新疆塔里木玉北井区早奥陶世古环境及生态组合时空分布

THE TEMPORAL-SPATIAL DISTRIBUTION OF THE EARLY ORDOVICIAN ECOASSEMBLAGES IN THE YUBEI AREA,TARIM BASIN,XINJIANG,NORTHWEST CHINA AND ITS PALEOENVIRONMENTAL SIGNIFICANCE

新疆塔里木板块玉北地区下奥陶统沉积于极浅海带碳酸盐岩沉积区,化石密度普遍很低,依据该地区6口钻井的化石碎片类型以及所赋存的围岩特征可划分出6种生态组合:三叶虫-介形类组合或介形类组合;介形类-三叶虫组合或三叶虫组合;棘屑-三叶虫组合;三叶虫-棘皮类组合;海绵-三叶虫-介形类组合和三叶虫-腕足类组合。生态组合和沉积微相分析表明,玉北地区该地质时期共有三次沉积环境变迁:蓬莱坝组顶部-鹰山组底部沉积期为局限台地潮坪环境;鹰山组下部沉积期为局限台地潮坪与潮沟交互环境;鹰山组中部沉积期为局限台地潮坪环境;鹰山组上部沉积期为局限台地潮坪与潮沟交互或者局部的局限台地潮坪环境。

The early Ordovician ecoassemblages in Yubei area,Tarim basin,Xinjiang,Northwest China was conducted in this study.Six ecoassemblages were recognized,including trilobite-ostracod or ostracod assemblage,ostracodtrilobite or trilobite assemblage,echinoderm-trilobite assemblage,trilobite-crinoid assemblage,sponge-trilobite-ostracod assemblage,and trilobite-brachiopod assemblage.We also found that different strata have different associations of assemblages.In the early Ordovician,the depositional environment changed three times,but the main environment is limited platform.During the deposition time of upper Penglaiba Formation to the bottom of the Yingshan Formation,the depositional environment is tidal-flat environment,while during the early deposition time of the Yingshan Formation,the sedimentary environment is tidal-flat alternative with tidal channel.In the middle deposition time of the Yingshan Formation,the sedimentary environment is dominated by tidal-flat.During the late deposition time of the Yingshan Formation,the dominated depositional environments include tidal-flats and tidal channels.