北天山上石炭统奇尔古斯套组中发现早二叠世珊瑚化石

新近于北天山艾维尔沟北原划为上石炭统的奇尔古斯套组火山岩系所夹灰岩中,采到了结节脊板杯珊瑚Cy-athocariniatuberculataSoshkina,其时代属于早二叠世,表明该区奇尔古斯套组的一部分应属下二叠统。另外,于头屯河原划为上石炭统的奇尔古斯套组火山-碎屑岩系所含灰岩砾石中,采到伊万诺夫格鲁特珊瑚GrootiaivanoviDubrolyubova,时代属于晚石炭世,与达拉阶(即莫斯科阶)相当,故地层时代应晚于晚石炭世达拉期,根据区域对比推测该地层的一部分也应属于下二叠统。艾维尔沟一带早二叠世珊瑚化石的发现,表明北天山石炭纪强烈的拉张事件可以持续到早二叠世。

Discovery of the Early Permian coral fossils in the Upper Carboniferous Qiergusitao Formation in the North Tianshan, Xinjiang

Fossils of the coral Cyathocarinia tuberculata Soshkina have been recently collected from lime-stone sandwicked in volcanic rocks north of Ewirgol in the North Tianshan,Xinjiang.The volcanic rocks were formerly ascribed to the Upper Carboniferous Qiergusitao Formation.These fossils are of Early Permi-an age,which indicates that a part of the Qiergusitao Formation should be Early Permian in age.More-over,fossils of the other coral Grootia ivanovi Dubrolyubova have been collected from limestone gravels in pyroclastic rocks assigned formerly to the Upper Carboniferous Qiergusitao Formation along the Toutun River in the North Tianshan,Xinjiang.The age of the fossils is Late Carboniferous ,equivalent to the Dalan Stage(i.e.Moscovian Stage)and the age of the strata containing the fossil should be later than the Late Carboniferous Dalan Stage.According to the regional correlation,it may be inferred that a part of the strata mentioned above is also of Early Permian age.The discovery of the above-mentioned Early Per-mian coral fossils in the vicinity of Ewirgol indicates that the upper part of the Qiergusitao Formation is assigned to the Lower Permian in the North Tianshan,Xinjiang,and the Carboniferous strong extension event may have continued to the Early Permian.This discovery has important significance for the recon-struction of the Late Paleozoic tectonic framework and further study of the tectonic evolution and back-ground of minerogenesis in the North Tianshan,Xinjiang.