Microbially Induced Sedimentary Structures

To date, microbialites include five groups: stromatolites, thrombolites, leiolites, and dendrolites. All these microbialites occur in carbonate or silica lithologies. However, research during the past 25 years has defined an additional group of microbialites that occurs predominantly in clastic deposits. These structures are called microbially induced sedimentary structures, commonly simply abbreviated to MISS. As outlined in this chapter, the morphologies of MISS do not resemble those of precipitated microbialites due to the much different formation and different location of these structural groups. The genesis of the main types of MISS has been elucidated in studies in modern environments. The results were key for the search of such structures in the fossil record. Systematic exploration from youngest to oldest stratigraphic successions has given rise to a data set that allows identification of MISS in respective paleoenvironments. MISS are biosignatures helpful to understanding aspects of prokaryote evolution and the search for life on other planets. This chapter first briefly focuses on the microbial communities that cause the structures, then discusses MISS formation, which is intimately related to the immediate setting. Next, the processes of their preservation is examined, and, finally, the chapter arrives at the classification of MISS.