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根据 6个火山岩样品的分析结果 ,得到北京西山髫髻山组的年龄为 188±19Ma。结合古生物资料分析 ,这个年龄结果表明西山地区髫髻山组的年代可能不晚于中侏罗世 Bajocian阶。因此 ,北京西山地区下侏罗统发育的褶皱构造可能代表了早侏罗世时期的燕山运动造山事件
According to the analysis results of six volcanic rock samples, the age of the Xijishanjiji Mountain Group in Beijing is 188 ± 19Ma. According to the palaeontological data analysis, this age result indicates that the Qianshan Formation in Xishan may not be later than the Middle Jurassic Bajocian. Therefore, the fold structure developed in the Lower Jurassic in the Xishan area of Beijing may represent the Yanshanian orogeny during the Early Jurassic