四川盆地构造沉降特征及成因机制分析  

Tectonic subsidence characteristics of Sichuan Basin and its enlightenment to basin genesis

作　　者：鲁国 何登发[1] 开百泽 Lu Guo;He Dengfa;Kai Baize(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083;Southwest Geophysical Research Institute,CNPC,Zhuozhou,Hebei 072750)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]中石油集团东方地球物理勘探有限责任公司研究院,河北涿州072750

出　　处：《地质科学》2023年第1期86-104,共19页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金联合基金项目“三大克拉通位置的恢复复原与相互关系及裂解—聚合过程、构造热体制”(编号:U19B6003-01-01)资助。

摘　　要：盆地的沉降过程能够反映盆地的演化历史及成盆机制。为深入分析四川盆地构造沉降特征,本文基于最新钻井资料和地震数据,通过回剥反演方法,进行去压实、沉积负载、古水深和海平面变化校正,重建了四川盆地不同构造单元的构造沉降史。同时根据瞬时均匀伸展模型和裂后热坳陷模型进行正演模拟,对盆地成因进行分析。构造沉降史的恢复揭示了四川盆地具有典型的克拉通盆地沉降特征。四川盆地的形成演化可划分为震旦纪—早古生代、石炭纪—三叠纪、侏罗纪—白垩纪3个构造沉降旋回,盆地经历了晚震旦世—早寒武世、早志留世、晚二叠世—早三叠世以及中晚侏罗世4幕快速沉降,第一幕和第三幕快速沉降期为岩石圈伸展减薄引起,另外两幕为前陆盆地发育过程中所引起的快速沉降。构造沉降正演结果表明四川盆地在寒武纪—奥陶纪和晚二叠世—三叠纪经历了两期“快速沉降—缓慢沉降”过程,快速沉降受控于岩石圈的伸展作用,缓慢沉降为岩石圈热冷却作用所主导。盆地在热冷却沉降阶段后进入前陆挠曲沉降,出现不同规模的剩余沉降。The subsidence process of the basin can reflect the evolution history and the basin-forming mechanism. In order to deeply analyze the characteristics of tectonic subsidence in Sichuan Basin, based on the latest deep drilling data and seismic data, this paper reconstructs the tectonic subsidence history of different tectonic units in Sichuan Basin by back-stripping inversion method to correct decompaction, sedimentary load, paleo-water depth and sea level change. At the same time, according to the instantaneous uniform extension model and post-fracture thermal depression model forward modeling, the basin genesis is analyzed.The reconstruction of tectonic subsidence history reveals that the Sichuan Basin has typical subsidence characteristics of craton basins. The formation and evolution of the Sichuan Basin can be divided into three tectonic subsidence cycles: Sinian-Early Paleozoic,Carboniferous-Triassic and Jurassic-Cretaceous. The basin experienced four episodes of rapid subsidence: Late Sinian-Early Cambrian, Early Silurian, Late Permian-Early Triassic and Middle-Late Jurassic. The first and third episodes of rapid subsidence were caused by lithospheric extension and thinning, and the other two episodes were caused by rapid subsidence during the development of foreland basins. The forward modeling results of tectonic subsidence show that the Sichuan Basin experienced two stages of rapid subsidence-slow subsidence in Cambrian-Ordovician and Late Permian-Triassic. The rapid subsidence is controlled by the extension of lithosphere, and the slow subsidence is dominated by the thermal cooling of lithosphere. The basin entered the foreland flexural subsidence after the thermal cooling subsidence stage, and there was residual subsidence of different scales.

关 键 词：四川盆地 构造沉降 回剥反演 正演模拟 沉降旋回 

分 类 号：P542[天文地球—构造地质学]