Biogeological chronology - Climate Change: Biological and Human Aspects - page 542

318.1 Carboniferous Pennsylvanian CO 2 levels low 318.1

359.2 Mississippian 359.2

416 Devonian CO 2 levels peak at over

22 times present level

416

443.7 Silurian 443.7

488.3 Ordovician 488.3

542 Cambrian 'Age of invertebrates' 542

635 Ediacaran 635

850 Cryogenian Snowball Earth II 850

1000 Tonian 1000

1200 Stenian 1200

1400 Ectasian 1400

1600 Calymmian 1600

2500 Snowball Earth I

(around 2.2 bya,
possibly 2.4-2.3 bya) O 2
photosynthesis begins to
increase

2500

Start of
Precambrian
not defined

Fossil evidence of
bacteria and algae

4000 (for start of
Archaean)

The dates given are those designated by the International Commission on Stratigraphy (2008). The spellings are English. The breakdown
of nomenclature includes commonly used terms such as 'Quaternary' which the ICS has made a move to discontinue, but debate goes on.
Yet because of common use and for student ease (especially by non-geologists) such terms are retained in this chart.