Easter Flashcards
What is the Caledonian orogeny associated to?
The closure of the Iapetus ocean
Scotland and England colliding
Grampian, Scandian, Acadian
What is a terrane?
An area bounded by a fault with distinct features and geological history
What is the hinterland and the foreland?
Hinterland- land near a deformation front
Foreland- land far away from a deformation front
What is type locality?
Internationally agreed location where the boundary between 2 periods can be seen.
Based of fossil assemblages, such as graptolites in Dob’s Lin, Scotland
What are the 5 main sutures in Scotland?
Moine Thrust
Great Glen Fault
Highland Boundary Fault
Southern Uplands Fault
Iapetus Suture
What are the 3 main orogenies and when did they occur?
Cadomian (Neoproterozoic- Cambrian)
Caledonian (Ordovician- Devonian)
Variscan (Carboniferous)
What are glaciations and evidence for them?
When ice isn’t only found at the poles
E.g. Quaternary glacial and interglacial cycles
Evidence are dropstones, boulder clay at Ketton Quarry found at the end of a glacier when it melts
How can past temperatures be determined?
Oxygen isotopes O18/O16
Look at foraminifera, greater means less O16 so more ice= colder temps
How does atmospheric CO2 correlate with length of subducting zones?
More subducting zones more CO2 in the atmosphere, this is due to volcanic gassing
So more CO2 is released, and may also be correlated with temp as it can act as a greenhouse gas
What is the difference between eustatic and isostatic?
Eustatic changes worldwide, in sea level
Isostatic local changes in topography due to uplift
What is extensional subduction?
Cold dense oceanic lithosphere subducting
Leads to slab roll back
Leads to extensional basin
What is contractional subduction?
Warm oceanic lithosphere subducts
Subducts as a flat slab, which can be detected by using seismography
Causes orogenic shortening
What is the arc-continental collision?
Causes flipping of subduction direction
e.g. Taiwan
What is continental- continental collision?
Causes the formation fold mountains
Plates are thrust up
e.g. Himalayas
What are the key points in the history of UK?
550Ma- Iapetus subducting beneath Gondwana, passive margin
490Ma- Iapetus subducting under, however no longer passive
470Ma- Taconic arc and Laurentia, Arc-continent collision
440Ma- Avalonia, Baltica and Gondwana close Iapetus
360Ma- Pangea forms
200Ma- Thulean plume opens up the Atlantic Ocean