The Proterozoic Eon CHAPTER 7. Proterozoic- Last chapter of Precambrian time The Proterozoic boundary is placed @ 2.5 By, mostly arbitrarily Essentially.
Unit 2. Record of geologic events and major changes in life forms (mass extinction or new life) By studying the characteristics of rocks and the fossils,
Proterozoic sedimentary rocks –in Glacier National Park, Montana The angular peaks, ridges and broad valleys –were carved by Pleistocene and Recent glaciers.
