四川盆地裂陷槽研究新进展——关于裂陷槽成因机制与形成时间的探讨

New progress in the study of aulacogen in Sichuan Basin——A discussion on the genetic mechanism and formation time of the aulacogen

最新钻井和地震资料研究表明,四川盆地裂陷槽内大部分地区缺失震旦系(埃辿卡拉系)灯影组灯四段、灯三段及灯二段上部地层,灯二段仅残留富藻层及以下地层,震旦系地层具有环状剥蚀特征;残留的灯二段岩性主要为泥粉晶白云岩、藻纹层白云岩、藻格架白云岩、雪花状构造白云岩及砂砾屑白云岩,局部层段葡萄花边构造发育,沉积相属于典型的局限台地,沉积特征与盆地内其它地区灯影组沉积特征相同,表明在震旦纪四川盆地碳酸盐台地内部并没有明显的构造分异。本文从地层、沉积特征及构造动力机制方面提出了四川盆地裂陷槽成因的解释意见,认为震旦系内部的裂陷槽形成于震旦系沉积之后,其成因可能与地幔柱拱升—地层剥蚀—地幔柱塌陷再沉降有关。

The latest drillings and seismic data show that the 4 th, 3 rd Member and upper part the 2 nd Members of the Dengying Formation, Sinian(Ediacaran) System are missed in most areas of the aulacogen, Sichuan Basin;and only algae-rich layers of the 2 nd Member more lower strata remain. The Sinian System strata are characterized by circular denudation. The remaining rocks of the 2 nd Members of the Dengying Formation, is mainly micritic dolostone, algae laminae dolostone, algal framework dolostone, snowflake-shaped structural dolostone and gravel dolostone. The grape lace structure is developed in some sections, and the sedimentary facies belong to a typical limited platform, which is the same as that of the Dengying Formation in other areas in the basin, indicating that there is no obvious structural differentiation in the Sinian Sichuan Basin carbonate platform. In this paper, the explanation of the genesis of aulacogen in the Sichuan Basin is put forward from the aspects of strata, sedimentary characteristics and tectonic dynamic mechanism. It is considered that the aulacogen in Sinian System was formed after Sinian System deposition, and its genesis may be related to mantle plume arching—stratum denudation—mantle plume collapse and re-settlement.