The recent licensing round in the deep-water areassouth-east of the Faeroe Islands has emphasised the con-tinued interest of the oil industry in the frontier areasof the North Atlantic volcanic margins. The search forhydrocarbons is at present focused on the Cretac-eous–Paleocene succession with the Paleocene deep-water play as the most promising (Lamers & Carmichael1999). The exploration and evaluation of possible playsare almost solely based on seismic interpretation andlimited log and core data from wells in the area westof the Shetlands. The Kangerlussuaq Basin in southernEast Greenland (Fig. 1) provides, however, importantinformation on basin evolution prior to and during con-tinental break-up that finally led to active sea-floorspreading in the northern North Atlantic. In addition,palaeogeographic reconstructions locate the southernEast Greenland margin only 50–100 km north-west ofthe present-day Faeroe Islands (Skogseid et al. 2000),suggesting the possibility of sediment supply to the off-shore basins before the onset of rifting and sea-floorspreading. In this region the Lower Cretaceous –Palaeogene sedimentary succession reaches almost 1 kmin thickness and comprises sediments of theKangerdlugssuaq Group and the siliciclastic lower partof the otherwise basaltic Blosseville Group (Fig. 2).Note that the Kangerdlugssuaq Group was definedwhen the fjord Kangerlussuaq was known as‘Kangerdlugssuaq’. Based on field work by theGeological Survey of Denmark and Greenland (GEUS)during summer 1995 (Larsen et al. 1996), the sedimen-tology, sequence stratigraphy and basin evolution of theKangerlussuaq Basin were interpreted and comparedwith the deep-water offshore areas of the North Atlantic(Larsen et al. 1999a, b).

In August 2000, key stratigraphic sections were revis-ited by geologists from GEUS and Norsk Hydro and anumber of additional localities described (Fig. 1). Theaims of the field work included: (1) sedimentologicaldescription of Lower Cretaceous sandstones; (2)

improved biostratigraphy in the Upper Cretaceous mud-stone succession; and (3) detailed description of the tran-sition between the uppermost sediments and the baseof the volcanic succession. In addition, macrofossils(mostly ammonites, bivalves and belemnites) were sam-pled throughout the Cretaceous succession. Based onresults from a preliminary diagenesis study (Larsen et

al. 1999b), sandstones were collected across the con-tact metamorphic zone around Palaeogene intrusionsin order to evaluate their thermal and diagenetic effects.The field work was financed with support from NorskHydro and formed part of a major field campaign inthe Kangerlussuaq area (EG 2000) reported on byNielsen et al. (2001, this volume).

Sedimentology

Lower Cretaceous (Christian IV Gletscher)

The oldest sediments in the Kangerlussuaq Basin areof Early Cretaceous (Aptian – Early Albian) age (Fig. 2).This succession is dominated by coarse-grained sand-stones and was first described by Larsen et al. (1996,1999a) from a locality north of Sødalen. At this localitya lower, alluvial succession is overlain by large-scalechannelled and cross-bedded fluvio-estuarine sand-stones (Larsen et al. 1999a). The general palaeocurrentdirection was towards the east, but the lack of refer-ence sections has hitherto hindered conclusions on dis-tribution and palaeogeography. In summer 2000 anumber of possible Lower Cretaceous reference sectionswere measured along the western side of Christian IVGletscher (Fig. 1). These sections were briefly describedduring a helicopter reconnaissance visit in 1995, but moredetailed measurements of sedimentological sectionsand sampling of ammonites was undertaken in 2000.

The sections are sandstone-dominated, and reachmore than 170 m in thickness. The lowest parts are

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Pre-basaltic sediments (Aptian–Paleocene) of theKangerlussuaq Basin, southern East Greenland

Michael Larsen, Morten Bjerager, Tor Nedkvitne, Snorre Olaussen and Thomas Preuss

Geology of Greenland Survey Bulletin 189, 99–106 (2001) © GEUS, 2001

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Fig. 1. Geological maps showing the distribution of Cretaceous–Palaeogene sediments and the Palaeogene flood basalts of the south-ern East Greenland volcanic province. The position of sections logged in 2000 (black dots) and localities mentioned in the text areindicated. Red line in lower map connects sections 1, 2 and 3 shown in Fig. 5. Based on Larsen et al. (1996).

poorly exposed and consist of coarse-grained, locallypebbly, sandstones rich in coalified wood debris. Theseare overlain by medium- to coarse-grained, large-scalecross-bedded sandstones, which are bioturbated andshow Thalassinoides isp. and Planolites isp. The upperboundary of the sandstone-dominated succession is astrongly carbonate-cemented horizon overlain by athick succession of silty mudstones with numerous het-eromorph ammonites. The Lower Cretaceous succes-sion along the west side of Christian IV Gletscher isinterpreted to consist of a lower alluvial part overlainby shallow marine deposits and finally offshore marinemudstones. The upwards change is thus the same asthat seen in the Upper Aptian – Lower Albian succes-sion at the locality north of Sødalen, and reflects an over-all rise in sea level.

Upper Cretaceous – Paleocene (‘Sequoia Nunatak’)

Monotonous silty mudstones and fine-grained sand-stones reaching several hundred metres in thickness(Fig. 3) dominate the Upper Cretaceous succession.The mudstones are best exposed in the area aroundPyramiden and between Sorgenfri Gletscher andChristian IV Gletscher where they reach their maxi-mum thickness. Nørgaard-Pedersen (1992) reported aprobable Cretaceous succession at ‘Sequoia Nunatak’(an unofficial name) north-east of Kulhøje, greatlyexpanding the then known extension of the Cretaceousbasin (Fig. 1). The sediments were described as a fewmetres of fine-grained sandstones containing internalcasts of echinoderms and ammonites. Field work in2000, however, revealed in addition a several hundredmetres thick succession of fine-grained micaceous sand-stones just east of the locality described by Nørgaard-Pedersen. These sandstones contain a rich fauna ofammonites, echinoderms and bivalves of Late Cretaceousage. The fine-grained sandstones are truncated at thetop of the succession by a 7 m thick conglomerate bedinterpreted as a fluvial channel-fill, which is overlainby volcaniclastic deposits. The stratigraphic position ofthe conglomeratic unit immediately underlying the firstvolcanic deposits, together with the abrupt change frommarine to continental deposits and the coarse-grainedlithology, suggest that it may be correlated with theSchjelderup Member of the coastal areas (Soper et al.

1976). Biostratigraphic samples collected in 2000 mayprovide the evidence for the correlation between thenunatak area around ‘Sequoia Nunatak’ and the coastalregion.

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Fig. 2. Lithostratigraphy of the Kangerlussuaq Basin. The suc-cession below the Sorgenfri Formation (Aptian – Early Albian)was not described until 1995 and therefore was not included inthe lithostratigraphic scheme by Soper et al. (1976). A revisionof this succession (below the dotted line) is in preparation bythe senior author (M.L.). Based on Soper et al. (1976), Nielsenet al. (1981) and Larsen et al. (1999a).

Paleocene (Ryberg Fjord)

The boundary between the Kangerdlugssuaq Groupand Blosseville Group is represented by a major uncon-formity which separates Upper Cretaceous or LowerPaleocene marine mudstones below from coarse-grainedfluvial deposits above (Soper et al. 1976; Dam et al. 1998;Larsen et al. 1999a). However, towards the coast (local-ities 2 and 3, Ryberg Fjord; Fig. 1) the unconformity cor-relates with a number of less distinct bounding surfacesseparating shallow marine, deltaic and fluvial units. AtRyberg Fjord, a thick sandstone-dominated successionis exposed (Fig. 4). It consists of marine, fossiliferousfine-grained sandstone unconformably overlain by anup to 7 m thick pebbly sandstone bed, in turn overlainby black carbonaceous mudstones and fine-grainedsandstones showing rootlets (Fig. 5). The erosionallybased pebbly sandstone is interpreted as a fluvial chan-nel-fill that marks a change from marine to dominantlycontinental deposition. Higher in the succession a returnto shallow marine conditions is marked by strongly bio-turbated sandstones interpreted as upper shoreface andbeach deposits. The siliciclastic succession is overlainby a thick succession of volcaniclastic deposits andhyaloclastites. The Paleocene succession at Ryberg Fjordcomprising shallow marine and deltaic deposits is thickerand more complete than that described from the inlandareas. This indicates that increasing accommodationroom was present in the more basinal areas to thesouth-east and that multiple episodes of shoreface anddelta progradation took place during the uplift phasepreceding the onset of volcanism in East Greenland.

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Fig. 3. Upper Cretaceous marine mudstone succession exposedalong the western side of Christian IV Gletscher. The section shownis approximately 450 m thick and consists of silty, mica-rich mud-stones with thin interbeds of fine-grained sandstones. Ammonitesand echinoderms are present in several horizons and may formthe basis for an improved Upper Cretaceous stratigraphy.

Fig. 4. Paleocene sandstones exposed atRyberg Fjord. The sandstone unit in theforeground is 7 m thick and is inter-preted as a fluvial channel-fill. Thesecoarse-grained channel sandstones weredeposited following regional uplift in themid-Paleocene, just before the onset ofvolcanism. In the background volcani-clastic deposits and hyaloclastites can beseen.

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Hummocky cross-stratified sandstone

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Fig. 5. Geological logs showing correlation of the Paleocene successions in the central part of the Kangerlussuaq Basin. Locations ofsections (1, 2, 3) are shown on Fig. 1. Note the thick shallow marine and deltaic succession present below the unconformity in thesouthernmost section (3) compared to the strong truncation that occurs inland. The succession indicates that repeated progradationof shallow marine and deltaic successions occurred during the mid-Paleocene pre-volcanic uplift. Colour coding refers to deposi-tional environments. For legend, see Fig. 2.

Stratigraphy

Biostratigraphy

Detailed understanding of the Kangerlussuaq Basin hashitherto been hampered by the low resolution of thebiostratigraphic data. This is partly a consequence offailure to collect macrofossils, and partly due to verylow yields of microfossils from the existing samplematerial. In order to overcome these problems specialattention was paid to the collection of macrofossils,and several mudstone sections situated away from majorintrusions were sampled for palynological work (Fig.3). The efforts put into the macrofossil collecting wererewarded, such that close to 50 ammonites represent-ing both Lower and Upper Cretaceous species werebrought back from the field.

Lithostratigraphy

The discovery of an Aptian–Albian, sandstone-domi-nated succession below the Sorgenfri Formation in 1995(Fig. 2) and the finds of new ammonite-bearing inter-vals made it clear that a revision of the existing lithos-tratigraphy was necessary (Larsen et al. 1999a). However,the lack of biostratigraphic control in the UpperCretaceous mudstone-dominated succession, and thepoor understanding of the lower volcanic successionwhich appeared to interfinger with the sedimentaryrocks, impeded interpretation. The results of the fieldwork in 2000 combined with biostratigraphical and sed-imentological data compiled by Cambridge Arctic ShelfProgramme (CASP) will enable a common lithostrati-

graphic scheme for the Kangerlussuaq Basin to be pub-lished in the near future. This new lithostratigraphy isa collaborative project between GEUS and CASP.

DiagenesisThe sandstones of the Kangerlussuaq Basin have beenstrongly diagenetically altered, due to their positionclose to major Palaeogene intrusive centres and a bur-ial history that included rapid pre-volcanic uplift followedby deep burial beneath continental flood basalts. Thecomplex diagenetic history comprises chlorite and illiteprecipitation, mechanical crushing, detrital feldspar dis-solution and albitisation followed by albite precipita-tion and quartz overgrowth. The last common phase iscalcite, while later kaolinite is only observed in thecoarse-grained fluvial sandstones of the SchjelderupMember (Larsen et al. 1999b). The original excellentporosity of the sandstones is only preserved in a fewplaces due to early chlorite coating of grains prevent-ing quartz overgrowth. Otherwise, the original poros-ity has been completely destroyed, and the presentporosity (5–10%) mainly reflects secondary porosityoriginating from dissolution of detrital feldspar. Thedissolution process seems to be significantly enhancedin the coarse-grained sandstones in areas with manyintrusions. The secondary pore space may be reducedby authigene albite growth on detrital grain remnantstogether with later syntaxial quartz overgrowths engulf-ing the albite (Fig. 6). In places, clay coatings or duc-tile clay clasts can be seen to inhibit quartz ingrowths,thus preserving the secondary porosity. The coarse-

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Qo

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Fig. 6. Scanning electron photomicro-graph of a coarse-grained Paleocenesandstone, showing secondary porespace formed by feldspar dissolution.The pore space is partly filled by growthof euhedral albite crystals (Ab) nucleatedon the detrital feldspar remnants. Illiticclay lining (Il) marks the boundaries ofthe former detrital grains (arrows). Later,euhedral quartz (Qo) overgrows the claylinings and engulfs the authigene albite.

grained sandstones in the north-eastern part of the basinshow the most complete feldspar dissolution, but alsoexperienced the most intensive phase of late quartzovergrowth, which nearly infilled all of the secondaryformed porosity.

In order to better understand the diagenetic historyand evaluate models for sandstone diagenesis in sub-basaltic settings, sandstone samples from the measuredsections were studied. However, local effects from cross-cutting basic dykes and sills have strongly influenceddiagenesis, and thus sandstones were collected acrossthe contact metamorphic zone from adjacent to theintrusion to a distance as far away as two to three timesthe thickness of the intrusion. The results of these inves-tigations will be compared with the samples unaffectedby intrusions in order to separate local and regionaleffects.

ConclusionsField work in the Kangerlussuaq Basin in 2000 hasadded much information to the understanding of thebasin evolution. Most important, perhaps, is theimproved biostratigraphic resolution that allows iden-tification and correlation of unconformities betweenmeasured sections. Unconformities mark major changesin basin configuration and are often associated withuplift and erosion. The unconformity present at thebase of the Schjelderup Member, and now recognisedthroughout the basin, thus suggests that coarse-grainedsediments bypassed the Kangerlussuaq area at this timeand were transported across the East Greenland mar-gin to offshore basins to the south-east. With a pre-driftposition only 50–100 km north-west of prospectiveareas around the Faeroe Islands the understanding ofthe pre-basaltic basin evolution in southern EastGreenland may be used to identify possible reservoirintervals and play types in the undrilled deep-waterareas of the northern North Atlantic volcanic margins.

Future workThe Palaeogene flood basalts along the Blosseville Kystare part of an extensive basalt province extending fromKangerlussuaq in the south to Scoresby Sund in thenorth. Sediments are exposed only at two isolated local-ities along the coastal stretch, at Kap Dalton and KapBrewster (Fig. 1). These two localities form importantdatapoints for reconstruction of the North Atlantic region

during continental break-up and for biostratigraphiccontrol of the onset and duration of the volcanism insouthern East Greenland. Both localities were visitedby geologists in the 1970s (Birkenmajer 1972; Soper et

al. 1976), but no recent sedimentological descriptionshave been published. In the summer of 2001 field workwill be carried out in the sedimentary successions at KapBrewster and Kap Dalton using sedimentological, bios-tratigraphical and sequence stratigraphical methods.The results will be integrated with basin models andstratigraphy in the areas to the south-west aroundKangerlussuaq and to the north in North-East Greenland.

AcknowledgementsWe gratefully acknowledge economic support by Norsk Hydrothat made it possible for T.N. and S.O. to participate in the fieldwork and supplied flexibility to the otherwise limited helicopterprogramme. Troels F.D. Nielsen (leader of EG 2000) is thankedfor his engagement and enthusiasm, which made the field cam-paign in Kangerlussuaq a success.

ReferencesBirkenmajer, K. 1972: Report on investigations of Tertiary sedi-

ments at Kap Brewster, Scoresby Sund, East Greenland. RapportGrønlands Geologiske Undersøgelse 48, 85–91.

Dam, G., Larsen, M. & Sønderholm, M. 1998: Sedimentary responseto mantle plumes: implications from Paleocene onshore suc-cessions, West and East Greenland. Geology 26, 207–210.

Lamers, E. & Carmichael, S.M.M. 1999: The deepwater sandstoneplay west of Shetland. In: Fleet, A.J. & Boldy, S.A.R. (eds):Petroleum geology of Northwest Europe. Proceedings of the5th Conference, 645–659. London: Geological Society.

Larsen, M., Hamberg, L., Olaussen, S. & Stemmerik, L. 1996:Cretaceous–Tertiary pre-drift sediments of the Kangerlussuaqarea, southern East Greenland. Bulletin Grønlands GeologiskeUndersøgelse 172, 37–41.

Larsen, M., Hamberg, L., Olaussen, S., Nørgaard-Pedersen, N. &Stemmerik, L. 1999a: Basin evolution in southern EastGreenland: An outcrop analog for Cretaceous–Paleogenebasins on the North Atlantic volcanic margins. AAPG Bulletin83(8), 1236–1261. Tulsa: American Association of PetroleumGeologists.

Larsen, M., Hamberg, L., Olaussen, S., Preuss, T. & Stemmerik,L. 1999b: Sandstone wedges of the Cretaceous – Lower TertiaryKangerlussuaq Basin, East Greenland – outcrop analogues tothe offshore North Atlantic. In: Fleet, A.J. & Boldy, S.A.R.(eds): Petroleum geology of Northwest Europe. Proceedingsof the 5th Conference, 337–348. London: Geological Society.

Nielsen, T.F.D., Soper, N.J., Brooks, C.K., Faller, A.M., Higgins,A.C. & Matthews, D.W. 1981: The pre-basaltic sediments andthe Lower Basalts at Kangerdlugssuaq, East Greenland. Their

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stratigraphy, lithology, palaeomagnetism and petrology.Meddelelser om Grønland Geoscience 6, 25 pp.

Nielsen, T.F.D., Hansen, H., Brooks, C.K., Lesher, C.E. & field par-ties 2001: The East Greenland continental margin, the Prinsenaf Wales Bjerge and new Skaergaard intrusion initiatives. Geologyof Greenland Survey Bulletin 189, 83–98 (this volume).

Nørgaard-Pedersen, N. 1992: Delta sequences and initial vol-canism in the Paleocene Kangerdlussuaq basin, East Greenland.In: Brooks, C.K., Hoch, E. & Brantsen, A.K. (eds): Kangerd-lugssuaq studies: processes at a continental rifted margin III.Proceedings from a meeting May 1992, 24–31. Copenhagen:Geological Institute, University of Copenhagen.

Skogseid, J., Planke, S., Faleide, J.I., Pedersen, T., Eldholm, O. &Neverdal, F. 2000: NE Atlantic continental rifting and volcanicmargin formation. In: Nøttvedt, A. et al. (eds): Dynamics ofthe Norwegian Margin. Geological Society Special Publication(London) 167, 295–326.

Soper, N.J., Downie, C., Higgins, A.C. & Costa, L.I. 1976:Biostratigraphic ages of Tertiary basalts on the East Greenlandcontinental margin and their relationship to plate separationin the North-East Atlantic. Earth and Planetary Science Letters32, 149–157.

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Authors’ addressesM.L., M.B. & T.P., Geological Survey of Denmark and Greenland, Thoravej 8, DK-2400 Copenhagen NV, Denmark. E-mail: mil@geus.dk

T.N., Norsk Hydro ASA, N-0246 Oslo, Norway.

S.O., Norsk Hydro Research Center, P.O. Box 7190, N-5020 Bergen, Norway. Present address: Norsk Agip A/S, P.O. Box 101 Forus, N-

4064 Stavanger, Norway.