Paleozoic Tectonics and Paleogeography

Callan Bentley, Karen Layou, Russ Kohrs, Shelley Jaye, Matt Affolter, and Brian Ricketts and Charlene Estrada

What Did the World Map Look Like 541 to 252 Million Years Ago??

Lauentia

During the Paleozoic Era, sea levels rose and fell four times. With each sea-level rise, most of North America was covered by a shallow tropical ocean. Evidence of these submersions is the abundant marine sedimentary rocks such as limestone with fossils, corals, and ooids. Widespread unconformities document extensive sea-level falls. Today, the midcontinent has extensive marine sedimentary rocks from the Paleozoic. Western North America has thick layers of marine limestone on block faulted mountain ranges such as Mt. Timpanogos near Provo, Utah.

pangea
The supercontinent of Pangea, which was assembled around 300 million years ago.

The assembly of supercontinent Pangea, sometimes Pangaea, was completed by the late Paleozoic Era. The name Pangea was originally coined by Alfred Wegener and means “all land.” This supercontinent existed when all the major continents were grouped by a series of tectonic events, including subduction island-arc accretion, continental collisions, and ocean-basin closures. The Appalachian Mountains are the erosional remnants of these mountain-building events in North America. Surrounding Pangea was a global ocean basin known as the Panthalassa. Continued plate movement extended the ocean into Pangea through rifting, forming a large bay called the Tethys Sea that eventually divided the land mass into two smaller supercontinents, Laurasia and Gondwana. Laurasia consisted of Laurentia and Eurasia, and Gondwana comprised the remaining continents of South America, Africa, India, Australia, and Antarctica.

The Late Paleozoic supercontinent Pangea at ca. 260 Ma, showing its two... | Download Scientific Diagram
The breakup of Pangea around 260 Ma, shows the two smaller supercontinents, Laurasia and Gondwana, along with the Panthalassa Ocean and Tethys Ocean. Can you find where the Appalachian mountains were 260 million years ago?

While the east coast of North America was tectonically active during the Paleozoic Era, the west coast remained mostly inactive as a passive margin during the early Paleozoic. The western edge of the North American continent was near the present-day Nevada-Utah border and was an expansive shallow continental shelf near the paleo equator. By the end of the Paleozoic Era, the east coast of North America had a very high mountain range due to continental collision and the creation of Pangea. North America’s west coast had smaller, isolated volcanic highlands associated with island arc accretion. During the Mesozoic Era, the size of the mountains on either side of North America would flip, with the west coast being a more tectonically active plate boundary and the east coast changing into a passive margin after the breakup of Pangea.

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Introduction to Historical Geology Copyright © by Chris Johnson; Callan Bentley; Karla Panchuk; Matt Affolter; Karen Layou; Shelley Jaye; Russ Kohrs; Paul Inkenbrandt; Cam Mosher; Brian Ricketts; and Charlene Estrada is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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