Rodinia, Rifting, Iapetus and the Great American Bank

1
Rodinia, Rifting, Iapetus and the Great American
Bank
2
General Structure of Continents

• Shields old, tectonically stable foundation of
  continent
• Cratons parts of shield with thin cover of
  sedimentary rocks
• Passive Margins continental shelves, mid-plate
• Convergent Margins zones of subduction and
  collision at edge of plate

3
Precambrian Shield

• Predominantly crystalline (granite gneiss)
• Divided into Provinces by age and structureal
  grain
• Provinces represent the roots of long gone
  mountains
• Each Province produced during a specific Orogeny
• Narrow greenstone belts
• Commonly between provinces
• Metamorphosed mafic volcanics
• Ophiolites
• Immature sedimentary rocks
• Remnants of subducted oceanic lithosphere

4
The Grenville Province

• Last Precambrian Orogeny in North America
• 1.2-0.9 Ga
• Regional metamorphism from Maritime Canada to
  Georgia
• Last event in the assembly of the supercontinent
  Rodinia

5
Grenville Gneiss
6
Assembling Rodiniathe Grenville Orogeny
7
Rodinia a supercontinent 700 Ma before Pangea
8
Potsdam (C) Grenville (Pre-C) Nonconformity in
New York
9
Precambrian Cambrian Nonconformity - Colorado
10
Precambrian Cambrian Nonconformity Grand
Canyon, AZ
11
Precambrian Cambrian Nonconformity

• Widespread across North America
• Extensive erosion of shield and Grenville Orogen
  (Mountains)
• Worldwide Transgression in Latest Precambrian
  into Cambrian
• Similar pattern on other continents
• Post-unconformity rocks are Quartz Arenites and
  Limestones
• Typical cratonic association

12
Rifting Rodinia Opening the Iapetus Ocean,
Birth of the Great American Bank
13
Great American Bank

• Opening of Iapetus Ocean
• Creates passive margin
• Thermal subsidence produces accommodation space
• Thousands of meters of quartz arenites and
  limestones/dolomites deposited in shallow water
• Stromatolites, Mudcracks, Intraclasts
• Exposed in Cumberland/Great Valley and Shenandoah
  Valley
• Sequence is thinner in New York
• more inboard position less subsidence

14
Wading in Iapetus - Stromatolites
15
Wading in Iapetus Quartz Arenites,
Limestones,Burrows Ripples
16
Great American Bank Carbonates Mohawk Valley,
New York