湘赣中、南部寒武系纽芬兰统-第二统沉积环境

The Cambrian Terreneuvian-Series 2 Sedimentary Environment of Central-Southern Area of Hunan and Jiangxi

为解决华南湘赣中、南部纽芬兰统-第二统沉积环境一直存在的深、浅海之争,通过对8条剖面岩石学特征、放射虫分布和岩相调查,结合地球化学数据等,分析了古水深等沉积环境特征.研究发现,湘赣中部娄底、邵阳、衡阳、萍乡地区可见疑似放射虫化石的分布,化石应沉积于当时的海盆中心区,且Si以生物来源为主.全区广泛发育弱水动力的水平层理,杂砂岩Td平均值为5.94,δ30Si平均值为0.1‰.本区牛蹄塘组、香楠组和牛角河组可划分5种岩相类型、3种岩相组合(海底扇中扇亚相、海底扇外扇亚相、陆隆亚相).结合主量、微量和稀土元素数据等综合分析,认为湘赣中、南部纽芬兰统-第二统沉积时期海水滞留缺氧,以半深海陆坡-陆隆环境为主,东南部略浅.

In order to solve the dispute-"deep sea"or"shallow sea"about the Cambrian Terreneuvian-Series 2 sedimentary environment of central-southern area of Hunan and Jiangxi,this paper further analyzed sedimentary environment such as paleowater depth by investigating the petrological characteristics,radiolarian distribution and lithofacies of eight sections for these strata.According to the investigation,suspected radiolarians found in Loudi,Shaoyang,Hengyang and Pingxiang areas were deposited in the basin center and the source of Si in these strata are biogenic.Horizontal beddings representing weak hydrodynamic force are developed in central and southern parts of Hunan and Jiangxi;the average value of Td of the greywacke is 5.94;the average value ofδ30 Si is 0.1‰;five types of lithofacies and three types of lithofacies associations(middle fan subfacies of submarine fan,outer fan subfacies of submarine fan,and continental rise subfacies).Taking major element,trace element and REE contents into consideration,we think that the sea water of the central-southern area of Hunan and Jiangxi was stagnant;the study area was a continental slope-rise with a bathyal environment in the Cambrian Terreneuvian–Series 2,relatively shallow in the southeast.