黔西南二叠纪早期陆源碎屑沉积体系对冈瓦纳冰川发育的响应

通常认为黔西南和黔南地区二叠纪栖霞组之下的一套陆缘碎屑岩地层，是石炭纪-二叠纪冈瓦纳大陆冰盖发育鼎盛时期大幅度海平面下降期间的沉积。最新研究表明，石炭纪-二叠纪冈瓦纳冰川是由多次不连续的冰川事件构成的。因此恢复该套以陆源碎屑岩为主地层的形成环境和堆积过程，探讨其成因与冈瓦纳冰川发育的关系，具有非常重要的科学意义。本研究查明了黔西南地区该套陆源碎屑岩的地层厚度和砂泥比值空间变化规律。在此基础上，选取碎屑岩发育最好的普安龙吟剖面开展沉积体系与成因研究。结果表明，沙子塘组主要是碳酸盐沉积体系，龙吟组和包磨山组主要为浅海陆棚三角洲沉积体系，梁山组以滨岸陆源碎屑沉积体系为主；二叠纪早期黔西南地区的陆棚相泥岩形成于冰川消融导致的海平面快速上升期间，三角洲沉积体系形成于海平面晚期高位域期间，而不是形成于冈瓦纳冰川增长期间的低位域沉积。冈瓦纳冰川的推进和消融是龙吟剖面二叠纪早期地层发育样式的主控因素。

Response of early Permian silisiclastic depositional system to the advance of Gondwana glaciation in Southwestern Guizhou

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.