Lichen stromatolite

Lichen stromatolites are laminar calcretes that are proposed as being formed by a sequence of repetitions of induration followed by lichen colonization. Endolithic lichens inhabit areas between grains of rock, chemically and physically weathering that rock, leaving a rind, which is then indurated (hardened), then recolonized.{{cite journal|title=Lichen Stromatolites: Criterion for Subaerial Exposure and a Mechanism for the Formation of Laminar Calcretes (Caliche)|author= Colin F. Klappa |journal=Journal of Sedimentary Petrology|volume=49|year=1979|number=2|pages= 387–400|url= http://archives.datapages.com/data/sepm/journals/v47-50/data/049/049002/0387.htm?doi=10.1306%2F212F7752-2B24-11D7-8648000102C1865D|doi= 10.1306/212F7752-2B24-11D7-8648000102C1865D }}Paleobotany: The Biology and Evolution of Fossil Plants, Edith L. Taylor, Thomas N. Taylor, Michael Krings, page 119, [https://books.google.com/books?id=_29tNNeQKeMC&dq=lichen+stromatolite&pg=PA119]