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- Title
川西地区雷口坡组风暴沉积特征及其地质意义.
- Authors
冯宇翔; 宋金民; 刘树根; 杨迪; 李智武; 金鑫; 范建平; 王佳蕊
- Abstract
In the Middle Triassic, the western margin of the Yangtze Platform experienced frequent hurricanes, and tempestites were developed as a result. The typical storm sedimentary characteristics of the Middle Triassic Leikopo Formation in the western Sichuan Basin were analyzed in this study from a profile survey and microscopic observations. Major storm deposit sedimentary structures were recognized (scouring-fill structures, storm-generated gravelstones, rip-up clasts, graded bedding and hummocky cross-bedding, etc.). Seven types of tempestite sequences were developed: Type I sequence consists of bottom scouring surface with storm-generated gravel bedding (A), graded bedding (B), and parallel bedding (C), mainly generated by the storm vortex and deposited between the normal wave base and the storm wave base. Type II sequence consists of bottom scouring surface with storm-generated gravel bedding (A), graded bedding (B), parallel bedding (C) and a storm turbidite layer (E1), mainly caused by storm inverse flow, and evident above and near the storm wave base. Type III sequence comprises bottom scouring surface with storm-generated gravel bedding (A) and graded bedding (B), mainly the result of storm inverse flow, appearing between normal- and storm wave base. Type IV sequence consists of bottom scouring surface with storm-generated gravel bedding (A), graded bedding (B), parallel bedding (C) and hummocky cross-bedding (E), mainly caused by the storm vortex and formed in the shallow water area between the storm wave base and normal wave base. Type V sequence consists of graded bedding (B) and parallel bedding (C), mainly caused by the storm vortex and formed above the normal wave base. Type VI sequence consists of storm-generated gravel bedding (A), mainly the result of storm tides and formed above the normal wave base. Type VII sequence consists of graded bedding (B) and micritic limestone (E2), mainly from storm turbidity current, formed near the storm wave base. The discovery of the tempestites confirms that the Leikoupo period in the upper Yangtze region was in a low latitude area, indicating that the western Sichuan Basin was located in the platform margin slope zone, which restricted the paleolatitude and paleogeographic pattern at that time. The second finding confirms the existence of a paleobay formed by uplift of the Longmen Mountain and the western Sichuan slope. Thirdly, the presence of tempestites not only restricts the location of the NE-SW paleocoastline in the paleo-gulf background, but also indicates the NE-SW zonal distribution of microbial rocks.
- Publication
Acta Sedimentologica Sinica, 2023, Vol 41, Issue 3, p661
- ISSN
1000-0550
- Publication type
Article
- DOI
10.14027/j.issn.1000-0550.2021.132