四川西南山区微体植物的地层指示意义

Reference Significance to Strata of Microplants in Mountain Area of Southwest Sichuan

摘要: 目前很多地层的命名不规范、不科学，其涵义是现代的，它们不能表示地质历史的实体。川西南的震旦系、寒武系地层由老至新为开建桥组、喇叭岗组、麦地坪组。作者综合文献资料，描述了各组地层的鉴别特征。开建桥组指代冰川搬运的黑色冰碛砾岩，喇叭岗组代表浅海相的变质杂岩，麦地坪组代表滨海相的暗红色基性熔岩。峨眉山玄武岩在四川西南山区分布广泛。冰碛岩是震旦系的特殊标志。由于各地层微体生物的诞生时间在近几年，选取10种较早出现的物种，按照其产地，用聚类分析的方法，求得各地层中数值最大的物种。即指示该地层的物种。结果显示，双核藻指代开建桥组，层迭层石未定形代表喇叭岗组，不规则皱纹管代表麦地坪组。

Abstract: Presently nomenclature of many strata is nonstandard and unscientific with contemporary implica-tion, so they could not express substance in geologic history. From old to new of geologic age, strata of the Sinian and Cambrian systems in southwest Sichuan are the Kaijianqiao formation, Labagang formation and Maidiping formation. Their identities are described based on synthetical document literature. The Kaijianqiao formation represents black moraine conglomerate rock transported by glacier, Labagang represents metamorphic mixtite of neritic facies, while Maidiping represents dull red basic lava of littoral facies. The Emei basalt is widely distributed in mountain area of southwest Sichuan. Tillite is a special mark of Sinian system. Microbody of these strata came into being in recent years, so ten species which emerged relatively early are selected, and species with the largest number of each stratum are obtained according to their locality of growth by clustering analysis. This species could point out this stratum. The result reveals that dinuclear algae represent Kaijianqiao, unshaped stratigraphic stone represents Labagang, while irregular wrinkle tube represents Maidiping.