云南兰坪盆地三叠纪沉积作用与古地理演化

Sedimentary facies and palaeogeographic evolution of the Lanping Basin in Yunnan

关键词:  沉积相  弧后前陆盆地  碎屑海盆  碳酸盐海盆

Key words:  sedimentary facies  back-arc foreland basin  siliciclastic marine basin  carbonate marine basin

摘要:

根据岩石沉积类型、物源供给、成因机制和沉积序列,结合区域地质特征,将兰坪盆地三叠系划分为陆相火山泥石流、河流相、三角洲相、潮坪相、浅海陆棚相、碳酸盐台地相和深水盆地相7种主要沉积类型。通过对沉积相的详细分析,恢复其古地理格架和面貌,探讨岩相古地理的变迁历史,从而表明三叠纪早期到晚期,其古地理经历了陆相环境※碎屑海盆※碳酸盐海盆到碎屑海盆的转换,即两次海侵-海退旋回。早期的海域分布范围较小,晚期的海域分布范围较宽,并成为统一的海盆。

Abstract:

Seven types of sedimentary facies have been distinguished for the Triassic strata in the Lanping Basin,Yunnan according to rock types,sediment supply,genetic mechanism and depositional sequences,including the continental volcanic debris flow facies,fluvial facies,delta facies,tidal-flat facies,shallow-marine shelf facies,carbonate platform facies and deep-water basin facies.The detailed studies of the above-mentioned sedimentary facies integrated with the reconstruction of the palaeogeographic frameworks indicate that the basin recorded the depositional evolution of two phases of transgressive-regressive cycles from the continental environment through the siliciclastic marine basin to the carbonate marine basin and finally to the siliciclastic marine basin again throughout the Triassic.In general,the sea area in the basin was relatively smaller during the early stage,while during the late stage,the increasing sea area led to the formation of the whole marine basin.