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冀北滦平盆地火斗山乡张家沟大北沟组—大店子组剖面连续、出露好、沉积序列全、化石十分丰富。介形类的研究可划分为1个延限带、4个组合带和7个亚带。其中第Ⅰ(Luanpingella-Torinina-Eoparacypris)组合带及所包含的1、2(Luanpingella Postacuta和Torinina obesa)亚带,分布于大北沟组,显示了晚侏罗世晚期的特征。第Ⅱ—Ⅳ(Yanshanina-Cypridea-Rhinocypris, Cypridea-Yanshanina-Timiriasevia和Cypridea sulcata-C．shanyingensis)组合带及所包含的3～7(Cypridea stenolonga,C．xitaiyangpoensis,C．luanpingensis,C．sulcata和C．shanyingensis)亚带分布在大店子组,Cypridea开始并相继大量出现和繁盛,明显地具有早白垩世早期的特征。故侏罗系—白垩系的界线应置于第Ⅰ组合带与第Ⅱ组合带,即第2亚带与第3亚带之间。
The profiles of the Dabeigou Formation and Dadukou Formation in Zhangjiagou, Doutou Gully, Liaoheping Basin, Hebei Province, are continuous and well-exposed with abundant sedimentary sequences and abundant fossils. Ostracoda research can be divided into a delay zone, four combination zones and seven sub-zones. The Luanpingella-Torinina-Eoparacypris belt and the 1, 2 (Luanpingella Postacuta and Torinina obesa) subbands distributed in the Dabeigou Formation show the characteristics of the Late Jurassic. Cyprissa stenolonga, C. xitaiyangpoensis, C.luanpingensis, C.sulcata, and C, which are comprised of Yanshanina-Cypridea-Rhinocypris, Cypridea-Yanshanina-Timiriasevia and Cypridea sulcata-C.shanyingensis, . Shanyingensis) subtropical distribution in the Dadianzi Formation, Cypridea began and appeared in large numbers and prosperous, obviously with early Early Cretaceous characteristics. Therefore, the Jurassic-Cretaceous boundary line should be placed between the first zone and the second zone, that is, between the second and third sub-zones.