内蒙古阿拉坦合力苏木汗贝布敦昭奥陶纪裸河组的重新厘定及其意义

Revision of the Ordovician Luohe Formation in Hanbeibudunzhao area of Altan Hil, Inner Mongolia

2010—2012年在内蒙古东乌旗阿拉坦合力苏木中蒙边境一带开展1∶5万区调时,根据岩性组合、古生物特征及地层对比等,将汗贝布敦昭地区的奥陶纪铜山组重新厘定为裸河组,并划分出3个岩性段。粒度分析等特征表明,裸河组总体上表现为动荡的滨—浅海沉积环境;化石及区域地层对比、沉积物源分析等特征表明,裸河组的形成时代为晚奥陶世。这些成果为兴安地层区奥陶纪地层的研究和对比提供了有价值的基础资料,对探讨西伯利亚板块南缘活动大陆边缘早古生代地质构造演化具有重要意义。

During the 1：50000 regional geological survey in Altan Hi] area ofDong Ujimqin Banner,Inner Mongolia, near the border between China and Mongolia, the Ordovician Luohe Formation in Hanbeibudunzhao was redefined on the basis of such factors as rock association, paleontological characteristics and stratigraphic correlation. The revised Luohe Formation can be divided into three lithologic members. The strata are characterized by shore - shallow sea sedimentation according to grain size analysis. Fossils, regional stratigraphic correlation and analysis of sediment source all indicate that Luohe Formation was formed in Late Ordovician. These results not only provide basic data for Ordovician study and correlation of the Hinggan stratigraphic region but also possess important theoret- ical and practical significance for the study of the Early Paleozoic tectonic evolution on the southern margin of the Siberia plate.