羌塘盆地侏罗纪双壳类化石组合及古环境

海相侏罗系是羌塘盆地发育最全、分布最广泛的沉积层系.作者根据详细的野外地质工作,收集了典型剖面的岩相、沉积构造和大量的化石,并借鉴、总结前人的研究成果,对该区双壳类生物地层进行较系统的、全面的分析研究,划分了五个双壳类化石组合:Camptonectes auritus-Pteroperna costatula,Eomiodon angulatus-Isognomon(Mytiloperna)bathonica,Camptonectes laminatus-Anisocardia beaumonti,Anisocardia tenera-Modiala biparta以及Gervillella aviculoides-Radulopecten fibrosus;认为该区雁石坪群的时代从巴柔期至牛津-基末里期,从而建立起生物地层格架及年代地层格架.根据沉积标志以及典型的化石组合,探讨了研究区古地理环境,并识别出滨海、潮坪、潟湖、碳酸盐台地以及碳酸盐缓坡等古沉积环境,揭示了各时期自然地理状况,对探索东特提斯地区的构造演化和双壳类的生态演变都有重要的意义.

Jurassic bivalves from the Qiangtang basin in northern Tibet and the palaeoenvironmental significance

There are the most complete and extensive Jurassic marine sedimentary strata in the Qiangtang basin.Numerous petroleum geologists hare paid much attention to it for a long time.Although many achievements have been obtained during recent years,research areas and contents are still limited and uncompleted.According to the detailed field investigations into the typical sections in the Yanshiping area,many pieces of information such as lithofacies,sedimentary tectonics,fossils,and so on have been collected.The paper aims to describe biostratigaphy based on abundant bivalves in order to build biostratigraphic and chronostratigraphic frameworks in Middle-Late Jurassic.Five bivalves assemblages are divided.They are Camptonectes auritus-Pteroperna costatula,Eomiodon angulatus-Isognomon(Mytiloperna)bathonica,Camptonectes laminatus-Anisocardia beaumonti,Anisocardia tenera-Modiala biparta and Gervillella aviculoides-Radulopecten fibrosus. In the study area,the marine bivalve fauna occurred generally from Bajocian to Oxifordian-Kimmeridgian,while the Yanshiping Group deposited in following palaeoenvironments: beach,tidal-flat,lagoon,platform and ramp of carbonate.