南盘江坳陷二叠系层序地层格架及古地理环境

Sequence stratigraphic framework and palaeogeographic environments of the Permian strata in the Nanpanjiang depression, Guangxi

南盘江坳陷二叠系划分为12个三级层序,平均每个层序延续时限为3Ma。进而将三级层序划分为4个Ⅰ型层序和8个Ⅱ型层序。三级层序虽然在不同地区发育完整性有所不同,但总体可以进行对比。三级层序构成两个超层序。超层序SS1沉积期,南盘江坳陷主要为台、盆相间古地理格局,具有狭窄的台地边缘—台地斜坡沉积。钦防地区为半深海环境。超层序SS2沉积末期,右江地区从台、盆相间格局演化到盆包台格局。上扬子古陆主体为开阔台地—局限台地,而靠近川滇古陆则变为陆相环境。

The Permian strata in the Nanpanjiang depression, Guangxi may be divided into twelve third-order sequences, each of which spans an average time duration of 3 Ma. These third-order sequences may be (subdivided) into four I-type ad eight II-type sequences according to sequence boundaries, and comparable in (general) in spite of sequence differences in different regions. They are also involved in two supersequences. (During) the deposition of the supersequence SS1, the Nanpanjiang depression displayed the platform-basin palaeogeographic framework, where the narrow platform margin-platform slope deposits are developed. The bathyal environments then occupied the Qinzhou-Fangcheng region. At the end of the deposition of the supersequence SS2, there was the transition from a platform-basin palaeogeographic framework to platform-in-basin framework in the Youjiang Basin. The main part of the Upper Yangtze ancient land was then an open platform-retricted platform, passing into the continental environments in the areas near the Sichuan-Yunnan ancient land.