Bulletin of the Geological Society of Denmark • Vol. 48/1
 | ContentsFinch, A.A., Mansfeld, J. & Andersen, T.:
U-Pb radiometric age of Nunarsuit pegmatite, Greenland: constraints on the timing of Gardar magmatism
Rose-Hansen, J. & Sørensen, H.:
Minor intrusions of peralkaline microsyenite in the Ilímaussaq alkaline complex, South Greenland
Davydov, Vladimir I., Nilson, I. & Stemmerik, L.:
Fusulinid zonation of the Upper Carboniferous Kap Jungersen and Foldedal Formations, southern Amdrup Land, eastern North Greenland
Schnetler, K. I., Lozouet, P. & Pacaud, J.–M.:
Revision of the gastropod family Scissurellidae from the Middle Danian (Paleocene) of Denmark
Note
Abrahamsen, H., Pesonen, L. & van der Voo, R.: Palaeomagnetic Databases: 4 th Nordic Palaeomagnetic Workshop
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U-Pb radiometric age of Nunarsuit pegmatite, Greenland: constraints on the timing of Gardar magmatism
Finch, A.A., Mansfeld, J. & Andersen, T.: U-Pb radiometric age of Nunarsuit pegmatite, Greenland: constraints on the timing of Gardar magmatism. Bulletin of the Geological Society of Denmark, Vol. 48, pp. 1–7, Copenhagen.
A precise U-Pb radiometric age of 1171±5 Ma has been obtained from zircons from a pegmatite in the Nunarsuit (previously spelt Nunarssuit) complex, Gardar Province, South Greenland. This age is slightly older than a corresponding Rb-Sr isochron determination. Since Nunarsuit is believed to be among the youngest Gardar centres, this radiometric age date more closely delimits the end of magmatism in the Gardar rift province. A comparison of our data with other published isotopic work may suggest that Gardar magmatism was a continuous rather than a punctuated process.
Key words: Nunarsuit complex, Gardar province, Mid-Proterozoic, alkaline rocks, zircons, cathodoluminescence.
Adrian A. Finch [
], Crustal Geodynamics Group, School of Geography and Geosciences, University of St Andrews, St Andrews, Fife KY16 9AL, UK. Joakim Mansfeld [joakim.mansfeld@ngu.no] Mineralogical-Petrological Museum, University of Oslo, Sars Gate 1, N-0562 Oslo, Norway, now at: Geological Survey of Norway, N-7491 Trondheim, Norway. Tom Andersen [t.h.andersen@toyen.uio.no] Mineralogical- Petrological Museum, University of Oslo, Sars Gate 1, N-0562 Oslo, Norway. 16 August 2000.
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Minor intrusions of peralkaline microsyenite in the Ilímaussaq alkaline complex, South Greenland
Rose-Hansen, J. & Sørensen, H.: Minor intrusions of peralkaline microsyenite in the Ilímaussaq alkaline complex, South Greenland. Bulletin of the Geological Society of Denmark, Vol. 48, pp. 9–29, Copenhagen.
The agpaitic part of the Ilímaussaq alkaline complex, South Greenland, is made up of a roof zone, an intermediate zone and a floor zone. Dykes and sills of peralkaline microsyenite intersect the rocks of the roof and floor zones, but do not appear to intersect the lujavritic nepheline syenites which make up the intermediate zone. The microsyenites consist of Na-poor microcline, K-poor albite, aegirine and arfvedsonite which are practically identical to those of the agpaitic nepheline syenites of the complex. Neptunite and pectolite are the commonest minor minerals. The microsyenites are silica-saturated, –oversaturated, or, more rarely, undersaturated. The agpaitic part of the Ilímaussaq complex is considered to have been formed in a closed magma chamber; the lujavrites of the intermediate zone representing residual melts left after the consolidation of the roof and floor zones. That the microsyenite intrusions intersect the roof and floor zones but not the youngest lujavrites lying between these zones presents a geometrical problem which is discussed at some length. It is difficult to explain the microsyenites as products of fractionation or contamination of melts within the agpaitic magma chamber. Furthermore, the microsyenites differ mineralogically and chemically from the abundant microsyenitic dykes of the regional Tugtutôq-Ilímaussaq dyke swarm. It is therefore proposed that they originated in the source region which fed the agpaitic melts of the Ilímaussaq complex and that their emplacement in fractures was accompanied by a loss of volatiles and incompatible elements.
Key words: agpaitic, Ilímaussaq, lujavrites, microsyenites.
J. Rose-Hansen & H. Sørensen, Geological Institute, University of Copenhagen, Øster Voldgade 10, DK- 1350 Copenhagen K, Denmark. 12 January 2001.
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Fusulinid zonation of the Upper Carboniferous Kap Jungersen and Foldedal Formations, southern Amdrup Land, eastern North Greenland
Davydov, Vladimir I., Nilson, I. & Stemmerik, L.: Fusulinid zonation of the Upper Carboniferous Kap Jungersen and Foldedal Formations, southern Amdrup Land, eastern North Greenland. Bulletin of the Geological Society of Denmark, Vol. 48, pp. 31–77, Copenhagen.
New fusulinid data from the Kap Jungersen and Foldedal Formations in southern Amdrup Land, eastern North Greenland allow the establishment of a detailed fusulinid-based zonation of the Upper Carboniferous succession in the Wandel Sea Basin. The fusulinid fauna is quite similar to that of the Russian Platform, the Ural Mountains, Spitsbergen, Bjørnøya, and the offshore areas of the Barents Sea, and therefore the Greenland strata are confidently correlated to the these regions. The Kap Jungersen Formation and the lower part of the Foldedal Formation are dated as late early Moscovian to latest Moscovian in age. The locally more than 450 m thick Moscovian part of the succession comprises four fusulinid zones: the Profusulinella prisca – Neostaffella subquadrata Zone and the Citrinoides paraozawai Zone of early Moscovian age, and the Fusulinella bocki – Pseduofusulinella pulchra Zone and the Protriticites ovatus Zone of late Moscovian age. Lower and middle Kasimovian deposits, characterized by two fusulinid assemblages of the Obsoletes obsoletus – Protriticites pseudomontiparus Zone and the Montiparus paramontiparus Zone, are recognised for the first time in Amdrup Land. The thin lower Gzelian succession is represented by two fusulinid assemblages that definine the Rugosofusulina flexuosa Zone and the Daixina crispa – Rauserites stuckenbergi Zone. The youngest Carboniferous strata, belonging to the Orenburgian part of the Gzelian are characterised by an assemblage of the Schellwienia ulukensis Zone.
Key words: Biostratigraphy, Fusulinid zonation, Upper Carboniferous, Wandel Sea Basin.
V.I. Davydov, Permian Research Institute, Department of Geosciences, Boise State University, Boise, Idaho, USA. I. Nilsson, Norsk Hydro ASA, N-9480 Harstad, Norway. L. Stemmerik, Geological Survey of Denmark and Greenland, Thoravej 8, DK-2400 Copenhagen NV, Denmark. 21 September 2000.
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Revision of the gastropod family Scissurellidae from the Middle Danian (Paleocene) of Denmark
Schnetler, K. I., Lozouet, P. & Pacaud, J.–M.: Revision of the gastropod family Scissurellidae from the Middle Danian (Paleocene) of Denmark. Bulletin of the Geological Society of Denmark, Vol. 48, pp. 79–90. Copenhagen.
The rich molluscan fauna from the Middle Danian (Early Paleocene) of Fakse contains five species of the gastropod family Scissurellidae Gray, 1847. This revision recognizes three new species, viz. Anatoma rosenkrantzi sp. nov., Praescissurella? ravni sp. nov. and Scissurella (s. l.) aliceae sp. nov. Anatoma danica Bandel, 1998 is considered a junior synonym of Leptomaria niloticiformis (von Schlotheim, 1820). The palaeoecoelogy of this scissurellid and pleurotomarid fauna and the associated mollusc fauna is noted.
Key words: Gastropods, Scissurellidae, palaeoecoelogy, Paleocene, Middle Danian, Fakse, Denmark.
K.I. Schnetler [
], Fuglebakken 14, Stevnstrup, DK-8870 Langå, Denmark. P. Lozouet [
], BIMM, Muséum National d’Histoire Naturelle, 55 rue Buffon, F- 75005, Paris, France. J.-M. Pacaud [
], Laboratoire de Paleontologie, Muséum National d’Histoire Naturelle, UMR 8569 CNRS, 8 rue Buffon, F-75005, Paris, France. 24 October 2000.
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