滇西兰坪–思茅地块晚三叠世诺利期(Norian)发育一套海相碳酸盐岩沉积(三合洞组)。对巍山三合洞剖面进行了实测与采样, 分离了三合洞组碳酸盐岩中的牙形石, 经鉴定其种属为 Epigondolella vialovi, Epigondolella uniformis和 Epigondolella aff. triangularis, 时代为早诺利期(Lacian亚期)。通过野外剖面及室内显微薄片观察, 采用微相分析的方法对剖面三合洞组碳酸盐岩的微相类型和沉积环境进行研究, 将巍山三合洞剖面三合洞组沉积归纳为 9 种微相, 并根据微相特征结合野外宏观特征, 将三合洞剖面划分为 3 种沉积相类型, 即局限台地相、开阔台地相和台地边缘礁相。在剖面不同层位的碳酸盐岩中发现的热液矿物石榴子石及发黑的牙形石化石(CAI 指数约为 5), 表明该区曾遭受热液作用的影响, 可能与三合洞组沉积后大陆边缘裂谷下陷或板块拼合引起的热卤水上涌有关。

The Norian (Upper Triassic) marine carbonate successions of the Sanhedong Formation were formed in the Lanping-Simao Block, western Yunnan Province. In this study, conodont fossils from the Sanhedong Formation were collected and identified. The conodont assemblage, dated as early Norian (Lacian), consists of Epigondolella vialovi,Epigondolella uniformis and Epigondolella aff. Triangularis. Facies and microfacies analyses of the Sanhedong Formation, in combination with field observation at the Sanhedong section, reveal three main facies, i.e., restricted-marine platform, open-marine platform and platform-margin reefs. They are further subdivided into nine microfacies. The presence of hydrothermal minerals, such as garnets, and the high conodont alteration index (CAI = 5) throughout the Sanhedong Formation indicate that hydrothermal actions may have affected the diagenetic process. The hydrothermal activities may be related to the upwelling of geothermal brine resulted from the subsidence of the continental rift margin and tectonic plate collision during the post-diagenetic process.

国家自然科学基金(41902106)与同济大学海洋地质国家重点实验室开放基金(MG201903)联合资助