The Cretaceous-Quaternary bedrock in Jlangsu is so poorly exposed that information on the sedimentary sequence has to be gathered from borehole.
As geological prospecting are carried out in recent years, the study of fossil Ostracoda has been incessantly developed in China too. A great number of Mesozoic and Cenozoic Ostracoda have been collected at various localities, especially the non-marine forms are widely distributed in many basins of different regions in China. It is worthy to note that being rich in quantity and well preserved, ostracods are the chief representatives of the fossil microfauna found in this region. Gastropoda, Pelecypoda, Conr.hostraca, Sporse(sic) and Charaphyta(sic) are also present. Some of the species of ostracods are known to be short-ranged forms and forming the characteristic assemblages. These ostracode species may be used for the correlation of certain strata within a limited region. Owing to certain genera and species with wide geographical distribution, the ostracode fauna may be compared with those from the corresponding beds at other localities of China as well as other parts of the world, but they show their own characteristics.
The Mesozoic and Cenozoic strata in this region are almost of non-marIne Deposits, in addition to a thin Quaternary layer being of littoral facies. From the lithological and the palaeontological viewpoints, the Cretaceous-Quaternary deposits may be classified ascendingly into 14 formations.
Here have been described and illustrated 74 genera and 13 subgenera totally 359 species. Of which 240 species and 7 genera are new belonging respectively to 21 famillies. According to the characteristics of the morphology, ornamentation and distribution of species, the ostracode fauna is divided ascendingly into 11 assemblages.