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                The Late Proterozoic

        Dalziel, I.W.D., 1977. Overview: Neoproterozoic - Paleozoic geography and tectonics: review, 
hypothesis, environmental speculation. BGSA, 109, no. 1, p. 16-42.

        The Late Proterozoic was a time of major plate reorganization, oceanic activity, and changes in 
climate (low latitude glaciations) and first-order paleoecological levels. In particular the Late Proterozoic 
marks the divergence of metazoan phylla leading eventually to the Cambrian biologic explosion of 
skeletalized metazoans, an event that peaked in the early Cambrian.
        Following the Grenville orogeny, the continents of the world were organized into a hypothetical 
supercontinent referred to as Rodinia, with North America located between east Gondwana 
(Australia, Antarctica, India), West Gondwana (Africa, South America), Baltica, and Siberia. Although 
during the Mesoproterozoic numerous depocentres existed within the amalgamated Archean and 
PaleoProterozoic terranes, following the Grenville orogeny sedimentary deposition encircled the North 
American continent during the reorganisation of Rodinia into Gondwana and Laurentia between 800 and 
600 Ma. In Northwestern Canada rifting and the break up of Rodinia is possibly marked by the 780 Ma 
old Little Dal volcanics and associated sills, and volcanism at 730 Ma in the younger Ekwi Supergroup. 
Along the Appalachian margin rifting took place at various stages with the final rifting at about 580 Ma.
        Limited evidence for the existence of late Proterozoic ocean crust and arc systems is preserved in 
the Anti-Atlas region of Morocco, central Asia, southern China, the Arabian-Nubian Shield and its 
extension into East Africa, the Avalonian terranes of southern Britain and the eastern Appalachians, and 
the Cadomian of France and Spain. Most late Proterozoic systems however display very little evidence of 
their interaction with oceanic plates, giving rise the 'lost arcs' paradox.


Structural Provinces of North America.


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