Caledonian sole thrust of central East Greenland: A crustal-scale Devonian extensional detachment?

Hartz, Ebbe H.; Andresen, Arild

doi:10.1130/0091-7613(1995)023<0637:cstoce>2.3.co;2

Cited by 92 publications

(65 citation statements)

References 5 publications

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“…After initial extension possibly related to gravitational spreading, belt-wide reversal in the polarity of deformation, from top-east to top-west, occurred in the Scandinavian Caledonides with exception of the thin-skinned foreland fold and thrust belt. Contemporaneous top-to-the-east extension characterised the East Greenland Caledonides (Hartz and Andresen, 1995;Andresen and Hartz, 1998). In the hinterland of the Caledonides in southern Norway, major top-to-the-west extension on the extensional detachments with heaves in the order of 50 to 100 km, in the Lower to Middle Devonian.…”

Section: Discussionmentioning

confidence: 99%

“…The late-to post-orogenic extension in southern Norway resulted in penetrative reworking and decompression of Caledonian high-pressure metamorphic rocks, formation of large extensional detachments and the Devonian supra-detachment basins Osmundsen, 1996;Osmundsen et al, 1998). Similarly, exhumed Caledonian high-pressure rocks (Gilotti, 1994), extensional detachments and associated Devonian basin formation have recently been identified in the East Greenland Caledonides (Strachan, 1994;Hartz and Andresen, 1995;Andresen and Hartz, 1998), documenting a belt-wide late-to post-orogenic extension of the North Atlantic Caledonides. This paper attempts a review of the geometry, regional distribution and relative age of the extensional structures across the south Norwegian Caledonides.…”

Section: Introductionmentioning

confidence: 99%

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Extensional tectonics in the Caledonides of southern Norway, an overview

1998

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The extensional collapse of the Scandinavian Caledonides resulted in rapid tectonic denudation of the orogen, exhumation of high-and ultra-high-pressure metamorphic rocks and provided a structural template for the formation of Devonian supra-detachment sedimentary basins. The geometry and intensity of the extensional deformation show considerable variation vertically in the crustal section as well as horizontally from east to west across the orogen. The most prominent structural feature related to the extension in central-south Norway is the change in the direction of tectonic transport, from the easterly directed nappe translation during the Silurian Scandian Orogeny, to top-westerly directed sense of shear during the extension. The Fennoscandian basement was little affected by extension in the eastern Caledonides. In the west, however, top-to-the-west shear zones are commonly observed in basement windows. Deformation affecting the Cambrian to Late Silurian rocks in the Caledonian foreland developed a typical of foreland fold and thrust belt geometry. Deformation in the foreland was apparently contemporaneous with the extension-related decompression of the high-pressure rocks in the hinterland. Thrusting in the foreland may thus have been driven by gravitational collapse, and as such have important similarities to the foreland-hinterland relationships of the Himalayan-Tibetan region. The basal contacts of the Jotun and other major nappes constitute prominent shear zones in which fabrics related to thrusting have been mostly destroyed by extensional shearing. The high structural levels of the Western Gneiss Region, adjacent to the western margin of the Jotun Nappe, were only moderately affected by the extensional deformation. Consequently, the Proterozoic orthogneiss complexes are generally well preserved in this area. The westernmost and structurally lowermost parts of the Western Gneiss Region have, however, been subjected to extreme overburden during the Caledonian continental collision. Initial, near-isothermal decompression of the high-pressure rocks occurred by non-rotational vertical shortening-horizontal stretching at eclogite-to amphibolite-facies conditions; at a later stage, decompression and cooling from amphibolite to greenschist facies occurred by rotational deformation associated with the large-scale extensional detachments. The initial extensional deformation in the hanging wall of the detachments in western Norway commenced at greenschist-facies conditions, and became progressively more brittle and localised as the complexes were exhumed in the Late Silurian to Middle Devonian. Major syn-depositional normal faults in the hanging wall of the extensional detachments eventually controlled sedimentation in the Devonian supra-detachment basins.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Extensional tectonics in the Caledonides of southern Norway, an overview

1998

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“…1). Although Higgins et al (1981) proposed that these allochthons were emplaced by westward thrusting, Hartz and Andresen (1995) and Andresen et al (1998a), have interpreted the kinematic indicators in the shear zone separating the Hagar-Niggli Spids and Høgedal allochthons as a record of top-to-the-east displacement relative to present-day horizontal. Given that the hanging wall in the northward continuation of this fault consists of upright, E-dipping Neoproterozoic sediment ary rocks, they argue from their kinematic reinterpretation and the juxtaposition of young on old rocks that this was a normal fault.…”

Section: Introductionmentioning

confidence: 97%

Geologic constraints on middle-crustal behavior during broadly synorogenic extension in the central East Greenland Caledonides

White

Hodges

Martin

et al. 2002

International Journal of Earth Sciences

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Structural and U-Pb geochronologic data from the Forsblad Fjord area of East Greenland (72°30′N) indicate close spatial and temporal ties between orogen-parallel shear and extensional deformation during Caledonian orogenesis. This territory is composed of three tectonostratigraphic units separated by two splays of the Fjord Region Detachment System (FRDS), a principal extensional fault system of the East Greenland Caledonides that was active in Silurian time. The oldest Caledonian fabrics in Forsblad Fjord, which developed at upper amphibolite facies metamorphic conditions, indicate that there was north-south, lateral extrusion of ductile middle-crustal material synchronous with approximately east-west shortening. U-Pb dating of synkinematic granitic leucosomes in migmatitic schists and gneisses demonstrates that this process was underway at ca. 425 Ma. Subsequently, east-west extension along the two splays of the FRDS truncated the older fabrics; the structurally highest of these shear zones -the Tindern detachment -was active as early as ca. 424 Ma. This implies either that there was a rapid transition from Caledonian shortening and possible transpressional deformation to post-orogenic collapse, or our preferred interpretation that extension was synorogenic. The FRDS shares many structural characteristics with the South Tibetan Detachment System of the Cenozoic Himalayan orogen but exhibits two important differences. First, while the South Tibetan system developed in the down-going Indian plate during the India-Eurasia collision, the Fjord Region system developed in the overriding Laurentian plate during the collision of Laurentia with Baltica. Second, whereas the exposed extensional structures in the Himalayas developed in the upper crust and are only inferred to have extended to deeper levels, those in the Forsblad Fjord area were demonstrably active at middle-crustal levels. Evidence for broadly coeval extension and contraction at differen t structural levels in both mountain belts emphasizes the general importance of crustal decoupling in the collisional orogenic process, and implies that synorogenic extensional deformation is not strictly an upper crustal phenomenon.

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“…Comparable crustal-scale extension has been reported in the Caledonides of East Greenland (Hartz and Andresen, 1995). Over the past decades there has been little record of syn-to post-Caledonian extension reported in the basement of northwestern Norway, although it has recently been recognized in the Lofoten archipelago others, 1995, 1996;Hames and Andresen, 1996a;Holloman, ms;Klein, ms;Mooney, ms;Waltman, ms).…”

Section: Introductionmentioning

confidence: 99%

Ductile and brittle extension in the southern Lofoten Archipelago, North Norway; implications for differences in tectonic style along an ancient collisional margin

Klein¹

1999

American Journal of Science

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ABSTRACT. The Lofoten archipelago, north Norway, occupies the most internal position of the Caledonian belt in northern Scandinavia, and rocks and structures exposed there are crucial to understanding processes of how the Baltic basement and its cover allochthons responded to continental lithospheric subduction and subsequent continental separation. Relatively little is published about the structural and metamorphic development and especially the timing of these events; consequently, it is unknown how features exposed on these spatially isolated islands relate to those of the adjacent mainland. Rocks in Lofoten were affected by Caledonian regional metamorphism, and structures record tops-east contraction and later extension related to late-to post-Caledonian basement exhumation. Tops-west extension is preferentially developed in meter to kmscale ductile shear zones containing west-dipping extensional shear bands, westverging rootless folds, and asymmetric feldspar porphyroclasts.

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Caledonian sole thrust of central East Greenland: A crustal-scale Devonian extensional detachment?

Cited by 92 publications

References 5 publications

Extensional tectonics in the Caledonides of southern Norway, an overview

Extensional tectonics in the Caledonides of southern Norway, an overview

Geologic constraints on middle-crustal behavior during broadly synorogenic extension in the central East Greenland Caledonides

Ductile and brittle extension in the southern Lofoten Archipelago, North Norway; implications for differences in tectonic style along an ancient collisional margin

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