Making of a Land - Chapter 7

Illustrations chapter 7.

Illustrations can be downloaded in the gallery further down.

 

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 Chapter 07 - pp. 232-233

The continent of Laurussia, which was formed when Greenland collided with Scandinavian in Silurian to Early Devonian time. The collision zone is marked by the large Caledonian mountain chain. (Small illustration: R. Blakey)

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Chapter 07 - p. 235

The mountain Litjehesten in the outer part of Sognefjorden. The boundary between the Devonian conglomerates in the Solund Basin and their substrate follows the edge of the shadow. (Phto: T.B. Andersen)

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Chapter 07 - p. 236a

After the basement was forced deep down into the crust during the Caledonian collision (a), and the collision forces died away, it was exhumed again and drawn back towards the east (b). By degrees, the crust was stretched out because new extensional shear zones formed (c)

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Chapter 07 - p. 236b

Such folds are common in large parts of the Caledonian nappe pile in southern Norway. They formed when the mylonites, which were produced during the inward thrusting of the nappes, were deformed whn the nappe pile slid back in the earliest Devonian. Bergsdalen Nappe, West Norway. (Photo: H. Fossen)

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Chapter 07 - p. 237a

The backward sliding of the nappes created structures that reflect the movement direction. The arrows show the directions in southern Norway. They swing from northwesternly in the central mountains to more westerly around the Devonian basins. Broken line mark Devonian extensional shear zones formed by segmantation of the crust after the backward sliding took place.

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Chapter 07 - p. 237b

This photograph shows an approximately 400 million-year-old microdiamond from the Møre coast. (Photo: IKU)

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Chapter 07 - p. 238

Examples of structures that serve to determine shearing movements in deformed rocks - tools for determining movement directions.

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Chapter 07 - p. 239a

Brurestakken on Atløy, west of Askwoll, is a distinct expression of the strong folding experienced by the Caledonian strata after the Caledonian collision had ceased and Devonian extension had begun. The light-coloured beds are quartzite, which is compacted, lithified and metamorphosed sand from the pre-Caledonian continental shelf. (Foto: H. Fossen)

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Chapter 07 - p. 239b

Devonian basement mylonites in the foreground demonstrate westward movement in the Nordfjord-Sogn Detachment. Lihesten, sculpted in Devonian conglomerates, towers in the north. A low-angle fault separates the Devonian rocks from their Cambro-Ordovician substrate. (Photo: H. Fossen)

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Chapter 07 - p. 240

Devonian extensional shear zones as they are mapped today. More will probably show up as mapping of such structures continues.

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Chapter 07 - p. 241a

Warm colours on geomagnetic maps indicate especially magnetic bedrock. The continuation of the Hardangerfjorden Shear Zone south-westwards along the Ling Depression is most distinct. The zone thus affected the Permian to Jurassic development of this part of the North Sea. HSZ - Hardangerfjorden Shear Zone.

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Chapter 09 - p. 241b

The Hardangerfjorden has been excavated along one of the longest shear zones or faults in the mountain chain. Basement rocks crop out high on the south side, whereas on the north side nappe rocks rest in what has been referred to as the fold depression.

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Chapter 07 - p. 242

Simplified block diagram depicting where the extensional shear zones occur in Trøndelag and Nordland, and how they are connected with basement windows.

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Chapter 07 - p. 243

Photograph of a brittle fault in Øygarden, west Norway. The fault is probably Devonian, and the shiny surface has a coating of finely crushed, green epidote. (Photo: H. Fossen)

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Chapter 07 - p. 244

The Devonian deposits in west Norway (yellow), together with Caledonian nappe rocks (violet and brown) have been separated from the basement by the Nordfjord-Sogn Detachment.

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Chapter 07 - p. 245

Death Valley in California is a basin formed between high mountains and faults. Avalanche fans originating at the faults line the foot of the mountains. This landscape probably resembles the original Devonian landscape in Norway. (Photo: H. Fossen)

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Chapter 07 - p. 246a

The first map of the entire Kvamshesten Basin, published by C.F. Kolderup in 1921. The mai aspects are correct, but the contact between the Devonian and its substrate was looked upon as a major thrust fault.

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Chapter 07 - p. 246b

Devonian conglomerate (breccia) in the Håsteinen Basin. Angular boulders imply short transport, perhaps as scree deposits. (Photo: V.V. Vetti)

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Chapter 07 - p. 247

Fish and plant life. (Photo fosil: H. Fossen)

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Chapter 07 - p. 248

A drwaing by Hans Reuschs of the unconformity between folded nappe rocks and Devonian conglomeratesn at Bulandet (Sogn & Fjordane). This unconfomrity is beautifully exposed in many places along the coas of western Norway.

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Chapter 07 - p. 249

Mountains composed of Devonian sandstones and conglomerates viewed from the west towards Kvamshesten.(Photo: P.T. Osmundsen)

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Chapter 07 - p. 250a

Rhythmic rock (Figure modified from R. Steel)

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Chapter 07 - p. 250b

A naked, barren "Devonian landscape" in the mountains near Ålfoten. (Photo: P.T. Osmundsen)

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Chapter 07 - p. 251a

The rhythmic bedding is distinct on the mountainsides near Haukå, east of Florø. (Photo: I. Bryhni)

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Chapter 07 - p. 251b

Simplified model of how enormous thicknesses of Devonian deposits in the Hornelen Basin are envisaged to have been formed. Owing to the curvature of the fault plane, the beds were gradually rotated as they slid down the fault, and new beds were deposited above them.

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Chapter 07 - p. 252

Folded beds at Grøndalen, at he southern boundary of the Hornelen Basin. The beds that are most resistant to erosion stand out as stripes in the hillside. The light-coloured patches left of centre are the tips of gravel fans stacked on top of one another and derived from the basin margin to the right of the massif. (Photo: H. Fossen)

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Chapter 07 - p. 251

Devonian sandstones near the Ålfotbreen glacier. (Photo: I. Bryhni)

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Chapter 07 - p. 254

The beds forming the transition between the Austfjorden Member (yellow, calcareous sandstone) and the Dicksonfjorden member (red sandstone) in the Wood Bay Formation, here beside the Orsabreen glacier, north of  Ekmanfjorden, James I Land. (Phto: W. Dallmann)

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Chapter 07 - p. 255

Feeder pipe to the Quaternary vulcano in the Wood Bay Formation. The locality is near the Breibogen Fault. (Photo: W. Dallmann)

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Chapter 07 - p. 256a

Geological map of part of Svalbard where Devonian deposits are preserved.

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Chapter 07 - p. 256b

A generalised E-W profile across the above map.

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Chapter 07 - p. 257a

Sedimentary facies associations in the Wood Bay Formation.

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Chapter 07 - p. 257b

Sedimentary facies associations in the Wood Bay Formation.

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Chapter 07 - p. 257c 

Sedimentary facies associations in the Wood Bay Formation.

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Chapter 07 - s. 257d

Part of the head of a Devonian armoured fish (Arctolepis sp.). Its eye cavity is visible at the upper right. A reconstruction of the fish is seen above. (Illustration: H. Fossen, Photo: Norsk Polarinstitutt)

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Chapter 07 - p. 258

Folding av Devonian beds belonging to the Grey Hoek Formation. These westward-facing folds belong to the Gråhuken Fold Zone at Bråvallafjella, Vårfluesjøen. (Photo: W. Dallmann)

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Chapter 07 - p. 259

Quartz vein along one of the faults in the Billefjorden Fault Zonewest of Austfjorden, Dicksons Land. Baryte is found locally in this vein. (Photo: W. Dallmann)

 

 

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