What major extinction took place before the Cambrian Explosion?

The Ediacaran (or Vendian) Biota existed prior to the Cambrian. Most of them were gone without leaving any descedants. Many of these fossils were strange and some looked like plants. After a major extinction, often the surviving species evolve within 5-10 million years to fill the empty ecological niches. Scientists call this adaptive radiation. The Cambrian explosion is an adaptive radiation that is unequaled in magnitude before or since.

The end of the Ediacaran was probably an ice age extinction event -- global climate changed to colder. The Cambrian began as that ice age thawed. Look for

Baykonur glaciation

at the link

http://en.wikipedia.org/wiki/Ediacaran#Boundaries_...

My favorite is the "Great Oxygenation Event" that occurred when cyanobacteria (blue-green algae) started producing oxygen and it killed off most of the life on earth at that time. Woo oxygen!

Before there was multicellular life that we define as beginning the Phanerozoic eon there was the single celled life in the Proterozoic Eon that lasted from 2,500 - 542 million years ago.

The first life 3.5 billion years ago was anaerobic. The first photosynthetic organisms used H2S as the electron donor.

There was a mass extinction following the rise of oxygen in the atmosphere. The evolution of photosynthetic cyanobacteria changed the atmosphere by using H2O as the electron donor. 2,400 mya began a series of great Oxidation Events that produces the banded iron sedimentary rock formations indicating iron oxidation produced precipitates in the worlds oceans.

http://news.wustl.edu/news/Pages/21010.aspx

After that came the Huronian Ice Age 2.4 – 2.1 billion years ago.

http://nature.ca/notebooks/english/iceage.htm

http://www.newscientist.com/article/dn18949-the-hi...

1,800 – 1,600 MYA Complex single-celled life appeared.

Oxygen builds up in the atmosphere above 10%.

- Formation of ozone layer starts blocking ultraviolet radiation from the sun.

- 1,500 mya: Eukaryotic (nucleated) cells appear in microfossils.

Cryogenean Ice Age 850 to 630 mya with glacial ice sheets reaching the equator - snowball earth resulted.

Since ice floats life persisted in the oceans.

http://www.princeton.edu/main/news/archive/S27/26/...

Ediacaran fossil group 630 - 555mya began as ice age ended

http://www.geol.umd.edu/~jmerck/bsci392/lecture20/...

History of continent formation and drift that began 4 billion years ago.

http://io9.com/5744636/a-geological-history-of-sup...

Map-http://www.scotese.com/precambr.htm

All of this is precambrian.