对川西汉源-荥经地区CYD2井下奥陶统弗洛阶大乘寺组的笔石进行研究，结果表明Baltograptus deflexus笔石带在这一覆盖区发育良好。CYD2井的该带笔石动物群共含2属5种。根据下垂对笔石类的始端发育型式，修正前人对波罗的笔石属（Baltograptus）和巅峰笔石属（Corymbograptus）内一些种的归属，并对CYD2井的上述5种笔石进行描述。可能受制于钻心标本的限制，该地区的Baltograptus deflexus带笔石动物群分异度较低。川西汉源-荥经-峨眉山地区的大乘寺组与上覆二叠系梁山组呈假整合接触，表明该地区长期遭受沉积间断和剥蚀作用，B. deflexus带的确定，指示了这一长期剥蚀作用的最大深度。

A graptolite fauna of the Baltogratus deflexus Biozone (Dachengsi Formation, Lower Ordovician) was obtained recently from the Well-CYD2 cores from Hanyuan-Yingjing area, western Sichuan. Five species belonging to two genera of graptolites have been identified and described in the present paper. They include Baltograptus deflexus (Elles and Wood, 1901), B. enshiensis (Ni, 1979), B. scanicus (Tjernvik, 1960), B. stratus (Chen and Xia, 1979), and Corymbograptus v-fractus minor (Li, 1979). The terminologies for the development types of the proximal end of the turbaria in the present material are after Malatz (1994, 2018). The validity of the genus Norvegiograptus Li, 2014 is discussed herein. The low diversity of the B. deflexus fauna in the Hanyuan-Yingjing area might be due to the limited specimens obtained from drilling core. The B. deflexus Biozone marks the top of the Dachengsi Formation in the studied area. It is overlain directly by the Lower Permian Liangshan Formation. This disconformity extends eastwards to the Emeishan area of SW Sichuan, indicating a regional, long-term erosion.

国家科技重大专项（No.2016ZX05034004-001），中国地质调查局能源矿产地质调查项目（No.DD20160176）资助。