DIVISION AND CORRELATION OF TERRESTRIAL CRETACEOUS STAGES IN CHINA

Nonmarine strata of Cretaceous age are well developed in North China.Their chronostratigraphic division and correlation with marine successions are a matter of intense debate in Cretaceous research.Lower Cretaceous strata have been well studied in northern Hebei and western Liaoning provinces,and the Upper Cretaceous is well developed in the Songliao area.These provide the reference sections to establish terrestrial Cretaceous stages in China.Correlation with the international geological time scale shows that the Jurassic-Cretaceous boundary is possibly placed in the upper Tuchengzi Formation,the Upper-Lower Cretaceous boundary is at the base of Quantou Formation,and the top Cretaceous boundary is in the upper part of the second member of the Mingshui Formation.Based on the distribution of nonmarine Cretaceous strata in the North China,the terrestrial Cretaceous chronostratigraphy can be subdivided into,in ascending order,the Jibeian,Jeholian and Liaoxian stages of Lower Cretaceous,and the Nonganian,Songhuajiangian,and Suihuanian stages of Upper Cretaceous.The bottom age of these stages is estimated at 145.5Ma,130Ma,119Ma,99.6Ma,86.1Ma,and 79.1Ma,respectively.