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Nr. 6, East Greenland Caledonides: stratigraphy, structure and geochronology


A.K. Higgins and Feiko Kalsbeek

West-dipping white and rusty brown quartzites of the Early Cambrian Slottet Formation, at Slottet in the Eleonore Sø foreland window
West-dipping white and rusty brown quartzites of the Early Cambrian Slottet Formation, at Slottet in the Eleonore Sø foreland window, resting unconformably on dark clastic sediments of the Palaeoproterozoic Eleonore Sø complex. The summit of Slottet (1933 m high) is 600 m above the glacier surface.

Abstracts

Preface
Higgins, A.K. & Kalsbeek, F. (eds) 2004: East Greenland Caledonides: stratigraphy, structure and geochronology. Geological Survey of Denmark and Greenland Bulletin 6, 93 pp.

The East Greenland Caledonides extend from 70° to 81°30'N, and have been the subject of a series of regional mapping programmes between 1968 and 1998. The entire orogen is now covered by five published 1:500 000 geological map sheets. The six papers in this bulletin concern a variety of topics relating mainly to Kronprins Christian Land (79°-81°30'N) and the Kong Oscar Fjord region (72°-75°N).

The paper by Smith et al. on Lower Palaeozoic stratigraphy proposes amendments to several stratigraphical units that occur in Kronprins Christian Land and nearby Lambert Land. In the Kong Oscar Fjord region, two new formations are defined for quartzite and limestone/dolostone units that crop out in foreland windows, and the Lower Palaeozoic succession of the fjord region of East Greenland is formally placed in the Kong Oscar Fjord Group. The second paper by Smith et al. describes and formally defines the Neoproterozoic Rivieradal Group of Kronprins Christian Land. The paper by Higgins et al. analyses the thin-skinned fold-and-thrust belt that marks the transition between foreland and orogen in Kronprins Christian Land, and presents a balanced cross-section restoration.

The two geochronological papers by Thrane report the results of ion microprobe zircon analyses from orthogneisses in the Charcot Land window (72°N), and results of reconnaissance Pb-Pb dating by the step-leaching method.

The final paper by Higgins & Leslie reviews the history of geological research in the Eleonore Sø and Målebjerg areas of the Kong Oscar Fjord region (72°-75°N). Recognition that the two areas are part of the Caledonian foreland implies that the two thrust sheets structurally overlying the Eleonore Sø and Målebjerg windows have large displacements (~ 100 km each), and that the 'stockwerke' concept of the orogen that focused on in situ vertical movements can finally be laid to rest.



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Abstracts:

Lower Palaeozoic stratigraphy of the East Greenland Caledonides

M. Paul Smith, Jan Audun Rasmussen, Steve Robertson, A.K. Higgins and A. Graham Leslie

The Lower Palaeozoic stratigraphy of the East Greenland Caledonides, from the fjord region of North-East Greenland northwards to Kronprins Christian Land, is reviewed and a number of new lithostratigraphical units are proposed. The Slottet Formation (new) is a Lower Cambrian quartzite unit, containing Skolithos burrows, that is present in the Målebjerg and Eleonore Sø tectonic windows, in the nunatak region of North-East Greenland. The unit is the source of common and often-reported glacial erratic boulders containing Skolithos that are distributed throughout the fjord region. The Målebjerg Formation (new) overlies the Slottet Formation in the tectonic windows, and comprises limestones and dolostones of assumed Cambrian–Ordovician age. The Lower Palaeozoic succession of the fjord region of East Greenland (dominantly limestones and dolostones) is formally placed in the Kong Oscar Fjord Group (new). Amendments are proposed for several existing units in the Kronprins Christian Land and Lambert Land areas, where they occur in autochthonous, parautochthonous and allochthonous settings.

Keywords: Early Palaeozoic, North-East Greenland, stratigraphy

M.P.S., Lapworth Museum, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. E-mail: m.p.smith@bham.ac.uk
J.A.R. & A.K.H., Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
S.R. (deceased) & A.G.L., British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, UK.

Geological Survey of Denmark and Greenland Bulletin 6, 5–28 © GEUS, 2004


The Neoproterozoic Rivieradal Group of Kronprins Christian Land, eastern North Greenland

M. Paul Smith, A.K. Higgins, N.J. Soper and Martin Sønderholm

The Rivieradal Group, formally defined here, is confined to the Vandredalen thrust sheet of the Caledonian orogen in Kronprins Christian Land, eastern North Greenland. It comprises a succession of Neoproterozoic siliciclastic sediments that represent the fill of a half-graben basin. The syn-rift Rivieradal Group is overlain by post-rift sediments of the Hagen Fjord Group. The latter succession is present in both the thrust sheet and the Caledonian foreland to the west. In the foreland, where the Rivieradal Group is not represented, the Hagen Fjord Group disconformably overlies Palaeoproterozoic–Mesoproterozoic sandstones of the Independence Fjord Group.

Keywords: Caledonian, North Greenland, Precambrian, Proterozoic, stratigraphy

M.P.S., Lapworth Museum, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. E-mail: m.p.smith@bham.ac.uk
A.K.H. & M.S., Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350, Copenhagen K, Denmark.
N.J.S., Gams Bank, Threshfield, Skipton BD23 5NP, UK. Also affiliated with: Department of Geology, University College, Galway, Ireland.

Geological Survey of Denmark and Greenland Bulletin 6, 29-39 © GEUS, 2004


The Caledonian thin-skinned thrust belt of Kronprins Christian Land, eastern North Greenland

A.K. Higgins, N.J. Soper, M. Paul Smith and Jan A. Rasmussen

Kronprins Christian Land in the extreme north of the East Greenland Caledonides, exposes a thin-skinned thrust belt up to 50 km wide developed in Ordovician-Silurian platform limestones and dolostones of the Iapetus passive margin. This thrust belt is characterised by a series of SSW-NNE-trending and east-dipping Caledonian thrusts with westward displacements of generally a few kilometres each. It passes westwards into undisturbed autochthonous foreland. Based on a line and area restoration, total displacement along a well-exposed WNW-ESE section through the thrust belt amounts to 17.6 km, which represents a shortening of 45% in the line of section. Biostratigraphic control in the limestone and dolostone succession is based on conodonts and macrofossils. The alteration colours of the conodonts provide estimates of maximum burial temperatures, which show that the thickness of the overlying thrust sheets ranged from about 6 to 12.5 km from west to east across the thrust belt. Since the estimated former thickness of the Vandredalen thrust sheet above the thin-skinned parautochthonous thrust belt is insufficient to yield the temperatures attained, higher thrust sheets must once have extended across the region.

Keywords: Caledonides, conodonts, Greenland, Ordovician, thrust tectonics

A.K.H. & J.A.R., Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: akh@geus.dk
N.J.S., Gams Bank, Threshfield, Skipton BD23 5NP, UK. Also affiliated with: Department of Geology, University College, Galway, Ireland.
M.P.S., Lapworth Museum, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.

Geological Survey of Denmark and Greenland Bulletin 6, 41-56 © GEUS, 2004


Palaeoproterozoic age of a basement gneiss complex in the Charcot Land tectonic window, East Greenland Caledonides

Kristine Thrane

The Charcot Land tectonic window exposes crystalline basement gneisses, which form part of the foreland of the East Greenland Caledonides. These gneisses were previously believed to be Archaean in age, on the basis of imprecise K-Ar analyses carried out in the early 1980s on hornblende from amphibolitic bands and inconclusive Rb/Sr isotope data. New U-Pb single-zircon ion microprobe analyses on the gneisses of the window yield upper intercept ages of 1916 +/-21 and 1928 +/-11 Ma, and are interpreted to represent the age of crystallisation of the igneous protolith. The foreland gneisses of the Charcot Land window are similar in age to parts of the allochthonous gneiss complexes of structurally overlying thrust sheets, but the two terranes have different lithological and structural characteristics. No Archaean rocks have been identified with certainty in any of the East Greenland Caledonian foreland windows.

Keywords: Caledonides, East Greenland, geochronology, Palaeoproterozoic

Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Present address: Geological Institute, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: Kthrane@geol.ku.dk

Geological Survey of Denmark and Greenland Bulletin 6, 57-66 © GEUS, 2004


Reconnaissance Pb-Pb dating of single mineral phases by the step-leaching method: results from the Caledonides of East Greenland

Kristine Thrane

Reconnaissance Pb-Pb step-leaching analyses have been carried out on garnet and kyanite from the Krummedal supracrustal sequence in East Greenland, yielding respectively Neoproterozoic and Caledonian ages. These data support previous analyses suggesting that the Krummedal supracrustal sequence, widespread in southern parts of the East Greenland Caledonides, was affected by both an early Neoproterozoic and a Caledonian thermal event. Titanite and apatite fractions from the underlying crystalline basement rocks were analysed in order to obtain metamorphic ages, as a contrast and supplement to the numerous existing protolith ages on ortho-gneisses. The titanite yielded a date of 486 +/-15 Ma which, if interpreted as a true age, is older than the usual range of Caledonian ages in East Greenland. The significance of this date is uncertain, but one possibility is that it reflects extension and subsidence taking place prior to Caledonian collision. The apatite, in contrast, yielded a very young Caledonian date of 392 +/-24 Ma that may reflect the cooling of the basement gneisses to <500°c subsequent to collision.

Keywords: Caledonian, East Greenland, geochronology, Neoproterozoic, step-leaching

Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Present address: Geological Institute, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: Kthrane@geol.ku.dk

Geological Survey of Denmark and Greenland Bulletin 6, 67-76 © GEUS, 2004


The Eleonore Sø and Målebjerg foreland windows, East Greenland Caledonides, and the demise of the 'stockwerke' concept

A.K. Higgins and A. Graham Leslie

Recognition of the Eleonore Sø and Målebjerg foreland windows during the 1997-1998 regional mapping expeditions to the East Greenland Caledonides provided critical evidence for large-scale, westward-directed thrusting in the Kong Oscar Fjord region (72°-75°N), a revelation that dealt a final blow to the 'stockwerke' concept of an in situ highly mobile infrastructure characterised by rising fronts of Caledonian migmatisation and metasomatism. This paper reviews earlier investigations in both the Eleonore Sø and Målebjerg areas, and the misinterpretations of rock units that initially obscured recognition of their foreland affinity. The Eleonore Sø and Målebjerg windows can now be placed in context, as part of the lowest structural level of the foreland-propagating thrust pile of the Kong Oscar Fjord region.

Keywords: Caledonides, East Greenland, tectonic windows

A.K.H., Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: akh@geus.dk
A.G.L., British Geological Survey, Murchison House, Edinburgh EH9 3LA, UK.

Geological Survey of Denmark and Greenland Bulletin 6, 77-93 © GEUS, 2004


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