中蒙边界中东部地区奥陶纪地层划分与对比

The Ordovician stratigraphic division and correlation at east-central boundary areas of China and Mongolia

在中蒙边界1∶100万系列地质图件编制过程中,有关中东部地区奥陶纪地层层序和时代归属问题存在一定的异议。文章根据中蒙两国1∶20万区域地质图件及生物地层学资料结合野外地质踏勘,讨论了中蒙边界中东部地区奥陶纪地层层序和时代归属。详尽的地质资料及野外踏勘显示,中蒙边界蒙古地区发育的奥陶纪地层可以和相邻地区的中国奥陶纪地层进行对比。蒙古北山地区的Ehenhaya组和Adagbaishint组下段可以和罗雅楚山组相对比;Adagbaishint上段可与咸水湖组相对比;Naransevestei组与白云山组应为同一套地层。在Saishand地区,除自中国境内延伸来的乌宾敖包组和巴彦呼舒组延伸到蒙古外,Zeeriinhural组可以与裸河组进行对比;Naransevestei组与白云山组应为同一套地层。蒙古东部Khalkh gol地区的Bukhat uul组应分为两部分,下段与多宝山组相似,其时代属于早-中奥陶世;上段可以与裸河组进行对比,时代为中-晚奥陶世。

During compiling serial geological maps of the boundary areas of China and Mongolia at scale1：1million appear some disputes about the Ordovician stratigraphic sequence and time problem of some stratigraphic units at east-central boundary areas.This paper deals with the disputes and problems according to the regional geological map and bio-stratigraphy and field reconnaissance.The detail regional geological data and the field reconnaissance results show that the Ordovician strata developed in Mongolia at the border area can be correlated with those in China.Ehenhaya Formation and the Lower member of Adagbaishint Formation in Mongolian Beishan area can be correlated to Luoyachushan Formation in China;the upper member of Adagbaishint Formation to Xianshuihu Formation in China.The Mongolian Naransevestei Formation and the Chinese Baiyunshan Formation are of the same stratigraphic unit.In addition to Wubinaobao Formation and Bayanhushu Formation stretched to Saishand area from China,Zeeriinhural Formation can be correlated to Luohe Formation completely.Bukhat uul Formation of Khalkh gol area in the east Mongolia should be divided into two members：the lower member can be correlated to the Chinese Duobaoshan Formation belonging to Mid-Lower Ordovician System;the upper to the Chinese Luohe Formation belonging to Mid-Upper Ordovician System.