Cambrian chronostratigraphy: Current state and future plans

Important steps have been made by the International Subcommission on Cambrian Stratigraphy (ISCS) toward global chronostratigraphic subdivision of the Cambrian. The consensus of opinion is that the system should be subdivided into four series representing subequal spans of time. The lower two series will correspond approximately to the traditional Lower Cambrian, the third series will correspond approximately to the traditional Middle Cambrian, and the fourth series corresponds approximately to the traditional Upper Cambrian. The fourth series, called the Furongian Series, was ratified by the International Commission on Stratigraphy (ICS) and the International Union of Geological Sciences (IUGS) in 2003.Selection of horizons representing evolutionary events that can be correlated on a global scale, and which can be used as stage or series boundaries, is much more difficult for the lower two series intervals of the Cambrian than it is for the upper two series intervals of the Cambrian. The most practical concept for subdividing the system into stages involves the establishment of two stages each for the first and second series and the establishment of three stages each for the third and fourth series. The lowermost stage of the Furongian, called the Paibian Stage, has been ratified by the ICS and the IUGS.