北京周口店三好砾岩的时代、物源背景及其古地理意义:来自沉积学和碎屑锆石年代学的证据

发布时间：2018-03-31 20:26

本文选题：北京周口店　切入点：三好砾岩　出处：《地质科技情报》2017年04期

【摘要】：三好砾岩出露于北京周口店地区太平山北坡,不整合覆盖于中奥陶统马家沟组之上,以分选好、磨圆好、胶结好为特征。研究表明:三好砾岩是一套二次改造的滨岸砾岩,代表了晚石炭世海侵过程中的底砾岩。来自于砾岩和其夹层中砂岩层的碎屑岩浆锆石年龄均集中在330~300 Ma之间,峰值年龄为约310 Ma,结合区域地层展布情况与华北北缘的构造热事件记录认为,它是晚石炭世至早二叠世沉积,具备准同生沉积特征。借助上述U-Pb年代学数据,结合碎屑组分特征、古流向分析及同期华北北缘岩相古地理分布特征表明,三好砾岩的物源区为内蒙古隆起。以三好砾岩为代表的上石炭统底砾岩反映了内蒙古隆起迅速隆升、剥蚀、搬运和沉积的过程,这套砾岩亦可以作为当时盆山边界的标识物。三好砾岩中高含量的晚石炭世岩浆锆石暗示了内蒙古隆起初始隆升的时限应在330~300 Ma之间。
[Abstract]:Sanhao conglomerate is exposed on the northern slope of Taiping Mountain in Zhoukoudian area, Beijing, and unconformity covers the Majiagou formation of the Middle Ordovician, characterized by good sorting, good grinding and good cementation.The study shows that Sanhao conglomerate is a set of secondary remade shoreline conglomerate, which represents the bottom conglomerate during the transgression of late Carboniferous.The zircon ages of clastic magma from conglomerates and sandstone beds in its intercalation are concentrated in the range of 330 ~ 300 Ma, with a peak age of about 310 Ma. It is considered that, in combination with the regional stratigraphic distribution and the tectonic heat event records in the northern margin of North China,It was deposited from late Carboniferous to early Permian and has the characteristics of quasi-syngenic deposition.According to the U-Pb chronological data and the clastic component characteristics, the paleodirection analysis and the paleogeographic distribution of lithofacies in the northern margin of North China during the same period, the provenance of Sanhao conglomerate is the Inner Mongolia uplift.The upper Carboniferous conglomerate represented by Sanhao conglomerate reflects the rapid uplift denudation transport and deposition of the Inner Mongolia uplift. The conglomerate can also be used as a marker of the basin-mountain boundary at that time.The high content of zircon from late Carboniferous magma in Sanhao conglomerate suggests that the time limit of initial uplift of Inner Mongolia uplift should be between 330 Ma and 300 Ma.
【作者单位】：中国地质大学(武汉)生物地质与环境地质国家重点实验室;中国地质大学(武汉)地球科学学院;
【基金】：国家级创新创业训练项目(201510491012)
【分类号】：P588.212.5;P597.3

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