Table 2.1 (cont.) The geologic timescale.
Era
Paleozoic
Precambrian
Period
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Epoch
Approximate Duration
(Millions of Years)
55
65
60
20
75
100
3,380
Approximate Number of
Years Ago (Millions of Years)
225
280
345
405
425
500
600
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32 PETROLEUM TECHNOLOGY, ECONOMICS, AND POLITICS