Proterozoic Lithospheric Evolution

Published by the American Geophysical Union as part of the Geodynamics Series, Volume 17.

There have been significant new results in many fields of the earth sciences as concerns the Proterozoic, and many of these originated from new techniques, new concepts and from increasing multidisciplinary research. The most significant result, perhaps, is the recognition of a major crust-forming event of global proportions some 1.7 to 2 Ga ago when juvenile crust was generated in a variety of tectonic settings that are still vigorously debated. Arguments for subduction-related horizontal accretion during the mid-Proterozoic are presented for North America and the Baltic Shield while the Australian crust does not seem to fit such a pattern, and vertical accretion is favored there. In northeast Africa arc and microplate accretion with extensive ophiolite obduction in the late Proterozoic is remarkably similar to modern tectonic processes such as in the SW Pacific, while crust-generation rates seem to have been abnormally high at that time and in this region. In contrast, models for intracrustal orogeny are preferred to explain the evolution of some late Proterozoic African terrains. Proterozoic foredeeps have been recognized adjacent to several major thrust belts in North America and contain major iron formations that may be genetically related to foredeep magmatism.