Since the coexistence of the Cretaceous and Palaeocene was ascertained in the Hengyang Basin of Hunan in the middle of the 1960's, the Cretaceous and Tertiary boundary has been discussed in several papers, but it still remains controversal. The points at issue are the connotation, stratigraphical position and lateral correlation of the Dongtang (or Chejiang) Formation.

The Cretaceous rocks of China are represented by both marine and nonmarine facies. Correlation of the marine sequences is based in particular in ammonites, foraminifera, rudists and palynomorphs, and that of the nonmarine sequences on reptiles (including dinosaur eggs), fish, bivalves, ostracodes, conchostracans, insects, plants, charophytes and palynomorphs.