Table 1 Classification of Wudaoliang stromatolites and laminae within

Fenestral stromatolite

(Figs. 2a, b, d, 3a, b, d-f)

Porous (spongy) laminae

Fenestrae fabric components are > 25%. Angular and elongated fenestrae are filled with microspars, between the massive microcrystalline and the filament-like (0.1–0.2 mm in length and 20–50 μm in width) vertically structured micrites. The angular fenestrae are sub-rhombic calcite pseudomorphs after evaporite crystals, possibly gypsum.

Clotted microcrystalline laminae

5%–25% fenestral (only tiny, irregular) fabric constitutes this kind of laminae. Irregular peloids of indistinct boundaries are closely clotted.

Thin massive microcrystalline (aphanitic) laminae

Few or no fenestral fabric components. Smooth, slightly undulating massive microcrystalline calcite is the primary component for this kind of laminae; and no void structures are found in the thin section.

Agglutinated stromatolite

(Figs. 2c, e, 3c-i)

Porous peloidal laminae

(Fig. 3c, g)

No fenestrae and composed of trapping (binding) particles, i.e., peloidal micrites and faecal pellets. Particles are loosely piled or packed between the microspar cements. The size of pellets ranges from 20 μm to 500 μm.

Dense peloidal laminae

(Fig. 3c, g)

Primary components: densely packed pellets and peloids, microcrystalline dense calcite in fairly low porosity.