含生命化石的最古老的岩石一 Figure 20-11 A3.5-billion-year-old fossil stromatolite from western Australia is one of the oldest known fossils above). Stromatolites were formed, layer by layer, by mats of blue-green algae or bacteria living in shallow water. Such algae may have been common in shallow seas when Earth was young(top). Stromatolites are still being formed today in similar environments (Mural by Peter Sawyer: photos courtesy Chip Clark, National Museum of Natural History.黄伟达 含生命化石的最古老的岩石