Quaternary, Tertiary and Late Cretaceous Igneous Rocks

Quaternary: Less than 2 million years ago

Pliocene-Miocene: 2 to 24 million years ago

Oligocene: 24 to 37 million years ago

Upper Tertiary: Less than 20 million years ago

Middle Tertiary: 20 to 40 million years ago

Laramide: 40 to 72 million years ago

Sedimentary Rocks

Quaternary-Tertiary: Less than 4 million years ago

Upper Tertiary: 4 to 37 million years ago

Lower Tertiary: 37 to 72 million years ago

Upper Cretaceous: 72 to 95 million years ago

Upper Cretaceous: 95 to 115 million years ago

Lower Cretaceous: 115 to 144 million years ago

Jurassic: 144 to 208 million years ago

Triassic: 208 to 245 million years ago

Permian-Pennsylvanian: 245 to 320 million years ago

Mississippian, Devonian, Ordovician, Cambrian: 320 to 570 million years ago

Cambrian & Precambrian Igneous and Metamorphic Rocks

Cambrian: 510 to 570 million years ago

Precambrian: 950 to 1,400 million years ago

Precambrian: 1,700 to 1,800 million years ago

Granitic: 1,000 to 1,400 million years ago

Granitic: 1,700+ million years ago