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Geological development of the Northeast Greenland Shelf

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					Geological development of the Northeast Greenland Shelf

                     N. E. HAMANN,1 R. C. WHITTAKER2 and L. STEMMERIK3

                     1
                       Nunaoil A/S, DK-3900 Nuuk, Greenland (Present address: DONG, Agern Alle 24-26, DK-2970 Hørsholm,
                     Denmark; e-mail: NEH@ dong.dk)
                     2
                       Geoarctic Ltd., 600 8th Avenue NW, Calgary, Alberta T2P 3P2, Canada
                     3
                       Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark

                     Abstract: Seismic data from the East Greenland shelf show that the northern part of the shelf, north of 758N, can
                     be subdivided into five, roughly northeast-trending, major tectonic elements. From west to east they are: the
                     Koldewey Platform, the Danmarkshavn Basin, the Danmarkshavn Ridge, the Thetis Basin and the Marginal High.
                     A sixth tectonic element, the Shannon High, has been defined in the southern part of this area. The offshore areas
                     between 728300 N and 758N are dominated by Tertiary plateau basalts, which obscure the acoustic signals from the
                     deeper sedimentary succession. Seismic data from the area north of 758N indicate the presence of a fairly
                     complete succession of ? Devonian to Neogene age, exceeding the recorded interval (8 sec TWT – 13 km) in
                     thickness in the deeper parts of the Danmarkshavn Basin. The succession has been subdivided into 15 seismic
                     mega-sequences. In absence of well control, they have been dated by comparison to the onshore successions of
                     East Greenland and eastern North Greenland, and the offshore successions in the southern Barents Sea and on the
                     mid-Norwegian shelf. The Upper Palaeozoic succession is broadly similar to that of the southern Barents Sea, i.e.
                     marine-dominated, with thick Upper Carboniferous – Lower Permian halite deposits in the northern
                     Danmarkshavn Basin. The Mesozoic succession seems to show greater similarities to the onshore basins of
                     East Greenland: rifting started during the mid-Jurassic and peaked near the Jurassic–Cretaceous boundary. The
                     post-volcanic succession reflects deposition on a passive margin subjected to temporary uplift during the early
                     Miocene and the latest Miocene to earliest Pliocene.

                     Keywords: Northeast Greenland Shelf, tectonic evolution, Carboniferous –Permian, Mesozoic, Cenozoic




The vast shelf areas offshore East Greenland form one of the few                 Greenland.) Marine Seismic (KANUMAS) Project. The KANU-
remaining ‘white spots’ in the geological understanding of the                   MAS Project was initiated in 1991 to allow the first comprehensive
post-Caledonian evolution of the Norwegian – Greenland Sea area.                 seismic reconnaissance survey of the frontier basins offshore
The more than 1200 km long and 200– 600 km wide shelf from                       northern Greenland. The project has been carried out by six major
Scoresby Sund in the south to the continental margin in the north                oil companies (BP, Exxon, Japan National Oil Company, Shell,
forms the conjugate margin to the well known shelf areas west of                 Statoil, Texaco and Nunaoil) with Nunaoil A/S, a joint Green-
Norway (Fig. 1). Also, the onshore areas of East Greenland and                   land – Denmark state-owned company, as operator. Nunaoil
eastern North Greenland are geologically well known, since the                   acquired a total of 6839 km of multichannel seismic data and
sedimentary succession in these areas form classical analogues to                gravity data offshore East Greenland in four surveys between 1991
the Mesozoic rift succession offshore Mid-Norway and the late                    and 1995 (Fig. 1). Due to the pack-ice and icebergs offshore East
                                                       ˚
Palaeozoic succession of the Barents Sea (e.g. Hakansson &                       Greenland the data form a very open grid with line spacing
Stemmerik 1989; Surlyk 1990, 2003; Stemmerik et al. 1993).                       between 50 – 80 km in the area between 728N and 798N. This paper
   The most comprehensive overview of the structure of the East                  is based on the interpretation of these data supplemented with
Greenland shelf is given by Larsen (1990) based on aeromagnetic                  5000 km of seismic data acquired by the Geological Survey of
data, supported by scattered seismic and marine gravity data from                Greenland in 1981 and 1982 (NAD Project) in the area south of
the area south of 748N. The data base for that overview included
                                                                                 728N. The relatively small amount of seismic data provides only a
the first multichannel reflection seismic surveys on the East
                                                                                 very open grid, and gravity data compiled from various sources
                                                    ¨
Greenland shelf in the late 1970s (Hinz & Schluter 1980; Hinz
                                                                                 have proved useful for mapping the trend of major structures in the
et al. 1987), reflection seismic and marine gravity data from the
                                                                                 subsurface. Fourteen seismic horizons have been interpreted, but
North Atlantic D (NAD) Project 1983–1989 (Larsen 1984), and
data from a regional aeromagnetic survey (Larsen & Thorning                      due to lack of deep wells on the Northeast Greenland Shelf only
1980). Thus, at that stage, the understanding of the stratigraphy                one of these has been properly dated based on a tie to ODP Site
and basin structure of the shelf north of 748N was based entirely on             987. All other seismic horizons are tentatively dated using a
aeromagnetic data (Larsen 1990). Since then, additional infor-                   variety of methods: (1) knowledge on the timing of regional
mation has been obtained from reflection seismic data acquired in                 tectonic events and eustatic sea level changes from the onshore
the outer shelf areas between 798 and 808300 N (Hinz et al. 1991).               areas in East Greenland and the Norwegian offshore areas has
   In this paper we describe the major structures of the East                    been used to determine major seismic sequence boundaries;
Greenland Shelf and the discuss the Late Palaeozoic – Neogene                    (2) lithological marker horizons like the top of the Paleocene
evolution based on proprietary regional seismic data acquired as                 volcanics and the top of the salt have been dated based on
part of the Kalaallit Nunaat (The Greenlandic name for                           correlation to East Greenland and the Barents Sea, respectively;

HAMANN , N. E., WHITTAKER , R. C. & STEMMERIK , L. 2005. Geological development of the Northeast Greenland Shelf. In: DORE , A. G. & VINING , B. A. (eds)
                                                                                                                         ´
Petroleum Geology: North-West Europe and Global Perspectives—Proceedings of the 6th Petroleum Geology Conference, 887 –902. q Petroleum Geology
Conferences Ltd. Published by the Geological Society, London.
888                                                          N. E. HAMANN ET AL.




Fig. 1. Simplified geology of North-East Greenland and the broad outline of the offshore areas covered by the KANUMAS project. KANUMAS seismic lines
acquired during the 1991, 1992, 1994 and 1995 surveys are shown in red. Onshore localities mentioned in the text are shown.


and (3) magnetic anomalies have been used to give a maximum                  (Figs 1 and 3). It is only 60 km wide at the southern tip of
age of the overlying sediments (Fig. 2).                                     Liverpool Land (708N) where the glacially deepened Scoresby
                                                                             Sund fjord reaches the shelf edge, and a thick sediment wedge
                                                                             extends over the continental margin to locally widen the shelf.
Study area                                                                      Sea-ice and icebergs in the study area offshore East Greenland
The Northeast Greenland Shelf from 758N and northwards covers                set major limitations on seismic acquisition, and would present an
an area approximately 200 km wide and 600 km long. Water                     even greater challenge to exploration drilling and production. The
depths are generally between 100– 300 m, ranging from less than              entire shelf is ice-covered most of the year by pack-ice carried
20 m over shallow shoals to the west to more than 500 m along the            down from the Arctic Ocean by the East Greenland Polar Current.
shelf edge. The shelf narrows to around 120 km between Traill Ø              The ice starts to melt in the Danmark Strait in April and May, and
and Shannon (72– 758N) and becomes even narrower southwards                  usually the areas around Jameson Land are ice-free in August and
                                                   NE GREENLAND SHELF DEVELOPMENT                                                             889




Fig. 2. The timing of major tectonic events to have affected the North Atlantic region. Also shown the interpreted mega-sequences from the KANUMAS
surveys. Please note the coloured boundaries between the mega-sequences. These are used in the seismic sections in this paper. Chronostratigraphic
scale based on Harland et al. (1989). The relative sea level rise is taken from Vail et al. (1978).


September. Further to the north, iceberg and pack-ice can be                 deepening to 4000– 5000 m north of 788N, where a thick Upper
encountered anywhere on the shelf in all seasons of the year.                Palaeozoic succession seems to be present in the inner part of the
                                                                             shelf (Fig. 4A). The onshore areas to the west, between 76 – 808N,
                                                                             consist mainly of crystalline basement with very scattered outliers
Tectonic elements                                                            of Jurassic and Upper Carboniferous sediments (Stemmerik &
The East Greenland Shelf consists of three broad regions with their          Piasecki 1990; Piasecki et al. 1994). Between 80– 818N, up to
own distinctive geological and tectonic style: (1) the North-East            1000 m of Upper Carboniferous – Permian carbonates, locally
Greenland Shelf; (2) East Greenland volcanic province; and (3) the           underlain by more than 1000 m of Lower Carboniferous
Liverpool Land –Blosville Kyst Shelf (Fig. 3). This subdivision              siliciclastics are exposed on Holm Land and Amdrup Land
corresponds roughly to that of Larsen (1990) and Hinz et al.                 (Stemmerik et al. 2000). The carbonate succession extends
(1993).                                                                      offshore as evidenced by outcrops on the islands of Henrik
                                                                             Krøyer Holme at 808450 N, to cover the northern part of the
                                                                             platform. The onshore succession is dissected by a series of
Northeast Greenland Shelf                                                    WNW-trending faults, which controlled sedimentation during the
The Northeast Greenland Shelf includes the areas north of the                Late Palaeozoic and was re-activated during the Mesozoic
island of Shannon at approximately 758N (Fig. 3). It is more than                              ˚
                                                                             (Stemmerik & Hakansson 1991; Stemmerik et al. 2000). Seismic
400 km long and 150–300 km wide. The southern boundary is here               data indicate that similarly trending structures are prominent in the
defined by the northern margin of thickly developed Tertiary                  northern part of the platform area and most likely related to strike-
volcanics of the East Greenland volcanic province and the northern           slip faulting along the Greenland Fracture Zone.
limit is the present-day shelf break. The Northeast Greenland shelf             The eastern margin of the platform is formed by a series of
is characterized by a number of northeast-trending structural highs          north– south-trending, en echelon faults separating the platform
first inferred from aeromagnetic data (Larsen 1984, 1990). Based              from the deep Danmarkshavn Basin to the east (Fig. 4a). The fault
on the KANUMAS seismic data it is possible to subdivide the                  system seems to have been active from the Late Carboniferous and
shelf into six major tectonic elements, described in detail below            onward, and evidence for late reactivation of faults and minor
(Figs 3 and 4).                                                              inversion is present in the southern part of the platform. This part
                                                                             of the platform is characterized by a stratigraphic punctuated
Koldewey Platform. The Koldewey Platform is a 30 – 70 km                     succession of Upper Jurassic and Lower Cretaceous sediments that
wide structural high stretching from the island of Store Koldewey            overstep basement and/or thin down-faulted remnants of older,
and northwards to at least 808N based on seismic and gravity data            most likely Carboniferous strata. The seismic data indicate a thin
(Fig. 5). It forms the western, landward portion of the shelf and is         succession punctuated by many unconformities just east of Store
characterized by relatively shallow basement depths, generally               Koldewey island, and the studies of the outcrops on the island
between 2000– 3000 m in the southern part of the platform                    confirm this interpretation (e.g. Stemmerik & Piasecki 1990).
890                                                              N. E. HAMANN ET AL.




Fig. 3. Tectonic elements of the East Greenland shelf. The gross outline of the offshore tectonic elements is based on interpretation of the KANUMAS seismic
data. Oceanic magnetic anomalies and the onshore geology are from Escher & Pulvertaft (1995). The main structural elements: The Koldewey Platform,
Danmarkshavn Basin, Danmarkshavn Ridge, Thetis Basin and Marginal High are described in the text, and generalized cross sections of the shelf are shown in
Figure 4. Note the salt basin in the northern axis of the Danmarkshavn Basin.
                                                      NE GREENLAND SHELF DEVELOPMENT                                                                  891




Fig. 4. Geoseismic cross sections of (a) the Northeast Greenland Shelf (north of 758N) and (b) the Jameson Land Basin – Liverpool Land Shelf (c. 718N). The
northern section is based on KANUMAS seismic data and illustrates the very different development of the inner and the outer shelf. Note the similarities
between the Jameson Land Basin and the Danmarkshavn Basin, including huge thicknesses of post-Caledonian sediments and an almost complete stratigraphic
succession. The seismic mega-sequences are described in the text.


Shannon High. The Shannon High is a relatively small feature,                    immediately to the east of Store Koldewey island (Larsen 1990).
only 100 km long and 20 km wide, located between 758N and 768N                   Seismic and gravity data show that basin extends northwards to at
(Fig. 3). The high was first identified onshore Shannon and its                    least 788N and more likely 808N, being at least 400 km long. It
offshore extension was suggested on basis of magnetic data                       widens from less than 50 km in the south to more than 100 km in
(Larsen 1990). The Shannon High is a steep-sided basement horst                  the north (Figs 3 and 5). The Koldewey Platform defines the
delineated by north– south-oriented normal faults that were active               western margin of the basin, and the eastern margin is a series of
during the Mesozoic, and most probably forms a northeastward                     northeast-trending structural highs, collectively referred to as the
extension of the well-described system of rotated fault-blocks at                Danmarkshavn Ridge. The basin is deep, more than 13 km in the
Wollaston Forland (e.g. Surlyk 1978, 2003). The northern limit of                south where the top basement reflector is below the recorded
the high seems to be controlled by a major fault zone that links a               seismic data (8 s TWT) (Fig. 4a). Northwards the basin becomes
transfer zone at the continental margin to a long-lived lineament in             shallower, judging from the limited data set. The basin includes a
the Bessel Fjord area, and is marked by a local Tertiary                         fairly complete sedimentary succession of ?Devonian to Recent
depositional basin.                                                              age. Numerous unconformities along the basin margins indicate
   In the offshore areas north of Shannon, the high is overlain by a             repeated tectonic activity throughout the basin history.
thin succession of Tertiary sediments, whereas Tertiary volcanics                   The central part of the basin is characterized by major salt
are seen to lie directly on basement on Shannon island. It is                    diapirism from 808N southwards to at least 778N (Figs 3 and 10).
therefore likely that the high extends southwards below the                      The salt is limited to the basinal areas and is seen to pass into time
basaltic cover into the East Greenland volcanic province (Fig. 3).               equivalent carbonates deposited on the tectonically more stable
                                                                                 Koldewey Platform. By comparison to the Nordkapp Basin in the
Danmarkshavn Basin. The Danmarkshavn Basin is a large, very                      Norwegian Barents Sea, the salt is inferred to be of Late
deep sedimentary basin, characterized by salt tectonics in the                   Carboniferous – earliest Permian age, and thus age equivalent to
centre (Figs 3 and 4a). It was originally defined as a narrow basin               the lower part of the carbonate succession in North Greenland
892                                                            N. E. HAMANN ET AL.




Fig. 5. Gravity anomaly map (contour interval 10 mgal): Bouguer (land), free air (sea). Processed by the Danish National Survey and Cadastre,
Copenhagen. The names of the main structural elements are superimposed. The main structural elements, especially the Danmarkshavn Basin and the
Shannon High, are clearly seen as gravimetric anomalies.

(e.g. Stemmerik 2000). Transition from carbonate-dominated                   with the main fault escarpment to the east, towards the Thetis
successions, over structural highs and stable platforms, to salt in          Basin (Figs 3,4a). The ridge trends northeast – southwest; it is a
more rapidly subsiding basins has been described from the Late               well defined basement high in the southwest, but north of 778N it
Palaeozoic of both the southern Barents Sea and the Sverdrup Basin           becomes a less well defined platform area. Gravity and magnetic
of Arctic Canada (e.g. Larssen et al. 2002), and by analogy the              data indicate that the ridge continues north of the seismic coverage
Danmarkshavn Basin is likely to represent the late Palaeozoic rift           to 788N and southwards beneath the Tertiary basalts for at least
axis between Norway and Greenland (e.g. Gudlaugsson et al. 1998).            80 km (Figs 3 and 5). The eastern, faulted boundary has in places a
   In the northern part of the basin many salt diapirs have penetrated       heave of over 10 km at basement level with a throw of more than
nearly to the seafloor, possibly reflecting increased Cenozoic uplift          7000 m. The faulting represents a major amount of extension
of this part of the shelf as also indicated by a general thinning of the     during several tectonic episodes but most intensely during the
Tertiary sedimentary succession in this direction (Figs 4a and 10).          latest Jurassic – earliest Cretaceous and in the Early Tertiary.
Faulting has controlled salt tectonism along the basin axis,                 Footwall uplift and erosion is estimated to have removed at least
producing NNE-trending salt walls. The salt movements took                   2000– 3000 m of Upper Palaeozoic and Mesozoic sediments from
place during several distinct phases, which correlate to tectonic            the top of the ridge, and Tertiary sediments overlie unconformably
events or pulses affecting the evolution of the basin (Fig. 2). Broad        older sediments (Figs 4a and 7). The depth to basement on the
anticlines along the margins in the Danmarkshavn Basin are related           ridge varies considerably along-strike; it is generally shallow in the
to Tertiary structural inversion, with a component of salt tectonism.        south and increases northwards and westwards where up to 4000 m
A seismic line acquired by BGR in 1988 at 798 300 N clearly shows            of Mesozoic and older sediments are preserved.
one of these broad anticlines (Hinz et al. 1991).
   Tertiary sills and basalts become increasingly common south of
                                                                             Thetis Basin. The Thetis Basin, situated east of the
778N and their cross-cutting relationship make interpretation more
                                                                             Danmarkshavn Ridge, is a relatively young basin probably
difficult in this area. The southern limit of the Danmarkshavn
                                                                             dominated by a thick Cretaceous and Tertiary succession (Figs 3
Basin is therefore obscured by thick Tertiary volcanics (Fig. 3).
                                                                             and 4a). The basin trends NNE, roughly parallel with the
                                                                             continental margin, and is approximately 200 km long and up to
Danmarkshavn Ridge. The Danmarkshavn Ridge consists of a                     60 km wide from 758300 N to 788N. To the east it is limited by the
series of westerly dipping tilted fault blocks, 10 – 60 km wide,             Marginal High. The presence of this deep ‘Cretaceous’ basin,
which form a platform area to the east of the Danmarkshavn Basin             equivalent to the Cretaceous Vøring Basin off Norway, on the
                                                    NE GREENLAND SHELF DEVELOPMENT                                                       893

outer part of the Northeast Greenland Shelf, was first predicted by        1991, 1993; Seidler et al. 2004). Later, Mesozoic rift phases are
Hinz et al. (1993) based on the BGR seismic profiles and                   mostly known from the northern part of the region, north of Kong
aeromagnetic data.                                                        Oscar Fjord (728N) (e.g. Surlyk 1978, 1990; Surlyk & Noe-
  The Cretaceous forms the acoustic basement in the basin but             Nygaard 2001); Devonian sediments are also best known from
comparison of mapped depths to the base of the Cretaceous with            this area. The thickness of the Devonian –Jurassic succession is
depths to magnetic basement in Haimilia et al. (1990), suggests           estimated to exceed 17 km (9 km Devonian) in the Jameson Land
that there is an older sedimentary succession beneath the                 basin in the south, thinning northwards. North of Kong Oscar
Cretaceous. The presence of this deep basin has been confirmed             Fjord, the cumulative thickness of the Devonian – Cretaceous
by gravity modelling (unpublished KANUMAS data).                          sediments is 14 – 15 km (8 km Devonian) but nowhere is the entire
                                                                          succession preserved. The thickness of the Jameson Land
Marginal High. A marginal high relief area forms the edge of the          succession is thus comparable to that of the Danmarkshavn
continental shelf in Northeast Greenland (Fig. 3). It is only crossed     Basin where the thickness of the sedimentary succession exceeds
by KANUMAS lines in the southern part and is not illustrated in           the recorded interval (8 seconds TWT – approximately 13 km)
this paper. The top of the volcanic succession forms a strong, high-      (Figs 4a, 4b and 7). However, the depositional successions in the
amplitude reflector, which obscures any acoustic signal from the           two basins are not directly comparable since thick salt deposits,
deeper part. The top of the basalts is subaerially eroded, suggesting     like those seen in the Danmarkshavn Basin, are not present in the
that the top of the high was above sea level during the Palaeogene,       Jameson Land basin.
finally being covered by a Neogene sedimentary wedge during                   The onshore areas between 75 – 778N have a fragmentary record
post-rift thermal subsidence. The eastern margin of the high is           of Jurassic and Cretaceous sediments, and between 77 – 808N, post-
characterized by seaward-dipping reflectors and pseudo-                    Caledonian sediments are only known from small, isolated
escarpments, and a single submarine volcano. The Marginal                 outcrops. North of 808N, along the east coast of Greenland,
High can be compared to the high-relief Vøring Plateau on the             onshore basins started to form during the Early Carboniferous and
Norwegian margin (Eldholm et al. 1990), which would suggest               subsidence continued into the Triassic. Following a prolonged
that it owes its origin to the extrusion of Tertiary basalts during the   uplift, deposition resumed during the late Jurassic; Mesozoic
opening of the Atlantic in the Early Eocene.                              deposition occurred in localized pull-apart basins related to stike-
                                                                                                                                 ˚
                                                                          slip movements in the Harder Fjord Fault Zone (Hakansson &
                                                                          Stemmerik 1989). The onshore geology thus indicates significant
East Greenland volcanic province                                          changes in both structural style, depositional evolution and uplift
The East Greenland volcanic province is defined as the offshore            history of the exposed basins from south to north (Fig. 8).
area from approximately 728300 N to 758N dominated by Tertiary            Stratigraphic and lithological data therefore have to be evaluated
plateau basalts (Fig. 3). The southern limit of the volcanic rocks is     carefully before being applied to the offshore areas, and evidently
close to the Jan Mayen Fracture Zone and the northern limit is            many of the offshore basins have no onshore counterpart. The
close to the Bivrost Fracture Zone. In the offshore areas, volcanic       stratigraphy and evolution of these offshore basins are more
rocks obscure any acoustic signal from the deeper parts of the            similar to the deep basins at the western margin of the Norwegian
basin; the volcanic rocks extend westwards and form the top of the        shelf.
outcrops between 73 – 758N. In this part of East Greenland, deep             Interpretation of the proprietary data set allows 15 seismic
Early Carboniferous – Cretaceous, N – S rift basins occur below the       megasequences, of proposed Devonian to Pleistocene age, to be
volcanic rocks (e.g. Surlyk 1978, 1990; Stemmerik et al. 1991,            identified on the Northeast Greenland Shelf (Fig. 6). They will not
1993), and it is therefore likely that similar age rift basins occur in   be described in detail in this overview paper where focus rather
the offshore areas beneath the thick basalt succession.                   will be on the gross stratigraphic development of the offshore
                                                                          basins.

Liverpool Land –Blosville Kyst Shelf
                                                                          Devonian –mid-Carboniferous
The region south of the Jan Mayen Fracture Zone (Fig. 3) has a
markedly different structural style to the areas to the north. It is      The oldest part of the offshore succession is included in Mega-
characterized by few but large faults blocks, rather than the much        sequences DCI and DCII, most likely of Devonian – mid-
narrower fault spacing to the north in the East Greenland Basin.          Carboniferous age (Fig. 2). The succession is believed to rest
The amount of extension, however, appears to be similar in the two        on basement, but seismic resolution of this part of the succession
areas. Further to the south, the offshore area is divided into the        is poor. The clearest evidence for the presence of Devonian –
Liverpool Land Shelf and the Blosville Kyst Shelf (Larsen 1990).          mid-Carboniferous deposits is on the northern part of the
Tertiary plateau basalts cover a large proportion of these areas, and     Danmarkshavn Ridge, where these strata are relatively shallow.
at the outer part of the shelf oceanic crust occurs beneath a thick       It has not been possible to map the distribution and thickness
Tertiary wedge. In this area, the location of the ocean – continent       variations of the succession. The Devonian– mid-Carboniferous
transition zone is marked by a series of pseudo-escarpments and           succession is characterized by chaotic and wedge shaped reflec-
seaward-dipping reflectors (Larsen 1990).                                  tion patterns.
                                                                             The seismic character indicates large lateral variations in the
                                                                          rate of deposition, which is characteristic for non-marine high-
                                                                          energy environments and deposition in half-grabens, and mega-
Geological Development
                                                                          sequences DCI and DCII are suggested to represent an offshore
Onshore East Greenland, the post-Caledonian basins started to             equivalent to the Devonian and Lower Carboniferous non-marine
subside during the mid-Devonian, and a stratigraphically almost           sediments onshore East Greenland (Figs 6 and 8) (Olsen 1993;
complete succession of mid-Devonian to Cretaceous sediments is            Vigran et al. 1999). In the onshore area, deposition took place in a
preserved between Scoresby Sund and Kuhn Ø (70 – 758N)                    N– S-trending series of basins from Jameson Land in the south to
(Fig. 6). Deposition took place during a prolonged period of              Hudson Land in the north (71– 748300 N). There is no evidence
rifting, which started near the Devonian – Carboniferous boundary         of Devonian and Carboniferous basins north of 748300 N in
and continued into the Cretaceous. Initial, Early and Late                East Greenland, and possibly the locus of subsidence was
Carboniferous, and latest Permian – Early Triassic rifting occurred       shifted to the offshore Danmarkshavn Basin along a linieament
along almost the entire length of the outcrop area from Jameson           conjugate to the Bivrost Fracture Zone/Lineament off Norway
Land in the south to Clavering Ø in the north (e.g. Stemmerik et al.      (Tsikalas et al. 2002).
894                                                                N. E. HAMANN ET AL.




Fig. 6. Correlation of major lithological units in the onshore sedimentary basin in eastern Greenland from 708N to 818N. For location of the basins see Figure 1.
Note the very different development of the Upper Carboniferous–Lower Permian succession between the Wandel Sea Basin in the north and the Jameson
Land Basin in the south and the stratigraphically more punctuated Mesozoic succession in the East Greenland basin. Chronostratigraphic scale based on
Harland et al. (1989).



Late Carboniferous – Early Permian                                                  Barents Sea and on Svalbard (e.g. Steel & Worsley 1984; Larssen
                                                                                    et al. 2002). By analogy to the onshore areas, mega-sequence CPI
Sediments of Late Carboniferous – Early Permian age have been                       is most likely composed of non-marine to marginal marine
interpreted on the Koldewey Platform, the Danmarkshavn Ridge                        sediments (Fig. 8). The high-amplitude, relatively high-continuity
and in Danmarkshavn Basin (see Figs 7, 8 and 9). On the west                        reflectors of mega-sequence CPII are interpreted as interbedded
flank of Danmarkhavn Ridge, the succession reaches a thickness of                    carbonates and evaporites of Late Carboniferous – Early Permian
2 seconds (TWT; approximately 5000 m) (Figs 4a and 7); it thins                     age (Figs 8 and 9). They reflect deposition on shallow-water
rapidly away from the central part of the basin. The seismic                        platforms along the margins of the Danmarkshavn Basin. The
resolution of this part of the section is generally poor. It has only               lateral transition between the platform facies and the time-
been possible to analyse it in some details close to the Koldewey                   equivalent basinal halite deposits in the northern Danmarkshavn
Platform and in shallowest part of the Danmarkshavn Ridge, where                    Basin is not clearly defined in the seismic data, but the outline of
it is possible to identify two mega-sequences, CPI and CPII (Figs 7                 the salt basin roughly corresponds to the area of active salt
and 8). In these areas, mega-sequence CPI is characterized by                       movement (Fig. 3).
variable amplitude, low-continuity reflectors, with rapid variation                     The seismic facies analysis of the CPII mega-sequence thus
in thickness, and CPII forms a relatively continuous package of                     indicates that the marine Late Carboniferous – mid-Permian
high-amplitude reflectors with little variation in thickness (Fig. 7).               depositional system known from the Barents Sea, Svalbard and
The mobilized salt in the central parts of the northern                             North Greenland continued southward to include the northern parts
Danmarkshavn Basin (Figs 3 and 10) is believed to be the basinal                    of the East Greenland Shelf (Stemmerik 2000).
correlative of CPII (Figs 8 and 9).
    The change in seismic facies from wedge-shaped basin fill (CPI)
to a relatively continuous, high-amplitude package of uniform                       Mid-Permian –Triassic
thickness (CPII) probably represents a transition from syn-rift                     The mid-Permian – Triassic succession is included in two
sedimentation to deposition in a thermally subsiding basin. A                       mega-sequences, PTI and PTII, both present on the Koldewey
similar change in depositional style is widely recognized in the                    Platform, the Danmarkshavn Ridge and in the Danmarkshavn
                                                     NE GREENLAND SHELF DEVELOPMENT                                                                 895




Fig. 7. A W–E striking seismic section across the southern part Danmarkhavn Ridge and Thetis Basin. The colour code for the seismic horizons is explained
in Figure 2, and the seismic mega -sequences are described in the text.



Basin (Figs 4a, 7 and 8). It is 700– 800 ms (TWT) thick and the                 Danmarkshavn Ridge, the mega-sequence onlaps the underlying
basal reflector marks locally an angular unconformity with erosion               succession in a similar fashion as seen on the Loppa High in the
of the underlying sediments (not present in Figs 7 and 9). A similar            western Norwegian Barents Sea (e.g. van Veen et al. 1993).
prominent unconformity is observed on the BGR seismic data on                   Throughout the region, the siliciclastic Upper Permian and Lower
the northernmost part of the shelf, where the base of a unit roughly            Triassic successions consist of deep marine shales, locally with
corresponding to mega-sequence PTI is seen to onlap the                         source potential, and shallow to deep marine sandstones and
underlying Carboniferous– Lower Permian sequence (Hinz et al.                   conglomerates (e.g. van Veen et al. 1993; Kreiner-Møller &
1991). The basal unconformity most likely correlates to an                      Stemmerik 2001; Bugge et al. 2002; Seidler et al. 2004). During
unconformity at the base of the upper Artinskian succession in                  the mid-Triassic, sedimentation in the Jameson Land basin shifted
North Greenland and on Spitsbergen, and the mid-Permian                         to dominantly continental mode, while the Middle and Upper
unconformity in East Greenland (e.g. Surlyk et al. 1986;                        Triassic succession is fully marine in the southwestern Barents
Stemmerik 2000) (Fig. 6). It apparently represents marginal uplift,             Sea. It is therefore most likely that the Triassic succession consists
since continuous sedimentation is known from the deep offshore                  of marine shales and sandstones (Fig. 8).
basins in the Barents Sea.
    The lower, PTI mega-sequence is characterized by low-angle
listric faults, which have broken the bedding into a series of small            Jurassic
fault blocks by quite brittle deformation and sole out in an                    The Jurassic succession in the shelf areas has been divided into
evaporite layers near the base of the section (Fig. 9). The listric             three seismic mega-sequences, JI, JII and JIII, roughly correspond-
faults are interpreted to be early, as the sequences above are                  ing to the Lower, Middle and Upper Jurassic (Figs 7 and 8). All
undisturbed. Faulting is probably related to dissolution of                     three mega-sequences are known from the Koldewey Platform, the
evaporites, possibly thin gypsum or halite layers at the base of                Danmarkshavn Ridge and the Danmarkshavn Basin (see Figs 4a, 7
sequence, during prolonged subaerial exposure at or near the                    and 10). Jurassic deposits could also be present int the deeper parts
Permian –Triassic boundary. The seismic character of mega-                      of the Thetis Basin (Fig. 4a). The lower JI mega-sequence is
sequence PTI, including the distinctive, small-scale faulting is                200– 300 ms (TWT) thick in most of the region but locally
remarkably similar to that of the Permian seismic sequence                      thickens in the northern part of the Danmarkshavn Basin where
onshore Jameson Land (Fig. 9), and provides a stratigraphic tie                 deposition took place in rim-synclines around growing salt pillows
between the two basins. The top of the unit reflects a marked shift              (Fig. 10). The base of Megasequence JI is a low-angle
in seismic character from a succession characterized by high-                   unconformity marked by a strong, high-amplitude reflector along
amplitude reflections to an overlying, well-bedded section                       the margins of the Danmarkshavn Basin (Fig. 7). Erosional
characterized by lower-amplitude reflections (Fig. 9). There is                  truncation related to minor footwall uplift of the major fault blocks
little evidence for erosional truncation at the surface, but it is              is seen along the basin margin. Mega-sequence JI is generally
interpreted to mark a major change in lithology from carbonates                 parallel-bedded and characterised by interbedded, high and low-
and chert to sandstones and shales comparable to that described                 amplitude intervals with very high continuity. A minor angularity
from the onshore areas (e.g. Surlyk et al. 1986; Stemmerik 2000).               divides a lower interval dominated by relatively high-amplitude
A similar transition is described from the Finnmark Platform in the             reflectors from an upper interval with a much lower amplitude and
Norwegian Barents Sea, where it is shown to be diachronous                      less reflection on the seismic data (Fig. 7).
(Samuelsberg et al. 2003).                                                         The high-amplitude reflectors at the base of the mega-sequence
    The overlying mega-sequence PTII is characterized by parallel-              JI suggest that it consists either of a shale-prone section or that coal
bedded internal reflectors (Figs 7 and 9). It is relatively thin in the          or evaporite layers are present (Fig. 7). The seismic character
westernmost offshore part of the Koldewey Platform, indicating                  favours correlation with the lacustrine Kap Stewart Formation of
either condensation or punctuated deposition in this area. On the                                                                    ˚
                                                                                Jameson Land (Fig. 6) or the marginal marineAre Formation of
896                                                           N. E. HAMANN ET AL.




Fig. 8. Chronostratigraphic cross section of the Northeast Greenland Shelf based on interpretation of KANUMAS seismic data. The lithology is
based on a combination of seismic facies analysis and comparison to onshore geology. Comparison to Figure 6 shows that the Upper Carboniferous–
Permian succession is broadly similar to that of the Wandel Sea Basin in eastern North Greenland, whereas the Mesozoic succession has more in
common with that of the East Greenland and Jameson Land basins.


offshore mid-Norway. The upper, low-amplitude and less                          The Upper Jurassic mega-sequence JIII forms a very high-
reflective part of the mega-sequence can be correlated to the                 amplitude interval, particularly where it is thin over intrabasinal
shallow marine, sand-prone Neill Klinter Group of Jameson Land               highs. The thinning is gradual by convergence around the margins
(Fig. 6) and the Tilje, Ile, Ror and Not formations of offshore mid-         of the Danmarkshavn Basin and across the smaller fault blocks and
Norway (e.g. Dam & Surlyk 1995).                                             salt features, suggesting condensation of the sequence rather than
   The overlying mega-sequence JII shows highly variable                     onlap (see Fig. 10). JIII also thins towards the western part of
thickness across the shelf and is missing over large areas along             Koldewey Platform; there the thinning is accompanied by a change
the margins of the Danmarkshavn Basin due to regional uplift and             in amplitude from high to low. The thickness variations suggest
erosion (Figs 7 and 8). The internal reflectors are generally low-            that the tectonic activity continued into the Late Jurassic. In the
amplitude, homogeneous with wavy discontinuous bedding, and                  northern Danmarkshavn Basin deposition took place in rim-
the lack of distinct reflectors at the base of the mega-sequence              synclines (Fig. 10). The high-amplitude sections of mega-
suggests a seismically homogeneous section across the boundary               sequence JIII are believed to represent the offshore continuation
(Figs 7 and 10). The thickness variations across the Danmarkshavn            of the Upper Jurassic oil-prone shales described from the onshore
Basin and the associated basin margin uplift suggest deposition in           basins in East Greenland (see Surlyk 2003). The amplitude shift at
tectonically active setting. The base of the succession marks the            the western Koldewey Platform suggests a change in facies from
onset of mid-Jurassic rifting and can be correlated to the base of           oil-prone shales to a more coarse-grained proximal section. A
the Pelion Formation in East Greenland (Surlyk 2003). The                    likely equivalent to this succession is exposed further to the west
succession is believed to be sand-prone, sourced from uplifted               on the island of Store Koldewey (southern Koldewey Platform)
fault blocks along the basin margins, and this mega-sequence, by             from where Stemmerik & Piasecki (1990) reported approximately
analogy to the Norwegian Shelf, is regarded as the primary                   60 m of marine medium- to fine-grained sandstones of Oxfordian–
reservoir target on the Northeast Greenland Shelf.                           Kimmeridgian age to rest directly on basement.
                                                       NE GREENLAND SHELF DEVELOPMENT                                                                   897




Fig. 9. Seismic section across the northern part of the Danmarkhavn Basin. The colour code for the seismic horizons is explained in Figure 2, and the seismic
mega-sequences are described in the text.



Latest Jurassic – Early Cretaceous                                                reflector, which oversteps the Danmarkshavn Ridge from the west.
                                                                                  The uppermost part of the succession oversteps the underlying
Uppermost Jurassic– Lower Cretaceous deposits are present over
                                                                                  units with a marked onlap onto the Danmarkshavn Ridge (Fig. 4a)
most of the northern shelf except for the eastern part of the
                                                                                  and more localized, erosional truncated intra-basinal highs, above
Danmarkshavn Ridge (Figs 4, 8 and 10). The Uppermost Jurassic–
                                                                                  salt pillows (Fig. 9).
Lower Cretaceous deposits are probably also present in the Thetis
                                                                                     Onshore East Greenland two different tectonic styles are
Basin (Fig. 4a). The basal boundary is marked by one of the
                                                                                  recognized to the north and south of the Kong Oscar Fjord– Jan
highest amplitude and regionally most extensive horizons on the
Northeast Greenland Shelf (see Figs 9 and 10). It marks an angular                Mayen Fracture Zone (728N). The northern area was broken up
unconformity over the Danmarkshavn Ridge and shows a                              into tilted fault blocks, which became progressively fragmented
characteristic low-angle erosional truncation of the underlying                   and narrower with time (e.g. Surlyk 1978, 2003). The Jameson
high-amplitude reflectors. The unconformity cuts deeper into the                   Land area to the south underwent only mild tilting, but enormous
section southeast of the Danmarkshavn Ridge and on the eastern                    quantities of coarse sand of the Raukelv Formation were shed into
flank of the Danmarkshavn Ridge it is overstepped by a later                       the basin during this period (Surlyk & Noe-Nygaard 1991; Surlyk
angular unconformity (Figs 4a and 7). The KI mega-sequence                        2003). Coarse-grained Hauterivian –earliest Albian sediments are
generally onlaps the reflector along the margins of the basin and                  known from an isolated structural high at Hold with Hope (748N)
over intra-basinal highs. The thickness variations show that                      (Kelly et al. 1998; Larsen et al. 2001). They pass laterally into a
accumulation took place in a number of major half-grabens.                        shale-dominated succession of Early Aptian– Early Albian age,
Major NNE– SSW-oriented faults along the flanks of the Shannon                     which eventually drowned the high. The succession is separated
High, Koldewey Platform and the Danmarkshavn Ridge controlled                     from the overlying mid-Albian –Turonian shales by an angular
deposition. In the northern part of the Danmarkshavn Basin, the                   unconformity, possibly reflecting a minor tectonic event during the
tectonic activity triggered major salt movements and a number of                  early Albian. The mid-Albian – Cenomanian succession has a
smaller fault blocks developed.                                                   highly diachronous base reflecting a continued onlap on the
   The seismic resolution is generally good in this interval,                     inherited Lower Cretaceous rift topography during overall sea-
particularly in the Danmarkshavn Basin and along the Danmark-                     level rise (Nøhr-Hansen 1993; Whitham et al. 1999).
shavn Ridge. The basal part of the succession is restricted to the                   The unconformity at the base of mega-sequence KI can
Danmarkshavn Basin and the flanks of the Danmarkshavn Ridge.                       be correlated to the mid-Volgian unconformity at the base
The base of an overlying sequence is marked by a high-amplitude                   of the Wollaston Forland Group onshore East Greenland
898                                                                N. E. HAMANN ET AL.




Fig. 10. Comparison of seismic character between the Jurassic and older succession in the Jameson Land Basin, and the offshore Danmarkshavn Basin,
East Greenland. The onshore seismic picks are well constrained by ties to surface outcrop and they correlate remarkably well with the offshore area, suggesting
that the areas have a very similar geological history. Note the distinctive small-scale listric faulting in the Permian carbonates in both sections, and that
the thickness of the Triassic to Jurassic succession is similar in both areas. The colour code for the seismic horizons is explained in Figure 2, and the seismic
mega-sequences are described in the text.


(see Surlyk 1978, 2003), and represents culmination of rifting                         Upper Cretaceous sediments are widespread on the northern
(Figs 2 and 3). The divergent bedding and the thickness variations                  shelf, except at the Danmarkshavn Ridge (see Figs 4, 7, 8 and 11).
suggest that the lower part of the mega-sequence is composed of                     The base of the succession is defined by a high-amplitude reflector
syn-rift deposits comparable to those described from the Wollaston                  with high continuity. There is little evidence for erosional
Forland Group by Surlyk (1978). The overlying seismically                           truncation beneath the reflector, but there is well-developed
homogeneous succession is believed to represent shale-dominated                     onlap or baselap just above, particularly along the margins of the
units, most likely of Hauterivian – early Albian and mid-Albian –                   Danmarkshavn Basin and around salt domes in the northern part of
Cenomanian age (Fig. 8). The uppermost Jurassic – Lower                             the basin. The transition from the underlying succession appears to
Cretaceous succession thus records deposition during decreasing                     be conformable in the centre of the basin (Fig. 10). In the southern
tectonic activity from onset of rifting in the latest Jurassic, very                part of the Danmarkshavn Basin the unit has been preferentially
similar to the events recorded onshore East Greenland and offshore                  intruded by Tertiary sills (Figs 4a and 11). The Upper Cretaceous
Norway. Deposition in the Danmarkshavn Basin was controlled by                      mega-sequence KII is slightly asymmetric in the Danmarkshavn
a few major faults similar to those at the margins of the Jameson                   Basin, being thickest in the west. It thins rapidly westwards on the
Land Basin (Fig. 4), in contrast to the large number of smaller-
                                                                                    Koldewey Platform due to erosional truncation of the top during a
scale faults described in the northern part of onshore East
                                                                                    later, Cenozoic uplift (Fig. 4a). The mega-sequence is absent over
Greenland.
                                                                                    most of the Danmarkshavn Ridge, apparently largely due to
                                                                                    depositional thinning towards the western margin of the ridge (Fig.
Late Cretaceous                                                                     4a). Parts of, or the whole, mega-sequence are also missing over
                                                                                    several of the large salt structures on the northern part of the shelf
During the Santonian, strike-slip faulting continued along the
                                                                                    (Fig. 10). In the Thetis Basin sedimentation was controlled by a
northern margin of Greenland whereas rifting and subsidence
                                                                                    major fault zone composed of several probably listric faults along
dominated in the areas to the south, until Maastrichian, where
domal uplift related to the development of a hot spot mantle plume                  the western margin of the basin (Fig. 7), and the KII mega-
started in the south. In East Greenland deposition is dominated by                  sequence thins towards the Marginal High and eastern part of the
offshore mudstones; turbidites of ?Middle Coniacian and Santo-                      Thetis Basin (Fig. 4a).
nian age most likely record minor rift events (Kelly et al. 1998;                      The KII mega-sequence has been divided into three seismic
Surlyk & Noe-Nygaard 2001). The Late Cretaceous to the end of                       sequences, KIIa– KIIc in the Danmarkshavn Basin (not described
the Paleocene marked a period of major uplift and erosion of the                    in detail in this paper). The KIIa sequence, the lower part of mega-
Greenland craton, west of the sedimentary basins. Deep marine                       sequence KII, is seismically opaque and probably represents shales
sandstones of the Lysing Formation, offshore Norway, seem to                        of Turonian–Coniacian age. The basal part may represent the
have been sourced from East Greenland (Morton & Grant 1998).                        Turonian transgression, known from most of the North Atlantic
                                                       NE GREENLAND SHELF DEVELOPMENT                                                                     899




Fig. 11 Paleocene deltaic sequence s in the southern part of the Danmarkshavn Basin, represented by prograding wedges. The delta is comparable in
thickness to the Paleocene delta of the UK sector of the North Sea, although less extensive. The colour code for the seismic horizons is explained in Figure 2,
and the seismic mega-sequences are described in the text.



Region. It is followed by an interval of Santonian–Maastrichtian age                  The Paleocene mega-sequence TI has been subdivided into four
characterized by fairly continuous reflectors with relatively high                  sequences of which the lower three form prograding wedges of
amplitude (KIIb and KIIc), which are interpreted as evidence for a                 Paleocene deposits and the last, TId, represents the plateau basalts.
more variable lithology of interbedded sandstone and shale. The                    The internal reflection pattern can best be observed in the southern
Danmarkshavn Ridge appears to have acted as a local sediment                       part of the Danmarkshavn Basin where most of the mega-sequence
source area at this time, indicating a considerable amount of footwall             has been preserved (see Fig. 11). In this area, up to 500 m of
uplift and erosion of the underlying section (Figs 4a and 7). In the               sediments are recorded. Sequences TIa– TIc consist of prograding,
northern part of the Danmarkshavn Basin, the tectonic pulse                        sigmoidal reflectors with classic offlap of the topset beds, and
triggered salt diapirism and the rim-synclines filled rapidly with                  downlap of the bottomset beds (see Tsikalas et al. 2004). The
sediments as the salt structures collapsed over what had previously                succession generally progrades from the western margin of the
been pillow or domal features. The sediments were sourced locally,                 Koldewey Platform and eastwards to form a depositional wedge in
probably from the eroded crests of salt structures. The overlying                  the Danmarkshavn Basin (Fig. 11). In the Thetis Basin the interval
Maastrichtian–Danian succession is of relatively uniform thickness                 has a homogeneous internal character and is generally reflection
and appears to be shale-prone (Fig. 8).                                            free, suggesting a much lower energy, shale-dominated section
                                                                                   (Figs 7 and 11). The Danmarkshavn Ridge apparently formed an
                                                                                   intrabasinal high at this time and acted as a barrier to siliciclastic
Paleocene                                                                          input into the outer basin. In areas south of Shannon island where
Onshore Greenland the Early Tertiary was mainly a period of                        thick basalt successions are present, only intra-volcanic reflectors
extension in the southern part of the region (East Greenland),                     are seen, and it is not possible to detect the base of the volcanics.
where the base is marked by an unconformity. In the northern                       Outside the volcanic area, mainly north of Shannon island, the
parts, in the Wandel Sea Basin area, the stress-regime changed                     lateral equivalent to the base of the lavas appears to be
from extension to a period of compression along the major dextral                  conformable with the underlying succession.
strike-slip fault zone (Fig. 2). This compressional phase is believed
to have occurred close to the Cretaceous – Tertiary boundary
   ˚
                                                                                   Post-volcanics (Eocene –Quaternary)
(Hakansson & Stemmerik 1989). In East Greenland, the volcanics
are often underlain by fluvial conglomerates and there is evidence                  Magnetic data have shown that the opening of the northern part of
of a marked Danian uplift of the onshore areas (e.g. Larsen et al.                 the North Atlantic Ocean was initiated in the Early Eocene (Fig.
1999). The Early Tertiary volcanics were extruded during three                     2). Subsequent tectonism in the area is generally considered to be
discrete events (Tegner et al. 1998). The main volcanic phase is                   related to the two-stage opening of the ocean. The first stage
the Blosseville – Scoresby Sund plateau basalts (55– 56 Ma), which                 involved the separation of Norway from the eastern margin of the
correlates to the time of continental break-up. Lavas of this age are              Jan Mayen Ridge micro-continent, which was at that time attached
known from 648N to Shannon Ø (Shannon Island) at 758N, a                           to Greenland south of the Jan Mayen Fracture Zone (Larsen 1990).
distance of approximately 1200 km. North of the volcanic                           The second stage is related to the transfer of the ocean spreading
province, age equivalent sediments were deposited, derived from                    centre to its present position off East Greenland, and which led to
the uplifted basin margins.                                                        the final separation of the Jan Mayen Ridge from Greenland in the
   The base of the Paleocene succession is defined by a marked                      Late Oligocene. Passive margin subsidence during the drift phase
reflector, which forms a distinctive, continuous but slightly uneven                has been interrupted by regional basin margin uplift and inversion
erosional horizon in the Danmarkshavn Basin. In the central parts                  in the Miocene. The final North Atlantic plate readjustment
of the basin it is a non-depositional hiatus with no evidence of                   occurred during magnetic anomalies 5 and 6 (Middle – Late
erosional truncation (Fig. 7). There it is downlapped from the west                Miocene) when movement along the Spitsbergen Fracture Zone
(Fig. 11). There is a marked, apparent increase in interval velocity               began between Greenland and Svalbard. During this period,
above the horizon, which suggests changes in facies. The basal                     Eurasia continued to move slightly obliquely northwest relative to
unconformity becomes less distinct into the Thetis Basin (Figs 7                   Greenland (Ziegler 1988). Inversion structures of Late Miocene
and 11). The basal horizon probably correlates to the Danian                       age have been recognized in the Vøring Basin; they are most likely
erosional event in the onshore areas.                                                                           ´
                                                                                   related to ridge-push (Dore & Lundin 1996). The post-volcanic
900                                                          N. E. HAMANN ET AL.

succession has been divided into three mega-sequences: TII-TIV,          section generally die out at the sequence boundary (Fig. 11).
of Eocene – Late Oligocene, early Miocene – Late Miocene and             Erosional truncation of the underlying sequences increases
Early Pliocene– Holocene age (Figs 4a and 8).                            towards the western margin of the Thetis Basin and across the
   Mega-sequence TII has a fairly uniform thickness of 500–              Danmarkshavn Ridge (Figs 7 and 11). Structural tilting and
1200 m throughout the shelf although it locally thins over               intense erosion occurred prior to deposition of the mega-
structural highs and is missing due to later erosion particularly        sequence. The removed section increases in age down to Lower
towards the west and north, on the Koldeway Platform and in the          Cretaceous along the western margin of the Koldewey Platform
western part of Danmarkshavn Basin (see Figs 4a, 7 and 11). The          (Figs 4a and 7), and deep erosion is demonstrated between 748
base is defined by the top volcanics horizon, which forms a strong        and 768 N. The prominent and extensive unconformity is
reflector at the base of the overlying siliciclastic sequence. To the     interpreted to be of Early Pliocene age and has previously been
north the base is represented by a volcaniclastic bed similar to (and    described from the Northeast Greenland Shelf margin (Hinz
approximately the of same age as) the Balder Formation tuffs in          et al. 1993). Mega-sequence TIV is over 1500 m thick in the
the North Sea. This horizon can be easily identified (see Fig. 7).        central parts of the Thetis Basin and is thin just east of the
The mega-sequence is characterized by continuous even-bedded,            Danmarkshavn Ridge; further towards west it disappears (Figs 4a
high-amplitude reflectors, which are parallel to sub-parallel. It         and 7). The mega-sequence can be subdivided into a number of
onlaps the eastern and western margins of the Danmarkshavn               sequences with a predominantly prograding depositional pattern.
Basin at a low angle and thins over the Danmarkshavn Ridge. In           It is characterized by channel fill deposits to the north and west of
the Thetis Basin there is a steeply onlapping surface onto the           the Thetis Basin, suggesting periods of non-deposition and
Danmarkshavn Ridge (Figs 7 and 11), and apparent distal downlap          erosion of the inner parts of the shelf.
against the outer ridge in the east. In the upper part, low-angle
prograding beds indicate a possible increase in depositional energy
towards the top of the section, possible caused by a relatively          Hydrocarbon potential
minor tectonic pulse (Fig. 7). The mega-sequence is also present
                                                                         The presence of an active hydrocarbon system in the area is
along the continental margin onlapping the eastern edge of the
                                                                         demonstrated by many direct hydrocarbon indicators (flatspots,
Marginal High and truncated against the apparent escarpment
                                                                         bright spots, gas chimneys, etc.), seen on the seismic data. A
formed by the oceanic basalts (see Tsikalas et al. 2004).
                                                                         number of favourable geological factors also point to the oil
   Mega-sequence TIII is separated from the underlying deposits
                                                                         potential of the area. The East Greenland Shelf is almost certainly
by a distinct erosional unconformity first reported by Hinz et al.
                                                                         underlain by the same prolific Upper Jurassic source rock that has
(1993). This unconformity is locally seen to be directly on oceanic
                                                                         sourced most of the major oil fields in the North Atlantic region,
basement on the outer continental slope, but in most of this area
                                                                         and by comparison with the onshore succession it is likely that
there is a thin layer of sediments below the unconformity. The
                                                                         several deeper source intervals are likely to be present (e.g.
overlying, TIII mega-sequence shows apparent onlap towards the
                                                                         Christiansen et al. 1992). The tectonic development of the
shelf (Fig. 4a). The unconformity has also been identified on the
                                                                         Danmarkshavn Basin indicates that the Upper Jurassic source
Liverpool Land Shelf. It is most likely of earliest Miocene age and
                                                                         rocks have been buried deeply enough to generate hydrocarbons,
related to basin margin uplift during the separation of the Jan
                                                                         and most likely these have migrated towards the eastern margin of
Mayen Ridge in the latest Oligocene – earliest Miocene (Hinz et al.
                                                                         the basin and the Danmarkshavn Ridge. Potential trapping
1993). In the Thetis Basin the mega-sequence shows downlap onto
                                                                         structures include large-scale fault blocks similar to those of the
the basal horizon, towards the shelf edge (Fig. 7). Slumping occurs
                                                                         major North Sea fields. Regionally extensive, excellent quality
along the western margin of the Thetis Basin and a distinct, deeply
                                                                         reservoir intervals are likely to be present in the Middle to Upper
incised erosional surface has been observed along the edge of the
                                                                         Jurassic succession, and additional reservoir potential exists
Danmarkshavn Ridge (Fig. 7). The horizon cuts up to 150–200 m
                                                                         throughout the Devonian–Paleocene syn-rift succession. The
into the underlying parallel laminated sequence, forming a very
                                                                         most prospective area for the Jurassic play is on the margins of
irregular surface, overlain by a chaotic or steeply downlapping
                                                                         the Danmarkshavn Basin and along the Danmarkshavn Ridge.
sequence (Fig. 4a). The unconformity runs approximately N – S
                                                                            Further potential may exist in the central and southern parts of
along the edge of the Danmarkshavn Ridge, and is interpreted to
                                                                         the shelf, but the geological understanding of these areas is
have formed a sharp palaeo-shelf edge. West of the palaeo-shelf
                                                                         complicated by the thick Tertiary volcanics. The post-rift Tertiary
edge, the horizon gently onlaps across the Danmarkshavn Ridge
                                                                         section may also have some potential in the outer parts of the shelf,
and into the Danmarkshavn Basin, where it is truncated by
                                                                         particularly in the northern part of the Blosseville Kyst Shelf.
Megasequence TIV (Figs 4a and 7). Mega-sequence TIII reaches a
                                                                            The KANUMAS seismic data have established the East
thickness of over 2000 m along the axis of the Thetis Basin, but
                                                                         Greenland Shelf as a potential major hydrocarbon province.
thins eastward over the marginal high, and across the continent –
                                                                         Large areas of the East Greenland shelf appear to be oil-prone and
ocean boundary. The megasequence shows rapid depositional
                                                                         include several potentially giant structures. Tertiary volcanism and
thinning west of the Thetis Basin, before it is erosionally truncated
                                                                         the later Cenozoic regional uplift events are unlikely to have
by the overlying sequence (Figs 4a and 7). The thickness and
                                                                         severely reduced the prospectivity of the region.
volume of Late Oligocene – Miocene deposits in the Thetis Basin
shows that a period of major uplift and erosion took place at the
time. The upper part of the succession displays low-amplitude
                                                                         Summary and conclusions
folds and faults. The faults occur throughout the shelf area, in NE
trending zones about 10 – 20 km wide, and are separated by wide          The more than 1200 km long and 200– 600 km wide shelf east of
areas of generally undisturbed sediments. The faults are steeply         Greenland forms the conjugate margin to the shelf areas west of
dipping and convergent and show evidence of drag and reversal,           Norway. The East Greenland Shelf can be divided into three broad
with throws of up to about 200 m along the eastern margin of the         regions based on interpretation of c. 6800 km of multichannel
Danmarkshavn Basin. This type of faulting is characteristic of           seismic data from the area between 728N and 798N and additional
strike-slip movement, and the inversion structures probably              5000 km of seismic data offshore Liverpool Land. The very open
formed during a period of compression during the Late Miocene.           seismic grid allows us to recognize five major, roughly northeast-
   Mega Sequence TIV is characterized by a strong, high-                 trending structural elements on the Northeast Greenland Shelf,
amplitude basal reflector in the outer parts of the shelf, and a          north of 758N (Fig. 3). The structures most probably extend south
marked decrease in interval velocity. The horizon has not been           of 758N for some distance, but the presence of a thick volcanic
affected by tectonism, and faults and folds seen in the underlying       succession obscure the seismic signal on this part of the shelf.
                                                        NE GREENLAND SHELF DEVELOPMENT                                                                   901

   The most prominent feature on the Northeast Greenland shelf is              Hinz, K., Meyer, H. & Miller, H. 1991. North-East Greenland shelf north of
the 50 – 100 km wide and more than 400 km long Danmarkshavn                         798N: results of a reflection seismic experiment in sea ice. Marine and
Basin (Fig. 3). It contains a more than 13 km (8 s TWT) thick                       Petroleum Geology, 8, 461 –467.
sedimentary succession of proposed Devonian to Palaeogene age                  Hinz, K., Endholm, O., Block, M. & Skoseid, J. 1993. Evolution of North
(Figs 4 and 8). The basin resembles the onshore Jameson Land                        Atlantic volcanic continental margins. Petroleum Geology of North-
Basin both in structural style and in having very thick, .13 km,                    west Europe. In: Parker, J. R. (ed.) Proceedings of the Fourth
and stratigraphically almost complete post-Caledonian succes-                       Conference. Geological Society, London, 901–913.
                                                                                 ˚
                                                                               Hakansson, E. & Stemmerik, L. 1989. Wandel Sea basin – A new synthesis
sions. However, the depositional evolution of the two basins is
                                                                                    of the late Paleozoic to Tertiary accumulation in North Greenland.
believed to be very different, particularly during Late Carbonifer-
                                                                                    Geology, 17, 683–686.
ous – Triassic times (see Figs 6 and 8).
                                                                               Kelly, S. R. A., Whitham, A. G., Koraini, A. M. & Price, S. M. 1998.
   The Devonian – Triassic development of the Northeast Green-                      Lithostratigraphy of the Cretaceous (Barremian –Santonian) Hold
land Shelf resembles that of the Norwegian Barents Sea, and the                     with Hope Group, NE Greenland. Journal of the Geological Society,
Danmarkshavn Basin is a likely southern continuation of the                         London, 155, 993–1008.
Nordkapp Basin rift (Gudlaugsson et al. 1998). The post-Triassic               Kreiner-Møller, M. & Stemmerik, L. 2001. Upper Permian lowstand fans of
evolution of the Greenland Shelf seems to be broadly similar to                     the Bredehorn Member, Schuchert Dal Formation, East Greenland. In:
that of the shelf areas west of Norway. Main rifting took place                     Martinsen, O. J. Dreyer, T. (eds) Sedimentary Environments Offshore
during the mid- and late Jurassic, and during the Cretaceous new                    Norway – Palaeozoic to Recent. NPF Special Publication, 10, 51 –65.
deep basins started to form on the more distant part of the shelf.             Larsen, H. C. 1984. Geology of the East Greenland shelf. In: Spencer, A. M.
                                                                                    et al. (eds) Petroleum Geology of the North European Margin.
We wish to acknowledge the companies that took part in the KANUMAS                  Norwegian Petroleum Society, 329 –339.
Project: BP, Exxon, Japan National Oil Company, Shell, Statoil, Texaco         Larsen, H. C. 1990. The East Greenland Shelf. In: Grant, A., Johnson, L. &
and Nunaoil for their permission to publish. We would also like to thank the        Sweeney, J. F. (eds) The Arctic Ocean region: Boulder Colorado,
Mineral Resources Administration for Greenland for their permission to              Geological Society of America. The geology of North America, L,
publish an example of seismic data from Jameson Land, and the Danish                185– 210.
National Survey and Cadastre for processing and modelling of the gravity       Larsen, H. C. & Thorning, L. 1980. Project EASTMAR; Acquisition of
data. The paper greatly benefited from very constructive reviews by                  high sensitivity aeromagnetic data off East Greenland. Rapport
A. Spencer and L. Gernigon. LS publishes with permission of the                     Grønlands Geologiske Undersøgelse, 100, 91– 94.
Geological Survey of Denmark and Greenland.                                    Larsen, M., Hamberg, L., Olaussen, S., Nørgaard-Pedersen, N. &
                                                                                    Stemmerik, L. 1999. Basin evolution in Southern East Greenland
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