川北南江地区中下寒武统混积特征研究

Mixed Sedimentation Features of the Middle and Lower Cambrian, Nanjiang Area,Northern Sichuan Basin1te(w

中下寒武统是四川盆地北部潜在的重要油气勘探层位。以米仓山地区杨坝剖面为研究对象,通过详细的剖面实测和薄片鉴定,对南江地区中下寒武统混合沉积特征进行了研究。研究结果表明:研究区混合沉积特征宏观上表现为由陆源碎屑与碳酸盐交互沉积、陆源碎屑与混积物交互沉积、碳酸盐与混积物交互沉积和混积物本身的交互沉积构成的混积层系,微观上表现为同一岩层内由陆源碎屑组分与碳酸盐组分混合沉积所形成混积岩;混合沉积类型有渐变式混合沉积和复合式混合沉积,但是两种类型的混合沉积常相互叠加,频繁交替,形成类型复杂的混合沉积复合体。最后结合混合沉积的成因、沉积机理、产出部位及沉积环境等因素,建立了南江地区中下寒武统的混合沉积模式,进而对混合沉积的控制因素进行了讨论。

The Middle and Lower Cambrian is the important and potential hydrocarbon exploration target in northern Sichuan Basin. In this study, the Yangpo profile in Micangshan Mountains area was taken as an example, and the mixed sedimentation features of the Middle and Lower Cambrian in Nanjiang area was researched according to detailed profile survey and thin-section analysis. Results show that(1)macroscopically, the features represent the alternative sedimentation of both terrigenous clastic and carbonate, both terrigeneous clastic and mixed deposits, both carbonate and mixed deposits, and deposits themselves;(2)microscopically,the features reflects the mixed rock formed from terrigenous clastic deposited with carbonate at the same strata;(3)there are two types of mixed sedimentation including gradually variable one and compound one;(4)these two types often stack each other or frequently alternate, forming a mixed-sedimentation compound with complicated mixed sedimentation. At last, some factors of mixed sedimentation, containing origin, mechanism, and environment were studied. And a mode of mixed sedimentation was developed for the study area.