Review of Greenland Avtivities 2001 - Geus

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95-06 ▲ ▲ 58° 95-12 95-10 56° 52° Svartenhuk Halvø Unit B A Unit A A 71° 95-08A D Unit D 95-08 B A 95-14 Ittlli fault zon e A A B 95-15 GRO#3 B B Nuussuaq B 70° Vaigat B 95-17 Disko B Hellefisk-1 A Flow directions Seismic unit 50 km B 69° 95-11 95-03 ▲ Unit C 95-01 Unit E ▲ Greenland 54°W 68° Hellefisk-1 Palaeogene intrusive complex Palaeogene basalts Albian–Paleocene sediments Precambrian basement 50 km ▲ Seismic lines aquired by GEUS in 1995 Extensional fault Fault with lateral or alternating displacements Reverse fault Deep well A Sediment basin Palaeogene basalts Fig. 1. A: Map of the study area showing structures at top volcanic level and the distribution of seismic units A–E. Onshore geology slightly modified from Chalmers et al. (1999). White areas are ice. B: The eruption zone in the offshore area marked by the en échelon segments interpreted from divergence of the volcanic foreset directions observed in seismic units A, B and D (indicated). tinent boundary lies close to the west coast of Disko. This hypothesis may be tested by modelling two scenarios of ocean crust offshore Disko: a warm, Icelandic plume type and a cool, normal type. In the ‘warm’ model, Moho is assumed to lie at a depth of 25 km, and the continental crust has been terminated a short distance offshore. This model results in a difference between the calculated and measured gravity data of 120–160 mGal in the area of assumed oceanic crust. In the ‘cool’ model, the Moho is assumed to lie at a depth of 12–13 km. This model shows an even greater difference between calculated and measured gravity data amounting to 250–300 mGal. The most likely solution to reducing the excess mass in these models is by incorporating a layer of sediment. Further modelling was carried out assuming continental crust in the offshore 98
Fig. 2. Part of seismic line GGU/95-08A, just north-west of Nuussuaq. Several basin fill structures can be seen as seismic units A–E. In this area seismic unit A has a strongly downlapping appearance where the top reflection passes into eastward prograding facies. The vertical height of the downlapping units is 700−800 m, which is directly equivalent to the 700 m high foresets observed in the Vaigat Formation on the south coast of Nuussuaq (Pedersen et al. 1993). W B C D E E 5500 5400 5300 5200 5100 5000 shotpoints A 5 km GGU/95-08A 500 1000 1500 2000 500 1000 1500 2000 twt (ms) twt (ms) WSW ENE 1000 2000 3000 4000 shotpoints Unit B Unit C Unit E 0 1000 2000 3000 twt (ms) GGU/95-17 4000 120 calculated observed 80 40 0 mGal 4 Itilli fault zone Fig. 3. Geological model of the region west of Disko based on gravity modelling assuming continental crust in the offshore area. Based on onshore geological data, a rather uniform thickness of 2.5–3.5 km has been assigned to the volcanic section. The depression in the gravity signal west of the Itilli fault zone is partly compensated by a postulated abrupt increase in thickness of the pre-volcanic sediments and by a change in the topography of the volcanic surface. 100 km 75 50 Distance from west coast of Disko Water Upper sediments Volcanic rocks Lower sediments 12 20 28 25 0 Crust Mantle depth km 99
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GEOLOGY OF GREENLAND SURVEY BULLETI
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Geology of Greenland Survey Bulleti
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Contents Numbers of articles corres
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■ ■ ■ ■ ■ ■ ■ ■ ■
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Canada Pituffik O 1 Thule Air Base
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Publications A complete list of geo
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Canada Greenland Greenland Inland I
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northern Nagssugtoqidian orogen (SN
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western to the north-eastern corner
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group consists of conjugate sets of
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y pure shear. Coincidence of the or
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The Precambrian supracrustal rocks
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68°25′ 52° 68°25′ BIF 0 3 km
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Fig. 4. Dolomitic marble in the sou
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Bugt (Fig. 1; Henderson 1969). The
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Keto, L. 1962: Aerial prospecting b
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▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲
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increases towards the south. We obs
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Kalsbeek, F. & Taylor, P.N. 1999: R
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Canada Nuussuaq 0 50 km PROTEROZOIC
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deposit. Descriptions of the differ
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Pegmatites The gneisses throughout
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tacts with quartzo-feldspathic coun
Page 50 and 51: Geological correlation of magnetic
Page 52 and 53: Fig. 2. The hand-held magnetic susc
Page 54 and 55: Susceptibility distribution (%) Sus
Page 56 and 57: have a reducing effect, which hinde
Page 58 and 59: ancy between the susceptibility val
Page 60 and 61: 67° Sisimiut • 53° 52° 51° 50
Page 62 and 63: Table 1. Range of Nb concentrations
Page 64 and 65: chemical composition - may indicate
Page 66 and 67: Concentration/C1 chondrite 100.00 1
Page 68 and 69: Menzies, M.A. & Hawkesworth, C.J. (
Page 70 and 71: 72°30´ Aeromag 2001 50 km Upernav
Page 72 and 73: 56° 54° 52° 72° 72° nT 71°30
Page 74 and 75: Conclusions The aeromagnetic survey
Page 76 and 77: 53° 51° Inland Ice Greenland 72°
Page 78 and 79: On the south coast of Nuussuaq, wes
Page 80 and 81: Fig. 5. Blocks and boulders in the
Page 82 and 83: 2000 SW NE 1500 Surface trace 1985
Page 84 and 85: 1979). Along other sections of the
Page 86 and 87: Petroleum geological activities in
Page 88 and 89: Seismic acquisition during summer 2
Page 90 and 91: Other petroleum geological work Alt
Page 92 and 93: A multidisciplinary study of the Pa
Page 94 and 95: Seismic interpretation The grid of
Page 96 and 97: Middle Eocene Lower Eocene Upper Pa
Page 98 and 99: Chalmers, J.A., Dahl, J.T., Bate, K
Page 102 and 103: 70° 71° 60° 2000 2000 2400 400 1
Page 104 and 105: Storey, M., Duncan, R.A., Pedersen,
Page 106 and 107: 24° 100 km 30° 27° 21 ° Jameson
Page 108 and 109: Oligocene Krabbedalen Fm Eocene Bop
Page 110 and 111: grading. Bivalve shell material is
Page 112 and 113: References Birkenmajer, K. 1972: Re
Page 114 and 115: B A 72° Palaeogene basalts Gl 50 k
Page 116 and 117: a b c d e f g h 20 µm i j k l Fig.
Page 118 and 119: offshore South-East Greenland, onsh
Page 120 and 121: ▲ Albert Heim Bjerge Wordie Gletc
Page 122 and 123: T D A CW NS placed the lowermost c.
Page 124 and 125: is abundant and highly diverse, and
Page 126 and 127: The Heimbjerge Formation comprises
Page 128 and 129: Late Permian carbonate concretions
Page 130 and 131: m 25 20 15 B3 L2 B2 Fig. 3. Simplif
Page 132 and 133: (2001), who pointed out the restric
Page 134 and 135: Piasecki, S. 1984: Preliminary paly
Page 136 and 137: 66° 68° • • • • • • 7
Page 138 and 139: absent at Tikeraussaq where a postu
Page 140 and 141: 72° 70° 68° 66° Sample locality
Page 142 and 143: Table 2. Summary of selected elemen
Page 144 and 145: Concluding remarks Observations dur
Page 146 and 147: Lake-catchment interactions with cl
Page 148 and 149: lakes. As in earlier reports (e.g.
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Discussion Global climate models pr
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Glaciological investigations on ice
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Fig. 2. The new one-mast design of
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A B N 20 km 1993 1995 Fig. 5. Satel
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Krabill, W., Frederick, E., Manizad
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2001/47: Calibration of stream sedi
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Hanghøj, K., Kelemen, P., Bernstei
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Danmarks og Grønlands Geologiske U
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GEOLOGY OF GREENLAND SURVEY BULLETI
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