中二叠世的上扬子地区开始经历大规模的海侵作用,形成了较为稳定的碳酸盐岩沉积建造.探究该时期四川盆地及邻区沉积充填规律与构造演化特征,是揭示原型盆地成因机制的关键,又是认识四川盆地多旋回叠加过程的重要一环.在前人研究成果的基础之上,综合利用钻井、野外剖面等地质资料,重建了梁山组、栖霞组沉积时期原型盆地构造-古地理格局,并分析其构造-沉积演化过程.主要受继承自晚石炭世以来的中部隆升,东西两侧下沉的的古地貌和初期大规模海侵作用的影响,中二叠世梁山组沉积时期,本地区以滨岸-潮坪沉积体系为特征;栖霞组沉积早期,逐渐过渡到碳酸盐岩台地沉积环境,受区域性伸展作用的影响,海平面相对上升,以开阔台地沉积环境为特征;栖霞组沉积晚期,海平面相对下降,以局限台地和台缘滩沉积环境为特征.因此,反映出四川盆地及邻区在该时期主要受伸展裂解作用的影响,可被认为是一个典型的克拉通内坳陷和边缘裂陷盆地.海平面升降的旋回性变化和盆地的差异性沉降对该时期原型盆地的沉积充填样式和古地理格局的演变产生了重要影响.%The upper Yangtze region began to experience in large-scale transgression and forming a relatively stable carbonate platform in Permian.Understanding the sedimentary-filling pattern and the tectonic characteristic of the prototype basin is the key to reveal the formation mechanism of the Sichuan Basin,and may also help to better understand evolution process of the typical Sichuan multicycle and superimposed basin.On the basis of predecessors' research results,we reconstruct the tectonic and palaeogeographic framework of the prototype basin and analyze the tectonic-sedimentary evolution process during Liangshan and Qixia deposition stages by comprehensively making use of borehole and outcrop data.Mainly controlled by the ancient land form of high in the central and low in the east and west from Late Carboniferous and the large scale transgression,the Liangshan stage was characterized by the tidal flat and shore face sedimentary system;and subsequently transitioned to an relatively stable carbonate platform sedimentary environmental during the early stage of Qixia deposition,influenced by extending action,the sea level rises relatively and characterized by open platform sedimentary environmental;and during the later stage of Qixia deposition,the sea level falls relatively and characterized by restricted platform,platform-margin beach sedimentary environmental.Thus,it reveals that the Sichuan basin and its adjacent areas mnainly influenced by extending action and could be recognized as a typical intracratonic depression with edge rift basin.The cyclical change of the sea level and differential settlement of the basin play an important role in the evolution of the sedimentary-filling pattern and palaeogeographic framework.
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