台江阶——我国寒武系一个新的年代地层单位

Taijiangian Stage:A New Chronstratigraphical Unit for the Traditional Lower Middle Cambrian in South China

台江阶是继湘西建立的 4个中 -上寒武统新阶之后在我国江南斜坡带黔东传统的中寒武统下部建立的又一个新阶 ,它的底界层型剖面位于贵州台江县革东镇八郎村 ,底界划在 Oryctocephalus indicus的首现位置 ,位于凯里组下部第 10层之底。

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.