., Keen, C.E., Falconer, R.K.H., Appleton, K.P., 1979. New geophysical evidence for seafloor spreading in central Baffin Bay. Can. J. Earth Sci. 16, 2122–2135. Japsen, P., Green, P.F., Chalmers, J.A., 2005. Separation of Palaeogene and Neogene uplift on Nuussuaq, West Greenland. J. Geol. Soc. Lond. 162, 200–314. Jokat, W., Ritzmann, O., Schmidt-Aursch, M.C., Drachev, S., Gauger, S., Snow, J., 2003. Geophysical evidence for reduced melt production on the Arctic ultraslow Gakkel mid-ocean ridge. Nature 423, 956–961. Keen, C.E., Barrett, D.L., 1972. Seismic refraction studies in Baffin Bay: an example of a developing ocean basin. Geophys. J. R. Astr. Soc. 30, 253–271. Keen, C.E., Courtney, R.C., Dehler, S.A., Williamson, M.-C., 1994a. Decompression melting at rifted margins: comparison of model predictions with the distribution of igneous rocks on the eastern Canadian margin. Earth Planet. Sci. Lett. 121, 403–416. Keen, C.E., Keen, M.J., Ross, D.I., Lack, M., 1974. Baffin Bay: small ocean basin formed by seafloor spreading. Am. Assoc. Petrol. Geol. Bull. 58, 1089–1108. Keen, C.E., Potter, P., Srivastava, S.P., 1994b. Deep seismic reflection data across the conjugate margins of the Labrador Sea. Can. J. Earth Sci. 31, 192–205. Kerr, J.W., 1967. A submerged continental remnant beneath the Labrador Sea. Earth Planet. Sci. Lett. 2, 283–289. King, A.F., McMillan, N.J., 1975. A mid-Mesozoic breccia from the coast of Labrador. Can. J. Earth Sci. 12, 44–51. Klose, G.W., Malterre, E., McMillan, N.J., Zinkan, C.G., 1982. Petroleum exploration offshore southern Baffin Island, northern Labrador Sea, Canada. In: Embry, A.F., Balkwill, H.R. (Eds.), Arctic Geology and Geophysics: Proceedings of the Third international symposium on Arctic geology, Memoir. Canadian Society of Petroleum Geologists, 8, pp. 233–244. Kristoffersen, Y., Talwani, M., 1977. Extinct triple junction south of Greenland and the Tertiary motion of Greenland relative to North America. Geol. Soc. Am. Bull. 88, 1037–1049. Larsen, J.G., Pulvertaft, T.C.R., 2000. The structure of the Cretaceous-Palaeogene sedimentaryvolcanic area of Svartenhuk Halv!, central West Greenland. Geol. Greenland Surv. Bull. 188, 40. þ enclosure. Larsen, L.M., Rex, D.C., Watt, W.S., Guise, P.G., 1999. 40Ar–39Ar dating of alkali basaltic dykes along the south-west coast of Greenland: Cretaceous and Tertiary igneous activity along the eastern margin of the Labrador Sea. Geol. Greenland Surv. Bull. 184, 19–29. Laughton, A.S., Berggren, W.A., et al., 1972. Initial Reports of the Deep Sea Drilling Project, XII, pp. 1243. Laxon, S., McAdoo, D., 1998. Satellites provide new insights into polar geophysics. Eos Transact. Am. Geophys. Union 79 (69), 73. Louden, K., Chian, D., 1999. The deep structure of non-volcanic rifted continental margins. Philos. Trans. R. Soc. Lond. 357, 767–804. Maclean, B., Falconer, R.K.H., Levy, E.M., 1981. Geological, geophysical and chemical evidence for natural seepage of petroleum off the northeast coast of Baffin Island. Bull. Can. Petrol. Geol. 29, 75–93. Marcussen, C., Skaarup, N., Chalmers, J.A., 2002. Structure and hydrocarbon potential of the Nuussuaq Basin: acquisition and interpretation of high-resolution multichannel seismic data, Geological Survey of Denmark and Greenland Report, 2002/33, p. 63. McWhae, J.R.H., Elie, R., Laughton, K.C., Gunther, P.R., 1980. Stratigraphy and petroleum prospects of the Labrador Shelf. Can. Soc. Petrol. Geol. Bull. 28, 460–488. Menzies, A.W., 1982. Crustal history and basin development of Baffin Bay. In: Dawes, P.R., Kerr, J.W. (Eds.), Nares Strait and the drift of Greenland: a conflict in plate tectonics, Meddelelser om Gr!nland, Geoscience, 8, pp. 295–312. Michael, P.J., Langmuir, C.H., Dick, H.J.B., Snow, J.E., Goldstein, S.L., Graham, D.W., et al., 2003. Magmatic and amagmatic seafloor generation at the ultraslow-spreading Gakkel ridge, Arctic Ocean. Nature 423, 956–961.

432


Midtgaard, H.H., 1996. Inner-shelf to lower-shoreface hummocky sandstone bodies with evidence for geostrophic influenced combined flow, Lower Cretaceous, West Greenland. J. Sediment. Res. 66, 343–353. Mutter, J.C., Karson, J.A., 1992. Structural processes at slow-spreading ridges. Science 257, 627–634. Neben, S., Brent, T.A., Harrison, J.C., Tessensohn, F., Jackson, H.R., 2003. New marine reflection data in north Baffin Bay, Kennedy Channel and Hall Basin: subsurface constraints on structure and stratigraphy of the Nares Strait region. International Conference on Arctic Margins, Halifax, Nova Scotia, Abstract Volume, pp. 65–66. N!hr-Hansen, H., 1998. Dinoflagellate cyst stratigraphy of the Upper Cretaceous to Paleogene strata from the Hellefisk-1, Ikermiut-1, Kangaˆmiut-1 and Nukik-1 wells, offshore central West Greenland. Danmarks og Gr!nlands Geologiske Unders!gelse Rapport, 1998/54, p. 58. N!hr-Hansen, H., 2003. Dinoflagellate cyst stratigraphy of the Palaeogene strata from the wells Hellefisk-1, Ikermiut-1, Kangaˆmiut-1, Nukik-1, Nukik-2 and Qulleq-1, offshore West Greenland. Marine Petrol. Geol. 20, 987–1016. ˜ ez-Betelu, L.K., 1993. Rock-Eval/TOC pyrolysis data from the Kanguk Formation (Upper Nuń Cretaceous), Axel Heiberg and Ellesmere Islands, Canadian Arctic. Geol. Surv. Can. Open File 2727, 30. Oakey, G.N., 2005. Cenozoic evolution and lithospheric dynamics of the Baffin Bay – Nares Strait region of Arctic Canada and Greenland. (Ph.D. Thesis), Vrije Universiteit, Amsterdam, p. 233. Pedersen, A.K., 1977a. Iron-bearing and related volcanic rocks in the area between Gieseckes Dal and Hammers Dal, north-west Disko. Rapport Gr!nlands Geologiske Unders!gelse 81, 5–14. Pedersen, A.K., 1977b. Tertiary volcanic geology of the Mellemfjord area, south-west Disko. Rapport Gr!nlands Geologiske Unders!gelse 81, 35–51. Pedersen, A.K., 1977c. Dyke intrusions along the south coast of Disko. Rapport Gr!nlands Geologiske Unders!gelse 81, 57–67. Pedersen, A.K., 1985. Reaction between picritic magma and continental crust: early Tertiary silicic basalts and magnesian andesites from Disko, West Greenland. Bulletin Gr!nlands Geologiske Unders!gelse, 152, 126. Pedersen, A.K., Larsen, L.M., Dueholm, K.S., 1993. Geological section along the south coast of Nuussuaq, central West Greenland. 1:20 000. Coloured geological sheet. Gr!nlands Geologiske Unders!gelse, Copenhagen. Pedersen, A.K., Larsen, L.M., Riisager, P., Dueholm, K.S., 2002. Rates of volcanic deposition, facies changes and movements in a dynamic basin: the Nuussuaq Basin, West Greenland, around the C27n-C26R transition. In: Jolley, D.W., Bell, B.R. (Eds.), The North Atlantic Igneous Province: Stratigraphy, Tectonic, Volcanic and Magmatic Processes, Geological Society (London) Special Publication, 197, pp. 157–181. Pedersen, G.K., Pulvertaft, T.C.R., 1992. The nonmarine Cretaceous of the West Greenland basin, onshore West Greenland. Cretaceous Res. 13, 263–272. Pegrum, R.M., Odegard, T., Bonde, K., Hamann, N.E., 2001. Exploration in the Fylla area, SW Greenland. VNIGRI/AAPG International Conference, St. Petersburg, Russia, Abstracts Volume, 09-2, p. 5. Piasecki, S., 2003. Neogene dinoflagellate cysts from Davis Strait, offshore West Greenland. Marine Petrol. Geol. 20, 1075–1088. ˆ k, Nu ˆ gssuaq, West Pulvertaft, T.C.R., 1979. Lower Cretaceous fluvial-deltaic sediments at Ku Greenland. Bull. Geol. Soc. Denmark 28, 57–72. Pulvertaft, T.C.R., 1989. The geology of Sarqaqdalen, West Greenland, with special reference to the Cretaceous boundary fault system. Gr!nlands Geologiske Unders!gelse Open File Series 89 (5), 36.

433


Ranero, C.R., Banda, E., 1997. The crustal structure of the Canary Basin: accretion processes at slow spreading centers. J. Geophys. Res. 102 (B5), 10185–10201. Rasmussen, J.A., Sheldon, E., 2003. Microfossil biostratigraphy of the Palaeogene succession in the Davis Strait. Offshore West Greenland. Rasmussen, J.A., N!hr-Hansen, H., Sheldon, E., 2003. Palaeoecology and palaeoenvironments of the lower palaeogene succession, offshore West Greenland. Marine Petrol. Geol. 20, 1043–1073. Reid, I., Jackson, H.R., 1997. Crustal structure of northern Baffin Bay: seismic refraction results and tectonic implications. J. Geophys. Res. 102 (B1), 523–542. Rice, P.D., Shade, B.D., 1982. Reflection seismic interpretation and seafloor spreading history of Baffin Bay. In: Embry, A.F., Balkwill, H.R. (Eds.), Arctic Geology and Geophysics, Can. Soc. Petrol. Geol. Memoirs 8, pp. 245–265. Riisager, P., Abrahamsen, N., 1999. Magnetostratigraphy of Paleocene basalts from the Vaigat Formation of West Greenland. Geophys. J. Int. 137, 774–782. Roest, W.R., Srivastava, S.P., 1989. Sea-floor spreading in the Labrador Sea: a new reconstruction. Geology 17, 1000–1003. Rolle, F., 1985. Late Cretaceous – Tertiary sediments offshore central West Greenland: lithostratigraphy, sedimentary evolution, and petroleum potential. Can. J. Earth Sci. 22, 1001–1019. Rosendahl, B.R., 1987. Architecture of continental rifts with special reference to East Africa. Ann. Rev. Earth Planet. Sci. 15, 445–503. Rosenkrantz, A., Pulvertaft, T.C.R., 1969. Cretaceous–Tertiary stratigraphy and tectonics in northern West Greenland. In: Kay, M. (Ed.), North Atlantic – geology and continental drift, Am. Assoc. Petrol. Geol. Memoirs 12, pp. 883–898. Ross, D.I., 1973. Geophysical Studies of Baffin Bay and Adjacent Continental Margins. Geol. Surv. Can. Paper 73–1, pp. 116–117. Ross, D.I., Henderson, G., 1973. New Geophysical Data on the Continental Shelf of Central and Northern West Greenland. Can. J. Earth Sci. 10, 485–497. Sandwell, D.T., Smith, W.H.F., 1992. Global marine gravity field from ERS-1, Geosat and Seasat. Scripps Institute of Oceanography, La Jolla. Sheldon, E., 2003. Palaeogene nannofossil biostratigraphy of the Kangaˆmiut-1 and Nukik2 wells, offshore West Greenland. Marine Petrol. Geol. 20, 1031–1041. Skaarup, N., 2001. Offshore Volcanic Rocks in Baffin Bay (Ph.D. Thesis). University of Copenhagen. Geological Survey of Denmark and Greenland Report, 2001/117. p. 109. þfigures. Skaarup, N., Chalmers, J.A., White, D., 2000. An AVO Study of a Possible New Hydroocarbon Play, Offshore Central West Greenland. Am. Assoc. Petrol. Geol. Bull. 84, 174–182. Skaarup, N., Jackson, H.R., Oakey, G., 2005. A seismic reflection and potential field study of Baffin Bay/Davis Strait, eastern Canada: implications for tectonic evolution. Marine Petrol. Geol. S!nderholm, M., N!hr-Hansen, H., Bojesen-Koefoed, J.A., Dalhoff, F., Rasmussen, J.A., 2003. Regional correlation of Mesozoic-Palaeogene sequences across the Greenland-Canada boundary, Geological Survey of Denmark and Greenland Report, 2003/25, p. 176. Srivastava, S.P., 1978. Evolution of the Labrador sea and its bearing on the early evolution of the North Atlantic. Geophys. J. R. Astr. Soc. 52, 313–357. Srivastava, S.P., 1983. Davis Strait: structures, origin and evolution. In: Bott, M.H.P., Saxov, S., Talwani, M., Thiede, J. (Eds.), Structure and Development of the Greenland–Scotland Ridge: New Methods and Concepts. Plenum Press, New York, pp. 159–189. Srivastava, S.P., Keen, C.E., 1995. A deep seismic reflection profile across the extinct midLabrador Sea spreading center. Tectonics 14, 372–389. Srivastava, S.P., Roest, W.R., 1995. Nature of thin crust across the southwest Greenland margin and its bearing on the location of the ocean-continent boundary. In: Banda, E., Torne´, M., Talwani, M. (Eds.), Rifted Ocean-Continent Boundaries. Kluwer Academic Publishers, pp. 95–120. Srivastava, S.P., Roest, W.R., 1999. Extent of oceanic crust in the Labrador Sea. Marine Petrol. Geol. 16, 65–84.

434


Srivastava, S.P., Falconer, R.K.H., MacLean, B., 1981. Labrador Sea, Davis Strait, Baffin Bay: geology and geophysics – a review. In: Kerr, J.W., Fergusson, A.J. (Eds.), Geology of the North Atlantic Borderlands. Can. Soc. Petrol. Geol. Memoir 7, pp. 333–398. Srivastava, S.P., MacLean, B., Macnab, R.F., Jackson, H.R., 1982. Davis Strait: structure and evolution as obtained from a systematic geophysical survey. In: Embry, A.F., Balkwill, H.R. (Eds.), Arctic Geology and Geophysics. Can. Soc. Petrol. Geol. Memoir 8, pp. 267–278. Srivastava, S.P., Arthur, M.A., Clement, B.M., Aksu, A.E., Baldauf, J.G., Bohrmann, G., et al., 1987. Proceedings of the Ocean Drilling Program; Baffin Bay and Labrador Sea; covering Leg 105 of the cruises of the Drilling Vessel JOIDES Resolution, College Station, Texas p. 1089. Storey, M., Duncan, R.A., Pedersen, A.K., Larsen, L.M., Larsen, H.C., 1998. 40Ar/39Ar geochronology of the West Greenland Tertiary volcanic province. Earth Planet. Sci. Lett. 160, 569–586. Stouge, S., Peel, J.S., 1979. Ordovician conodonts from the Precambrian Shield of southern West Greenland. Rapport Gr!nlands geologiske Unders!gelse 91, 105–109. Torsvik, T.H., Carlos, D., Mosar, J., Cocks, L.R.M., Malme, T., 2002. Global reconstructions and North Atlantic palaeogeography 400 Ma to Recent. In: Eide, E.A. (Ed.), BATLAS – Mid Norway plate reconstructions atlas with global and Atlantic perspectives. Geological Survey of Norway, pp. 18–39. Tucholke, B.E., Fry, V.A., 1985. Basement structure and sediment distribution in Northwest Atlantic Ocean. Am. Assoc. Petrol. Geol. Bull. 69, 2077–2097. Umpleby, D.C., 1979. Geology of the Labrador Shelf. Geol. Surv. Can. Paper 79–13. Ulff-M!ller, F., 1977. Native iron bearing intrusions of the Hammers Dal complex, north-west Disko. Rapport Gr!nlands Geologiske Unders!gelse 81, 15–33. Wheeler, J.O., Hoffman, P.F., Card, K.D., Davidson, A., Sanford, B.V., Okulitch, A.V., Roest, W.R., 1996. Geological Map of Canada. Geological Survey of Canada, Map 1860A, scale 1:5 000 000. Whittaker, R.C., Hamann, N.E., Pulvertaft, T.C.R., 1997. A new frontier province offshore northern West Greenland: structure, basin development and petroleum potential of the Melville Bay area. Am. Assoc. Petrol. Geol. Bull. 81, 979–998. Williamson, M.-C., Villeneuve, M.E., Larsen, L.M., Jackson, H.R., Oakey, G.N., MacLean, B., 2001. Age and petrology of offshore basalts from the Southeast Baffin Island Shelf, Davis Strait, and western Greenland continental margin. Geological Association of Canada/ Mineralogical Association of Canada Joint Annual Meeting, St. John’s, Newfoundland, Canada, p.162. Wilson, R.W., Klint, K.E.S., Jensen, F.K., van Gool, J.A.M., McCaffrey, K.J.W., Holdsworth, R.E., et al. 2008. Faults and fractures in central West Greenland: Nagssugtoqidian influence on Cretaceous-Eocene opening of the Labrador-Baffin Bay Sea. Geol. Surv. Denmark Greenland Bull.

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In this chapter 12.1 Introduction

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12.2 The western Mediterranean sub-basins Valencia trough 443 Balearic Promontory 445 Alboran basin 446 Liguro-Provençal and Algerian basins The Corsica–Sardinia block 451 The Tyrrhenian Sea 453

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12.3 Lithospheric structure from S-wave velocities The method

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