4. Variscan Orogenesis

1. Caledonian Orogeny 2. Variscan Orogeny 4. Alpine Orogeny 3. North Atlantic Tertiary Igneous Province (NATP)

Mid-Devonian ~400 Ma Old Red Sandstone Continent

Pre-Cambrian ~ 850 Ma Carboniferous ~300 Ma Pangaea Supercontinent

Upper Carboniferous 300 MYA – Variscan Orogenesis 1. Intense Folding 2. Batholiths e.g. Dartmoor 3. Regional Metamorphism e.g. Delabole Slate, North Cornwall 4. Faulting e.g. Lizard Thrust Fault 5. Ophiolites e.g. Lizard Ophiolite Complex e.g. Hartland Quay

CornwallDevon Somerset South Wales Very complex folding & extensive thrusting. 65% shortening of crust Very strong cleavage Complex folding & thrusting. 50% shortening of crust Good cleavage Open, asymmetric folds with steep southern limb 10% shortening of crust No cleavage Gentle folds 2% shortening of crust No cleavage Less intense, more irregular folds, Bude, Devon Recumbent folds, Millook Haven, north Cornwall Gentle open folds, Broad Haven, South Wales Granite Batholith Carboniferous rocks Lizard Thrust Lizard Ophiolite Complex

Recumbent folds, Millook Haven, north Cornwall

Less intense, more irregular folds, Bude, Devon

Gentle open folds, Broad Haven, South Wales

Plates Involved Location in Britain AgeGeological Structures & Trends Igneous RocksMetamorphic Rocks Caledonian Variscan Alpine Avalonia Laurentia ORS continent Gondwana Europe Africa Scottish Highlands Lake District North Wales Anglesey South Wales Cornwall Devon Somerset SE England Lower Palaeozoic 400 mya Upper Palaeozoic 300 mya Cenozoic 40 mya Faults: Moine Thrust Belt e.g. Glencoul Thrust Great Glen Folds: Tay Nappe Shap Fell Harlech Dome NE-SW trend Faults: Lizard Thrust Folds: Millook Haven Hartland Quay Broad Haven E-W trend Folds: North & South Downs E-W trend Granite batholiths: Cairngorms Skiddaw Shap Eskdale Ennerdale Ophiolites – Ballantrae Granite batholiths: Dartmoor Bodmin Moor Land’s End Scilly Isles Regional: Dalradian schists Ballachulish slates Easdale slates Llanberis slates Skiddaw slates Dynamic: Mylonite Regional: Delabole slates