Historical Geology 102
Paleozoic Era I

Phanerozoic Eon

542 million years - present
More complete rock record than the Precambrian
Divided into three Eras - Paleozoic  542 - 251 m.y. - Mesozoic  251 - 65.5 m.y. - Cenozoic  65.5 m.y. - present

Cambrian Period

542 - 488 m.y.
Beginning based on appearance of hard-body parts in the fossil record.
All earlier fossils are soft-body parts.
Tommatian Stage - time unit within the Cambrian Period which marks the first appearance of hard-body parts.

Geologic Time Scale

Geologic events in North America do not match the standard time scale very well.
Geologic Time Scale is based on European geologic events.
Sequence - major, informal lithostratigraphic units covering large areas and separated by periods of erosion.

Sauk Sequence

Named for the Sauk Sea
Transgression of the ocean onto North America beginning in the LateProterozoic
Transgression facies deposited.

Cambrian Paleogeography

North America was located at the Equator.
Shallow, epicontinental sea covered large portion of the continent
Transcontinental Arch

Ordovician - Silurian

Ordovician Period - 488 - 444 m.y.
Silurian Period - 444 - 416 m.y.
Major erosional unconformity marks the end of the Sauk Sequence.
Erosion during the Ordovician

Tippecanoe Sequence

Second major transgression
Began with deposition of a very clean quartz sandstone
Sandstone deposits are followed by extensive limestone (altered to dolomite).

Tippecanoe Sequence

Silurian Period
Michigan - Ohio - Pennsylvania
Development of a restricted basin
Low marine areas rimmed by coral reefs - reefs act as a barrier
Water flow is restricted - areas of evaporation

Western N. America

Subduction zone along western margin of the continent.
Volcanic chain develops with associated volcanic and sedimentary deposits.

Taconic Orogeny

Beginning of Paleozoic - eastern margin is a passive margin
Area of deposition during Sauk Sea Transgression
Middle Ordovician - subduction zone develops due to closure of Iapetus Ocean
Start of the Taconic Orogeny
Late Ordovician - well developed volcanic chain
Western flank of volcanic chain - large clastic wedges
Sediments eroded from the Taconic highlands
Coarse sediments in the east part of the wedge - finer sediments to the west.

Ordovician Paleogeography

Silurian Paleogeography

Cambrian Summary

Sauk Transgression - Regression
Erosion of the continental interior

Ordovician Summary

Sauk Sequence Regression
Erosion of the continental interior
Tippecanoe Sequence transgression
Subduction zone - volcanic chain along western margin of continent
Subduction zone - volcanic chain along eastern margin of continent - start of the Taconic Orogeny

Silurian Summary

Subduction zone dominates eastern margin.
Convergence with Baltica begins
Evaporite basins develop in interior
Western margin - deep marine sedimentation

World Summary

Cambrian Paleogeography
- most continents are located at the Equator.
Ordovician Paleogeography
- Gondwanaland has moved south.
Silurian Paleogeography
- Gondwanaland is located at the south pole.
- Baltica is closing with N. America.
- Baltica is closing with Siberia

Additional Resources

Paleogeography Maps

The following are a series of incredible maps researched, drawn and copywrited by Dr. Ron Blakey at Northern Arizona University.

Permian Paleogeography
- Global - 260 m.y.
- North America - 260 m.y.
- North America - 275 m.y.
- Global - 280 m.y.
- North America - 290 m.y.
Pennsylvanian Paleogeography
- Global - 300 m.y.
- North America - 300 m.y.
- North America - 315 m.y.
Mississippian Paleogeography
- North America - 325 m.y.
- Global - 340 m.y.
- North America - 345 m.y.
Devonian Paleogeography
- North America - 360 m.y.
- Global - 370 m.y.
- North America - 385 m.y.
- Global - 400 m.y.
- North America - 400 m.y.
Silurian Paleogeography
- North America - 420 m.y.
- Global - 430 m.y.
- North America - 430 m.y.
Ordovician Paleogeography
- Global - 450 m.y.
- North America - 450 m.y.
- Global - 470 m.y.
- North America - 470 m.y.
- North America - 485 m.y.
Cambrian Paleogeography
- Global - 500 m.y.
- North America - 500 m.y.
- North America - 510 m.y.
- Global - 540 m.y.

Additional paleogeographic maps and animations can be found at the PALEOMAP Project by Christopher R. Scotese.