桐柏蔡家凹岩片内寒武纪高肌虫的发现及其地质意义

Cambrian Bradoriids from Caijia'ao Marble Body, Tongbai,Henan and Their Geological Significance

本文描述了河南桐柏西北部蔡家凹大理岩岩片中丰富的高肌虫化石Tongbaiella xinjiensis gen.et sp.nov.、Xianzheella henanensis sp.nov.和Mononotella cf.chuanshanensis Huo et Shu及小壳化石Conotheca sp.共4属4种。据此确定含化石地层为寒武系,属浅海沉积环境。该生物群的发现为解决桐柏—大别造山带与秦岭造山带的衔接、北秦岭加里东褶皱带的东延问题提供了可靠证据,并为该造山带区域地层序列的建立奠定了基础。

Caijia'ao marble body is a upper superimposed on the Guozhuang litho-formation of Lower Proterozoic, and bounded by the Haohanpo ductile-shear zone and Songpa ductile fracture. That marble body may originally be a part of the Cambrian Liushanyan litho-formation, according to the results of 1 : 50000 reginal geological survey in the Tongbai area. However, the Caijiawa marble was placed into the Proterozoic Yindonggou Formation of the Maojie Group, or into the Cambrian Dahe Formation, and correlated with the Yanlinggou Formation of the Qingling Group by previous researchers. That marble, about 30 km long and 50-1000 m wide, crops out about 15 km away from northwest Tongbai. It consists of serpentinous olivine marable, dolomite marble, dolomitic marble, graphite marble, and marble intercalated with plagioclase hornblende schist. Fairly abundant bradoriids including Tongbaiella xinjiensis (gen. et sp. nov. ), Xi-angzeella henanensis (sp. nov. ), and Mononotella cf. chuanshanensis, a few small shelly fossils Conotheca sp. , and some spherical fossils have been found from the crystalline limestone lens in the Caijiawa marble, Xiemaling Hill, Laoheshangmao Hill and Wawuzhuang Village, Tongbai County. Those fossils the Cambrian (most possibly Early Cambrian) in age. This is the only locality of Cambrian rocks with sufficient paleontological evidence in the Tongbai-Dabie orogenic belt (Henan part). Bradoriids of Caijiawa marble such as Xiangzheella and Mononotella chuang-shanensis are the very common members of contemporaneous bradoriids of the South China region. Among them, Xiangzheella was found in the Yangtze biogeographic and Jiannan Provinces; while Mononotella in the western part of the Yangtze biogeographic province. Furthermore, Conotheca came from the South China biogeographic province of small shelly fossils.