The Proterozoic formations are unconformable on the Archean in most places where their relations are known.
The Proterozoic formations have a wide distribution.
In some places this is because the regions where they occur have net been carefully studied since the subdivision into Archeozoic and Proterozoic was made, and in others because of the inherent difficulty of separation, as where the Proterozoic rocks are highly metamorphosed.
On the whole, the Proterozoic rocks are predominantly sedimentary and subordinately igneous.
The first of these differences between the two systems is significant of the dynamic changes suffered by the Archean before the beginning of that part of the Proterozoic era represented by known formations.