Appalachian structure and tectonics

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Appalachian structure and tectonics
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Classic orogenic events

• Greenville OrogenyContinentcontinent collision,
  formed global supercontinent 1.1 Ga
• Rifting 600 Ma
• Taconic OrogenyArccontinent collision 460 Ma
• Acadian OrogenyComposite Avaloncontinent
  collision 400370 Ma
• Alleghenian OrogenyContinentcontinent
  collision, formed global supercontinent 320290
  Ma
• Rifting 200 Ma

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Paleogeographic elements

• LaurentiaNorth American crust, includes
  Greenvillian crust and inboard Archean and
  Paleoproterozoic rocks
• Oceanic- and arc-affinity accreted terranesOften
  divided into Peri-Laurentian and Peri-Gondwanan
• Peri-Gondwanan continental fragmentsPieces of
  continental crust and volcanic arcs accreted
  during Acadian orogeny
• GondwanaEurope and Africa, other side of super
  continent

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Acadian Orogeny

• Dominant event in northern Appalachians
• Transpressional
• Variety of exotic peri-Gondwanan terranes
  collided with N. America

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Alleghenian Orogeny

• Dominant event in southern Appalachians
• Transpressional in south, strike-slip in north
• Formation of AppalachianCalledonide system

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Structure of the Appalachians

• Promontories and embayments (reentrants)
• Northern and southern divided at NY promontory

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Southern Appalachians

• Master décollement zone beneath thin thrust
  sheets
• Type locality of a thin-skinned orogenic belt

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Northern Appalachians

• Large-scale structural geology less well
  understood
• Oceanic and arc-affinity terranes overlain by
  cover sequence all metamorphosed and deformed
  during Acadian
• Most terranes bounded by high-angle faults

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Maine regional geology
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Maine regional geology