陆相渐新统划分中的问题及新进展

近年来国际上关于始新世－渐新世界线的研究取得了重大进展，其同位素年龄被确认为３４Ｍａ，北美哺乳动物年代表已据此重新厘定。通过对哺乳动物群的分析和对比，论证了我国原认为是早渐新世的乌兰戈楚期和呼尔井期的时代应改归晚始新世，原认为是中渐新世的三达河期的时代应为早渐新世。在亚洲始新世－渐新世的界线不是在乌兰戈楚期之末，而是在呼尔井期与三达河期之间。

Deposits of the volcanic eruption event from the basal Lower Cambrian phosphatic sequence in eastern Yunnan and their significance

The lithologic,mineralogic and geochemical characteristics of the claystone lay ers at the base of the Xiaowaitousham Member of the Meishucun section in Jinning County,and Daibu Member of the Lower Cambrian Meishucun Formation of the Deze section in Qujing City demonstrate that these claystone layers are metabentonites which were formed through alteration of acidic volcanic ashes.They represent the simultaneous deposits of the volcanic eruption event,consequently,they could be taken as the important geological event marker for the stratigraphic correlation of the base of the Lower Cambrian Meishucun Formation in eastern Yunnan.Based on the features of the metabentonite layer and of the lower phosphatic succession,the Xiaowaitoushan Member of the Meishucun section could be correlated with the dolomite beds of the lower Daibu Member in east of the Xiaojiang Fault,and there lacks the siliceous rock beds of the upper Daibu Member at Meishucun section.Therefore,the stratigraphic succession of the Xiaowaitoushan Member at Meishucun section could not reflect the sedimentary sequence of the Lower Meishucun Formation in eastern Yunnan.