Carbonate reticulated ridge structures from the lower middle triassic of the luoping area, yunnan, SouthWestern China: Geobiologic features and implications for exceptional preservation of the luoping biota

摘要: Exceptionally preserved carbonate reticulated ridge structures are documented from the lower Middle Triassic Guanling Formation of Luoping area, eastern Yunnan Province, southwestern China. Macrostructures suggest these morphologically similar to growth-related in ancient and modern microbial mats. Other such features as minute load pyrite crystals beneath layers on bedding surfaces overlain by a black carbonaceous shale layer. Clay minerals oriented parallel at top, they usually form wavy laminae. These characteristics indicate that share microstructure their siliciclastic analogs, also comparable with wrinkle structures. SEM imaging shows many tiny objects—coccoid spheres, rod-like filamentous fibrils—are distinct within those ultra-thin, laminae, suggesting accretion growth models Accordingly, biogenic origin. mats associated early Biota thought have played crucial role preservation fossils through sealing coats. An SEM-EDS analysis fossil fragments surrounding matrix reveals an important phosphatization fossils.