青海南部通天河群的地质时代

<正> 青海省南部及四川省西北部,沿通天河—金沙江两岸展布有一套浅至中变质碎屑岩及火山岩夹大理岩,厚度可达8193m。1959年科学院南水北调考察队命名为通天河群,由于未采到可靠的化石,时代归属上有早古生代、泥盆纪及石炭二叠纪等不同认识。青海省地质局区调队1970年把该地层归入下二叠统第四岩组,即火山岩夹碎屑岩组,下分三个岩段,即下部火山岩及碎屑岩段、中部碎屑岩段及上部火山岩段,三个岩段之间为整合接触。剖面上未采到化石,依据在四川省石渠县觉悟寺北西相当于下部火山岩及碎屑岩

The geological age of the Tongtianhe Group in Southern Qinghai

The Tongtianhe Group is distributed along the Tongtianhe-Jinshajiang in southern Qinghai and northwestern Sichuan. It is composed o?epimetamorphic and low-grade metamorphic and middle-grade metamorphic clasolites as well as volcanic rocks intercalated with marble. The Tongtianhe Group is about 8193m thick and may be divided into three formations. In the past, the geological age of the Tongtianhe Group was regarded as Permo-Carboniferous, but there were no reliable evidences of fossils to prove it. In recent years we have collected abundant fossil cephalopods, brachiopods, lammellibranchs, gastropods and so on from the Tongtianhe Group, based on these fossils we sonsidered the Tongtianhe Group to be Late Triassic.