新疆乌鲁木齐地区上石炭亚系祁家沟组介形类及其古环境和古地理意义*

新疆乌鲁木齐地区上石炭亚系祁家沟组地层出露较完整,沉积序列清晰,古生物化石丰富,但一直以来对祁家沟组的时代多有争论,且介形类研究薄弱。笔者在新疆乌鲁木齐地区祁家沟剖面上石炭亚系祁家沟组中鉴定出的介形类共计11属19种,并系统研究了这些介形类的组合面貌、地层分布,探讨了其古环境和古地理意义。结果表明: (1)根据介形类的组合面貌推断,祁家沟剖面祁家沟组的时代应为晚石炭亚纪莫斯科期—卡西莫夫期; (2)祁家沟组介形类生态类型属于古足目类和光滑速足目类的混合集群,符合构造活动区域的介形类OA1-OA3组合特征; (3)根据介形类的生态组合变化以及沉积学的证据,推断祁家沟剖面祁家沟组整体为滨、浅海沉积,存在海退序列; (4)祁家沟组介形类面貌与同时期的塔里木、准噶尔、中天山以及俄罗斯乌拉尔地区等产出的介形类最为相近,与北美、西欧和华北等板块的介形类也较为相似,表明晚石炭亚纪准噶尔、塔里木等块体聚集,并且距离劳俄大陆较近,所以其可与欧洲、北美板块的介形类进行属种交流。研究结果不仅进一步丰富了祁家沟组的化石材料,也对探索古亚洲洋演化特征和区域矿产开发具有重要的意义。

Ostracods from the Upper Carboniferous Qijiagou Formation,Urümqi region,Xinjiang and their implications on palaeoenvironment and palaeobiogeography

The overall occurrence,stratigraphical distribution,palaeoenvironmental and palaeobiogeographical significances of the ostracod faunas from the Upper Carboniferous Qijiagou Formation in the Qijiagou section of the Urümqi region,China,are documented in this study. Nineteen species belonging to 11 genera are identified and figured herein. The ostracod fauna in the Qijiagou Formation indicates an age of the Moscovian-Kasimovian. The ostracod assemblages from the Qijiagou Formation belong to palaeocopid and smooth-podocopid associations,and ecologically equivalent to the OA1-OA3 assemblages in the active plate margin. The changes of ostracod assemblages and sedimentary evidences from the Qijiagou section indicate littoral and shallow sea facies,and there was probably a regression when the Qijiagou Formation were being deposited in the Qijiagou section of the Urümqi region. The ostracods of the Qijiagou Formation have strong affinities with the taxa of Tarim,Junggar,central Tianshan and Urals,and also share some similarities with those from North America,West Europe and North China. This implies that the Junggar and Tarim blocks converged and were relatively close to the Laurasia during the Pennsylvanian(Late Carboniferous),and ostracods experienced faunal exchanges between Junggar-Tarim blocks and Laurentia. The above ostracods, further enriched the fossil materials of Qijiagou Formation, is of great sinificance for exploring the evolutionary characteristics of the acient Asian Ocean and regional mineral devdopment.