Drumian

39.5117°N 112.9915°W / 39.5117; -112.9915 The Drumian is a stage 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 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.

Drumian
~504.5 – ~500.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Chronology
−540 — – −535 — – −530 — – −525 — – −520 — – −515 — – −510 — – −505 — – −500 — – −495 — – −490 — – −485 — N ♇ P a l e o z o i c Ediacaran C a m b r i a n O T e r r e n e u v i a n S e r i e s 2 M i a o l i n g. F u r o n g. E Fortunian "Stage 2" "Stage 3" "Stage 4" Wuliuan Drumian Guzhangian Paibian Jiangshanian "Stage 10" Tremadocian               ← Orsten Fauna ← Burgess Shale ← Kaili biota ← Archaeocyatha extinction ← Emu Bay Shale ← Sirius Passet biota ← Chengjiang biota ← First Trilobites ← SSF diversification, first brachiopods & archaeocyatha ← First halkieriids, mollusсs, hyoliths SSF ← Baykonurian glaciation ← Dresbachian extinction   Major Glacial period Subdivision of the Cambrian according to the ICS, as of 2024.[1] Vertical axis scale: Millions of years ago
Etymology
Name formality	Formal
Name ratified	2006[2]
Former name(s)	Cambrian Stage 6
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Age
Stratigraphic unit	Stage
First proposed by	Babcock et al., 2006[3]
Time span formality	Formal
Lower boundary definition	FAD of the Trilobite Ptychagnostus atavus
Lower boundary GSSP	Drumian section, Wheeler Shale, Utah, U.S.A. 39.5117°N 112.9915°W / 39.5117; -112.9915
Lower GSSP ratified	2006[2]
Upper boundary definition	FAD of the Trilobite Lejopyge laevigata
Upper boundary GSSP	Luoyixi section, Luoyixi, Guzhang, Hunan, China 28.7200°N 109.9647°E / 28.7200; 109.9647
Upper GSSP ratified	2008[4]

GSSP

The GSSP is defined in the Drumian section (39.5117°N 112.9915°W / 39.5117; -112.9915) in the Drum Mountains, Millard County, Utah, United States.^[2] 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 (203 ft) above the base of the Wheeler Formation.^[5]

Major events

The Cambrian Drumian carbon isotope excursion (DICE) event is associated with the beginning of this age.^[6] The cause of this event was the shallowing of anoxic deep waters simultaneously with their transgression. DICE hampered the recovery of reef ecosystems already affected by the early–middle Cambrian mass extinctions.^[7] In the middle–late Drumian, there was a radiation interval, before the next extinction event.^[8]

Paleontology

Numerous sponges, palaeoscolecids and euarthropods (including radiodonts) are known from the Drumian deposits.^[9][10][11]