Transcript Geological starter orogenies

GL5 Geological Evolution of Britain
OROGENIES
1. What is an OROGENY ?
2. When would an orogeny occur ?
3. What kind of features do OROGENIES form ?
4. Name one OROGENY that affected the UK.
Credit: U.S. Geological Survey
OROGENIES that affected the UK :
• Caledonian
• Variscan/Hercynian/Amorican
• Alpine
*** Remember - these mountain building phases can have an effect
over very large areas so the evidence for them may not only be found
in the UK but may be found on other continents too.
THE CALEDONIAN OROGENY
• Effects seen in Scotland, the Southern Uplands, the Lake
District and Snowdonia
• Effects seen in Pre-Cambrian, Ordovician and Silurian rocks
• Occurred between 600 & 400Ma
• Created the Caledonian fold belt
• A result of the Laurentian continent (Greenland and Canada)
colliding with Gondwanaland (Scandanavia and Baltic continent)
• Involved the closure of the Iapetus Ocean – between Scotland
and England
• Resulted in volcanics in Snowdonia (Mount Snowdon) and the
Lake District (ScaFell Pike, Old Man of Coniston etc.)
• Main trend of fold axes = NE-SW
• Associated with the Moine Thrust, the Highland Boundary
Fault, the Great Glen Fault and the Southern Uplands Fault –
with NE-SW trends
• Associated with major intrusions in Scotland eg. the Carrock
Fell gabbro
THE VARISCAN OROGENY
• Also known as the AMORICAN OROGENY
• Also known as the HERCYNIAN OROGENY
• Effects seen in Devon and Cornwall, South Wales, and northern
England
• Effects seen in Devonian & Carboniferous rocks
• Occurred about 290Ma
• Created the Variscan mountain belt
• A result of southern Europe colliding with the Caledonian continent
to from Pangaea - supercontinent
• Involved the closure of the Rheic Ocean – between South Wales
and Devon and Cornwall
• Resulted in intrusions and volcanics in Devon and Cornwall –
including the Cornubian batholith - granites
• Resulted in intense folding such as that at Hartland Quay, Devon
and Millook, Cornwall along with folding of the South Wales coal
fields
• Main trend of fold axes = E – W
• Associated with the formation of the Lizard Thrust, the Pennine
Block faults and renewed subsidence in the Scottish Rift valley
•Associated with the intrusion of the Whin Sill
THE ALPINE OROGENY
• Effects seen mainly in South East of England
• Effects seen in Permian, Triassic, Jurassic, Cretaceous and
Tertiary rocks.
• Occurred about 25 - 30Ma
• Created the Alpine mountain belt – the Alps
• Created the Wealden Anticline
• Created the Lulworth Crumple, Dorset
• Main trend of fold axes = E-W
• Re-activated many pre-existing fault lines
•Was centred in Southern Europe and the UK only on the edge of
the mountains formed
• A result of northward movement of Africa colliding with Europe
• The north Atlantic was opening up at the same time – producing
the flood basalts seen in Northern Ireland (Giants Causeway) and
north-east Scotland (Staffa and Fingal’s Cave) and dyke swarms
across northern England and southern Scotland.