生物地层间断(biostratigraphic gaps)频率分布图是根据8个化石物种作出来的.这种分布图有助于估计生物带界线的置信区间,它提供给人们合理地预测剖面中可见化石的最低和最高层位之间间断大小的数据.但实际上,最低和最高层位的化石在岩层中未见到,因为它们超出了这个范围.这种间断常服从随机(泊松或近泊松)分布,只有少数例外,后者似可代表沉积速率异常增加或生物丰度异常减少的时期. The frequency distribution of biostratigraphic gaps is based on eight fossil species, a distribution that helps to estimate the confidence interval of the zonation of the zonules, and provides the lowest and highest probability that one can reasonably predict the fossils visible in the profile However, in fact, the lowest and highest fossils are not found in the rock because they are beyond this range, and the discontinuities often follow random (Poisson or Poisson) distributions, With only a few exceptions, the latter may seem to represent an anomalous deposition rate or an abrupt decrease in biological abundance.