黔西南贞丰中-上三叠统竹杆坡组微相与沉积环境演化

摘要

Aiming at understanding the Middle-Late Triassic drowning of the Yangtze carbonate platform, this paper analyzes the microfacies of the Middle-Upper Triassic Zhuganpo Formation in Zhenfeng area, Southwestern Guizhou and discusses its depositional environment evolution. Using standard microfacies type methods of Flügel, nine microfacies including laminated bindstone, peloidal packstone, micritic limestone, bioclastic wackestone, encrinite packstone, intraclastic-ooid-bioclastic grainstone, lump-bioclastic wackestone, bioclastic wackestone-pelagic, and micritic limestone-pelagic are recognized. The ordered combination and stratigraphic distribution of these 9 microfacies show that they were formed during the rapid transition from tidal flat to carbonate platform margin environments, and the prolonged deep shelf and basin environments. The analysis of sea-level changes of the Zhuganpo Formation indicates that they were different from the main part of Yangtze Platform, but their third-order cycles and second-order cycles were briefly concordant with global sea-level changes.%针对中-晚三叠世扬子台地的淹没事件，分析了黔西南贞丰挽澜中-上三叠统竹杆坡组的微相，并讨论了其沉积环境演变。采用Flügel标准微相的判别方法共识别出九种微相，包括：纹层状粘结灰岩、微晶藻球粒灰岩、泥晶灰岩、含生物碎屑泥晶灰岩、棘皮泥晶灰岩、亮晶砂屑鲕粒生物碎屑灰岩、藻团块生物碎屑泥晶灰岩、含生物碎屑泥晶灰岩-P和泥晶灰岩-P。九种微相的有序组合和分布位置显示它们形成于快速的潮坪-台地边缘转变过程和漫长的深水陆棚及盆地环境。海平面变化分析显示，黔西南中-晚三叠世竹杆坡组沉积期的海平面变化不同于扬子台地主体，无论是二级旋回还是三级旋回都响应于全球海平面变化。