Stromatolites are the earliest geological record of life on Earth. These curious biotic structures are made of algae carpets growing toward the light and precipitating carbonates. After their first appearance 3.48 Ga ago, stromatolites dominated the planet as the sole living carbonate factory for almost three billion years. Stromatolites are the earliest geological record of life on Earth. These curious biotic structures are made of algae carpets growing toward the light and precipitating carbonates. After their first appearance 3.48 Ga ago, stromatolites dominated the planet as the sole living carbonate factory for almost three billion years. Earth Sciences Phys.org – latest science and technology news stories