"The Pre-Vendian fossil record is dominated by stromatolites, sheets of calcium carbonate associated with cyanobacteria. Carbonate material is trapped and precipitated on the surface of the filamentous bacteria to generate a distinctive laminated structure. Stromatolites are generally rare in Archaean rocks, becoming more common during the late Archaean and early Proterozoic. By the end of the early Proterozoic a range of stromatolite architectures had developed including stratiform. columnar, conical, domal and nodular growth forms; during the mild- and late Proterozoic the columnar growth types diversified. Many groups of stromatolite were much reduced during the early Cambrian as burrowing and grazing metazoans together with the meiofauna and the influx of coarse siliclastic sediment inhibited and often destroyed stromatolite growth. The stromatolites provide an example of the functional morphology of a pre-Phanerozoic design. Stromatolites were built by photosynthesizing organisms occupying shallow-water environments within the photic zone. The range of growth forms shows adaptations to a range of environmental conditions controlled by current and wave energy together with sedimentation rates. These simple morphologies show a very direct relationship to environmental conditions, indicative of early modes of adaptation."
From Benchley and Harper, Palaeoecology, p.121