内蒙古宁城地区道虎沟化石层同位素年代学

Isotope geochronology of the fossil-bearing beds in the Daohugou area, Ningcheng, Inner Mongolia

在内蒙古宁城道虎沟地区新发现了一套化石层,该化石层所代表的道虎沟生物群是研究燕辽生物群灭绝原因和探寻热河生物群起源之迷的关键。精确的Ar-Ar和SHRIMPU-Pb测年表明,道虎沟化石层之上的中—酸性火山岩的年龄在164～165Ma左右,道虎沟化石层的时代大于或等于165Ma。据此认为,道虎沟生物群在时代上比热河生物群早数千万年以上,应属于燕辽生物群,或者属于燕辽生物群与热河生物群之间的过渡类型。

A new set of fossil-bearing beds, Daohugou fossil-bearing beds, is found in the Daohugou area, Ningcheng, Inner Mongolia. The Daohugou biota represented by the fossil beds is the key to the study of the cause for the extinction of the Yanliao biota and the origin of the Jehol biota. The accurate Ar-Ar and SHRIMP U-Pb dating shows that the age of intermediate-acid volcanic rocks overlying the Daohugou fossil-bearing beds is about 164-165 Ma, and that the age of this fossil-bearing beds is older than or equal to 165 Ma. Therefore the authors draw the conclusion that the age of the Daohugou biota is tens of million years earlier than that of the Jehol biota, and it should belong to the Yanliao biota or to a transitional type between the Yanliao biota and Jehol biota.