age_terms Archean Arikareean Bridgerian Bull Lake Cambrian Cambrian-Precambrian Cambrian-Proterozoic Carboniferous Cenozoic Chesterian Cretaceous Cretaceous-Jurassic Cretaceous-Permian Cretaceous-Precambrian Cretaceous-Proterozoic Desmoinesian Devonian Devonian-Cambrian Devonian-Ordovician Eocene Holocene Jurassic Jurassic-Permian Jurassic-Triassic Laramide Leonardian Ludlow Maastrichtian Meramecian Mesoproterozoic Mesozoic Mesozoic-Paleozoic Mesozoic-Permian mid-Campanian Miocene Mississippian Mississippian-Cambrian Mississippian-Devonian Missourian Morrowan Neogene Neoproterozoic Oligocene Ordovician Ordovician-Cambrian Ordovician-Proterozoic Osagean Paleocene Paleoproterozoic Paleozoic Paleozoic-Proterozoic Pennsylvanian Pennsylvanian-Mississippian Permian Permian-Cambrian Permian-Devonian Permian-Devonian Permian-Pennsylvanian Permian-Triassic Pinedale Pleistocene Pliocene pre-Belt pre-Beltian pre-Bull Lake Precambrian pre-Flathead pre-Kinnikinic present Proterozoic Proterozoic-Archean Proterozoic-Early Quaternary Quaternary-Tertiary Recent Silurian Silurian-Ordovician Tertiary Tertiary-Cretaceous Tertiary-Precambrian Triassic Triassic-Jurassic Triassic-Permian Wenlock Wisconsin Wolfcampian