Remarkably similar deposits representing two Neoproterozoic glaciations are present on the west and east sides of Laurentia. Although now located near the margins of Laurentia, these glaciogenic successions were formed within supercontinents. The older glaciogenic succession (Rapitan-Sturtian, ∼700 Ma) is preserved in a series of pull-apart basins formed when the supercontinent Kanatia fragmented to produce the proto–Pacific ocean. The younger Varangerian glaciogenic rocks (∼600 Ma) are now scattered throughout the North Atlantic region, but formed in basins that reflect the demise of a second Neoproterozoic supercontinent (Rodinia) and heralded the formation of the Iapetus ocean.

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