Geosynclinal Development of the British Isles during the Silurian Period

• Published in: The Journal of geology 1970-07, Vol.78 (4), p.445-479
• Main Author: Ziegler, Alfred M.
• Format: Article
• Language: English
• Subjects: Geological facies; Geology; Graywackes; Highlands; Rocks; Sediments; Shales; Valleys; Volcanology
• ISSN: 0022-1376; 1537-5269
• DOI: 10.1086/627539

The British geosynclinal complex was bounded on both northwest and southeast by continental margins during the Lower Paleozoic. The northern margin, in Scotland and the northern parts of Ireland, consisted of a mountain range, the Scottish Highlands, which was technically active and was positioned between a stable continental foreland to the northwest, and an uncoupled oceanic crustal plate to the southeast. The southern margin, in Wales and the Welsh Borderland, was characterized by a horst and graben structure and was gradually subsiding during most of the Silurian period. The Scottish margin produced tremendous quantities of immature graywacke sands which accumulated in a trench adjacent to the source area, on the site of the present Southern Uplands. A pattern developed about the middle of the Silurian in which deposits in this trench became deformed and uplifted shortly after deposition and, in turn, contributed sediments to the trench which was progressively displaced to the south toward the Lake District. In this way, the marine area was gradually overwhelmed by crustal foreshortening, deformation, and sedimentation, and by the end of the Silurian, continental conditions were established.