Figure 18 in Baghuk Mountain (Central Iran): high-resolution stratigraphy of a continuous Central Tethyan Permian-Triassic boundary section

Figure 18. Field photographs of Early Triassic bedding surfaces with structures of possible microbial origin. (a) Flower-shaped structure in the pale-brown micritic matrix containing filaments, bivalve shell fragments, ammonoids and high-spired gastropods. (b) Kidney-shaped "twin" morphology characterized by an irregular, partly concentric structure, where micrite and sparite alternate. (c) Structures of different size, some of which grow on the margin of a previous generation. (d) Dark-grey, ovoidal, lenticular sparry calcite structure, filled by an argillaceous micrite, in pale-brown micritic matrix containing abundant filaments (probably sponge spicule remains).