Stromatolite fossils big 1.5-3\" ancient earth life 1 billion years 2 fossil lots For Sale

Stromatolites in 2 fossil lots sized bigger approximately 1.5 -3 inches wide by 1 to 3 inches deep scooped from fossils as pictured. Stromatolites or stromatoliths are layered mounds, columns, and sheet-like sedimentary rocks that were originally formed by the growth of layer upon layer of cyanobacteria, a single-celled photosynthesizing microbe.Fossilized stromatolites provide records of ancient life on Earth. Lichen stromatolites are a proposed mechanism of formation of some kinds of layered rock structure that are formed above water, where rock meets air, by repeated colonization of the rock by endolithic lichens. Stromatolites are layered bio-chemical mounds formed in shallow water by the trapping, binding and cementation of sedimentary grains by microbial mats of microorganisms, especially cyanobacteria. They exhibit a variety of forms and structures, or morphologies, including conical, stratiform, branching and columnar types. Stromatolites occur widely in the fossil record of the Precambrian, Very few ancient stromatolites contain fossilized microbes. While features of some stromatolites are suggestive of biological activity. They peaked about 1.25 billion years ago and subsequently declined in abundance and diversity so that by the start of the Cambrian they had fallen to 20% of their peak. The most widely supported explanation is that stromatolite builders fell victim to grazing creatures (the Cambrian substrate revolution, this theory implies that sufficiently complex organisms were common over 1 billion years ago.These fossils are great educational and hands on learning specimens and come from North Africa near the Sahara desert.