辽西朝阳盆地位于燕山构造带东段,属于松辽外围中生代的断陷盆地,勘探认识程度不高。前人研究认为,朝阳盆地下白垩统九佛堂组为湖相沉积,而忽略了火山事件对于湖盆沉积的重要影响。对此笔者通过区域地质资料调查、钻井岩心描述、岩心薄片资料观察以及分析测试资料等手段,在火山碎屑岩分类基础上,根据火山碎屑含量划分出沉积-火山碎屑岩以及火山碎屑沉积岩,并结合粒度、组分、沉积构造等特征细分出11种岩相类型以及9种岩相组合,进而提出火山碎屑流、火山异重流、火山灰异轻流、热液侵入和微生物诱导5种成因机制。结合钻井岩心观察识别出火山沉积序列及沉积特征,建立了朝阳盆地九佛堂组火山-湖泊沉积模式,为研究区油气资源的勘探开发提供理论依据。研究发现,火山物质对湖盆内有机质富集起到积极的影响。朝阳盆地九佛堂组烃源岩地化测试显示:含有火山细粒物质参与沉积的样品有机质丰度指标更好,有机质更富集。由于燕山构造带内其他盆地同样具有相似的火山活动地质背景,研究结果也为这些地区沉积学及油气资源研究起到良好的对比参照作用。

The Chaoyang Basin in western Liaoning, situated in the eastern section of the Yanshan tectonic belt, is a fault basin from the Mesozoic era on the periphery of Songliao. The level of exploration understanding in this region is relatively low. Previous studies on the Lower Cretaceous Jiufotang Formation in the Chaoyang Basin primarily focused on lacustrine deposits, overlooking the significant impact of volcanic events on the basin’s sedimentation. To address this gap, regional geological data investigation, drilling core description, core thin section data observation, and test data analysis were conducted. By classifying pyroclastic rocks into sedimentary pyroclastic rocks and pyroclastic sedimentary rocks based on their content and subdividing them into 11 lithofacies types and 9 lithofacies combinations according to particle size, composition, and sedimentary structure characteristics, five causal mechanisms were proposed: pyroclastic flow, volcanic hyperpycnal flow, volcanic ash heterogeneous light flow, hydrothermal intrusion, and microbial induction. The establishment of the volcanic-lake sedimentary model of the Jiufotang Formation in the Chaoyang Basin, based on volcanic sedimentary sequences and core observation findings, offers a theoretical foundation for oil and gas resource exploration and development in the area. Research indicates that volcanic material positively influences organic matter enrichment in the lake basin. Geochemical tests on source rocks of the Jiufotang Formation in the Chaoyang Basin revealed that samples containing volcanic fine particles involved in sedimentation exhibited better organic matter abundance and enrichment. Given the similar volcanic activity geological background in other basins within the Yanshan tectonic belt, these findings also serve as valuable comparative references for sedimentology and oil and gas resource research in those regions.