对湘鄂西地区 8个晚奥陶世剖面的 3个时段 (Caradoc中期 ,晚期及 Ashgill早期 )地层作了详细采集 ,获得了丰富的三叶虫材料 ,根据动物群的组成、分异度和各组成分子的相对丰度 ,识别出外陆棚—棚外深水区的 9种三叶虫相 ,它们在时空分布上具有逐渐过渡更替的特征。根据水中浮游类型三叶虫 (圆尾虫类 )的分异度、相对丰度以及与它们共生的底栖三叶虫生态特征 ,对各种三叶虫相所指示的水体深度作了推测。三叶虫相研究表明 ,区内Caradoc中期处于海侵高峰 ,古地理样式显示了以拉张为主的区域构造背景 ;Caradoc晚期开始发生持续海退 ,同时扬子陆块南缘受到构造挤压 ,广大外陆棚区地形变得起伏不平。晚奥陶世古地理变迁证明华夏和扬子陆块的会聚事件始于 Caradoc晚期 Based on detailed analysis of the three sections of the Late Ordovician section in the western Hubei and western Hubei Provinces (the middle and late stages of Caradoc, early Ashgill), the trilobite material was obtained. According to the composition, The relative abundance of each component identified nine kinds of trilobite phases in the outer shelf and deep shelf outside the shelf, which have the characteristics of gradual transition and replacement in the spatial and temporal distribution. According to the diversity, relative abundance and the ecological characteristics of benthic trilobites accompanying with the planktonic trilobites in the water, the depths of water bodies indicated by various trilobites were presumed. Trilobite phase studies show that the middle Caradoc in the region is at the peak of transgression and the paleogeographic pattern shows the regional tectonic setting dominated by extensional. Caradoc continued to regress late in the late stage and the southern margin of Yangtze block was tectonic crushed. The terrain of the vast outback shed area has become undulating. Late Ordovician palaeogeographic changes proved that the convergence events of the Huaxia and Yangtze terraces began in the late Caradoc