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2. The Caledonian fold belt

The Caledonian fold belt

The who­le eas­tern rim of the old shield was severely ‘dama­ged’ once again a good 400 mil­li­on years ago, when again two con­ti­nents col­li­ded. This pro­cess is cal­led the Cale­do­ni­an oro­ge­ny (‘moun­tain buil­ding pha­se’), the resul­ting moun­tains are accord­in­gly the Cale­do­n­i­des. The col­li­ding con­ti­nents do rough­ly cor­re­spond to today’s north Ame­ri­ca (with Green­land) and Euro­pe. In Green­land, remains of the Cale­do­n­i­des can be found at the who­le east coast, from the Scores­by­sund in the south to the nor­the­as­tern cor­ner. But tho­se Cale­do­n­i­des are not the spec­ta­cu­lar moun­tain and fjord sce­ne­ry which we can see today, this came much later. It is rather a moun­tain sys­tem in a more geo­lo­gi­cal sen­se: the rocks which for­med the deep-sea­ted root of the Cale­do­ni­an moun­tain chain are now expo­sed at the sur­face. The moun­tains as such, the peaks and val­leys, were ero­ded qui­te quick­ly and accord­in­gly disap­peared to give way to a rol­ling low­land at – or part­ly even below – sea level.

The Caledonian fold belt: Nordvestfjord

Almost 1000 m high rock­wall of defor­med gra­ni­tes, gneis­ses and mig­ma­ti­tes (which have been lar­ge­ly, but not com­ple­te­ly, mol­ten) in the Nord­vest­fjord.

The Cale­do­ni­an rocks are most­ly recy­cled older rocks, most­ly belon­ging to the Pre­cam­bri­an basement/old shield. Thus, ano­t­her chan­ge was impo­sed on the­se old rocks, which did alrea­dy have a long and com­plex histo­ry. It is not at all easy to tell the traces of the Cale­do­ni­an oro­ge­ny apart from tho­se of older, simi­lar events, it is actual­ly often rather dif­fi­cult even for sci­en­tists. Depen­ding on the degree of chan­ge, a rock may be rather Cale­do­ni­an or rather Pre­cam­bri­an (much older), the bounda­ry is tran­si­tio­nal. In both cases, it may be a gra­ni­te, a gneiss or any other rock type and both lock very simi­lar or actual­ly total­ly the same to the naked eye. The geo­lo­gi­cal map 1:500 000 says the fol­lowing: “Cale­do­ni­an Fold Belt. Cale­do­ni­an and Pre­cam­bri­an par­ti­al­ly, influ­en­ced by Cale­do­ni­an reac­ti­va­ti­on”. That’s clear, isn’t it…?

But gene­ral­ly, all rock mas­ses whe­re traces of Cale­do­ni­an influ­ence can be found are regar­ded as part of the Cale­do­ni­an moun­tains or, may­be bet­ter, Cale­do­ni­an Fold Belt.

Such a hotch­potch of Precambrian/Caledonian rocks can be found in wide are­as in the inner Scores­by­sund (see scetch map abo­ve). The­re is the so-cal­led »Ves­t­fjord-Hinks Land Gneis- and Schist zone« stret­ching N-S from Ves­t­ford, west of Rødefjord and in the inner Nord­vest­fjord. A simi­lar, direct­ly neigh­bou­ring belt is the »Gåsefjord-Stau­ning Alper mig­ma­ti­te- and gra­ni­te zone«, com­pri­sing most of Gåse Land, Mil­ne Land, Ren­land and the Stau­ning Alper. A third area is the Liver­pool Land, whe­re you can find various gra­ni­tes, gneis­ses and schists; some of them of Cale­do­ni­an age (450-400 mil­li­on years old), others much older, again with tran­si­tio­nal bounda­ries.  The sett­le­ment of Itto­q­qor­toor­mi­it, at the sou­thern end of Liver­pool Land, is loca­ted on gneiss which most­ly belongs to the Pre­cam­bri­an base­ment and which was only slight­ly alte­red during the Cale­do­ni­an pha­se.

Gra­ni­tic vein in Liver­pool Land

Granitic vein in Liverpool Land

The mag­ma­tic and meta­mor­pho­sed rocks of the Pre­cam­bri­an shield as well as the ones of the Cale­do­ni­an fold belt are most­ly very hard. Nevertheless, during many mil­li­on years after the Cale­do­ni­an oro­ge­ny, they were worn down to low­land near sea level, but after strong uplift in the lower Ter­tia­ry, they are now able to with­stand ero­si­on for qui­te a while, thus forming the impres­si­ve land­s­capes of Liver­pool Land, the Stau­ning Alper and the inner Scores­by­sund.



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last modification: 2013-10-12 · copyright: Rolf Stange