Geologic Map Colors:
U.S. Geological Survey Standard

In general, these colors apply only to sedimentary rocks, and plain colors apply only to marine rocks. Sedimentary rocks that form on land are depicted with these colors plus patterns, such as dots or stripes.

The other major rock classes—igneous and metamorphic—have their own color traditions, rather than standards. Reds and oranges are reserved for the igneous rocks: volcanics take orange while plutonics take red, and in both of these older rocks are shown with darker colors. Metamorphic rocks tend toward browns, olives, and other "complex" colors. All of them use patterns freely as well. This makes the production of geologic maps, whether for print or online publication, a skilled art.

These colors are those specified by the current standards of the U.S. Geological Survey, which tend to govern maps produced by the individual states and American scientists. Their history goes back to the 1880s (see older color lists). For the time spans associated with these units, see the Phanerozoic geologic time scale and the Precambrian geologic time scale. The International Commission on Stratigraphy maintains its own color standard.

Eon	Era	Period	Epoch
Phanerozoic	Cenozoic	Quaternary	Holocene
			Pleistocene
		Neogene	Pliocene
			Miocene
		Paleogene	Oligocene
			Eocene
			Paleocene
	Mesozoic	Cretaceous	Upper Cretaceous
			Lower Cretaceous
		Jurassic	Upper Jurassic
			Middle Jurassic
			Lower Jurassic
		Triassic	Upper Triassic
			Middle Triassic
			Lower Triassic
	Paleozoic	Permian	Lopingian
			Guadalupian
			Cisuralian
		Carboniferous	Pennsylvanian
			Mississippian
		Devonian	Upper Devonian
			Middle Devonian
			Lower Devonian
		Silurian	Pridoli
			Ludlow
			Wenlock
			Llandovery
		Ordovician	Upper Ordovician
			Middle Ordovician
			Lower Ordovician
		Cambrian	Upper Cambrian
			Middle Cambrian
			Lower Cambrian
Proterozoic	Neoproterozoic	Ediacaran
		Cryogenian
		Tonian
	Mesoproterozoic	Stenian
		Ectasian
		Calymmian
	Paleoproterozoic	Statherian
		Orosirian
		Rhyacian
		Siderian
Archean	Neoarchean
	Mesoarchean
	Paleoarchean
	Eoarchean
Undifferentiated Precambrian time
Eon	Era	Period	Epoch

_{(c) 2005 Andrew Alden, licensed to About.com, Inc. Data from Geologic Time Scale of 2004. (fair use policy)}

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