PALEOZOIC OUTLINE FOR NORTH AMERICA

Overview

"North America" was composed of parts of the current North American continent, including Canada and the northern and northeastern United States. Joined to this were Greenland and parts of northwestern Europe. The resulting continent was called Laurentia. The continent went through cycles of being largely covered by seas to times of mountain building and retreat of the seas. Each cycle is called a cratonic sequence. Laurentia was located in the tropics and equatorial regions during the Paleozoic. Laurentia and the Baltica craton "sutured" in the Devonian creating Laurasia.

The compass directions in the following table refer to the current orientation of the continent. During the Paleozoic, what is now the eastern margin of the continent was on the south and the current western margin was on the north. Hence, when a reference to the eastern margin is made in the table, it means the current margin orientation, not that during the Paleozoic.

Period	Eastern Margin	Craton	Cordilleran	Life
Cambrian	Passive, marine sedimentation	Transgression of Sauk Sea	Passive, marine sedimentation	"Cambrian Explosion": Appearance of all but one phylum (Bryozoa)
Ordovician	Taconic orogeny	Regression of Sauk Sea and Transgression of Tippecanoe.	Mostly passive with marine sedimentation	Seas dominated by invertebrates. Bryozoa appear. Large reefs. Simple plants move onto land. Mass extinction at end.
Silurian	Acadian Orogeny. Assembly of Laurasia begins	Michigan Basin deepens. Retreat of Tippecanoe Sea by late Sil.	Passive, marine sedimentation	Massive reefs, jawed fish, insects, land plants
Devonian	Acadian Orogeny continues. Laur-asia assembled.	Transgression of Kaskaskia Sea. Sedimen-tation in basins.	Antler Orogeny	Modern fish appear. Amphibians. Evolution of the seed and forests. Mass extinction at end.
Mississip-pian	Acadian highlands eroded. Gondwana approaches S margin.	Retreat of Kaskaskian sea followed by advance of Absoroka Sea	Erosion of Antler highlands	Crinoids in seas. Giant insects. Possible appearance of reptiles. Many amphibians. Swamp forests. Gymnosperms.
Pennsylvanian	Allegheny and Ouachita orogenies	Cyclothems in east, ancestral Rockies west	Passive	Reptiles. Coal forests.
Permian	Allegheny orogeny continues. Assembly of Pangea complete	Major retreat of sea. Dry. Continental deposits except in SW and W.	Still largely marine. Large reef complex in SW.	Advanced mammal-like reptiles. Abundant gymnosperms. Greatest ever mass extinction at end.