Coordinates: The Drumian is a stage of 3rd series of the Cambrian. It succeeds still unnamed 5th stage of the Cambrian and precedes the Guzhangian. The base is defined as the first appearance of the trilobite Ptychagnostus atavus around ~504.5 million years ago. The top is defined as the first appearance of another trilobite Lejopyge laevigata around ~500.5 million years ago.
The GSSP is defined in the Drumian section ( ) in the Drum Mountains, Millard County, Utah, USA. The stage was also named after the Drum mountains. The section is an outcrop of the Wheeler Formation, a succession of calcareous shales. The precise base of the Drumian is a laminated limestone 62 m above the base of the Wheeler Formation.
- Babcock, Loren E.; Richard A. Robison, Margaret N. Rees, Shanchi Peng, Matthew R. Saltzman (2007). "The Global boundary Stratotype Section and Point (GSSP) of the Drumian Stage (Cambrian) in the Drum Mountains, Utah, USA". Episodes 30 (2): 85–95. Retrieved 14 September 2012.
- "GSSP for Drumian Stage". Retrieved 12 November 2012.
|Preceded by Proterozoic Eon||542 Ma - Phanerozoic Eon- Present|
|542 Ma - Paleozoic Era -251 Ma||251 Ma - Mesozoic Era - 66 Ma||66 Ma - Cenozoic Era - Present|