Abstract:

Extensive occurrence of hiatus in geological record imposes bad effects on the study of chronostratigraphic correlation,organic evolution,catastrophic or episodic depositional layers,and on analysis precise.Hiatus could be classified into syn-depositional and post-depositional ones according to their formation stages,and into micro,small,median,large and giant ones according to their scales.The micro and small hiatus generally formed in syngenetic stages;the large and giant ones resulted from global eustatic movements,paleogeographic and paleoclimatic changes,tectonic activities in epigenetic stage;the median ones formed in both the syngenetic and epigenetic stages.The completeness of a stratigraphic section is defined as the fraction of time intervals of some specified length(t) that left a record.The value of the completeness of any section is less than one but greater than zero.How to determine the completeness of a section is still a unsolved problem.In recent ten years or more,some research workers proposed a number of approaches such as the ratio between long-term and short-term sedimentation rates,the ratio of thicknesses between a section and globle average synchronous deposits,tired trace fossiles and paleomagnetic data methods.These methods have laid down a firm foundation for future work.