内蒙古扎鲁特旗地区中侏罗统塔木兰沟组的厘定

扎鲁特旗地区发育的一套中性火山岩，前人曾将其置于二叠纪“大石寨组”、“青凤山组”，缺少古生物资料和测年数据.本次1：25万区域地质调查，在原1：20万划分的“大石寨组”、“青凤山组”的安山岩中采集了同位素测年样品，采用全岩激光40Ar/39Ar法测年，对火山岩样品进行了年代学研究，结果表明火山岩年龄为（172.7±2.0）~（165.2±1.3）Ma.鉴于这套火山岩地层岩石组合特征清楚，时代依据充分，在区域上具有一定的延展性和可填图性，故将这套火山岩地层重新厘定为中侏罗统塔木兰沟组.

REVISION OF THE JURASSIC TAMULANGOU FROMATION IN THE JARUD QI AREA,INNER MONGOLIA

A suite of intermediate volcanic rocks in the Jarud Qi area of Inner Mongolia was defined as the Permian Dashizhai Formation and Qingfengshan Formation by previous researchers, but they were lack of paleontological and dating data. In the recent 1:250 000 regional geological survey, the isotopic dating samples are collected from the andesites of Dashizhai and Qingfengshan Formations defined in the former 1:200 000 geological survey. The chronology of volcanic rock samples is studied based on the laser ⁴⁰Ar/³⁹Ar dating method. The result shows that the age is(172.7±2.0)-(165.2±1.3) Ma. In consideration of the clear characteristics of stratigraphic rock assemblages, sufficient time basis and certain extensibility and mapping possibility, this suite of volcanic strata is redefined as the Middle Jurassic Tamulangou Formation.