The Drumian is a stage of the

Miaolingian The Miaolingian is the third Series of the Cambrian Period, and was formally named in 2018. It lasted from about to million years ago and is divided in ascending order into 3 stages: the Wuliuan, Drumian, and Guzhangian. The Miaolingian is prec ...

Series of the

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

. It succeeds the

Wuliuan The Wuliuan stage is the fifth stage of the Cambrian, and the first stage of the Miaolingian Series of the Cambrian. It was formally defined by the ICS in 2018. Its base is defined by the first appearance of the trilobite species ''Oryctocephalu ...

and precedes the

Guzhangian The Guzhangian is an uppermost stage of the Miaolingian Series of the Cambrian. It follows the Drumian Stage and precedes the Paibian Stage of the Furongian Series. The base is defined as the first appearance of the trilobite ''Lejopyge laevigat ...

. The base is defined as the first appearance of the

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

Ptychagnostus atavus ''Ptychagnostus atavus'' is a species of agnostid trilobite. It was originally described by Swedish paleontologist Sven Axel Tullberg as ''Agnostus atavus'' in 1880. It is used in biostratigraphy as an index fossil. Its first appearance at the G ...

'' around million years ago. The top is defined as the first appearance of another trilobite ''

Lejopyge laevigata ''Lejopyge laevigata'' is a species of agnostid trilobite belonging to the genus '' Lejopyge''. It existed during the Guzhangian to the Paibian Age (around to million years ago) of the Cambrian. It has a cosmopolitan distribution and is an ...

'' around million years ago. The GSSP is defined in the ''Drumian section'' () in the

Drum Mountains The Drum Mountains or Detroit Mountains are a desert range in Juab and Millard counties of western Utah. They lie within the Basin and Range Province, which is a series of generally north-south trending mountain ranges and valleys (or basins) ext ...

, Millard County,

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

, United States. The stage was also named after the Drum Mountains. The section is an outcrop of the

Wheeler Formation The Wheeler Shale (named by Charles Walcott) is a Cambrian ( 507 Ma) fossil locality world-famous for prolific agnostid and ''Elrathia kingii'' trilobite remains (even though many areas are barren of fossils) and represents a Konzent ...

, a succession of calcareous shales. The precise base of the Drumian is a laminated limestone above the base of the Wheeler Formation.

References

Cambrian geochronology Geological ages Cambrian United States {{geology-stub