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|
Age (millions of years ago) |
Era
|
Period
|
Common
Rocks
|
|
0
— 1.6
|
Cenozioc (Recent Life) |
Quaternary
|
Boulder clay from Ice Ages |
|
1.6
— 23
|
Neogene
|
Clays and lignite around Lough Neagh | |
|
23
— 65
|
Palaeogene
|
 Basalts,
dolerites and granites |
|
|
65
— 142
|
Mesozoic (Middle Life) |
Cretaceous
|
 Chalk
- widespread extinctions at the end of this period |
|
142
— 206
|
Jurassic
|
 Lias
clay — Age of the dinosaurs |
|
|
206
— 248
|
Triassic
|
Sandstones — first true mammals | |
|
248
— 290
|
Paleozoic (Old Life) |
Permian
|
Limestones - mass extinctions at the end of this period |
|
290
— 354
|
Carboniferous
|
Carboniferous Limestone | |
|
354
— 417
|
Devonian
|
Old Red Sandstone | |
|
417
— 443
|
Silurian
|
 Shale
and greywache |
|
|
443
— 495
|
Ordovician
|
 Shale,
sandstones, conglomerate |
|
|
495
— 545
|
Cambrian
|
 Schists |
|
|
545
— 4600
|
Proterozoic (First Life) |
Precambrian
|
Oldest rocks in Ireland (at Inishtrahull, off Inishowen, Co. Donegal) 1750 Million years old Gneiss |
A mnemonic to learn the Geological Column from Precambrian to Cretaceous is:
Pregnant camels ordinarily sit down carefully, perhaps their joints creak.