Some of its fossils also occur in the Oamaru series, but the two series are unconformable.
Its inner border affords admirable examples of topographical discordance where it sweeps north-westward square across the trend of the piedmont belt, the ridges and valleys, and the plateau of the Appalachians, which are all terminated by dipping gently beneath the unconformable cover of the coastal The, lain strata.
The Proterozoic formations are unconformable on the Archean in most places where their relations are known.
A few geologists regard the sedimentary rocks here classed as Keweenawan as Palaeozoic; but they have yielded no fossils, and are unconformable beneath the Upper Cambrian, which is the oldest sedimentary formation of the region which bears fossils.
In all but a few places where their relations are known, the Proterozoic rocks are unconformable beneath the Palaeozoic Where conformity exists the separation is made on the basis of fossils, it having been agreed that the oldest rocks carrying the Olenellus fauna are to be regarded as the base of the Cambrian system.