摘要
青海省同仁地区处于祁连和秦岭造山带的接合部,构造演化历史悠久。本次工作在该地区隆务河一带发现较好的二叠—三叠系剖面。将该剖面从下而上划分为上二叠统石关组、下三叠统果木沟组和江里沟组,其中江里沟组又进一步划分为下部的浊积岩段和上部的风暴岩段,初步确定了二叠—三叠纪的界线。沉积序列、沉积相和沉积物表明上二叠统石关组和下三叠统果木沟组为一套陆源碎屑浊积岩,下三叠统江里沟组下部为一套不纯的内碎屑浊积岩,而下三叠统江里沟组上部为风暴岩沉积。根据沉积相和火山岩夹层的地球化学特征认为该地区上二叠统石关组和下三叠统果木沟组处于半深海的活动大陆边缘,下三叠统江里沟组早期的浊积岩段处于较稳定的半深海大陆边缘。根据沉积相和遗迹化石,恢复了晚二叠世—早三叠世的海平面变化特征。
Tongren area of Qinghai province is located on the copulae of Qilian and Qinling orogene, of which the structure evolution history is very famous. A continuous Permian-Triassic stratum was found in Longwuhe area during this work. In ascending order, this section is divided into Shiguan Formation of upper Permian, Guomugou Formation and Jiangligou Formation of lower Triassic, while Jiangligou Formation is divided into turbidite Member at the lower and tempestite Member at the upper. Primary Permian-Triassic Boundary is definited in this work. Sedimentary sequence, sedimentary facies and sediments indicate the Shiguan Formation of upper Permian and Guomugou Formation of lower Triassic are terrigenous clastic turbidite, while the lower parts of Jiangligou Formation of lower Triassic is intraclast turbidite and upper is tempestite. According to the sedimentary facies and geochemistry of interlayer igneous rock, the Shiguan Formation and Guomugou Formation were located at active hemi-pelagic continental margin, while the Turbidite Member of Jiangligou Formation was located at steady hemi-pelagic continental margin. The sea level turns down and the sedimentary environment transited into neritic shelf during the tempestite Member of Jiangligou Formation. Based on the sedimentary facies characteristic, this paper reconstructed the eustatic changes during Late Permian and Early Triassic.
出处
《沉积学报》
CAS
CSCD
北大核心
2007年第3期332-342,共11页
Acta Sedimentologica Sinica
基金
高等学校全国优秀博士学位论文作者专项资金项目(No.200228)
教育部长江学者和创新团队发表计划项目(No.PCSIRT0546)
中国地质调查局"I48C001001(临夏市幅)
I48C001002(定西县幅)1:25万数字区域地质调查"(No.200413000007)资助
关键词
沉积相
沉积环境
西秦岭
晚二叠世
早三叠世
sedimentary facies,sedimentary environment, west Qinling,Late Permian, Early Triassic
