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3. Old Red and New Red:
Erosion products of the Caledonian mountains

Erosion products: Old Red & New Red

The ero­si­on of the Cale­do­ni­an moun­tains star­ted as soon as it was uplifted about 400 mil­li­on years ago. Rock­falls and rivers kept wea­ring the moun­tains down slow­ly and tur­ned them into hills and final­ly into low­lands. 

Parts of the crust in the vicini­ty of the ero­ding moun­tain chain were sub­si­ding along frac­tures: so-cal­led ‘gra­bens’ deve­lo­ped. The sur­face sub­si­ded several kilo­me­tres during many mil­li­on years. Here, the debris from the ero­si­on of the moun­tains collec­ted. This hap­pen­ed in several pha­ses bet­ween about 360 and 250 mil­li­on years ago, during the Palaeo­zoic, more pre­cise­ly in the Devo­ni­an, Car­bo­ni­fe­rous and Permi­an.

The who­le area was not too far from the equa­tor during tho­se times. The cli­ma­te was rather warm and not too dry, so che­mi­cal wea­the­ring could pro­du­ce a cer­tain iron oxi­de cal­led hema­ti­te, which has a nice, red­dish-brown colour. Lar­ge volu­mes of the sand­stones and con­glo­me­ra­tes (sand mixed with peb­bles) which were depo­si­ted in the gra­bens have accord­in­gly a very nice red­dish colour. As the­se sedi­ments are old and red, they are usual­ly refer­red to as the ‘Old Red’. The youn­ger part from the upper Car­bo­ni­fe­rous and Permi­an is some­ti­mes cal­led ‘New Red’ to dis­tin­guish them from each other, alt­hough they are qui­te simi­lar.

New Red on the western side of the Rødefjord

New Red on the wes­tern side of the Rødefjord

Uplift brought both Old Red and New Red to the sur­face. The­re is no Old Red in the Scores­by­sund area (but fur­ther north), but we can see the New Red bet­ween the Stau­ning Alper and nort­hern Jame­son Land and on the wes­tern side of the Rødefjord in the inner Scores­by­sund fjord sys­tem. Here, the land­s­cape has a strikin­gly beau­ti­ful, red­dish colour and the slo­pes have rather soft shapes, dis­sec­ted by steep can­yons. Com­pa­red to the sur­roun­ding, older gneis­ses and gra­ni­tes, the New Red is rela­tively soft. The Rødefjord even owes its name to the red sedi­ments.

In places,fossils have been found, which are well pre­ser­ved and have achie­ved some fame in sci­en­ti­fic cir­cles, as they docu­ment some of the oldest crea­tures which made the tran­si­ti­on from water to land. The­se finds have been made north of the Scores­by­sund.

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