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 Ordovician Late Precambrian ‘Vendian’ supercontinent England and Wales Scotland Avalonia Acadia Laurentia Gondwana Baltica Laurentia Avalonia Armorica Iapetus Ocean South pole

Cambrian - Breakup of Vendian supercontinent - Ocean forms between Laurentia, Gondwana and Baltica - volcanic arcs and continental fragments within ocean 2. Cambrian events Laurentia Passive margin carbonates - Durness Limestone Avalonia Passive margin clastics

3. Early Ordovician events Laurentia Passive margin carbonates Avalonia Passive margin clastics Acadia Ordovician - Arcs and continental fragments begin to collide - mixture of marine sediments and volcanics Highland border ophiolite Ballantrae ophiolite Dalradian metamorphism The Grampian orogeny

4. Ordovician/ early Silurian events Laurentia Avalonia Lake District Welsh Basin Iapetus Ocean Spreading ridge Midland Valley Southern Uplands Accretionary prism - scraped off subducting slab. Fault bounded units young south, but within tracts rocks young northwards Silurian - early marine sedimentation and subduction related volcanism

5. Iapetus closure Silurian - ends in soft sediment and then continental collision - Caledonian orogeny - this marks the closure of Iapetus Oblique collision Highlands Midland Southern Lakes Wales valley Uplands Moine Great Highland Southern thrust Glen Boundary Uplands Major terrane boundaries Sinistral movements on major faults

6. Devonian events Devonian - Formation of large land mass, shedding large volumes of terrestrial material into inland basins Lizard region Armorica Laurentian margin Scotland England Rheic Ocean Gondwana Devonian ‘Old Red Sandstone’ Diachronous deposits Local basins

7. Building the UK Moine thrust Great Glen fault Highland Boundary Fault Southern Uplands fault Variscan front Originally Laurentia Originally Avalonia Iapetus suture Lake District Welsh basin 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