Fig. 5

Macro- and microscopic characteristics of the columnar stromatolites. a Vertical view of the micro-columnar stromatolites from sample ZK01-b2 with column diameters less than 1 mm. Some stromatolites askew grew unevenly due to the wave action; and there are small amounts of silty quartz detritus in the dark laminae; b Vertical view of a cut slab of the columnar stromatolites from sample ZK02-b13 with column diameters less than 1 cm and increased upward. The laminar shapes are slightly arched, and the laminae of adjacent columns grew synchronously; c Line drawing of the (b)