论文部分内容阅读
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 in the northwestern Hunan belongs to the stable sedimentary area of the ancient passive continental margin in the southeastern margin of the Yangtze platform. This paper focuses on the sequence stratigraphy of Neoproterozoic strata (1000-570 Ma) in this area, In the sequence of stratigraphic division, 14 Ⅲ-grade sequences were divided in the stable shallow marine zone through fine outcrop work, in which 4 are Laoshanlian Formation (equivalent to Banxi Group), 4 are similar to Lianshuihe Formation ), 2 in Dongshanfeng Formation (equivalent to Jiangkou Formation) - 1 in Xiangmian Formation, 1 in Nantuo Formation, 2 in Doushantuo Formation and 4 in Dengdeng Formation. Seven type Ⅰ sequence boundaries, seven type Ⅱ sequence boundaries and one submerged unconformity were identified. Through the sequence stratigraphy comparison of the whole area (including the Dongkou area), an isochronal framework of the Sinian (800 ~ 570 Ma) is developed on the basis of the sequence of the Ⅱ group. The working methods of the Neoproterozoic outcrop sequence stratigraphy suitable for this area are summarized. Based on the sequence stratigraphy work, the authors put forward a new view on the stratigraphic location, lithofacies palaeogeography and palaeotectonic evolution in this area.