关键词: 二叠纪早期, 陆源碎屑, 沉积体系, 海平面变化, 冈瓦纳冰川

Abstract:

Silisiclastics strata underlying the Permian Qixia Formation in Southwestern and Southern Guizhou were commonly supposed to be accumulated while the waxing of the PermoCarboniferous glaciation. However recent works indicated that the Gondwana glaciation consists of eight discontinuous glacial advances. Thus, it is of great significance to recover the depositional environment and process of this silisiclastic succession and to correlate its evolution with the Gondwana glaciation. Present study delineates the spatial variation of the thickness and the sandstone/mudstone ratio of the succession based on literature survey, and describes depositional system at the wellexposed Longyin section. Results demonstrate that the Shazitang Formation is mainly shallow water carbonate deposition, the Longyin Formation and the Baomoshan Formation is dominated by shelf and delta facies, and the Liangshan Formation is composed of near shore clastic deposits in ascending order. The Lower Permian shelf mudstone of the southwestern Guizhou was formed during the rapid sealevel rise correlating with glacial retreating, and the delta depositional system deposited in the late highstand of sealevel fluctuation, rather than the lowstand during the expansion of the Gondwana glaciation. In conclusion, the wax and wane of the Gondwana glaciation is the dominant controlling factor for the architectural pattern of early Permian strata at Longyin section, Southwestern Guizhou.

Key words: early Permian, silisiclastics, depositional system, sea level change, Gondwana glaciation