Publications

The use of “lower,” “middle,” and “upper” has persisted for a generation as a convenient and needed way to divide the Cambrian despite agreement that the system is to be divided globally into four series and ten stages. The traditional tripartite division of the system into regional series (Lower, Middle, Upper) reflected local geological and biotic developments not interprovincially correlatable with any precision. However, published use of “lower,” “middle,” and “upper” is unsatisfactory as these informal adjectives have no standard definition, confusingly evoke the earlier use of regional Cambrian series, and are regularly misused. Unacknowledged in the geologic literature is an almost 50 year-long use of three Cambrian subsystems that group as many as five regional Cambrian series. The proposal beginning in 1997 to divide the Avalonian and global Cambrian into four series and three subsystems is detailed herein, with the system divided into three unambiguously defined subsystems: a very long (ca. 32.6 Ma) Lower Cambrian Subsystem (=Terreneuvian and Series 2/proposed Laolingian Series), a short (ca. 9.8) Middle Cambrian Subsystem (=Miaolingian Series), and an Upper Cambrian Subsystem (=Furongian Series) with a corrected age at its top (ca. 486.8 Ma) and a very imprecisely determined ca. 10 Ma duration. The designations “Lower Cambrian Subsystem” or “global Lower Cambrian” serve to distinguish the proposed new chronostratigraphic units from traditional units as the “Lower Cambrian Series” and substitute for the needed, convenient, but undefined adjectives “lower,” “middle,” and “upper.”