lateprot

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.

FIGURES

Structural Provinces of North America.

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