4. Variscan Orogenesis. 1. Caledonian Orogeny 2. Variscan Orogeny 4. Alpine Orogeny 3. North...
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Transcript of 4. Variscan Orogenesis. 1. Caledonian Orogeny 2. Variscan Orogeny 4. Alpine Orogeny 3. North...
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4. Variscan Orogenesis
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1. Caledonian Orogeny
2. Variscan Orogeny
4. Alpine Orogeny
3. North Atlantic Tertiary Igneous Province (NATP)
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Mid-Devonian ~400 Ma
Old Red Sandstone Continent
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Pre-Cambrian ~ 850 MaCarboniferous ~300 Ma
Pangaea
Supercontinent
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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
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CornwallDevonSomersetSouth 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
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Recumbent folds, Millook Haven, north Cornwall
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Less intense, more irregular folds, Bude, Devon
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Gentle open folds, Broad Haven, South Wales
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Plates Involved
Location in Britain
Age Geological Structures & Trends
Igneous Rocks Metamorphic 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