The Drumian is a

stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...

of the Miaolingian Series of the Cambrian. It succeeds the Wuliuan and precedes the Guzhangian. 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 ...

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

GSSP A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. The effort to define GSSPs is conducted ...

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) ex ...

Millard County Millard County ( ) is a county in the U.S. state of Utah. As of the 2010 United States Census, the population was 12,503. Its county seat is Fillmore, and the largest city is Delta. History The Utah Territory legislature created the county o ...

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