SUMMARY: In addition to the large continents of N America, Scandinavia and
Gondwana, the regions around the early Palaeozoic Iapetus Ocean contained several small terranes. These included an island arc, which collided with various parts of N America to produce, in succession, the Grampian, Humberian and Taconic orogenies. They also included the terrane ofAvalonia, a later...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1030.7496 http://sp.lyellcollection.org/content/38/1/405.full.pdf |
| Summary: | Gondwana, the regions around the early Palaeozoic Iapetus Ocean contained several small terranes. These included an island arc, which collided with various parts of N America to produce, in succession, the Grampian, Humberian and Taconic orogenies. They also included the terrane ofAvalonia, a later Precambrian arc which had rifted off amargin of Gondwana by the middle Ordovician. Large sinistral strike-slip faults in Scotland suggest a total displacement of around 1500 km, so that by the Silurian an elongate Scotland lay to the W of Norway. Continental collisions took place in three stages: aLlandovery stage, perhaps related to eastward subduction below Svalbard, when W-verging nappes were emplaced in E Greenland, a later Silurian (Scandian) stage when westward subduction below Scotland can be related to E-verging nappes in Norway, and an early Devonian stage when Avalonia collided with N America (Acadian orogeny). The first suggestion that a wide ocean was present in the early Palaeozoic between America and Europe (Wilson 1966) was based primarily on faunal differences. This ocean was named Iapetus (Harland & Gayer 1972) after the father of Atlas (from whom the Atlantic Ocean takes its name). Dewey (1969) was the first to propose amodel for the development of Iapetus in terms of plate tectonics; since then, later models have had to take account of new data which are slowly revealing the increasing complexity of this devel-opment. As well as distinguishing the times during which the various margins were active and passive, we now recognize the presence of island |
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