Divergent Plate Boundaries

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Divergent Plate Boundaries

• Lithologic Associations

2
Global Patterns of Divergence
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Doming continental lithosphere
What Processes are Illustrated? What Geologic
Features would be Preserved?
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Processes Accompanying Doming

• Normal Faulting
• Earthquakes
• Volcanism
• What is the source of the magma?
• Based on this source, what type of volcanism
  would you expect?

5
The Dome Collapses Rift Valleys, Horsts,
Grabens and Half Grabens
In Addition to the Faulting and Volcanism, What
Other Processes would Operate Here? What types of
rocks would you expect?
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Additional Processes Accompanying Collapse of the
Dome

• Weathering
• Erosion
• Deposition

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Additional Processes Accompanying Collapse of the
Dome

• How much weathering would you expect in this
  setting?
• What would be the composition of the sediment?
• How much modification of sediment would take
  place during transport?
• What textures would you expect?
• What patterns of deposition would you expect?

8
As Lithosphere Stretches

• Lithosphere thins
• Mafic magma is added intrusively and extrusively
• What happens to the density of the lithosphere?
• Why?
• What happens to the buoyancy of the lithosphere?
• What is the result of this?

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Lithosphere Subsides Below Sea Level

• Modern Linear Seas Red Sea, Dead Sea, Persian
  Gulf
• What would be the geologic record of this?
• What happens to the tectonic activity on the
  edges of the continents?

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From Rifting to Drifting

• Passive Margins of Continents drift away from
  axis of tectonic activity - Mid-Ocean Ridge (MOR)
  
• As distance from MOR increases, continental
  margins cool, become more dense and subside
  continental shelves
• What kinds of sediments would you expect?

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From Doming to Rifting to Drifting
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Example of Rift Lithologic Association

• Mesozoic rift basins up and down the Eastern
  Seaboard
• Igneous and Sedimentary record in rift basins

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Evidence of Rifting Palisades Sill
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Palisades Sill lower contact
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Evidence of Relief Fanglomerates
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Evidence of Relief - Arkose
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Rift Basins Closed Drainage - Lakes