Historical Geology Chapter Vocabulary
Chapter 9-Precambrian-Proterozoic Eon
based upon Historical Geology-by Wicander and Monroe


The PROTEROZOIC eon represents nearly 42% of Earth's geologic history from 2.5 bya
to 0.542 bya (542 million).
It is the second portion of the Precambrian.

Some of the Proterozoic rocks are metamorphosed, but most have not been. 
This is in strong contrast to the Achaean.
However, there are few fossils in the Proterozoic rocks.

A famous Proterozoic rock at the bottom of the Grand Canyon is the Vishnu Schist. (Fig. 9.1)

LAURENTIA is the landmass that eventually became N. America (Fig. 9.2)
CONTINENTAL ACCRETION was major story for Laurentia.
Terranes added on: Slave, Rae, superior, Hearne, Wyoming, etc.
 

WILSON CYCLE-continents rifting, then colliding again. (Fig. 9.3)
In Arizona, we have the Yavapai and Mazatzal orogens.
 

Big Event: continental red beds (iron ore) were deposited 1.8 bya.
 

Grenville Province was the most recent Proterozoic addition to Laurentia. (Fig. 9.2c)
1.1 bya MID-CONTINENT RIFT. Rift contains nearly 1 million cubic kilometers of igneous materials.
(Fig.9.6a)
 

Interesting match-up of continents to form a super continent. Fig.9.9 RODINIA.
 

Snowball planet theory; major glaciation 900 mya to 600 mya.
 

Atmosphere: major changes
Addition of oxygen (blue-green bacteria or algae); evidence of stromatolites 2.3 bya.
Cause of oxidation of iron minerals and deposition of CO₂ in the form of carbonates.
BANDED IRON FORMATIONS (some oxygen came from solar processes-ultraviolet light)
 

PROKARYOTE CELLS-slow evolution, later came EUKARYOTE CELLS-faster evolution.
2.1 bya Negaunee iron formation in Michigan has the oldest evidence of eukaryote cells.
Bitter Springs, Australia fossils are 1.0 bya.
Theory that eukaryote cells were formed by symbiosis of prokaryote cells.
 

Multicellular life: maybe 2.1 bya- Negaunee formation.
 

Edicaran multicellular organisms. Australia.  First good fossils of complex creatures.
Many of these animals (?) have no relationship to modern day groups.
All Proterozoic organisms were soft-bodied and without shells.  WHY?