Review of Greenland Avtivities 2001 - Geus

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▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ Boye Sø Nuussuaq Puiattup Qaqqaa shear zone Puiattup Qaqqaa ▲ Itilli ▲ ▲ Saqqaq Ikorfat Oqaatsut Itilliarsuup Nuua ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ Torsukattak Inussuk Anap Nunaa 70° Greenland R Ataa domain ▲ ▲ ▲ ▲ ▲ N ▲ ▲ ▲ Laksebugt Ataa ▲ ▲ ▲ ▲ ▲ ▲ ▲ 69° ▲ Quaternary deposits Cretaceous–Palaeogene province Arveprinsen Ejland ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ Palaeoproterozoic ▲ ▲ ▲ ▲ ▲ ▲ Shear zone ▲ ▲ ▲ ▲ ▲ Archaean Ductile thrust Albitised rocks Dolerite dykes and sills Anap nunâ Group: sandstone, siltstone Anap nunâ Group: marble Discordant granitic bodies (c. 2750 Ma) Qitermiunnguit 'Falcon cliff' Paakitsoq ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ 69° Atâ tonalite (c. 2800 Ma) Rodebay granodiorite Inland Ice Tonalitic–granodioritic orthogneiss Dioritic gneiss Augen granite (Saqqaq, Nuussuaq) Rodebay Itilli diorite (Nuussuaq) Acid metavolcanic rocks Pillow lava and undifferentiated amphibolite Nunatarsuaq Metagabbro Garnet-mica schist Muscovite schist Anorthosite 10 km Ilulissat 52° 50° Fig. 1. Geological sketch map of the area north-east of Disko Bugt with place names used in the text, modified from Garde (1994). Dash lines: domain boundaries. Filled circles: towns, settlements. Open circle: abandoned settlement. Dash-dot lines: faults. N and R on the inset map of Greenland denote the Nagssugtoqidian and Rinkian belts, with the map area at the arrow (also shown on van Gool et al. 2002, this volume, fig. 1). 34
Archaean acid metavolcanic rocks and the Torsukattak shear zone, south coast of Nuussuaq The Survey’s field work in Nuussuaq in 1988–1991 was largely restricted to helicopter reconnaissance; due to difficult ice conditions and lack of a suitably large boat, the south coast was not mapped. Nevertheless, a preliminary lithostratigraphy of the main, supposedly Archaean supracrustal sequences in southern Nuussuaq was established (Garde & Steenfelt 1999a), and two major Proterozoic shear zones were proposed: (1) the well-exposed, NW–SE-trending Puiattup Qaqqaa shear zone in southern Nuussuaq, and (2) the Torsukattak shear zone, a largely unexposed younger extensional shear zone along the fjord Torsukattak with oblique downthrow to the south-east (Fig. 1). The existence of the latter shear zone was mainly inferred from numerous inland observations of intense SE-plunging extension lineations, apparent tectonic reworking of the Puiattup Qaqqaa shear zone towards Torsukattak, and an abrupt decrease in the overall metamorphic grade between southern Nuussuaq and the Ataa domain (for details see Garde & Steenfelt 1999b). In 2001, it was possible to study the outcrops along the coast of Nuussuaq by boat in spite of much ice (Fig. 2). An acid metavolcanic rock with pale, finegrained volcanic clasts (Fig. 3) from a previously reported supracrustal sequence north of Itilliarsuup Nuua (Fig. 1; Garde 1994) was sampled in order to obtain a depositional age for the metavolcanic rock by U-Pb dating of its igneous zircons (using the conventional thermal ionisation method, TIMS); this will also provide a minimum age for the underlying Nuussuaq gneisses, and will allow us to compare the timing of volcanism at the continental margin of southern Nuusuaq with the arctype volcanism in the Ataa domain, which was previously dated at c. 2800 Ma (Kalsbeek & Taylor 1999). In addition, the zircon U-Pb system might also provide a discordia age for the Torsukattak shear zone. During a boat traverse of the excellently exposed, SSE-dipping acid metavolcanic and associated metasedimentary rocks we observed asymmetric volcanic clasts and garnet porphyroclasts within the intense, SE-plunging LS fabric. The asymmetric fabric elements clearly indicate relative downthrow of the southern hanging wall towards the south-east along the steep lineation (Fig. 4), corroborating Garde & Steenfelt’s (1999b) interpretation that the Torsukattak structure is a major, oblique extensional shear zone. It was previously noted in inland areas that the intensity of the LS strain fabric Fig 2. M/S Søkongen in the ice-filled waters of Torsukattak, northwest of Anap Nunaa. Fig. 3. Fragmental acid metavolcanic rocks at Itilliarsuup Nuua. Pencil for scale. Fig. 4. Asymmetric fabric elements (volcanic clasts) at Ililliarsuup Nuua, indicating relative downthrow of the southern (right-hand) side of the Torsukattak shear zone. View eastwards along the south coast of Nuussuaq. 35
Page 1: GEOLOGY OF GREENLAND SURVEY BULLETI
Page 4: Geology of Greenland Survey Bulleti
Page 7 and 8: Contents Numbers of articles corres
Page 9: ■ ■ ■ ■ ■ ■ ■ ■ ■
Page 12 and 13: Canada Pituffik O 1 Thule Air Base
Page 14 and 15: Publications A complete list of geo
Page 16 and 17: Canada Greenland Greenland Inland I
Page 18 and 19: northern Nagssugtoqidian orogen (SN
Page 20 and 21: western to the north-eastern corner
Page 22 and 23: group consists of conjugate sets of
Page 24 and 25: y pure shear. Coincidence of the or
Page 26 and 27: The Precambrian supracrustal rocks
Page 28 and 29: 68°25′ 52° 68°25′ BIF 0 3 km
Page 30 and 31: Fig. 4. Dolomitic marble in the sou
Page 32 and 33: Bugt (Fig. 1; Henderson 1969). The
Page 34 and 35: Keto, L. 1962: Aerial prospecting b
Page 38 and 39: increases towards the south. We obs
Page 40 and 41: Kalsbeek, F. & Taylor, P.N. 1999: R
Page 42 and 43: Canada Nuussuaq 0 50 km PROTEROZOIC
Page 44 and 45: deposit. Descriptions of the differ
Page 46 and 47: Pegmatites The gneisses throughout
Page 48 and 49: 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
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Middle Eocene Lower Eocene Upper Pa
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Chalmers, J.A., Dahl, J.T., Bate, K
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95-06 ▲ ▲ 58° 95-12 95-10 56°
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70° 71° 60° 2000 2000 2400 400 1
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Storey, M., Duncan, R.A., Pedersen,
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24° 100 km 30° 27° 21 ° Jameson
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Oligocene Krabbedalen Fm Eocene Bop
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grading. Bivalve shell material is
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References Birkenmajer, K. 1972: Re
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B A 72° Palaeogene basalts Gl 50 k
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a b c d e f g h 20 µm i j k l Fig.
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offshore South-East Greenland, onsh
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▲ Albert Heim Bjerge Wordie Gletc
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T D A CW NS placed the lowermost c.
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is abundant and highly diverse, and
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The Heimbjerge Formation comprises
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Late Permian carbonate concretions
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m 25 20 15 B3 L2 B2 Fig. 3. Simplif
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(2001), who pointed out the restric
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Piasecki, S. 1984: Preliminary paly
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66° 68° • • • • • • 7
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absent at Tikeraussaq where a postu
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72° 70° 68° 66° Sample locality
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Table 2. Summary of selected elemen
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Concluding remarks Observations dur
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Lake-catchment interactions with cl
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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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