湘西北新元古界露头层序地层学研究

SEQUENCE STRATIGRAPHY ON NEOPROTEROZOIC OUTCROPS, IN NORTHWEST HUNAN, SOUTH CHINA

殷勇 范小林 高长林 张玲华

Yin Yong Fan Xiaolin Gao Changlin Zhang Linghua

地矿部石油地质中心实验室, 无锡, 214151 2. 中国地质大学地矿系, 北京, 100083

Central Laboratory of Petroleum Geology, MGMR 2. Department of Geology and Mineral Resources, China University of Geosciences

湘西北地区新元古界属于扬子地台东南缘古被动大陆边缘稳定沉积区,本文重点研究了该区新元古代地层(1000～570Ma)的层序地层学、采用廊带式剖面和综合层序地层划分方案,在稳定浅海相区通过精细的野外露头工作共划分出14个Ⅲ级层序,其中老山崖组(相当于板溪群)4个、渫水河组(相当于莲沱组)2个、东山峰组(相当于江口组)—湘锰组1个、南沱组1个、陡山沱组2个和灯影组4个.识别出7个Ⅰ型层序边界、7个Ⅱ型层序边界和1个淹没不整合面.通过全区(包括汀中洞口地区)的层序地层对比,在Ⅱ组层序的基础上建立了该区震旦系(800～570Ma)等时地展格架．总结了适合于本区的新元古代露头展序地层学工作方法,在层序地层工作的基础上对该区地层的定位、岩相古地理和古构造演化提出了新的看法.

The Neoproterozoic successions in northwest Hunan,South China belong to a stable sedimentary region of paleo-continental margin along the southeast border of Yangtze platform.The paper deals with the sequence stratigraphy on Neoproterozoic (1000-57OMa) outcrops in the area.Adopting a dividing plan of gallery-typed section and comprehensive sequence stratigraphy,14 Ⅲ order sequences are divided from Neoproterozoic successions in the stable shallow marine area,based on careful field investigations on outcrops,i.e.4 sequences in Laoshanya Formation (equal to Banxi Group);2 in Dieshuihe Formation (equal to Liantuo Formation);1 in Dongshanfeng (equal to Jiangkou Formation)——Xiangmeng Formations;1 in Nantuo Formation;2 in Doushantuo Formation and 4 in Dengying Formation.Altogether 7 type-I sequence boundaries and 7 type-II sequence boundaries and 1 immersed uncomformity are identified on outcrops.By a orrelation of sequence stratigraphy over the whole area (including Dongkou area in central Hunan),a Sinian (800-570Ma) synchronous stratigraphic framework is established in norhtwest Hunan.It is concluded that a synthetic approach suitable to the Neoproterozoic sequence stratigraphy on outcrops across the area should be adopted.And further the paper ptosposed new concepts about the location of stratigraphy,lithofacies-paleogeography and the evolution of paleo-tectonics.

中国古大陆及其边缘层序地层及海平面变出项目

https://doi.org/10.11781/sysydz199703252