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在发现陆相侏罗系—白垩系界线地层连续剖面的基础上,补充大北沟组和大店子组的含义,将2组系统分为7个岩段,命名4个标志层;确定年代地层层序,完善大北沟阶和义县阶定义内容;研究重点门类化石分布和演化,建立系统生物地层分带序列,包括7个介形虫带和6个叶肢介带;划分陆相生物群发展阶段,将侏罗系—白垩系界线置于“早期热河生物群”阶段的底部;开展旋回地层和层序地层学研究,建立地层等时格架,识别盆地演化的3个阶段和5个构造期;测得界线层型剖面点存在O同位素高值异常;锆石206Pb/238U测得张家口组顶部年龄为135.4Ma±1.6Ma,大北沟组中部为133.9Ma±2.5Ma和130.1Ma±2.5Ma。综合多学科研究成果,将界线层型剖面点定在张家沟剖面第9层底,以介形虫化石Cyprideastenolonga的首现为标志。
On the basis of finding the continuous section of the continental Jurassic-Cretaceous boundary line, adding the meanings of Dabeigou Formation and Dadianzi Formation, the two systems are divided into seven rock sections and named as four landmark layers. Stratigraphic sequence and perfecting the definitions of Dabeigou step and Yixian order. Studying the distribution and evolution of key fossil fossils, establishing a systematic bio-stratigraphic zoning sequence, including 7 ostracods and 6 exodulants, In the development stage of the biota, the Jurassic-Cretaceous boundary line was placed at the bottom of the “Early Jehol Biota” stage. Cyclospheric and sequence stratigraphy studies were carried out to establish the isochronal stratigraphic framework and to identify the three stages of basin evolution And 5 tectonic periods. The O isotopic high value anomaly existed in the boundary layer of the boundary line. The top of Zhangjiakou Formation of 206Pb / 238U zircon was 135.4Ma ± 1.6Ma and the middle of Dabeigou Formation was 133.9Ma ± 2.5Ma and 130.1Ma ± 2.5Ma. According to the results of multidisciplinary research, the boundary layer-type profile point is set at the bottom of the ninth Zhangjiagou section and marked by the first occurrence of the fossil Cyprideastenolonga.