Calcareous Tube-Worm Fossils in Microbialites after End-Permian Mass Extinction and Their Paleoenvironmental Implications

摘要

Calcareous tube-worm fossils, forming dense aggregations, are very common in the Permian-Triassic microbialites and laminated, micritic limestone in South China. They usually have the closed, elliptical to kidney-shaped outlines in cross sections, 50-200 μm in diameters. The walls are composed of micritic calcites. Worm tubes appear various outlines in vertical sections, but micritic tube walls are always pronounced and don't have any optic change under the crossed polarization of microscope.