滹沱群究竟是震旦下部地层,还是独立于震旦之前的地层?争论焦点之一在于滹沱群上下时限认识不同。目前滹沱群上限有1700Ma与1900Ma之争,下限有2000Ma、2300Ma及2500Ma三种不同认识。七十年代以前,滹沱群只有K-Ar年龄,如今滹沱群已有Rb-Sr和U-Pb年龄。尽管数目较小,它却开辟了新的领域,可以从不同角度对滹沱群的上下限进行讨论。一、滹沱群上限 (一)K-Ar年龄 Whether the Hutuo group is the lower part of Aurora or the strata independent of Aurora? One of the focuses of the debate lies in the different understandings of the upper and lower Hutuo groups. At present, the upper limit Tuo Tuo 1700Ma and 1900Ma dispute, the lower limit of 2000Ma, 2300Ma and 2500Ma three different understanding. Before the seventies, Hutuo Group only K-Ar age, and now Hutuo Group Rb-Sr and U-Pb age. Despite its small size, it opens up new areas where the limits of the Hutuo group can be discussed from different perspectives. First, the upper limit Tuoyu group (a) K-Ar age