Publikationer

Stratigraphy and age of the Eocene Igtertivâ Formation basalts, alkaline pebbles and sediments of the Kap Dalton Group in the graben at Kap Dalton, East Greenland

Larsen, L.M., Pedersen, A.K., Sørensen, E.V., Watt, W.S. & Duncan, R.A., 2013-08-01. Stratigraphy and age of the Eocene Igtertivâ Formation basalts, alkaline pebbles and sediments of the Kap Dalton Group in the graben at Kap Dalton, East Greenland.
©2013 by Bulletin of the Geological Society of Denmark, Vol. 61, pp. 1–18. ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2013-61-01

Abstract: A NE–SW-trending graben at Kap Dalton on the Blosseville Kyst contains an at least 600 m thick succession of Eocene basalt lavas and sediments. The succession has been investigated by new field work, geochemical analysis and radiometric dating by the 40Ar-39Ar incremental heating method.

The results show that the volcanic succession comprises about 220 m of the uppermost plateau basalt formation, the Skrænterne Formation. This is separated from the overlying lava flows of the Igtertivâ Formation by 7 m of sediments that represent a period of around six million years. The two formations can be distinguished by different trace element ratios.

The Igtertivâ Formation comprises an at least 300 m thick main succession of flows dated to 49.09 ± 0.48 Ma, overlain by sediments of the Bopladsdalen Formation. A basal conglomerate in the sediments contains pebbles of alkaline igneous rocks of which three were dated at 49.17 ± 0.35 Ma, 47.60 ± 0.25 Ma, and 46.98 ± 0.24 Ma. The sediments are thus younger than 47 Ma. Above 30 m of sediments occur two Igtertivâ Formation lava flows dated to 43.77 ± 1.08 Ma.

The overlying sediments of the Bopladsdalen and Krabbedalen Formations are therefore not older than about 44 Ma and palynological evidence shows that they are also not much younger than this. Use of the Geological Time Scale 2012 has resulted in good agreement between radiometric and palynological ages.

The Igtertivâ Formation lava flows were fed from a regional coast-parallel dyke swarm indicating a new rifting episode at 49–44 Ma. This coincides with a major mid-Eocene plate reorganisation event in the North Atlantic and the start of northward-propagation of the Reykjanes Ridge through the continent. The Igtertivâ rift may have been directly instrumental for the initiation of this process.

Keywords: Igtertivâ Formation, plateau basalts, alkaline pebbles, Bopladsdalen Formation, radiometric ages, Kap Dalton, East Greenland, ridge propagation.

Addresses: Lotte Melchior Larsen, Erik Vest Sørensen , W. Stuart Watt , Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Asger Ken Pedersen, Natural History Museum of Denmark, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark (also GEUS).
Robert A. Duncan, College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA.

Download additional data on geochemical composition:

Supplementary data file 1 – xls-file

and 39Ar/40Ar age determinations

Supplementary data file 2 – xls-file and Supplementary data file 3 – xls-file
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Depositional environments of Lower Cretaceous (Ryazanian– Barremian) sediments from Wollaston Forland and Kuhn Ø, North-East Greenland

Pauly, S., Mutterlose, J. & Alsen, P., 2013-08-23. Depositional environments of Lower Cretaceous (Ryazanian– Barremian) sediments from Wollaston Forland and Kuhn Ø, North-East Greenland.
©2013 by Bulletin of the Geological Society of Denmark, Vol. 61, pp. 19–36. ISSN 2245-7070.
https://doi.org/10.37570/bgsd-2013-61-02

Abstract: Lower Cretaceous sediments from the Wollaston Forland–Kuhn Ø area in North-East Greenland have been analyzed for stable carbon isotopes, total organic carbon (TOC) content, and major and trace elements, aiming at a lithological characterization and reconstruction of the depositional environments.

The marine sediments of Ryazanian–Barremian age were deposited in North-East Greenland directly after a major Late Jurassic – earliest Cretaceous rifting event.

The Lower Cretaceous post-rift sediments are composed of fossiliferous calcareous mud- and marlstones assigned to the Albrechts Bugt (upper Ryazanian – Valanginian) and Rødryggen (Hauterivian) Members. The calcareous sediments are commonly sandwiched between black mudstones of Late Jurassic – earliest Cretaceous (Bernbjerg Formation) and mid Cretaceous (unnamed formation) age.

The carbon isotope curves present the first record for the Lower Cretaceous (upper Ryazanian – Barremian) of North-East Greenland. The Ryazanian – Hauterivian sediments are characterized by a mixture of terrigenous detrital matter (quartz, clay minerals, heavy minerals) similar to average shale, with varying CaCO3 concentrations. The Barremian black mudstones on the contrary have lower CaCO3 and higher clay mineral contents. The deposition of the Bernbjerg Formation took place under anoxic bottom water conditions.

The depositional environment of the Albrechts Bugt and Rødryggen Members is characterized by well-oxygenated sea-floor conditions, hemipelagic sedimentation of fine-grained terrigeneous detrital matter, and biogenic carbonate settling. After this relatively short interval of carbonate sedimentation under oxic conditions, bottom waters were affected by dysoxic conditions, responsible for the burial of organic matter in the Barremian.

Keywords: Carbon isotope record, TOC, sediment geochemistry, North-East Greenland, Bernbjerg Formation, Albrechts Bugt Member, Rødryggen Member, depositional environment.

Addresses: Sebastian Pauly, Jørg Mutterlose, Institute of Geology, Mineralogy and Geophysics, Ruhr-University Bochum, Universitätsstrasse 150, D-44801, Germany.
Peter Alsen, Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.

Download additional data on major and trace element data from the Rødryggen section:

Supplementary data file 1 – xls-file

and data on major and trace element data from the Perisphinctes Ravine section:
Supplementary data file 2 – xls-file and Supplementary data file 3 – xls-file

Associated skeletal and dental remains of a fossil odontaspidid shark (Elasmobranchii: Lamniformes)from the Middle Eocene Lillebælt Clay Formation in Denmark

Hansen, B.B., Cuny, G., Rasmussen, B.W., Shimada, K., Jacobs, P. & Heilmann-Clausen, C., 2013-09-20. Associated skeletal and dental remains of a fossil odontaspidid shark (Elasmobranchii: Lamniformes)from the Middle Eocene Lillebælt Clay Formation in Denmark.
©2013 by Bulletin of the Geological Society of Denmark, Vol. 61, pp. 37–46. ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2013-61-03

Abstract: A set of associated vertebrae and teeth of a fossil shark was collected from the lower Lutetian (Middle Eocene) part of the Lillebælt Clay Formation in Denmark.

Its vertebral morphology indicates that the individual belongs to an odontaspidid lamniform shark. Although it is here identified as Odontaspididae indet., its tooth morphology suggests that the fossil shark possibly belongs to an undescribed taxon closely allied to Odontaspis or Palaeohypotodus.

Based on comparisons with extant Odontaspis, the fossil individual possibly measured about 333 cm in total length. The disarticulated nature of the specimen in a low-energy deposit indicates that the shark carcass must have been lying on the sea floor for some time before its burial. The fossil individual was found along with a possible shed tooth of another indeterminate odontaspidid taxon.

Keywords: Denmark, Eocene, Lamniformes, shark, teeth, vertebrae.

Addresses: Bitten Bolvig Hansen, Gilles Cuny, Bo Wilhelm Rasmussen ], Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark.
Kenshu Shimada, Department of Environmental Science and Studies and Department of Biological Sciences, DePaul University, 2325 N. Clifton Avenue, Chicago, Illinois 60614, USA, and Sternberg Museum of Natural History, 3000 Sternberg Drive, Hays, Kansas 67601, USA.
Perri Jacobs , Department of Biological Sciences, DePaul University, 2325 N. Clifton Avenue, Chicago, Illinois 60614, USA.
Claus Heilmann-Clausen , Department of Geoscience, Aarhus University, DK-8000 Aarhus C, Denmark.

For rotating CT-reconstructions of DK541h see – download the files to computer if they don’t show in browser:

New data on eudialyte decomposition inerals from kakortokites and associated pegmatites of the Ilímaussaq complex, South Greenland*

Karup-Møller, S. & Rose-Hansen, J. 2013-12-20. New data on eudialyte decomposition minerals from kakortokites and associated pegmatites of the Ilímaussaq complex, South Greenland.
©2013 by Bulletin of the Geological Society of Denmark, Vol. 61, pp. 47–70. ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin). *Contribution to the mineralogy of Ilímaussaq no. 143
https://doi.org/10.37570/bgsd-2013-61-04

Abstract
A suite of samples with eudialyte and eudialyte decomposition minerals from the kakortokite and associated pegmatites of the Ilímaussaq complex in South Greenland has been investigated by electron microprobe analysis.

Extensive decomposition of eudialyte has resulted in the formation of catapleiite as host for a number of rare and hitherto unknown REE minerals besides known minerals such as monazite and kainosite.

Mineral A1 is present in very small amounts in nearly all eudialyte decomposition aggregates and comprises two varieties: Ca-rich A1 with composition HCa3REE6(SiO4)6(F◊) and presumed apatite structure, and Ca-poor A1 with composition (Fe,Mn,Ca)1.5REE6Si6FO22 and unknown structure.

Mineral A2 with composition (Ca,Fe)1.2REE4Si6O19−y(OH)2y · nH2O is indistinguishable from A1 in EMP-backscattered light and has only been found at a limited number of localities. Mineral A2 also occurs as a primary mineral at one locality.

Additional rare and new REE-minerals are mineral A3 with composition Na0.2Ca0.6Fe0.2Mn0.5 Al0.5REE2.8Si6F0.5O)18-y(OH)2y · nH2O; mineral Uk2 with composition REE2.00F1.50O2.25-y(OH)2y · nH2O; mineral Uk3 with composition CaREE4O7-yOH)2y · nH2O; and mineral Y1 with composition Na2Ca4Y2.7REE1.3F18 (OH)4. The Ce:(Y+La+Pr+Nd+Sm+Gd) molar ratio for A1, A2, A3, Uk2, Uk3 and monazite is close to 1:1.

Characteristic for A1, A2 and monazite are substantial solid solutions between La and (Pr+Nd+Sm+Gd) with slowly increasing content of Ce as the content of La increases. A similar pattern does not exist for the REE in fresh eudialyte. Kainosite, identified in one decomposition aggregate, has not previously been found in the Ilímaussaq complex.

Keywords: Greenland, Ilímaussaq, kakortokite, pegmatite, eudialyte decomposition, unknown REE mineral, monazite, kainosite, apatite group.

Addresses: S. Karup-Møller , Department of Civil Engineering, Technical University of Denmark, Brovej, Bygning 118, DK-2800 Lyngby, Denmark.
J. Rose-Hansen , Department of Geoscience and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.

For individual microprobe analyses, see:

Supplementary data file 1 –xls-file
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