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Coal - its origin and occurrence
Periods during which the Rocks were formed
| Periods | Millions of years since formed | ||
| RECENT | |||
| PLEISTOCENE | 1 | ||
| PLIOCENE AND MIOCENE | 1 | to | 25 |
| OLIGOCENE AND EOCENE | 25 | to | 60 |
| CRETACEOUS | 60 | to | 120 |
| JURASSIC | 120 | to | 145 |
| TRIASSIC | 145 | to | 170 |
| PERMIAN | 170 | to | 210 |
| CARBONIFEROUS | 210 | to | 285 |
| DEVONIAN | 285 | to | 325 |
| SILURIAN | 325 | to | 350 |
| ORDOVICIAN | 350 | to | 410 |
| CAMBRIAN | 410 | to | 500 |
| PRE-CAMBRIAN | over 500 | ||
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