Continental Rifting PDF

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Continental Rifting 70015

12/01/2016

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Fractures allows movement takes place and that sedimentation is a key component   Key place where hydrocrabonds are found world wide  

02 Extension of continental lithospheric plates:  Active  

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Lithosphere has a crustal component and the underlying mantle  Asthenosphere is the 03 – Active Role of mantle mantle material rise up  although it is solid over time the solid can flow  the rise causes the lithosphere to thin  

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Passive Role of mantle convection and upwelling

eventually it will cause the lithosphere to part decompression mantling occurs

04 passive role of the mantle  the lithosphere is being pulled apart and there for the mantle can rise up due to there now being space

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05 continental Raifting formation stages  Graben formation  Rift basens 

Initial stages of oceanic flor spreading

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06 Graben formation  vally of compression   

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the asphenosphere rises up as soild and when the the fractures allow the crust to thin

the faults are arranged in a symmetrical patterns  pre-ridt sedimentart rock they are recognised a valuable sourse for geothermal activity  futures o High heat flow; o Geothermal springs; o Minor volcanism; o Extensional faulting.

07 Rift vallies  East African Rift  Scale of the extention is greater  Much more mature development of the plate rising u         

Terrane accretion & continental collision 12/01/2016 

When an ocean c,kses

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The continental margin may experience o Magmatic activity o Terrance accretion and deformation o A and eventually - deformation resulting from plate collision

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The result of ocean closure is  Mountain building i.e.  Orogeny – mountain building

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Terranes  Blocks of crust that have internally coherent geological structures and histories but differ markedly in these respects from adjacent blocks  

10’s to 100’s of km in extent Are separated by major (commonly strike-slip) faults

Origins  However they orrigionate they end up far from their resting place  

Accretion and addition to north America over a hunder years  Terrance orrigonated over a thousand years and in the northan hermesphere  Evidence to say this is the biodistribution of fossils

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Paleomagnetism can also be used – the orientation of the magnetic minerals within the rocks

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Oceans are messy things they

Terrane Accretion  Sheet 1  When the terrance accreated to the margin and previous to theat they had a different history Continental  Brittle deformation of the forelands(fold-thrust belts)  Crustal thickening resulting in: o Ductile deformation – form in a plastic matter o Regional metamorphism o Melting and intrusion of plutons  Especially granites o gravitationalcollapse 

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push of the two plats stop the mountain bet is no longer stable os the mountain collapses and spreads out

hand out 2 blue dots = earth quakes The Alpine-Himalayan Orogeny

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Resulted from the closure of the Tethys Ocean During the break-up of Pangaea, coincident with the opening of the Mid- and North Atlantic

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Began in the west during the Cretaceous and spread eastwards during the Cenozoic

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Includes fragments of ocean crust

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Eastern as aisa are being pused south earstward  This is done in ta britle way  There are hug fault lines Mountbelts erode while the formation is mountainds occur 

Sediments are delivered to the worlds ocean as part of the collision

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Ocean that is still in the finial stage of the closure

Middle set of handout witht the Rheic Ocean  Closure of this ocean resulted in the super continent  Pangaea – all the continental plates in a super oceans Top maps of the hand out  Map is draw to look at the south pole The Caledonide-Appalachian Orogen  Resulted from the closure of the Iapetus Ocean  during the Ordovician and Silurian - with considerable late Silurian to mid- Devonian strike-slip movement

the Wilson cycle  continental drifting  Ocean Opening  Convergence  Terrane accretion   

Continent-continet collision Erosion of Orgen(mountain belt) and crustial thinning

The Assembly of the Brittish Isle 1 

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12/01/2016

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island that we see today is a modern feture

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02 The British Isles is a collage of terranes assembled during the Caledonian Orogeny  England & Wales and southern Ireland - terranes comprising part of Avalonia  Scotland and much of northern Ireland - terranes from Laurentia and its margins  

Ocean becime added to the continental margin Different sides of the oceans in the …

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03  The Proterozoic supercontinent of Rodinia o All o the continental crust are grouped together in one mass o Assemle – 1100Ma o Breack up- 750Ma o Shown of the map = modern continent would be marked o Brock up in a complicated way

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04  rhondina started to breack up leading to the massive mountain build up in Africa

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05 separation of continents  mid auditition is when they were more dispersed

06 – first handout slide missed 07 

diversity of rocks and ages and types and showing a huge range of deformation, metamorphism or not metamorthism

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geological map stipes of rocks the reason on the strikes is they are made up of lotes of terrane

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09 Hebridean terrane - part of the stable Laurentian craton  Cambrian & Ordovician marine sedimentary rocks (youngest rocks) they sit unconformly on top of the Torizordian Supergroup ~~~~~~~~~~~~~~unconformity~~~~~~~~~~~~~~~~~~

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The Torridonian Supergroup (late Proterozoic non- marine sedimentary rocks)

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Lewisian Gneiss – (Archaean and early Proterozoic high grade metamorphic rocks)

10 11  oldest rocks in the brittish ilse and maybe the oldest in the world  not fell asleep the highland boreder complex  tracing of the pactched to...