Discovery of ostracods in the Dabeigou and Dadianzi Formations at Zhangjiagou, Luanping County, northern Hebei Province of China and new progress in the biostratigraphic boundary study
Discovery of ostracods in the Dabeigou and Dadianzi Formations at Zhangjiagou, Luanping County, northern Hebei Province of China and new progress in the biostratigraphic boundary study
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发表时间：
2002
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通讯作者：
Pang Qiqing;Li Peixian;Tian Shugang;L. Yongqing
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作者：
Pang Qiqing;Li Peixian;Tian Shugang;L. Yongqing
河北省滦平县火斗山村张家沟大北沟组和大店子组有一个连续剖面和完整的沉积序列，剖面中发现了丰富的介形类化石，可划分为三个组合带：Ⅰ.滦平-la-Eoparacypris-Pseudoparacyprodopsis组合带，Ⅱ.燕山-Cypridea-Rhinocypris组合带，Ⅲ.Cypridea-Yanshanina-Timiriasevia组合带。而发现于大店子组的组合带Ⅱ、Ⅲ，Cypridea开始大量出现，明显显示出早白垩世早期的特征，因此侏罗-白垩系界线应置于组合带Ⅰ与组合带Ⅱ之间，即大北沟组与大店子组之间，两组之间的砾岩和桑迪岩在相界上发生了交替变化。在张家沟剖面上，未发现化石的地层厚度由大店子东沟剖面的56 m减少到仅9.11m，因此张家沟剖面优于大店子东沟剖面，是一个理想的陆相侏罗系候选剖面。中国北方白垩纪界线层型。
There are a successive section and a complete sedimentary sequence of the Dabeigou and Dadi-anzi Formations at Zhangjiagou,Huodoushan Village,Luanping County,Hebei Province.Abundant ostra-cod fossils were found in the sections ;they may be grouped into three assemblage zones:Ⅰ.Luanpingel-la-Eoparacypris-Pseudoparacypridopsis assemblage zone,Ⅱ.Yanshanina-Cypridea-Rhinocypris assemblage zone,andⅢ.Cypridea-Yanshanina-Timiriasevia assemblage zone.Assemblage zoneⅠ,distributed in the Dabeigou Formation,shows the late Late Jurassic features;whereas assemblage zonesⅡandⅢ,which are found in the Dadianzi Formation and in which Cypridea began to appear in large amount ,evidently show the early Early Cretaceous features.So the Jurassic-Cretaceous boundary should be placed between assem-blage zoneⅠand assemblage zoneⅡ,i.e.between the Dabeigou Formation and the Dadianzi Formation.The conglomerate and sandy conglomerate between the two formations have facially changed into alternat-ing beds of sandstone and mudstone at the Zhangjiagou section.The thickness of the strata in which no fossils have been found decreases from56m at the Dadianzi Donggou section to only9.11m at the Zhangjiagou section.Therefore the Zhangjiagou section is better than the Dadianzi Donggou section and may serve as an ideal candidate section for the non -marine Jurassic-Cretaceous boundary stratotype in northern China.