Ordovician Paleogeography, Southwestern US

Ordovician Paleogeography, Southwestern US (~470 Ma). Two views are shown, one focuses on the Western Interior and the second focuses off the west coast. They match across the zone of overlap. Note the continuation of Cambrian depositional and tectonic patterns. The western view show a rapidly approaching oceanic arc. As the ocean off western North America subducts below the arc, the arc closes in on the North American coast. The area of origin of this arc is unknown but highly debated -- some geologist derive it from far across the Paleo-Pacific and others argue for an origin not far off North America

View to west of above

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