Caledonian plate tectonics and the place of the English Lake District

Abstract

Research Article| June 01, 1977 Caledonian plate tectonics and the place of the English Lake District FRANK MOSELEY FRANK MOSELEY 1Department of Geological Sciences, University of Birmingham, B15 2TT England Search for other works by this author on: GSW Google Scholar Author and Article Information FRANK MOSELEY 1Department of Geological Sciences, University of Birmingham, B15 2TT England Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1977) 88 (6): 764–768. https://doi.org/10.1130/0016-7606(1977)88<764:CPTATP>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation FRANK MOSELEY; Caledonian plate tectonics and the place of the English Lake District. GSA Bulletin 1977;; 88 (6): 764–768. doi: https://doi.org/10.1130/0016-7606(1977)88<764:CPTATP>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Since Wilson's (1966) suggestion of a proto-Atlantic ocean, there have been many attempts to explain the relationships between ancient America and Europe and the Ordovician closure of the ocean which separated the two continents. Most of the interpretations (Dewey; Fitton and Hughes; Church and Gayer) have placed the greater part of Scotland in “America,” with the Southern Uplands as a relic of the now extinct ocean (Iapetus, as some prefer). England and Wales have been regarded as the northern limit of “Europe,” with the Lake District and much of Wales as part of a complex volcanic arc, with compositional range from tholeiitic in the north to alkaline in the south. Subsequent geophysical investigations then gave a strong indication that the Southern Uplands were, after all, composed of continental crust (Powell), and this led to a revised interpretation in which Scotland's Midland Valley was regarded as the oceanic remnant, with the Highland Border and Girvan ophiolites dipping north and south beneath the opposing continents (Gunn, Jeans). Paleontological studies, however, had already indicated that Girvan (and therefore the Midland Valley) belonged to ancient America; this was reiterated (Williams), and by mid-1975, the chances of a proto-Atlantic relic were becoming slim. In the LISPB experiment (1975–1976), the Moho was determined to be at a depth of between 30 and 40 km for the length of Britain, and this appeared to have finally resolved many of the arguments. Continental crust must now be the acceptable conclusion, and exotic ideas of any remaining fraction of the old ocean have to be abandoned.It therefore seems likely that after initial closure of the proto-Atlantic during the upper Ordovician, with gentle encroachment of the two continents, there was subsequently latest Silurian to Early Devonian continental collision with much crustal shortening, which can be seen in the sedimentary cover as intense folds and cleavage. The junction between ancient America and Europe is here taken to be along the Solway trough, but it is suggested that the ophiolites of Girvan and the Highland Borders are possibly related to earlier episodes of back-arc spreading, and subsequently were caught up in fault wedges during renewed movements. Geochemical evidence now suggests that it is unlikely that the Lake District and Wales represent an island-arc environment but were part of the continental margin on the northern flank of ancient “Europe.” This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.