Drumian
Second age of the Miaolingian epoch
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39.5117°N 112.9915°W 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 | ||||||||||||||||||||||||||||||||||||||
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A render of Laurentia during the Drumian | ||||||||||||||||||||||||||||||||||||||
| Chronology | ||||||||||||||||||||||||||||||||||||||
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| 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 | |||||||||||||||||||||||||||||||||||||
| 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 | |||||||||||||||||||||||||||||||||||||
| Upper GSSP ratified | 2008[4] | |||||||||||||||||||||||||||||||||||||
GSSP
The GSSP is defined in the Drumian section (39.5117°N 112.9915°W) 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]
