The role of stratotypes in stratigraphy

The definition of “biochron” in the International Stratigraphic Guide is unacceptable because in defining biochronologic units in terms of biostratigraphic units, said definition confuses the concepts of the biochron and parachron, does not take into account the problem of reworking, and fails to consider the often enormous difference between the total time subtended by a biostratigraphic unit and the span of time defined by its analogous biochronologic unit. In order to call attention to and solve these problems, a proposal is made for the codification of biochronologic units.