Review of Greenland Avtivities 2001 - Geus

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m 25 20 15 B3 L2 B2 Fig. 3. Simplified sedimentological log showing the typical five-fold division of the Ravnefjeld Formation. L1 and L2 are laminated intervals, and B1, B2 and B3 are bioturbated intervals. The compilation is based on lithological features observed at Kap Stosch and Triaselv, and elsewhere in the region (Piasecki 1990; Piasecki & Stemmerik 1991; Nielsen 2001). A Py 0.50 mm L1 B 10 Calcareous, micaceous mudstone Bioturbated siltstone Py 5 0 B1 Carbonate beds Carbonate concretions Fish remains 0.50 mm slightly elliptical and range from a few centimetres to more than three metres in diameter. Their long axes are parallel to the bedding, but they show no sign of parallel orientation. Although fish remains have been found both in the concretions and in the surrounding sediments since the late 1920s (e.g. Bendix-Almgreen 1993), knowledge of the nature of concretion formation was very limited prior to initiation of the present project. The Ravnefjeld Formation comprises most of the former Posidonia (originally Posidonomya) Shale (Newell 1955; Maync 1961) considered to be of Kazanian age, which is roughly equivalent to the European Zechstein cycle 1 (Piasecki 1984; Rasmussen et al. 1990; Utting & Piasecki 1995); it is of latest Wuchiapingian age, based on the conodont fauna (Stemmerik et al. 2001). Biological constituents of the carbonate concretions Both pellets and trace fossils are very common in the carbonate concretions. The pellets show signs of bedding-parallel, compactional deformation, indicating loading due to overburden before cementation. Fig. 4. Micrographs of the abundant calcispheres, partially replaced by euhedral pyrite (Py) as viewed in transmitted light (A) and ultraviolet fluorescence (B) (sample GGU 446352). The pyrite contains fluorescent calcite inclusions. Some carbonate concretions contain a rich skeletal fauna consisting mostly of small fragments due to mechanical breakage before final deposition. No systematic investigation of the skeletal fauna has been undertaken, but some aspects that are important for the facies analysis and diagenesis of the Ravnefjeld Formation are pointed out. Calcispheres (calcareous, hollow, spherical bodies about 75–200 microns in diameter) are very abundant in the laminated concretions from the L1 and L2 intervals (Fig. 4A, B). The origin of calcispheres has been a matter of debate, but most are believed to represent reproductive cysts of green algae belonging to the family Dasycladaceae (Wray 1977). Upper Palaeozoic calcispheres are often encountered in shallow-water deposits (especially in restricted or back-reef environments), and as such they provide a useful palaeoenvironmental indicator. This interpretation is in good agreement with Piasecki & Stemmerik (1991) and Nielsen 128
A B Ba Ba 0.5 mm 0.5 mm C E 0.5 mm D 0.5 mm 0.5 mm F G 0.5 mm 0.5 mm Fig. 5. Micrographs of the millimetre-sized gastropods containing authigenic calcite and baryte (Ba) viewed in transmitted light (A) and cathodoluminescence (B); compaction has not affected these shells. Bivalve shell in transmitted light (C) and cathodoluminescence view (D) is affected by micritisation and authigenic calcite crystals. The youngest calcite generation (E) is confined to veins and displays orange luminescence. Weak disintegration and displacement of the prismatic crystals of a thin-shelled fossil (F, G) followed by calcite cementation of the cavity (sample GGU 446370-2). 129
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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
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Geological correlation of magnetic
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Fig. 2. The hand-held magnetic susc
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Susceptibility distribution (%) Sus
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have a reducing effect, which hinde
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ancy between the susceptibility val
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67° Sisimiut • 53° 52° 51° 50
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Table 1. Range of Nb concentrations
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chemical composition - may indicate
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Concentration/C1 chondrite 100.00 1
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Menzies, M.A. & Hawkesworth, C.J. (
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72°30´ Aeromag 2001 50 km Upernav
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56° 54° 52° 72° 72° nT 71°30
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Conclusions The aeromagnetic survey
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53° 51° Inland Ice Greenland 72°
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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 100 and 101: 95-06 ▲ ▲ 58° 95-12 95-10 56°
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 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.
Page 150 and 151: Discussion Global climate models pr
Page 152 and 153: Glaciological investigations on ice
Page 154 and 155: Fig. 2. The new one-mast design of
Page 156 and 157: A B N 20 km 1993 1995 Fig. 5. Satel
Page 158 and 159: Krabill, W., Frederick, E., Manizad
Page 160 and 161: 2001/47: Calibration of stream sedi
Page 162 and 163: Hanghøj, K., Kelemen, P., Bernstei
Page 165 and 166: Danmarks og Grønlands Geologiske U
Page 167: GEOLOGY OF GREENLAND SURVEY BULLETI
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