Fig. 3

Microscopic images of Wudaoliang stromatolites. a Porous lamina (left side of the dashed line) and clotted lamina (right side of the dashed line) of fenestral stromatolite; b Elongated fenestrae (arrows) in a spongy layer, with few peloids (lines) and detrital components; c Dense peloidal lamina (the upper) and porous peloidal lamina, and the arrow showed an elongated pellet resembled to Artemia pellet by similar size (380 μm long); d Microscopic image of the thin section of Fig. 2e, showing spongy layers (with voids and spar cements) alternated with thin microcrystalline layers (no voids or spar cements), and abundant fenestral fabrics in spongy layers; e Zoomed area of rectangle zone in the Fig. 3d. Note that the angular, microspar-filled crystals (or voids) are possibly traces of the former evaporite minerals; f Zoomed area of rectangle zone in the Fig. 3d; g Pellets-rich laminae of agglutinated stromatolites, either densely packed or loosely packed; h Zoomed area of rectangle zone in the Fig. 3g. Note the almost constant size of the pellets (refer to the Fig. 3i); i Different sized (up to 500 μm) faecal pellets due to cross-section (cutting) effect in an agglutinated stromatolite