川中地区北部下寒武统沧浪铺组一段风暴岩特征及沉积地质意义

Characteristics and sedimentary geological significance of tempestites in first member of Lower Cambrian Canglangpu Formation in north central Sichuan Basin

田立洲 宋金民 叶玥豪 刘树根 李智武 金鑫 杨迪 赵玲丽 丁一 任佳鑫 王瀚 李柯然 邓豪爽

TIAN Lizhou SONG Jinmin YE Yuehao LIU Shugen LI Zhiwu JIN Xin YANG Di ZHAO Lingli DING Yi REN Jiaxin WANG Han LI Keran DENG Haoshuang

1. 成都理工大学 能源学院, 成都 610059; 2. 油气藏地质与开发工程全国重点实验室(成都理工大学), 成都 610059; 3. 西华大学, 成都 610039

1. College of Energy, Chengdu University of Technology, Chengdu, Sichuan 610059, China; 2. State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan 610059, China; 3. Xihua University, Chengdu, Sichuan 610039, China

川中地区北部下寒武统沧浪铺组风暴岩发育，但对该风暴岩沉积以及该区早寒武世沉积环境、古地理和沉积古地貌的研究较为薄弱。通过详细岩心观察及镜下薄片鉴定，研究了沧浪铺组风暴沉积序列和沉积模式，并揭示其地质意义。研究区沧浪铺组发育砾屑层、粒序段、平行层理和丘状交错层理等风暴沉积构造，可划分出5个风暴沉积序列，即：序列Ⅰ由砾屑段(A)、平行层理段(C)和丘状交错层理段(D)组成，在正常浪基面之上沉积；序列Ⅱ由平行层理段(C)、丘状交错层理段(D)和水平层理泥岩段(E)组成，位于风暴浪基面附近；序列Ⅲ由底冲刷面和砾屑段(A)和粒序段(B)构成，于正常浪基面和风暴浪基面之间；序列Ⅳ由粒序段(B)和平行层理段(C)组成，距离风暴中心远，沉积环境更靠近风暴浪基面附近；序列Ⅴ由底冲刷面和砾屑段(A)构成，位于平均海平面与正常浪基面之间且靠近正常浪基面。川中地区北部风暴岩的发现证实，沧浪铺组一段为陆棚—斜坡—台地边缘沉积，指示上扬子板块在沧浪铺组沉积期处于低纬度地区，这为岩相古地理恢复提供了约束；同时风暴作用形成连片分布的颗粒滩，有效提升储集相带的规模，有助于对颗粒滩相带的分布进行预测。

Tempestite has been discovered in the Lower Cambrian Canglangpu Formation in the north central Sichuan Basin. However, there has been limited research on storm sedimentation and the Lower Cambrian sedimentary environments, ancient geography, and ancient sedimentary geomorphology in this region. By conducting detailed core observations and thin section identifications, the storm sedimentation sequence and sedimentation model of the Canglangpu Formation have been investigated, revealing its geological significance. Various storm sedimentation structures, such as gravel sections, graded sections, parallel laminated sections, and hummocky cross-stratifications (HCS), are present in the Canglangpu Formation. The tempestites within this formation can be categorized into five types of storm sedimentation sequences: Sequence Ⅰ includes gravel sections (A), parallel laminatedsections (C), and HCS (D) above the fair-weather wave base (FWB). Sequence Ⅱ comprises parallel laminated section (C), HCS (D), and horizontally laminated mudstone section (E) deposited near the storm wave base (SWB). Sequence Ⅲ includes scouring-fill structures and gravel section (A), as well as a graded section (B) deposited between the fair-weather wave base (FWB) and SWB. Sequence Ⅳ is characterized by a graded section (B) and parallel laminated section (C) located far from the storm center, above and near SWB. Sequence Ⅴ consists of scouring-fill structures and gravel section (A) located between the mean sea level (MSL) and FWB, close to FWB. The analysis of tempestites in north central Sichuan Basin suggests that the initial member of the Canglangpu Formation was deposited on the shelf-ramp-platform margin and shelf, indicating that the Upper Yangtze Plate was situated in a low latitude region during the sedimentation period of the Canglangpu Formation. This information provides valuable insights into lithofacies paleogeography reconstruction. Storm events have resulted in the formation of storm mudflats in the study area, which are favorable for reservoir development. The investigation of storms in the Canglangpu Formation aids in predicting the distribution of shoal facies in the study area.

国家自然科学基金重点项目(42230310)、国家自然科学基金(41872150)和国家自然科学基金企业联合创新发展联合基金项目(U19B6003)联合资助。

https://doi.org/10.11781/sysydz202402299