Some Basic Rules of Geology

1
Some Basic Rules of Geology

• The seas come in (transgression), and the seas go
  out (regression)
• Convergence leads to orogeny by way of crustal
  deformation and/or subduction
• Orogeny leads to erosion

2
Paleozoic Paleogeography

• The Paleozoic Era began about 565 mya
• 6 major continents were present, as well as
  several microplates and island arcs
• Baltica, China, Gondwana,
• Kazakhstania, Laurentia, and Siberia
• What pieces of real estate made up Gondwana?
• How do you think paleogeographic reconstructions
  are made?
• What about magnetic anomaly data preserved in
  seafloor crust?

3
Continental Architecture Cratons and Mobile Belts

• Cratons
• stable and immobile parts of continents
• Epeiric seas
• widespread shallow seas that transgressed and
  regressed over the craton
• Mobile belts
• located along the margins of continents, receive
  sediment, and are deformed during collisions

4
Early-Middle Paleozoic Global History

• Continents at low latitudes, free water
  circulation, polar regions ice-free
• by the late Cambrian, epeiric seas had covered
  large parts of the continents, with major
  highlands being rapidly eroded

5
Early-Middle Paleozoic Global History

• During the Ordovician, plate movement caused
  major changes in the positions of the continents
• Taconic Orogeny began as Baltica and Laurentia
  move closer together

6
Appalachian Mobile Belt

• Taconic Orogeny
• resulted from plate convergence as the Iapetus
  plate subducted under Laurentia and Baltica
• a clastic wedge of sediment called the Queenston
  Delta collected at the base of the Taconic
  Highlands raised by this collision
• represent the erosion of mountains up to 4000m
• Caledonian Orogeny occurred along the west border
  of Baltica

7
Appalachian Mobile Belt

• The Acadian Orogeny began during the Late
  Silurian and continued to Late Devonian
• sedimentary rocks from Newfoundland to
  Pennsylvania were folded and thrust against the
  craton in an oceanic-continental collision
  between Laurentia and Baltica
• the Catskill Delta contains nearly three times as
  much coarse clastic material as the Queenston
  Delta

8
Appalachian Mobile Belt

• Mountain building continued in southern Larentia
  and Baltica even as the two continents were
  sutured into Laurasia
• the Hercynian orogeny represents the collision of
  Laurasia and Gondwana in what is now eastern
  Europe
• the Alleghenian orogeny deformed rocks in the
  southeastern US, and the Ouchita orogeny affected
  rocks in Arkansas and Oklahoma

9
Cordilleran Mobile Belt

• The cordillera was a passive continental margin
  for much of the Proterozoic and Paleozoic
• collision with an island arc took place in Early
  Mississippian time - the Antler orogeny
• sediments eroded from these highlands were
  deposited to the east

10
Ouachita Mobile Belt

• Extends from the subsurface of Mississippi to
  Texas
• the Ouchita Mts. and Marathon Mts. are exposed
  areas of shallow-water clastic and carbonate
  sediments deformed by compressive forces
  generated as Gondwana collided with Laurasia

11
The Role of Microplates in the Formation of
Pangaea

• Accretion along cratonic margins is more
  complicated than the big-picture view presented
• Numerous microplates have been mapped in the
  regions discussed and define areas of discrete
  plates that were caught up in the collision of
  the larger continents mentioned
• These exotic terranes make it clear that the
  history is complex while explaining previously
  anomalous geologic occurrences