scholarly journals Structural evolution of the Ikerasak area, Umanak district, central West Greenland

1981 ◽  
Vol 105 ◽  
pp. 33-35
Author(s):  
J Grocott
Keyword(s):  
Structural Evolution ◽  
The South ◽  
West Greenland ◽  
Structural Style

The 1980 season was the last of the three seasons allocated for the mapping of the 1:100000 sheet 70 V. 2 Nord-Agpat (for background and references see Pulvertaft, 1979). The most important area that remained to be mapped in 1980 consisted of the islands Ikerasak and Talerua, which were known from the 1965 reconnaissance by T. C. R. Pulvertaft to have a structural style somewhat different from that of the northern part of the sheet area where low dips are prevalent. The author was invited to join the team of geologists from Copenhagen University responsibie for the Agpat sheet to map these islands and the mainland peninsula of Akuliaruserssuaq to the south-east (fig. 11).

Structural evolution of the external zones derived from the Flysch trough and the South Iberian and Maghrebian paleomargins around the Gibraltar arc: a comparative study

2006 ◽  
Vol 177 (5) ◽  
pp. 267-282 ◽  
Author(s):  
Ana Crespo-Blanc ◽  
Dominique Frizon de Lamotte
Keyword(s):  
Large Scale ◽  
Structural Evolution ◽  
Accretionary Prism ◽  
Point Of View ◽  
Low Grade ◽  
The South ◽  
Sedimentary Sequences ◽  
Structural Style ◽  
Thrust Belts ◽  
Orogenic Wedge

Abstract The Betics and Rif cordillera constitute the northern and southern segments of the Gibraltar arc. Two different fold-and-thrust belts, deriving from the South Iberian and Maghrebian paleomargins respectively, developed in front of this orogenic system. By contrast, the Flysch Trough units and the overlying Alboran crustal domain (internal zones), which are situated in the uppermost part of the orogenic wedge, are common to both branches of the arc. The Flyschs Trough units constitute an inactive accretionary prism, derived from a deep elongated trough. From three large-scale profiles and some lithostratigraphic features of the involved sedimentary sequences, the Betic and Rif external domains are compared, mainly from a structural point of view. Although they are generally considered to show major similarities, the Betic and Rif external domains are in fact strikingly different, mainly concerning the structural style, deformation timing and metamorphism: a) the thick-skinned structure in the External Rif domain vs thin-skinned in the Subbetic domain; b) the pre-Oligocene and Miocene stacking in the External Rif domain vs the exclusively Miocene one in the Subbetic domain, and c) the metamorphism present only in part of the External Rif domain (low-grade greenschists facies). By contrast, it was not possible to establish any difference in structural style and deformation timing between the Flysch units outcropping in both branches of the Gibraltar arc.

New structure maps over the Nuussuaq Basin, central West Greenland

1998 ◽  
pp. 18-27
Author(s):  
James A. Chalmers ◽  
T. Christopher R. Pulvertaft ◽  
Christian Marcussen ◽  
Asger K. Pedersen
Keyword(s):  
Structural Model ◽  
Gravity Data ◽  
Geological Survey ◽  
The South ◽  
Seismic Line ◽  
West Greenland ◽  
Structural Style ◽  
Sea Bed ◽  
Large Step ◽  
Total Lack

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Chalmers, J. A., Pulvertaft, T. C. R., Marcussen, C., & Pedersen, A. K. (1998). New structure maps over the Nuussuaq Basin, central West Greenland. Geology of Greenland Survey Bulletin, 180, 18-27. https://doi.org/10.34194/ggub.v180.5081 _______________ In 1992 the Geological Survey of Greenland (GGU) discovered bitumen in vugs and vesicles in Upper Paleocene basalts in western Nuussuaq (Christiansen et al. 1994). Since then the search for surface oil showings by GGU (from 1995 by the Geological Survey of Denmark and Greenland, GEUS) has resulted in finds over an area extending from northern Disko through Nuussuaq to the south-east corner of Svartenhuk Halvø (Christiansen et al. 1997, 1998, this volume). In addition, slim core drilling by GGU and grønArctic Energy Inc., the holder of an exclusive licence in western Nuussuaq, penetrated oil-saturated rocks at four localities (Christiansen et al. 1996). Encouraged by these results, grønArctic drilled a conventional exploration well (GRO#3) to 2996 m in 1996 (Christiansen et al. 1997), but details about this have not been released. The net effect of these efforts has been to dispel partially the formerly widespread view that the West Greenland area is entirely gas-prone and to promote the Cretaceous– Tertiary Nuussuaq Basin from being a model for what may occur in offshore basins to being a potential petroleum basin in its own right. Evolving conceptions of the Nuussuaq Basin took a large step forward when GGU in 1994 acquired a 13 km 15-fold seismic line on the south coast of Nuussuaq (Christiansen et al. 1995). This showed a sedimentary section 6–8 km thick, much greater than the 2–3 km previously measured from onshore outcrops alone. This showed how little was understood about the structure of the basin, as well as where hydrocarbons might have been generated and where exploration could best be directed. A first step to rectify this situation was taken in 1995 when multichannel seismic and gravity data were acquired by the Survey in Disko Bugt and the fjords north and south of Nuussuaq, as well as west of Disko (Christiansen et al. 1996). The new data have been integrated with older gravity, magnetic and seismic data from both onshore and offshore. This report summarises the results of interpretation of all available geophysical data together with a reappraisal of all available data on faults onshore. Detailed accounts are being published elsewhere (Chalmers 1998; J.A. Chalmers et al. unpublished data). Although the open spacing of the seismic lines and the almost total lack of reflections below the first sea-bed multiple on these lines make it impossible to present a definitive structural model at this stage, the structural style in the basin is now apparent and a number of the major structures in the area have been identified with confidence.

The Archaean Atâ intrusive complex (Atâ tonalite), north-east Disko Bugt, West Greenland

1999 ◽  
pp. 103-112
Author(s):  
Feiko Kalsbeek ◽  
Lilian Skjernaa
Keyword(s):  
Intrusive Complex ◽  
The South ◽  
Original Series ◽  
Early Proterozoic ◽  
West Greenland ◽  
North East ◽  
The North ◽  
Southern Border ◽  
Area North ◽  
Igneous Layering

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Kalsbeek, F., & Skjernaa, L. (1999). The Archaean Atâ intrusive complex (Atâ tonalite), north-east Disko Bugt, West Greenland. Geology of Greenland Survey Bulletin, 181, 103-112. https://doi.org/10.34194/ggub.v181.5118 _______________ The 2800 Ma Atâ intrusive complex (elsewhere referred to as ‘Atâ granite’ or ‘Atâ tonalite’), which occupies an area of c. 400 km2 in the area north-east of Disko Bugt, was emplaced into grey migmatitic gneisses and supracrustal rocks. At its southern border the Atâ complex is cut by younger granites. The complex is divided by a belt of supracrustal rocks into a western, mainly tonalitic part, and an eastern part consisting mainly of granodiorite and trondhjemite. The ‘eastern complex’ is a classical pluton. It is little deformed in its central part, displaying well-preserved igneous layering and local orbicular textures. Near its intrusive contact with the overlying supracrustal rocks the rocks become foliated, with foliation parallel to the contact. The Atâ intrusive complex has escaped much of the later Archaean and early Proterozoic deformation and metamorphism that characterises the gneisses to the north and to the south; it belongs to the best-preserved Archaean tonalite-trondhjemite-granodiorite intrusions in Greenland.

scholarly journals New hornblende and muscovite 40Ar/39Ar cooling ages in the central Rinkian fold belt, West Greenland

2006 ◽  
Vol 11 ◽  
pp. 115-124 ◽  
Author(s):  
Ann-Sofie Sidgren ◽  
Laurence Page ◽  
Adam A. Garde
Keyword(s):  
Metamorphic Grade ◽  
Fold Belt ◽  
The South ◽  
Igneous Complex ◽  
West Greenland ◽  
Structural History

The Palaeoproterozoic Rinkian fold belt in West Greenland consists of reworked Archaean basement, mainly orthogneiss, and the unconformably overlying Palaeoproterozoic Karrat Group. Both parts were intensely deformed and metamorphosed at around 1.87 Ga, at which time the crustal anatectic Prøven igneous complex was emplaced into the northern part of the belt. Seven new hornblende and muscovite 40Ar/39Ar cooling ages are presented from the central–northern parts of the Rinkian fold belt. Four 40Ar/39Ar hornblende ages ranging from 1795 ± 3 to 1782 ± 3 Ma were obtained from amphibolite and hornblendite enclaves in the Archaean orthogneiss, and two from relict dyke fragments in the latter that may be of Palaeoproterozoic age. Three 40Ar/39Ar muscovite ages of 1681 ± 6 Ma, 1686 ± 3 Ma and 1676 ± 3 Ma were obtained from samples of Karrat Group metagreywacke, andalusite schist and metasiltstone. The new 40Ar/39Ar ages, from hornblende and muscovite respectively, are very uniform and probably unrelated to local metamorphic grade and structural history, and are interpreted as regional late orogenic cooling ages. The new hornblende ages are significantly older than those previously obtained from the central and northern parts of the adjacent Nagssugtoqidian orogen to the south, and point to different uplift histories, which may suggest that the orogeny was not synchronous in the two regions.

scholarly journals Glaciological Reconnaissance of the Sukkertoppen Ice Cap, South-West Greenland

1963 ◽  
Vol 4 (36) ◽  
pp. 813-816 ◽  
Author(s):  
C. Bull
Keyword(s):  
Snow Accumulation ◽  
The South ◽  
West Greenland ◽  
Ice Cap ◽  
South West ◽  
Eastern Edge

AbstractGravity studies indicate that the Sukkertoppen ice cap is about 400 m. thick. The annual snow accumulation increases westwards from about 13 g. cm.−2near the eastern edge of the ice cap to about 34 g. cm.−2near Mount Atter, in the south-west. Probably all of the ice cap is “temperate”.

The Hawasina Nappes: stratigraphy, palaeogeography and structural evolution of a fragment of the south-Tethyan passive continental margin

1990 ◽  
Vol 49 (1) ◽  
pp. 213-223 ◽  
Author(s):  
F. Bechennec ◽  
J. Le Metour ◽  
D. Rabu ◽  
Ch. Bourdillon-de-Grissac ◽  
P. de Wever ◽  
...  
Keyword(s):  
Continental Margin ◽  
Structural Evolution ◽  
Passive Continental Margin ◽  
The South

scholarly journals Archaean Plate Tectonics in the North Atlantic Craton of West Greenland Revealed by Well-Exposed Horizontal Crustal Tectonics, Island Arcs and Tonalite-Trondhjemite-Granodiorite Complexes

2020 ◽  
Vol 8 ◽  
Author(s):  
Adam Andreas Garde ◽  
Brian Frederick Windley ◽  
Thomas Find Kokfelt ◽  
Nynke Keulen
Keyword(s):  
North Atlantic ◽  
Plate Tectonics ◽  
Plate Tectonic ◽  
Island Arcs ◽  
West Greenland ◽  
Structural Style ◽  
Modern Style ◽  
Greenstone Belts ◽  
Lower Crustal ◽  
North Atlantic Craton

The 700 km-long North Atlantic Craton (NAC) in West Greenland is arguably the best exposed and most continuous section of Eo-to Neoarchaean crust on Earth. This allows a close and essential correlation between geochemical and isotopic data and primary, well-defined and well-studied geological relationships. The NAC is therefore an excellent and unsurpassed stage for the ongoing controversial discussion about uniformitarian versus non-uniformitarian crustal evolution in the Archaean. The latest research on the geochemistry, structural style, and Hf isotope geochemistry of tonalite-trondhjemite-granodiorite (TTG) complexes and their intercalated mafic to intermediate volcanic belts strongly supports previous conclusions that the NAC formed by modern-style plate tectonic processes with slab melting of wet basaltic oceanic crust in island arcs and active continental margins. New studies of the lateral tectonic convergence and collision between juvenile belts in the NAC corroborate this interpretation. Nevertheless, it has repeatedly been hypothesised that the Earth’s crust did not develop by modern-style, subhorizontal plate tectonics before 3.0 Ga, but by vertical processes such as crustal sinking and sagduction, and granitic diapirism with associated dome-and-keel structures. Many of these models are based on supposed inverted crustal density relations, with upper Archaean crust dominated by heavy mafic ridge-lavas and island arcs, and lower Archaean crust mostly consisting of felsic, supposedly buoyant TTGs. Some of them stem from older investigations of upper-crustal Archaean greenstone belts particularly in the Dharwar craton, the Slave and Superior provinces and the Barberton belt. These interpreted interactions between these upper and lower crustal rocks are based on the apparent down-dragged greenstone belts that wrap around diapiric granites. However, in the lower crustal section of the NAC, there is no evidence of any low-density granitic diapirs or heavy, downsagged or sagducted greenstone belts. Instead, the NAC contains well-exposed belts of upper crustal, arc-dominant greenstone belts imbricated and intercalated by well-defined thrusts with the protoliths of the now high-grade TTG gneisses, followed by crustal shortening mainly by folding. This shows us that the upper and lower Archaean crustal components did not interact by vertical diapirism, but by subhorizontal inter-thrusting and folding in an ambient, mainly convergent plate tectonic regime.

Sign in / Sign up

Export Citation Format

Share Document