Abstract:

According to the study of the grain size in the Changjiang Delta, the Luanhe River Delta, the Nanliujiang Delta and Qinzhou Bay, following conclusions are obtained: 1. As far as our information goes, grain size parameters, C-M plots,probability cumulative curves and multivariate analysis can be important in studying depositional environments. 2. Multivariate analysis is a process in which large amount of grain size data are turned into dynamic classification, therefore the hydrodynamic conditions in deposition can be interpreted by it. 3. Probability cumulative curves once had been used to analyse subenvi-ronments. Since they are controlled by various factors, they can not be simply used to distinguish depositional environments. However,in the same depositional system, the curves are regarded as more ideal for distinguishing sedi-mentary environments. 4. The study of grain size distribution can be helpful to the identificationof depositional environments. But it provides simply the information of the general kydrodynamic conditions in the deposition. Only when it is considered together with sedimentary structures, bioturbation and geological settings, canit be good environmental index.