印支期泸州-开江古隆起演化过程及其动力学机制

Evolution Process and Dynamic Mechanism of Luzhou-Kaijiang Paleo-Uplift during Indosinian,China

印支期泸州-开江古隆起位于四川盆地东部,由于其顶部广泛发育的岩溶不整合面是四川盆地重要的油气储集层而受到广泛关注,但是关于该古隆起的形成时间及成因机制长期存在很大分歧,既影响了对印支期上扬子地区构造演化的认识,也不利于四川盆地油气勘探工作.基于地震、钻井和野外露头资料,详细分析泸州-开江古隆起顶部不整合面,结合区域构造事件、全球海平面变化等资料,利用前陆盆地系统演化模型对泸州-开江古隆起的演化过程及动力机制进行系统分析.认为泸州-开江古隆起的形成及发展期在晚三叠世卡尼期-诺利期,消亡于瑞替期,该古隆起是晚三叠世龙门山前陆盆地系统的一个组成单元——前缘隆起,其演化过程主要受控于晚三叠世龙门山造山楔的构造负载和前陆盆地沉积物的沉积负载.晚三叠世,在华北板块和羌塘地体共同向扬子陆块西缘汇聚的构造背景下,扬子陆块西缘发生NW-SE向地壳缩短,导致龙门山造山楔向扬子克拉通的逆冲推覆作用,控制了泸州-开江古隆起的形成与演化.

The Indosinian Luzhou-Kaijiang paleo-uplift is located in the eastern part of Sichuan basin.It has been paid more attention due to the petroleum geological significance of the karst unconformity on the paleo-uplift.However,there is a debate to the evolution process and dynamic mechanism of Luzhou-Kaijiang paleo-uplift,which has affected both the understanding on the Indosinian tectonic evolution of Upper Yangtze block and the exploration of oil and gas in Sichuan basin.The unconformity on the Luzhou-Kaijiang paleo-uplift will be analyzed in detail,based on the seismic,drilling and field outcrop data.Combined with regional tectonic events and global sea level change,the evolution process and dynamic mechanism of the paleo-uplift will be studied systematically using the evolution model of foreland basin system.It is considered that the Luzhou-Kaijiang paleo-uplift was formed and developed in the Late Triassic Carnian to Norian,and died in the Rhaetian.The Luzhou-Kaijiang paleo-uplift is a component unit(forebulge)of the Late Triassic Longmenshan foreland basin system.Its formation was driven by the tectonic load of the Longmenshan orogenic wedge and the sedimentary load in the foreland basin.The evolution process of the paleo-uplift was mainly controlled by the thrust and nappe of the Longmenshan orogenic wedge toward the Yangtze block,which was probably resulted from southeastward shortening of the western margin of the Yangtze block in response to the Late Triassic convergence among Qiangtang,Yangtze and North China blocks.