The Continental Shelf Project of the Kingdom of Denmark – status and issues

Christian Marcussen, Finn Mørk, Thomas Funck, Willy Lehmann Weng and Mikael Pedersen

Th is paper summarises the status of the Continental Shelf Th e CLCS examined the partial submission regarding Project of the Kingdom of Denmark aft er the recent submis- the area north of the Faroe Islands between 2012 and 2014 sion for an extended continental shelf in the area to the north and gave special attention to: (1) the morphological continu- of Greenland. We discuss some of the similarities between ation of the Ægir Ridge and (2) the continuity of sediments the submission areas north of the Faroe Islands and north throughout the Northern Deep. In a strict morphological of Greenland including the morphological continuation of sense, the land mass of the Faroe Islands is connected to the ridges extending seaward of the geomorphical continental Faroe–Iceland Ridge (Fig. 2). Furthermore, the Faroe–Ice- shelf. Documentation of the sediment thickness in the ad- land Ridge coalesces with and is morphologically linked to joining basins and sediment continuity with the continental the Ægir Ridge. Th is means that the Ægir Ridge is morpho- slope plays a vital role in the delineation of the outer limits of logically continuous with the rest of the continental margin the extended continental shelf. Here, we compare how these issues were addressed around the well-studied Faroe Islands A 150°E and in the sparsely surveyed Arctic Ocean. US Th e Kingdom of Denmark ratifi ed the 1982 United Na- tions Convention on the Law of the Sea (UNCLOS) in NGM R u 2004. According to Annex II of UNCLOS, the particulars s s i a n of the outer limits of the extended continental shelf beyond F e d e r 200 nautical miles shall be submitted to the Commission on a t i o the Limits of the Continental Shelf (CLCS) within a period n of ten years aft er ratifi cation. To acquire the necessary data for delineating the extended continental shelf, the Continen- NorwayNorway tal Shelf Project of the Kingdom of Denmark was launched 70°N Canada 30°E by the Ministry of Higher Education and Science in coopera- NEGM tion with the Government of the Faroe Islands and the Gov- ernment of Greenland (Marcussen et al. 2004; Marcussen & Heinesen 2009). NFM Five partial submissions have been submitted by the King- dom of Denmark regarding areas north of the Faroe Islands Greenland ds an in 2009, south of the Faroe Islands in 2010, south of Green- sl I e o land in 2012, north-east of Greenland in 2013 and north of r a F Greenland in 2014 (Fig. 1). SGM

The area north of the Faroe Islands SGM SFM 50°N North of the Faroe Islands, the extinct Ægir sea-fl oor spread- 50°N ing ridge is a prominent feature of the continental margin 1 000 km (Figs 1, 2). Th e initial opening of the North Atlantic oc- 30°W curred along the Ægir Ridge with active sea-fl oor spreading Fig. 1. The five partial submissions of the Kingdom of Denmark. Red line: in the Eocene and Oligocene. Subsequent thermal subsid- The 200 nautical mile limit of the five Arctic coastal states in the Arc- ence of the oceanic crust resulted in the formation of the tic Ocean. NEGM: North-east Greenland Margin. NFM: North Faroes Northern Deep with a sediment accumulation of up to 3 km. Margin, NGM: North Greenland Margin. SFM: South Faroes Margin. SGM: South Greenland Margin. Colour scale: see Fig. 3.

© 2015 GEUS. Geological Survey of Denmark and Greenland Bulletin 33, 41–44. Open access: www.geus.dk/publications/bull 41 4°W 68°N north of the Faroe Islands as originally listed in the submis-

Ridge sion. Vøring N Jan Mayen o Plateau rt he rn The area north of Greenland e D g ee d p Th e Lomonosov Ridge is a sliver of continental crust that i

R extends for a distance of almost 1800 km across the Arc-

tic Ocean (Fig. 3). Th e ridge is 45 to 200 km wide, mostly r i fl at-topped to slightly rounded at its crest and rises from wa- g F ter depths of more than 4300 m in the adjacent basins to a Æ r o typically 1000 to 1300 m. Th e shallowest part of the ridge e 64°N - I c is found towards Greenland. Th e Lomonosov Ridge was e la n separated from the Barents and Kara shelves during the d R Paleocene (55 to 60 Ma), when sea-fl oor spreading started to id ge open the Eurasia Basin. Th is process continues today along 62°N hannel C the ultraslow-spreading Gakkel Ridge. Th e geological devel- Faroe Islands opment of the Amerasia Basin is not well understood, but 100 km 8°W8°W8°W Faroe-Shetland 0° most authors agree that the Alpha and Mendeleev Ridges in Fig. 2. The Northern Continental Shelf of the Faroe Islands showing the that basin comprise a large igneous province of Cretaceous submission area. The continental shelf beyond 200 nautical miles in the age (e.g. Jackson et al. 1986) and that sea-fl oor spreading has area north of the Faroe Islands, as delineated in the submission, amounts occurred in the Canada Basin (e.g. Grantz et al. 1998). to 87 792 km2 in area and is highlighted. Green: agreed maritime bounda- Th e Lomonosov Ridge is morphologically continuous with ries within 200 nautical miles. Red: Faroese 200 nautical mile limit. Yel- the Lincoln Shelf north of Greenland and furthermore shares low: Iceland’s and Norway’s 200 nautical mile limits. Orange: outer limit geological characteristics with the land mass of Greenland. of the continental shelf north of the Faroe Islands. Colour scale: see Fig. 3. Th ese geological characteristics are based on evidence for con- tinuous continental crust (Jackson et al. 2010), similar lith- and lies within a common envelope of the foot of the con- ologies and ages of rocks sampled from the fl anks of the ridge tinental slope. Th us, in the sense of UNCLOS, the Ægir compared to rocks of the adjacent land masses, and a common Ridge is an integral part of the continental margin of the tectonic history. In the sense of UNCLOS, this means that Faroe Islands, notwithstanding the tectonic and crustal dif- the Lomonosov Ridge is a submarine elevation that is a natu- ferences between the two terrains (Recommendations of the ral component of the continental margin of Greenland and Commission 2014). therefore the extended continental shelf north of Greenland Th e sediment thickness in the Northern Deep was docu- extends across the Arctic Ocean to the 200 nautical mile line mented primarily using modern seismic refl ection data. Se- from Russia (Executive Summary 2014). lected seismic lines were re-processed in order to improve the Facing the Amerasia Basin, the Lomonosov Ridge is mor- defi nition of the base of the sediments as well as the determi- phologically amalgamated with the Alpha and Mendeleev nation of the seismic velocities used for the depth conversion. Ridges and the Chukchi Borderland, which together are re- Th e CLCS agreed with the procedure used to establish the garded as one complex but coherent morphological sea-fl oor sediment thickness, i.e. the methodology of depth conver- high relative to the adjacent deep ocean fl oor within the Eur- sion and the seismic interpretations. However, the CLCS in- asia and Amerasia Basins. Th at is, all of this complex sea-fl oor itially disagreed with the method by which the Kingdom of high lies within a common envelope of the foot of the conti- Denmark demonstrated sedimentary continuity throughout nental slope. However, the existing geological data for some the Northern Deep. To satisfy the CLCS, additional seismic of the individual sea-fl oor highs are insuffi cient to prove that lines, a sediment thickness map and gravity maps were pro- they share geological characteristics with the Greenland land vided and subsequently deemed suffi cient for this purpose. mass. For this reason, and in accordance with UNCLOS, the In March 2014, the CLCS adopted the recommendations extended continental shelf, based on the Alpha and Mend- regarding the partial submission north of the Faroe Islands. eleev Ridges and the Chukchi Borderland, is constrained to Th e Commission agreed with the determination of the fi xed a distance of 350 nautical miles from the territorial sea base- points establishing the outer limits of the continental shelf line of Greenland (Executive Summary 2014).

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70°N 180° East Siberian Shelf 140°E Laptev Shelf 75°N 160°W x Siberia100°E

Chukchi Shelf

Alaska x Mendeleev Ridge

x x Podvodnikov

Chukchi Gakkel Ridge

Lomonosov Severnaya

x

Borderland x

B Basin

x Zemlya e a

80°E

u

x

f

x Kara

o x x x

r Amerasia Basin Eurasia

t Shelf

Canada Basin 80°N

AlphaRidge

S x x Makarov x

h x Basin Basin Franz e Nansen l Josef

f Ridge

x North Land

Canadian Arctic Archipelago Shelf Pole x Basin

Bathymetry Amundsen x x Barents 0 m

Shelf8 x 0 °

1 000 m Basin N

2 000 m x x

Morris 20°E

x 3 000 m x x Jesup x 4 000 m Rise Lincoln Lena Trough Svalbard

x Ellesmere Shelf

400 km x

100°W 80°Wx 60°W 20°W 0° Island Greenland x

Fig. 3. Bathymetric map showing the main features of the Arctic Ocean.

By analogy with the Ægir Ridge north of the Faroe Islands, Ocean. However, ice conditions only allowed for a maxi- bathymetric and morphological data show that the Gakkel mum streamer length of 300 m, which is too short to extract Ridge coalesces with the continental slope north of Green- velocities from the seismic refl ection data. For this reason, land. Th e oceanic, sea-fl oor-spreading characteristics of the sonobuoys were deployed along the profi les to record the seis- Gakkel Ridge diff er geologically from the continental crust of mic energy at larger off sets of up to 34 km. Ray-tracing mod- Greenland; hence the extended continental shelf based on the elling was then used to obtain velocity models of sediments Gakkel Ridge cannot exceed 350 nautical miles from the ter- in the Amundsen Basin. Th e velocities show little scatter ritorial sea baseline of Greenland (Executive Summary 2014). (Fig. 4). Assuming normal compaction, the data points can Published seismic data from the Amundsen Basin north be approximated by an exponential function of instantane- of Greenland (Weigelt & Jokat 2001) indicate the presence ous slowness versus burial depth (Al-Chalabi 1997) using re- of sediments of suffi cient thickness (i.e. at least 1200 m) for duced major axis regression techniques. Th e velocity–depth use in extending the continental shelf. For this reason, a pur- relationship obtained from this approach is shown in Fig. 4 pose-built seismic acquisition system was developed (Hopper and can be used to convert the sediment thickness from time et al. 2012) that could operate in the Arctic sea ice and at to depth. sub-zero temperatures. To locate the most promising regions Th e seismic refl ection lines surveyed were generally less for seismic data acquisition, a sediment thickness map was than 50 km long and focused on regions that were more derived from gravity inversion (Døssing et al. 2014). Th is than 60 nautical miles away from the Lomonosov Ridge. As study was based on the LOMGRAV airborne gravity data the CLCS requires the documentation of sediment continu- (Døssing et al. 2013). ity, supplementary data had to be used. In ice-covered areas Th ree GEUS LOMROG expeditions were carried out in gravity data can supplement a sparse seismic database. For 2007, 2009 and 2012 to acquire seismic data in the Arctic this reason, the results of the gravity inversion (Døssing et

43 0.0 before the middle of the next decade. It represents a signifi - cant challenge to keep both data and knowledge within the project updated and state of the art. 0.5

References Al-Chalabi, M. 1997: Instantaneous slowness versus depth functions. 1.0 Geophysics 62, 270–273. Døssing, A., Hopper, J.R., Olesen, A.V., Rasmussen, T.M. & Halpenny, J. 2013: New aero-gravity results from the Arctic: Linking the latest Cretaceous–early Cenozoic plate kinematics of the North Atlantic and 1.5 Arctic Ocean. Geochemistry, Geophysics, Geosystems 14, 4044–4065. Døssing, A., Hansen, T.M., Olesen, A.V., Hopper, J.R. & Funck, T. 2014: Depth below seafloor (km) Gravity inversion predicts the nature of the Amundsen Basin and its continental borderlands near Greenland. Earth and Planetary Science 2.0 Letters 408, 132–145. Executive Summary 2014: Partial Submission of the Government of the 1.5 2.0 2.5 3.0 3.5 4.0 Kingdom of Denmark together with the Government of Greenland to Velocity (km/s) the Commission on the Limits of the Continental Shelf – Th e North- ern Continental Shelf of Greenland. http://www.un.org/depts/los/clcs_ Fig. 4. Sediment velocities in the Amundsen Basin obtained from ray-trac- new/submissions_fi les/dnk76_14/dnk2014_es.pdf ing of the sonobuoy recordings from the three GEUS LOMROG expedi- Gernigon, L., Gaina, C., Olesen, O., Ball, P.J., Péron-Pinvidic, G. & Yama- tions. Green circles show individual data points; the red line indicates an saki, T. 2012: Th e Norwegian Basin revisited: from continental break- approximation obtained from reduced major axis regression techniques. up to spreading ridge extinction. Marine and Petroleum Geology 35, 1–19. Grantz, A. et al. 1998: Phanerozoic stratigraphy of Northwind Ridge, al. 2014) were used to document continuity of the sediments magnetic anomalies in the Canada basin, and the geometry and timing supported by additional subbottom profi ler and seismic re- of rift ing in the Amerasia basin, Arctic Ocean. Geological Society of America Bulletin 110, 801–820. fl ection data. Hopper, J.R., Trinhammer, P., Marcussen, C. & Funck, T. 2012: Acquisi- tion of seismic data in ice fi lled waters. American Geophysical Union, Fall Meeting 2012, abstract #C13E-0680. Concluding remarks Jackson, H.R., Forsyth, D.A. & Johnson, G.L. 1986: Oceanic affi nities of Th e Continental Shelf Project of the Kingdom of Denmark the Alpha Ridge, Arctic Ocean. Marine Geology 73, 237–261. Jackson, H.R., Dahl-Jensen, T. & the LORITA working group 2010: Sedi- mapped fi ve areas relevant to extended continental shelf be- mentary and crustal structure from the Ellesmere Island and Greenland yond 200 nautical miles. Th e project gathered bathymetric, continental shelves onto the Lomonosov Ridge, Arctic Ocean. Geo- geodetic, geological and geophysical data to compile the sub- physical Journal International 182, 11–35. mission documents required by the CLCS. Despite diffi cult Marcussen, C. & Heinesen, M. 2010: Th e Continental Shelf Project of the Kingdom of Denmark – status at the beginning of 2010. Geological logistics, challenging climatic conditions and permanent ice Survey of Denmark and Greenland Bulletin 20, 51–54. cover in some of the fi ve areas, the project was completed Marcussen, C., Christiansen, F.G., Dahl-Jensen, T., Heinesen, M., Lom- within the initially allocated budget of 330 million DKK holt, S., Møller, J.J. & Sørensen, K. 2004: Exploring for extended con- (44 million €) and the given time frame. tinental shelf claims off Greenland and the Faroe Islands – geological perspectives. Geological Survey of Denmark and Greenland Bulletin Large data sets have been acquired in the fi ve submis- 4, 61–64. sion areas and key results have been or will be published in Recommendations of the Commission on the Limits of the Continental scientifi c journals. Particularly valuable are the datasets in Shelf in regard to the partial Submission made by the Government of the Arctic Ocean as this remains a poorly studied frontier Denmark together with the Government of the Faroes in respect of the Continental Shelf North of the Faroe Islands on 29 April 2009. Adopted region. Furthermore, the project was able to support other by the Commission, with amendments, on 12 March 2014. http://www. science projects by sharing logistics, in particular by provid- un.org/depts/los/clcs_new/submissions_fi les/dnk28_09/2014_03_14_ ing access to icebreakers. Th e results could not have been SCDNK_REC_COM_20140521.pdf achieved without extensive international cooperation. Due Weigelt, E. & Jokat, W. 2001: Peculiarities of roughness and thickness of oceanic crust in the Eurasian Basin, Arctic Ocean. Geophysical Journal to the modus operandi of the CLCS, recommendations for International 145, 505–516. the latest submission north of Greenland cannot be expected

Authors' address Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: [email protected]

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