Second age of the Miaolingian epoch
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 million years ago. The top is defined as the first appearance of another trilobite "Lejopyge laevigata" around million years ago.
GSSP.
The GSSP is defined in the "Drumian section" () in the Drum Mountains, Millard County, Utah, United States. 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 above the base of the Wheeler Formation.
Major events.
The Cambrian Drumian carbon isotope excursion (DICE) event is associated with the beginning of this age. 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. In the middle–late Drumian, there was a radiation interval, before the next extinction event.
Paleontology.
Numerous sponges, palaeoscolecids and euarthropods (including radiodonts) are known from the Drumian deposits.
References.
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