Characteristics and redefining of the Cambrian Shuangmaidi Group in the middle part of the Baoshan block of western Yunnan Province

On the basis of the latest data obtained from 1∶50000 regional geological survey of the Banqiao Sheet, the authors redefined the Early-Middle Cambrian Shuangmaidi Group as the Late Cambrian Hetaoping Formation. The lithologic association is composed of microclastic rocks and marbles with some basalts and andesitic basalts. The authors discovered for the first time the Late Cambrian trilobites Blackwelderia baoshanensis Luo，Blackwelderia sp.，Parashengia elongata Luo , revealing the loss of Early and Middle Cambrian sediments. It is interesting that the bottom-living and planktonic trilobites lived together in mixture. This study will be of great significance in the study of tectonic property, evolution and unit subdivision in Baoshan block.