摘要
The age of the Yukiang （Yujiang） Formation has been shrouded in controversy for more than 75 years. New investigation at the Liujing section, Hengxian County, Guangxi, has revealed a conodont sequence assignable to two Early Devonian conodont zonations： the Eognathodus kindlei？-Polygnathus pireneae Zone and the Polygnathus nothoperbonus Zone from oldest to youngest. The Gaoling and Mahuangling members of the Nahkaoling （Nagaoling） Formation and the overlying Xiayiling Member and lower part of the Shizhou Member of the Yukiang Formation are proven to belong to the Pragian Eognathodus kindlei？-Polygnathus pireneae Zone. The co-occurrence of Polygnathus pireneae and Pol. sokolovi in the lower part of the Shizhou Member demonstrates that this interval can be approximately correlated with the uppermost part of the Polygnathus pireneae Zone. However, precise level identification of the Pragian-Emsian Boundary （PEB） in the Liujing section remains dfficult due to the scarcity of suitable limestone samples for conodont analysis from the middle and upper parts of the Shizhou Member. The Daliancun and Liujing members of the Yukiang Formation and the lower part of the overlying Moding Formation are assigned to the Polygnathus nothoperbonus Zone with the nominal species of this biozone ranging from the bottom of the Daliancun Member to the lower part of the Moding Formation.
The age of the Yukiang （Yujiang） Formation has been shrouded in controversy for more than 75 years. New investigation at the Liujing section, Hengxian County, Guangxi, has revealed a conodont sequence assignable to two Early Devonian conodont zonations： the Eognathodus kindlei？-Polygnathus pireneae Zone and the Polygnathus nothoperbonus Zone from oldest to youngest. The Gaoling and Mahuangling members of the Nahkaoling （Nagaoling） Formation and the overlying Xiayiling Member and lower part of the Shizhou Member of the Yukiang Formation are proven to belong to the Pragian Eognathodus kindlei？-Polygnathus pireneae Zone. The co-occurrence of Polygnathus pireneae and Pol. sokolovi in the lower part of the Shizhou Member demonstrates that this interval can be approximately correlated with the uppermost part of the Polygnathus pireneae Zone. However, precise level identification of the Pragian-Emsian Boundary （PEB） in the Liujing section remains dfficult due to the scarcity of suitable limestone samples for conodont analysis from the middle and upper parts of the Shizhou Member. The Daliancun and Liujing members of the Yukiang Formation and the lower part of the overlying Moding Formation are assigned to the Polygnathus nothoperbonus Zone with the nominal species of this biozone ranging from the bottom of the Daliancun Member to the lower part of the Moding Formation.
基金
funded by the National Natural Science Foundation of China(40872009,41272009,41290260,41303001 and J1210006)
