江油含增地区中三叠统雷口坡组-天井山组界线沉积微相分析

he distribution range of Middle Triassic Tianjingshan Formation is limited to the northwest Sichuan area in Sichuan basin, affected by the Indosinian movement. The in-depth study of Middle Triassic Tianjingshan Formation is of great significant to understand the sedimentary environment change of Leikoupou Formation to Tianjingshan Formation and the sedimentary evolution characteristic of Sichuan Basin. By measuring the field profile of the Middle Triassic Leikoupo formation- Tianjingshan Formation boundary in Hanzeng of Jiangyou and observing microfacies characteristics indoor, five types of microfacies can be identified on the basis of fossil assemblages and granular characteristics of carbonatite. Four sedimentary facies belts can be recognized according to microfacies assemblages and these are platform-margin sand shoal, open platform, restricted platform and evaporitic platform. According to longitudinal change characteristics of sedimentary facies belts, our analysis shows that Hanzeng area sea level presents overall rise for a long period ( sea level rise and decline fluctuatingly for a short period), and salt sea desalts gradually between Anisian Age and Ladinian Age in Middle Triassic.