Taijiangian Stage:A New Chronstratigraphical Unit for the Traditional Lower Middle Cambrian in South China
PENG Shan chi 1) , YUAN Jin liang 1) , and ZHAO Yuan long 2) ( 1)Nanjing Institute of Geology and Palaeontology, the Chinese Academy of Science, Nanjiang, 210008; 2)Department of Resource Engineering, Guizhou University of Technology, Gu
A new stage, named as Taijiangian, is proposed for the lower Middle Cambrian in the Jiangnan Slope Belt of the Yangtze Platform. The lower boundary of the new stage is defined by the first appearance datum (FAD) of the cosmopolitan trilobite species Oryctocephalus indicus . This point lies at the base of the Bed 10 in the boundary stratotype section at Balangcun Village in Taijiang County, eastern Guizhou Province. The stage and its 4 succeeding stages, the Wangcunian, the Youshuian, the Waergangian, and the Taoyuanian in western Hunan, proposed by Peng et al ., (1998), constitute a Middle Upper Cambrian chronostratigraphical standard for South China. The lower boundary of the overlying Wangcunian Stage is defined by the FAD of Ptychagnostus punctuosus . The globally distributed agnostoid species P. gibbus and P. atavus are also known from the Taijiangian in western Hunan, but have not recorded their FADs yet. Because the Taijiangian is widespread in the eastern Guizhou western Hunan area, further investigation may be able to reveals the FAD of either P. gibbus or P. atavus , with which the Taijiangian may be subdividable.