The occurrence of Silurian rocks in western Guizhou Province is very limited and poorly known only in Hezhang County and its age has not been defined for a long time as the absence of palaeontologic evidence. Most recently, a shelly fauna including brachiopods, trilobites and bivalves has been discovered in Caoziping section of Hezhang, western Guizhou. For the brachiopods, Nikiforovaena-Retziella assemblage belonging to the Retziella Fauna is recognized. The Caoziping section is composed of the fossil bed at its upper part and its underlying purple mudstone strata. They arc considered to be near shore, shallow water, variegated clastic rocks, which can be correlated with part of the Kuanti Formation from Qujing, eastern Yunnan Province. The strata are defined as late Ludlow in age. The determination of the age of Silurian strata in Hezhang has revised traditional knowledge on the Late Silurian lithofacies palaeogeography in South China and drew a conclusion that the transgressive scope in late Ludlow is larger than that revealed previously.%志留系在黔西的分布范围很小,已知仅限于赫章县境内.赫章的志留系发育不全,由于缺少古生物证据,其具体时代长期难以肯定.最近在赫章草子坪志留系中发现腕足动物、三叶虫和双壳类化石群.腕足类研究结果显示,它应属于小莱采贝动物群(Retziella Fauna)和新建立的Nikiforovaena-Retziella组合.该化石层下伏紫红色泥岩地层.这段近岸、浅水、杂色碎屑岩层在岩性上与滇东曲靖的关底组类同,可部分对比,推测其时代为罗德洛世晚期(Late Ludlow),但不宜另立新名,仍称关底组为好.在讨论关底组含义之后,笔者赞同取消岳家山组的意见.对赫章志留系具体时代的确定使对华南志留纪晚期岩相古地理的传统认识得到修正,罗德洛世晚期的海侵从滇东的曲靖地区扩大到黔西的赫章一带.
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