Similar to calcretes, these organosedimentary structures typically form when cyanobacteria present in algal mats acts to trap and laminate sediment in thread-like filaments on the floor of a body of water.
Six types of these formations have been listed by Robert Riding, including tufa and skeletal. First coined in name by Kalkowsky in 1908, one group of them, Conophyton, is characteristic of Late Precambrian sequences. The study of fossilized ones in general was driven by a discovery of Stanley Tyler and Elso Barghoorn in the Gunflint Formation, where these have created a namesake form of chert. A rare example of a living one of these can be seen at Shark Bay in Australia. Similar to calcretes, these organosedimentary structures typically form when cyanobacteria present in algal mats acts to trap and laminate sediment in thread-like filaments on the floor of a body of water. For 10 points, name these formations which provide the oldest macroscopic evidence of life on Earth, whose name comes from the Greek for "stony carpet."
Six types of these formations have been listed by Robert Riding, including tufa and skeletal.
stromatolites