东天山七角井大向斜外围塔克尔巴斯陶组化石新发现和地质意义

Redefinition of Tuckerbasitao Formation Based on Newly Discovered Fossils in Eastern Tianshan

东天山塔克尔巴斯陶组中发现Choristites、Chonetes carbonlferus Keyserling、Brachythyrina strangwaysi Verneuil、Brachytryhis、Isogramma、Paramuirwoodia和Stenoscisma等腕足化石,组合时代为晚石炭世早期。前人据该组中发现袁氏珊瑚Yuanophyllum将该地层厘定为早石炭世。1:25万三道岭幅区调项目对该组地层微体化石进行研究,于灰岩中发现蜓Profusulinella和Schubertella;非蜓有孔虫Tetrataxis、Palaeotextularia和Climacammina;介形化石Bairdia longicalida Shi等,其组合时代特征与腕足化石一致。据腕足化石、微体化石及植物化石Noeggerathiopsis theodori Tschirkova et Zalessky,将该组地层厘定为晚石炭世早期。据地层接触关系、植物化石Neoggerathiopsis和Calamites及SHRIMP U-Pb年龄,将上覆地层七角井组定为晚石炭世。

The geological age of Tuckerbasitao Formation in bogda minor strata area in Eastern Tianshan is the late carboniferous accordingto those brachiopod fossils, it is the late early carboniferous according to coral fossils, most researchers supported the geological age of TuckerbasitaoFormation is the late early carboniferous.Recently, a wealth of microfossils been collected in the limestone strata of Tuckerbasitao Formation,especially the discovery of Profusulinella and Schubertella provided new evidences for strata division and correlation.The analysisshowed Non-foraminifera foraminifers can built up Tetrataxis- Palaeotextularia-Climacammina fossil assemblage zones and two genera foraminiferas：Profusulinella and Schubertella be found in limestone in Mashansayi.The collection of micro-fossils has obvious characteristics of earlystage of late carboniferous strata. Those brachiopod fossils found in the Tuosibasitao Formation can be grouped into Choristites-Paramuirwoodiafossil assemblage zones in North Xinjiang region and the geological age is early stage of late carboniferous.Though the early carboniferouselements is advantageous in number, some late carboniferous elements, especially the Choristites which is the characteristic element of late carboniferousstrata have widespread.Those new fossil evidences can confirmed the geological age of Tuosibasitao Formation is early stage of latecarboniferous.The research can also reveal that its overlying formation Tuckerbasitao Formation and Qijiaojing Formation is early stage of latecarboniferous too.