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Lower Palaeozoic history of UK 1. Continental motions 2. Cambrian events 3. Ordovician events The Grampian Orogeny 4. Ordovician and Silurian The history of the Iapetus Ocean 5. Silurian - Iapetus closure 6. Devonian - Acadian Orogeny Development of major continent 7. Building the UK 1. Continental motions Late Silurian Laurentia Armorica Avalonia Ordovician Baltica Laurentia Avalonia Acadia Gondwana Iapetus Ocean England and Wales Late Precambrian Scotland ‘Vendian’ supercontinent South pole 2. Cambrian events Laurentia Passive margin carbonates - Durness Limestone Passive margin clastics Avalonia Cambrian - Breakup of Vendian supercontinent - Ocean forms between Laurentia, Gondwana and Baltica - volcanic arcs and continental fragments within ocean 3. Early Ordovician events Laurentia Acadia Passive margin carbonates Ballantrae ophiolite Dalradian metamorphism Highland border ophiolite The Grampian orogeny Passive margin clastics Avalonia Ordovician - Arcs and continental fragments begin to collide - mixture of marine sediments and volcanics 4. Ordovician/ early Silurian events Laurentia Accretionary prism scraped off subducting slab. Fault bounded units young south, but within tracts rocks young northwards Midland Valley Southern Uplands Iapetus Ocean Lake District Avalonia Avalonia Spreading ridge Welsh Basin Silurian - early marine sedimentation and subduction related volcanism 5. Iapetus closure Moine thrust Great Highland Southern Glen Boundary Uplands Highlands Major terrane boundaries Midland Southern Lakes Wales valley Uplands Sinistral movements on major faults Oblique collision Silurian - ends in soft sediment and then continental collision - Caledonian orogeny - this marks the closure of Iapetus 6. Devonian events Scotland England Laurentian margin Rheic Ocean Lizard region Armorica Devonian ‘Old Red Sandstone’ Diachronous deposits Local basins Gondwana Devonian - Formation of large land mass, shedding large volumes of terrestrial material into inland basins 7. Building the UK Moine thrust Great Glen fault Originally Laurentia Highland Boundary Fault Southern Uplands fault Iapetus suture Lake District Originally Avalonia Welsh basin Variscan front Stable Precambrian crust New crust generated in Lower Palaeozoic extends from Moine thrust to Wales, and to deep crustal levels between Highland Boundary fault and the English Midlands
