Beginning of the Paleozoic. First abundant fossils → 4
1 billion 8
Maximum age of black dikes → 10
Oldest known fossils 15
2 billion 16
Old granite and pegmatite 20
3 billion 24
Gneisses and schists formed sometime in this interval 20-27
Oldest dated rocks → 28
4 billion → 32
Minimum age of the earth 36