冀西北地区早、中侏罗世地层划分及其区域对比

摘要

The Early-Middle Jurassic strata in Northwestern Hebei even though has been researched for a long history, but t is still different with that in western Beijing (in the same region--Yanshan orogenic belt) as to the specific division and correlation. The strata in Northwestern Hebei area are divided into Nandaling Formation, Xiahuayuan Formation, Jiulongshan Formation,Tiaojishan Formation and Houcheng Formation while in the western Beijing area the strata that is considered the same layer to the Xiahuayuan Formation are divided into Yaopo Formation and Longmen Formation. Writers consider that,there is also the Longmen Formation in Northwestern Hebei area, the same layer to that in western Beijing, which are used to be considered as a part of the Xiahuayuan Formation or the Jiulongshan Formation. Writers also find that the Xiahuayuan Formation still contains a part of the Nandaling Formation. In this paper,the conclusions of a re-division are as follows: the Lower Jurassic Nandaling Formation, the Middle Jurassic Xiahuayuan Formation, Jiulongshan Formation,Tiaojishan Formation and Houcheng Formation, and they can be completely correlated with those in western Beijing area. These conclusions are very important to the establishment of the Early—Middle Jurassic stratigraphic framework and the study of the tectonic evolution in the Yanshan region.%冀西北早、中侏罗世地层尽管已有较长的研究历史,但在具体划分对比上与同处于燕山造山带的京西地区仍有所不同.前者划分为南大岭组、下花园组、九龙山组、髫髻山组和后城组,后者与下花园组相当的地层又分为窑坡组和龙门组.笔者通过研究认为,冀西北地区也发育有与京西相同层位的龙门组,只是以往将其或划归于下花园组,或分属到九龙山组;同时发现下花园组尚包含了部分南大岭组地层.重新划分后的地层层序为:侏罗系下统南大岭组,中统下花园组、龙门组、九龙山组、髫髻山组、后城组,完全可以与京西地区对比.本研究结论对于建立统一的燕山地区早、中侏罗世地层格架和地质构造演化过程的研究有重要意义.