摘要
四川盆地下古生界寒武系沧浪铺组勘探潜力巨大。文中结合钻井和野外地质剖面实测成果等最新资料，研究了四川盆地北部地区沧浪铺组沉积演化规律。结果表明：1）沧浪铺组沉积期，研究区内可识别出开阔台地相、局限台地相和潮坪相3种沉积相类型，纵向上具有明显的分异特征，横向上沉积厚度西薄东厚。沧一段沉积期，开阔台地相发育以鲕粒石灰岩、砂屑石灰岩为主要岩性并可见小型槽状交错层理的台内滩亚相，和以泥晶石灰岩为主要岩性的滩间海亚相；局限台地相发育以具有残余结构的砂屑白云岩和鲕粒白云岩为岩性并可见重结晶作用的台内滩亚相，和以灰质泥晶白云岩、砂质白云岩为主要岩性的滩间海亚相；在裂陷槽和古隆起之间区域，发育以泥质白云岩、泥灰岩和砂质白云岩为主要岩性的混积潮坪相。沧二段沉积期，发育以紫红色泥岩、砂岩等为主要岩性的碎屑潮坪相，见小型水平层理、羽状交错层理和砂岩透镜体。2）沧浪铺组沉积期，以大规模海退为主，水体总体逐渐变浅。沧一段沉积期，碎屑物质输入受到裂陷槽隔档作用影响，发育碳酸盐岩沉积，在构造高部位发育以颗粒岩为主的台内滩亚相。至沧一段沉积末期，裂陷槽逐渐被填平，碎屑物质得以向东持续迁移。沧二段沉积期，发生了小规模的海侵—海退过程，水体由深变浅，最终形成以砂泥岩互层沉积为主要特征的碎屑潮坪沉积环境。
Abstract
The Lower Paleozoic Cambrian Canglangpu Formation in Sichuan Basin has great exploration potential. The sedimentary evolution law of Canglangpu Formation in northern Sichuan Basin was studied based on the latest data of drilling and field geological section measurement. The results show that: (1) during the sedimentary period of the Canglangpu Formation, three types of sedimentary facies can be identified in the study area, including open platform facies, restricted platform facies and tidal flat facies. There are obvious features of vertical differentiation, and the horizontal sedimentary thickness is thin in the west and thick in the east. During the sedimentary period of the first Member of Canglangpu Formation, the intra?鄄platform beach subfacies with oolitic limestone and sand?鄄debris limestone as the main lithology and visible small trough cross?鄄bedding, and the beach interact sea subfacies with micritic limestone as the main lithology were developed within the open platform facies. And the intra?鄄platform shoal subfacies with sand?鄄debris dolomite and oolitic dolomite with relict texture as lithology and visible recry?鄄stallization, and the beach interact sea subfacies with calcareous micrite dolomite and sandy dolomite as the main lithology were developed within the restricted platform facies. The mixed tidal flat facies with argillaceous dolomite, marl and sandy dolomite as the main lithology are developed in the area between the taphrogenic trough and the paleo?鄄uplift. The clastic tidal flat facies with purplish?鄄red mudstone and sandstone as the main lithology were developed during the sedimentary period of the second Member of Canglangpu Formation, and small horizontal bedding, pinnate cross bedding and sandstone lens can be seen. (2) During the deposition period of the Canglangpu Formation, it was dominated by large?鄄scale regression, and the water body gradually became shallow on the whole. During the sedimentary period of the first Member of Canglangpu Formation, the import of clastic materials was affected by the barrier effect of the taphrogenic trough, and the carbonate rocks were deposited. The intra?鄄platform shoal subfacies dominated by granular rock were developed at the high position of the structure. At the end of the deposition of the first Member of Canglangpu Formation, the taphrogenic trough was gradually filled up, and the clastic materials were able to continuously migrate eastward. During the sedimentary period of the second Member of Canglangpu Formation, the small?鄄scale transgression?鄄regression process occurred, and the depth of the water body changed from deep to shallow, and eventually, the clastic tidal flat sedimentary environment characterized by sand?鄄mudstone interbedded deposition was formed.
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