Cambrian (geology)

The Cambrian is both a system of strata and a period of time. The name refers to a chronostatrigraphic or a geochronological unit of geological measure. The Cambrian is roughly the period between 543 to 490 million years ago in the Paleozoic Era of the Phanerozoic Eon. It encompasses four chronostatrigraphic series and ten epochs and correspondingly, four geochronological stages and ten ages.

Erathem/Era	System/Period	Series/Epoch	Stage/Age
Paleozoic	Cambrian	Furongian	Unnamed
			Unnamed
			Paibian
		Unnamed	Unnamed
			Drumian
			Unnamed
		Unnamed	Unnamed
			Unnamed
		Unnamed	Unnamed
			Unnamed

The name is derived from Cambria, the Roman word for Wales, the area where the rocks of the Cambrian was first studied.

Boundries

The Cambrian is geochronolocally the period from 542 million years ago (mya) with an error factor (plus or minus 1.0 mya) to 488.3 (plus or minus 1.7 mya). The lower boundry is characterised by trace fossils, the lowest occurrence of Treptichnus (Phycodes) pedum and a near base of negative carbon-isotope excursion. The end or upper boundry is characterised by Conodont fossils, and the lowest occurrence of Iapetognathus fluctivagus; just above the base of Cordylodus lindstromi conodont Zone, and just below lowest occurrence of planktonic graptolites. Historically it was subdivided into three epochs (no longer recognized by the ICS)

• Early Cambrian (542 - 513 mya)
• Middle Cambrian (513 - 501 mya)
• Late Cambrian (501 - 488.3 mya)

Currently the Furongian Series (or Epoch) and the Paibian and Drumian Stages (or Ages) are defined and designated by name. The earliest undefined series (unamed) encompasses the as yet unamed Stage 1 and Stage 2 (earliest to latest). Series 2 extends from 521 mya to 510 mya with two stages. Series 3 (from 510 to 501 mya) is composed of Stage 5, the Drumian Stage (or Age). and Stage 7. The final and last series to be created in the Cambrian, the Furongian, encompasses the Paibian Stage, Stage 9 and Stage 10

System/Period	Series/Epoch	Stage/Age	Span in millions of years ago
Cambrian	Furongian
		Unnamed
			492 to 488.3 mya
			496 to 492 mya
		Unnamed
		Paibian
			501 to 496 mya

System/Period	Series/Epoch	Stage/Age	Span in millions of years ago
Cambrian	Series 3
		Stage 7
			503 to 501 mya
			506 to 503 mya
		Drumian
		Stage 5
			510 to 506 mya

System/Period	Series/Epoch	Stage/Age	Span in millions of years ago
Cambrian	Series 2
		Stage 4
			517 to 510 mya
			521 to 517 mya
		Stage 3

System/Period	Series/Epoch	Stage/Age	Span in millions of years ago
Cambrian	Series 1
		Stage 2
			534.6 to 531 mya
			542 to 534.6 mya
		Stage 1

Sources

Proposed Global Standard Stratotype-Section and Point for the Paibian Stage and Furongian Series (Upper Cambrian) International Subcommission on Cambrian Stratigraphy, International Commission on Stratigraphy (ICS), International Union of Geological Sciences (IUGS). Subcommission on Neoproterozoic Stratigraphy International Commission on Stratigraphy (ICS), International Union of Geological Sciences (IUGS).