system
idealized composite unit of the geologic record representing the totality of rock strata laid down during a certain period of the geologic time scale
Cretaceous
third and final period of the Mesozoic Era
Devonian
fourth period of the Paleozoic Era
Tertiary
obsolete term for the geological period 66–2.58 million years ago
Hesperian
Era of Mars' history
Quaternary
third and current period of the Cenozoic Era
Silurian
third period of the Paleozoic Era
Cambrian
first period of the Paleozoic Era
Neogene
second period of the Cenozoic Era
Tonian
first period of the Neoproterozoic Era
Paleogene
first period of the Cenozoic Era
Columbian
proposed period of the paleoproterozoic era
Jurassic
second period of the Mesozoic Era
Carboniferous
fifth period of the Paleozoic Era
Permian
sixth and final system and period of the Paleozoic erathem and era
Triassic
first system and period of the Mesozoic erathem and era
Ordovician
second period of the Paleozoic Era