Hence, uplift alone cannot account for extensive glaciation in subtropical latitudes during the Permian and Proterozoic.
Similar forms are abundant in late Proterozoic strata of Montana.
But how may we separate the Proterozoic rocks from the Archeozoic?
Proterozoic fossils have been found in places where the present average temperature approaches 0°C.
This second series of rocks is called the Proterozoic (beginning of life) series, and marks a long age in the worlds history.
We shall now turn our attention briefly to a consideration of the second great subdivision of geologic time—the Proterozoic era.
Proterozoic , the age of invertebrate dominance, containing an early and a late ice age.
Thus, igneous rocks distinctly predominate in the Archeozoic, while stratified rocks predominate in the Proterozoic.
The later Proterozoic strata have been much less deformed and in many cases they are practically unaltered.
Why are the very early Paleozoic strata so rich in fossils, while the immediately preceding Proterozoic rocks show so few?
The later of the two divisions of the Precambrian Eon, from about 2.5 billion to 540 million years ago. The Proterozoic was characterized by the formation of stable continents, the appearance of abundant bacteria and archaea, and the buildup of oxygen in the atmosphere. By about 1.8 billion years ago the oxygen buildup was significant enough to cause many types of bacteria to die out. At this time eukaryotes, including multicellular algae and the first animals, first appear in the fossil record. See Chart at geologic time.