摘要： 近年来，四川盆地上三叠统是陆相还是海相的争议越来越多。正确认识该问题不仅是正确解读印支运动和四川盆地形成的关键，更是预测须家河组天然气勘探潜力的关键。晚三叠世四川盆地物源、沉积构造、黏土矿物、硼钾比和有机地球化学5个方面的证据证实，须家河组须一段—须三段为海相沉积，须四段—须六段沉积时期，由于龙门山南段的隆升，四川盆地与外海逐渐失去联系，但仍受到海侵作用的影响。①1000多口单井岩石薄片资料分析表明，须四段—须六段沉积时期，龙门山南段尚未抬升或仍为水下隆起，四川盆地与外海依旧相连；②不仅须一段—须三段岩心和露头中发育大量潮汐成因沉积构造，须四段—须六段也非常发育，表明该时期仍然受到潮汐作用的影响；③须四段—须六段高岭石开始出现，但仍有大量伊利石和绿泥石存在，表明该时期酸性古水介质虽开始出现，但仍受到盐碱性古水介质的影响；④硼钾比分析表明，须三段沉积时期古水体盐度开始降低，但仍远远大于正常淡水湖泊水体盐度（平均值为0.5‰），表明该时期仍有大量咸水的注入；⑤有机地化分析表明，须四段—须六段姥植比（Pr/Ph）明显较低，烃源岩的饱和烃十分特殊，甲基甾烷丰富，烃源岩芳烃组成具有明显的特殊性，反映该时期明显受到海侵作用的影响。

关键词: 海侵, 沉积记录, 双黏土层结构, 四川盆地, 上三叠统

Abstract: In recent years，the controversy about whether continental facies or marine facies of the upper Triassic in Sichuan Basin is increasingly attracting attention.Correct understanding of this problem is not only the key to our interpretation of the formation and evolution of Sichuan Basin，but also the key to natural gas exploration of the Xujiahe Formation.Based on comprehensive investigation of provenance，sedimentary structures，clay minerals，boron and organic geochemical analysis of potassium and other evidence，it is believed that Member 1，Member 2 and Member 3 of the Xujiahe Formation were deposited in marine environment，while Members 4， 5 and 6 were effected by transgression because of uplifting of the southern section of the Longmen Mountain and gradually lost contact with the open sea of Sichuan Basin.Five aspects showing transgression exists: ①Petrographic thin section analysis of 1000 wells shows that the southern section of Longmen Mountain was not lifted or not lifted completely out of water in the Late Triassic，and Sichuan Basin was still connected to the open sea;② There exists a large number of plumes and bidirectional cross-bedding，double-clay layer structure，layer and fold the whole vortex structure in the Members 4-6，indicating tidal influence during this period;③ After deposition of the Member 4，kaolinite began to appear along with predominant presence of illite and chlorite，indicating that acidic water body has started to appear，but it was still contaminated by alkaline water body;④Boron-potassium ratio analysis shows that the ancient water salinity decreased after depositional period of the Member 3，but it was still significantly higher than normal salinity of freshwater lakes(mean 0.5‰)，which manifested there was still a lot of salt water injection during this period;⑤ Organic geochemical analysis indicates that source rock of the Xujiahe Formation has distinct specificities，showing obvious influence of transgression.

Key words: transgression, sedimentary records, double-clay layers texture, Sichuan Basin, Upper Triassic

中图分类号: 

• P521