Reviews and syntheses: Tufa microbialites on rocky coasts towards an integrated terminology

Abstract. Microbialites are known from a range of terrestrial, freshwater, marine, and marginal settings with the applied descriptive terminology depending largely on the historical legacy derived from previous studies in similar environmental settings. This has led to a diversity of nomenclature and a lack of conformity in the terms used to describe and categorise microbialites. As the role of microbial mats and biofilms is increasingly recognised in the formation of tufa and terrestrial carbonates, deposits such as tufa microbialites bridge the spectrum of microbialites and terrestrial carbonate deposits.

Groundwater spring-fed tufa microbialites in supratidal rock coast environments occur at the interface of terrestrial and marine domains and necessitatethe adoption of an integrative and systematic nomenclature approach. To date, their global distribution and complex relationships with pre-defined deposits have resulted in the application of a variety of descriptive terminologies, most frequently at the macro- and meso-scale. Here we review and consolidate the multi-scale library of terminologies for microbialites and present a new geomorphological scheme for their description and classification. This scheme has greater alignment with terrestrial carbonate nomenclature at the macroscale and with marine and lacustrine microbialites at the mesoscale. The proposed terminology can primarily be applied to tufa microbialites in spring-fed supratidal settings but may also be applied to other relevant environmental settings, terrestrial carbonates, microbial mats and other microbialites.