新疆塔里木盆地中侏罗世塔尔尕组孢粉植物群及地层和古地理意义

新疆塔里木盆地侏罗系分布广泛,在库车凹陷和塔西南区发育最好。目前对库车凹陷的三叠纪和侏罗纪孢粉植物群研究较为深入,而对塔西南区侏罗纪孢粉化石专题研究不多,尚未建立孢粉组合。作者基于塔西南区乌恰中侏罗统塔尔尕组发现的孢子花粉33属48种的研究,建立了塔尔尕组孢粉组合。该组合以掌鳞杉科花粉Classopollis的优势和真蕨目桫椤科孢子Cyathidites的繁盛为特征,并含有丰富多样且颇具侏罗纪色彩的孢子花粉化石类型。该组合与西欧和俄罗斯巴柔期至巴通期孢粉组合以及北美和澳大利亚巴柔期至卡洛夫期孢粉组合可以进行对比;与我国新疆库车恰克马克组、陕西延安直罗组和湖北兴山沙溪庙组等孢粉组合也可对比。根据孢粉学证据,塔尔尕组的时代应属于中侏罗世晚期(巴通期至卡洛夫期)。当前孢粉植物群支持我国侏罗纪南北植物地理区系之西端分界之划分方案,即塔西南乌恰处于界线以南,而库车处于分界以北。

MIDDLE JURASSIC PALYNOFLORA FROM THE TAERGA FORMATION IN THE TARIM BASIN, XINJIANG AND ITS BEARINGS ON STRATIGRAPHY AND PALAEOGEOGRAPHY

The Jurassic system is extensively developed in the Tarim Basin,Xinjiang,and is particularly well-outcropped in the Kuqa Depression and SW Tarim region.The Triassic and Jurassic palynofloras in the Kuqa Depression are intensively investigated,however,little attention was paid for fossil palynomorphs in SW Tarim region.Here we report 48 species of spores and pollen referred to 33 genera from the Middle Jurassic Taerga Formation in the southwestern region of the Tarim Basin,Xinjiang.The sporopollen assemblage of the Taerga Formation is characterized by the dominance of the cheirolepidiaceous pollen of Coniferales and the abundance of cyatheaceous spores of Filicales.The index species of this assemblage are represented by a varietry of fossil spores and pollen with Jurassic aspects.The present assemblage is comparable with those of the Bajocian to Bathonian of West Europe and Russia as well as those of the Bajocian to Callovian of North America and Australia.This assemblage is also comparable with those of the Tikmak Formation in Kuqa of the Tarim Basin,the Zhiluo Formation in Yan'an of Shaanxi Province,and the Shaximiao Formation in Xingshan of Hubei Province of China.Our palynological evidence suggests that the age of the Taerga Formation is of late Middle Jurassic,corresponding to the Bathonian to Callovian.In addition,the palaeogeographical implications of this palynoflora are discussed.Our palynotogical evidence supports the division scheme of the western part of boundary between Northern and Southern Floristic Provinces,i.e.the Wuqia of SW Tarim is located in southern of the boundary,whereas Kuqa is located in northern of the boundary.