Dresbachian

The Dresbachian is a Maentwrogian regional stage of North America, lasting from 501 to 497 million years ago.^[1] It is part of the Upper Cambrian and is defined by four trilobite zones. It overlaps with the ICS-stages Guzhangian, Paibian and the lowest Jiangshanian.^{[citation needed]}

The Dresbachian overlies the Middle Cambrian Albertan series, and is the lowest stage of the Upper Cambrian Croixian series, followed by the Franconian stage. The Dresbachian extinction event, about 502 million years ago, was followed by the Cambrian–Ordovician extinction event about 485.4 million years ago.