The ending and the beginning of the Proterozoic Era?

Question

is there any events that mark the ending or the begining of the proterozoic era? ex. ice age or mass extintion. thanks!

Answer 1

A. the lower boundary of the Proterozoic is characterized by the development of the banded iron formations, and the beginning of oxygenation of the earth's atmosphere. First known glaciations. Advanced single-celled and multicellular life.

B.

The upper boundary of the Proterozoic is set at the base of the Cambrian when fossils of sea creatures (not land) such as trilobites and archaeocyathids appeared. It used to be thought to be the beginnings of multi-cellular fossil life, but, no longer. Now, Proterozoic localities with soft-bodied multicellular marine creatures have been found. What can be said about the Cambrian is that there was an explosion of hard-body fossils and the appearance of certain kinds of fossilized burrows in marine strata.  The absolute age of this boundary is about 542 million years ago.

http://en.wikipedia.org/wiki/Timetable_o...

http://en.wikipedia.org/wiki/Proterozoic

Answer 2

It begins with the first fossils of any life (all aquatic) and ends with the first fossils of land creatures.