Sisters Country Geologic History

About 200 to 165 million years ago “accreted terranes” (in green and maroon) were rafted and sutured to the North American continent. The yellow plate in the diagram suggests a possible mechanism of an ancient plate moving to the northeast and carrying terranes with it. The dark blue area shows the present day continental margin AFTER accretion. Terranes first docked in northeast Oregon and then docked in southwest Oregon (and other places). These migrating micro-plates (terranes) added to the land surface of Oregon.

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