worksheet 6 Flashcards
what happened during the caledonian orogeny
the iapetus ocean closed
what happened during the variscan orogeny
the rheic ocean closed
what were the principle continents before pangea formed
gondwana, siberia, baltica, laurentia
- avalonia was a microcontinent
what were the principle oceans before pangea formed
panthalassic ocean, rheic ocean, iapetus ocean
what was in gondwana
present-day south america, africa, antarctica, new zealand, southeastern USA, arabia, southern europe, india
what was in siberia
siberia and kazakhstan
what was in baltica
scandinavia, eastern russia, north europe
what was in laurentia
most of present day north america
where was ireland and uk before pangea
southern ireland, england and wales are in avalonia
northern ireland and scotland were part of laurentia
what happens during the late cambrian to early silurian period
the iapetus closes (between avalonia and laurentia) and rheic opens
when did avalonia form and how
in the cambrian by rifting away from gondwana
what is rifting
when crust pulls apart and thins which decompresses the mantle so magma rises
how do avalonia and laurentia move during the late cambrian/early silurian
avalonia drifts up from 80S to 35 while laurentia moves east and north. avalonia is moving at a faster rate and catching up with laurentia
what happened to the island arc in the iapetus during middle ordovician
it collided with laurentia and oceanic material was over thrusted onto the continental crust. this is part of the grampian phase
what happens in the late silurian period
the iapetus ocean closes due to subduction and collision between avalonia, laurentia and baltica
what is the acadian phase
the final period of the caledonian orogeny in which the mountain belt is formed between canada –> ireland –> scotland –> greenland –> noway
where did subduction occur for the caledonia orogeny
oceanic crust subducted towards the north in the oceanic trench on the northern laurentian margin
what type of collision was the one between avalonia and laurentia
bleak, non head on collision. there was some sliding past one another
what is geological evidence of the avalonian and laurentian blocks colliding in ireland
distinction sections of precambrian rocks align with laurentian margin in the north and avalonian margin in the south
what is an accretionary wedge/prism? where can they be found?
deformed sediments created as iapetus seafloor sediments were scraped off the oceanic crust during subduction. the younger sediments are further south of the laurentian margin
what accompanied the closure of the iapetus and how old are the rocks
granite emplacement which is 360-480 myo (from late devonian to early ordovician)
what happened to the mountains that were created by the caledonia orogeny and what did they form
they were eroded and weathered down which formed an angular unconformity
how did the continents move to close the rheic
gondwana drifted northwards to form with the laurentia-avalonia-baltica continent
when was the rheic closed
by the late devonian (360-380 mya)
what was the last step of all of the continents combining? what is the evidence for this?
baltica came together with siberia (the ural mountains were formed as baltica collided with kazakhstan during caroniferous)
when was pangea formed by
335 mya
what are the appalachian mountains proof of
the rheic ocean closing
