Paleozoic

Early Paleozoic Paleogeography:
- In late Proterozoic, all continents formed a single supercontinent.
- By the beginning of the Paleozoic, six major landmasses existed
- Each continent contains a craton (stable/immobile) and surrounding mobile belts (along margins of continents - active/unstable)
- Platform: sediment-covered craton
- Eperic Seas: shallow seas that spread over the craton

Cambrian Period:
- All continents at low latitudes with free ocean circulation.
- Epeiric seas
- Sauk Sequences: Sea level rises
  👉 Ocean floods the continent (transgression)
- Sediments are deposited in order:
  👉 sand → mud → limestone
Ordovician Period:
- Plate Movement caused shifts in the continents' positions.
- Gondwana moved south and developed glaciers, evidenced by current glacial deposits in the Sahara.
Silurian Period:
- Baltica + Laurentia collide, forming Laurasia during the Caledonian Orogeny.
Devonian Period:
- Narrowing of the southern lapetus Ocean between Laurasia and Gondwana.
- Mountain-building activities such as Acadian Orogeny impacting the sedimentation in northeast regions.
Carboniferous Period:
- Early Carboniferous: Continental glaciers covered southern Gondwana leading to global sea level fall.
- Late Carboniferous: Continued collision of Gondwana and Laurasia, forming parts of Pangaea and resulting in complex geological configurations.
Permian Period:
- Formation of Pangaea complete with moderate global temperatures.
- Panthalassa Ocean facilitated the circulation of waters creating desert environments and evaporite formations.

Evolution of the Paleozoic Era:
- Six cratonic sequences or Sloss sequences represent transgressive and regressive cycles of sedimentary rocks marked by unconformities.
- Events include the emergence of diverse marine organisms and structures such as reefs which developed in favorable conditions during specific periods.
Tippecanoe Sequence:
- Explosive growth of reef-building organisms from late Ordovician to Devonian due to the presence of warm, shallow seas favorable for reefs without competing detrital sediments.
- Organic Reefs primarily formed from limestone structures created by organisms such as corals and calcareous algae.
Kaskaskia Sequence: transgressions of the sea during the Late Devonian to Early Mississippian period, leading to the deposition of carbonates and shales.
Clastic Wedge Formation:
- thick pile of sediments that builds up next to growing mountains
- The Antler and Taconic Highands particularly contributed to the deposition of sediments leading to widespread black shales indicating anaerobic conditions in ancient oceans.

Mobile Belts:
- Cordilleran Mobile Belt: Transition from passive to active continental margins impacting the sedimentation history.
- and Appalachian mobile belt: Taconic orogeny helped build
- Accretion of microplates during the formation of Pangaea and subsequent orogenic (mountain-building) episodes had significant impacts on regional climates and geological evolution.
Role of Microplates in Geologic History:
- Microplates = small tectonic plates that helped “fill in the gaps” during continent collisions
- Avalonia is notably recognized for its collisions with larger landblocks which shaped the current geological landscape in places such as Newfoundland and European regions.

🏔 3 Appalachian belts (orogenies)

👉 Thick pile of sediments next to mountains

👉 All are tied to different mountain-building events:

👉 Each formed from:
➡ erosion of mountains from that specific orogeny

👉 Addition of smaller pieces (microplates, terranes) to a continent