Definition: Geological time

Subdivision into MA (million years):

Quaternary: from 0 to -3 million years ago (MA)

Tertiary: from 3 to -65 Ma

Secondary: from -65 to -225 Ma

Cretaceous: from -65 to -140 Ma

Jurassic: from -140 to -195 Ma

Triassic: from -195 to -225 Ma

Primary: from -225 to -570 million years ago

Permian: from -225 to -280 million years ago

Carboniferous: from -280 to -345 million years ago

Devonian: from -345 to -395 Ma

Silurian: from -395 to -435 Ma

Ordovician: from -435 to -500 Ma

Cambrian: from -500 to -570 Ma

Precambrian: from -570 to -4500 Ma