冀北地区早、中侏罗世地层划分及其区域对比

Stratigraphic division and correlation of the Early-Middle Juras-sic in northern Hebei, China

冀北地区是燕山造山带的重要组成部分,尽管已有较长的研究历史,但在早、中侏罗世地层划分对比问题上仍存在着明显的分歧。通过对冀北下板城一带早、中侏罗世地层的详细研究,重新划分了该区的早侏罗世地层,对早、中侏罗世地层进行了区域对比。主要结论有:①原冀北地区的“下花园组”依岩石组合、碎屑成分变化可解体为3个组,即下花园组、龙门组和九龙山组;②原冀北地区使用的“九龙山组”与京西地区的九龙山组含义不同,建议归入髫髻山组;③经过重新划分后,冀北地区的早、中侏罗世地层与京西地区可以完全对比。本研究结论对于燕山地区早、中侏罗世地层格架的建立和构造地质演化过程的研究有重要意义。

Northern Hebei is an important component part of the Yanshan orogenic belt. Although it has long been studied, obviously divergent views still exist as to the problem of the stratigraphic division and correlation of the Early-Mid Jurassic in the area. In this paper, a re-division of the Early Jurassic and regional correlation of the Early-Mid Jurassic are made based upon a study of the Early-Mid Jurassic in the Xiabancheng area, northern Hebei. The conclusions are as follows： （1） the original ＂Xiahuayuan Formation＂ may be disintegrated in ascending order into three parts, i.e. ： the Xiahuayuan Formation, Longmen Formation and Jiulongshan Formation, based on the rock associations and variation in clastic composition; （2） the connotation of the original ＂liulongshan Formation＂ in northern Hebei is difference from that of the Jiulongshan Formation in western Beijing, so it is advisable to assign it to the Tiaojishan Formation; and （3） after such re-division, the Early-Mid Jurassic in northern Hebei can be completely correlated with that in western Beijing. These conclusions are very important to the establishment of the Early-Mid Jurassic stratigraphic framework and the study of the.tectonic evolution in the Yanshan region.