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小壳动物化石产于川、陕、鄂三省边界地区的鲁家坪组中(图1)。该组岩性为一套轻变质的浅海相沉积建造,厚700—900米,地层层序较清楚,分层标志明显。其下部为炭质板岩、含钙泥板岩及白云岩,中部为硅质岩及硅质板岩,上部为炭质板岩夹泥灰岩。该组地层在下寒武统含俞氏库蜒虫的箭竹坝组之下,超覆于下震旦统耀岭河群火山岩之上。原建组者将其统划为下寒武统((?)_1L)。七十年代以来,多数研究者认为该组下部有上震旦统存在,但未找到化石作为依据,分层界线有较大争议。一种意见将该组中部硅质岩(相当本文(?)_1L~2层)及其以
Small shell fossils produced in Sichuan, Shaanxi and Hubei provinces border region Lu Jiaping group (Figure 1). The group of lithology is a light metamorphic shallow marine sedimentary deposition, thickness 700-900 meters, the stratigraphic sequence more clearly, stratification mark is obvious. The lower part of the carbonaceous slate, calcareous mud slate and dolomite, the central part of siliceous rocks and siliceous slate, the upper part of the carbonaceous slate clip marl. This group of formations below the Jianzhuba Formation of the Lower Cambrian with the Yushuankuansu overlies the volcanic rocks of the Lower Sinian Yao-ling Group. The former group planted it as the Lower Cambrian ((?) _1L). Since the 1970s, most researchers believe that there is the existence of the Upper Sinian in the lower part of the group. However, no fossils have been found as the basis for the controversy. One suggestion is that the middle group of siliceous rocks in this group (equivalent to this paper? 1L ~ 2 layers)