In the southeast area of Chongqing Middle Carboniferous Huanglong Formation , found a wealth of Silurian conodont fossils, so the Huanglong Formation must be disintegrated into 2 .lithostratigraphic units.The Silurian strata will create a new lithostratigraphic unit---Shuijiang Formation. It is a Gray white--Pale yellow fine― microcrystalline limestone, calcareous dolomite, The Formation and the underlying Silurian Hanjiadian Formation conformity contact, and overlying the Carboniferous Huanglong Formation or Permian Liangshan Formation disconformable contact.