Dalslandian orogeny

The Sveconorwegian orogeny was an orogenic system active 1140 to 960 million years ago and currently exposed as the Sveconorwegian orogenic belt in southwestern Sweden and southern Norway. In Norway the orogenic belt is exposed southeast of the front of the Caledonian nappe system and in nappe windows. The Sveconorwegian orogen is commonly grouped within the Grenvillian Mesoproterozoic orogens. Contrary to many other known orogenic belts the Sveconorwegian orogens eastern border does not have any known suture zone with ophiolites.

The Sveconorwegian orogen orogenic belt is composed of five segments largely made up of gneiss that were disrupted by both extension and compression in the timespan between 1140 and 980 million years ago. From west to east the segments are the terranes of Telemarkia, Bamble, Kongsberg and Idefjorden plus the Eastern Segment. The segments are separed from each other by large-scale shear zones.

The period between 1050 and 980 millions years ago was the Sveconorwegian orogeny's most active phase with the Telemarkia and Idefjord Terranes being subject to metamorphism, thickening of their crust and deformation. This episode, known as the Agder phase, was followed by the Falkenberg phase that lasted until 970 million years ago during which the orogeny propagated eastward. There are differing views on the nature of the orogeny. One view, known as the "classical", postulates that a continent–continent collision, possibly with Amazonia, was responsible for giving the orogenic belts its current characteristics. An alternative view postulated in 2013 claims such collision did likely not occur as the characteristics of the orogen would be explained solely as the result of subduction and accretion of smaller terranes. These different views have implications for the configuration of the ancient supercontinent Rodinia.

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