中扬子区晚印支期三级层序充填特征及沉积古地理格局
摘要: 晚印支期是中扬子区结束海相沉积开始转向以河流湖泊为主的陆相沉积新格局的重要过渡时期。应用陆相层序地层学和沉积学的基本理论，在中扬子区各次级盆地建立若干基干剖面，采用分辨率较高的露头分析，进行三级层序划分、对比与沉积相分析及古地理恢复。发现中扬子区晚印支期陆相沉积体系最多可识别出3个三级层序，但地层不发育或剥蚀导致一般仅可识别出1～2个三级层序，西部地区三级层序数量总体多于东部地区。各三级层序主要为一套夹丰富煤线（层）与古植物残片的陆相碎屑沉积，全区岩相古地理总体由曲流河及其三角洲和残留湖泊、辫状河及其三角洲和残留湖泊两套沉积相组合构成，其中前者占主导。区内存在多沉降沉积中心，但荆当盆地与中扬子西缘地区为最主要的沉降沉积中心，沉降机制主要来自中扬子陆壳继承性向北俯冲的挠曲沉降与强烈的陆内挤压褶皱变形，秦岭—大别山碰撞带及中扬子陆内挤压变形形成的隆起为邻近的次级盆地沉积作用提供了物源。
Third-order Sequence Filling Feature and Sedimentary Palaeogeography in Late Indosinian for the Middle Yangtze
Abstract: Late Indosinian is the key transition period in which the middle Yangtze area shifted to the new sedimentary pattern from marine sedimentary environment to continental sedimentation of rivers and lakes. On the basis of information from fundamental stratigraphic sections established in sub-basins in the middle Yangtze, the third-order sequence division and correlation, sedimentary facies analysis and lithofacies palaeogeography recovery were studied through high-resolution outcrop analysis on the guidance of basic theories of continental sequence stratigraphy and sedimentology. It shows that late Indosinian continental sedimentary system in the middle Yangtze is divided into 3 third-order sequences at most but generally 1～2 third-order sequences can be identified only as a result of strata undevelopment or erosion. There are 3, 2, 1 and 1 third-order sequences in the western margin of middle Yangtze, Jingdang Basin, Zigui Basin and Edong Basin, respectively. In contrast, the quantity of sequences in the west area is more than that in the east area. Sedimentary facies analysis indicates that all third-order sequences are characterized by continental clastic sediments which are rich in coal and palaeobotanic fragments, and also shows that the lithofacies paleogeography in the middle Yangtze area is totally made up of 2 types of sedimentary facies sets which are meandering river-delta-residue lake facies set and braided river-delta-residue lake set, and the former which mainly distributes in the west of middle Yangtze and Zigui Basin is dominant, while the latter develops in Edong Basin comparatively. It’s also concluded from study results that the middle Yangtze has a couple of subsidence and sedimentation centers in late Indosinian, and the ones in Jingdang Basin and the western margin of middle Yangtze are most important. The subsidence mechanism is the middle Yangtze crust northward subduction which results in flexural subsidence and intense extrusion deformation. The provenance is probably provided for sub-basins by Qingling-dabie collision and adjacent uplift created by deformation.
中扬子区晚印支期三级层序充填特征及沉积古地理格局[J]. 沉积学报, 2014, 32(4): 724-733.
| 引用本文: |
中扬子区晚印支期三级层序充填特征及沉积古地理格局[J]. 沉积学报, 2014, 32(4): 724-733.
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Third-order Sequence Filling Feature and Sedimentary Palaeogeography in Late Indosinian for the Middle Yangtze[J]. Acta Sedimentologica Sinica, 2014, 32(4): 724-733.
| Citation: |
Third-order Sequence Filling Feature and Sedimentary Palaeogeography in Late Indosinian for the Middle Yangtze[J]. Acta Sedimentologica Sinica, 2014, 32(4): 724-733.
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