| Microbialites have been forming on the Earth for over three billion years and are potentially the oldest macrofossils. Understanding how these microbially influenced structures form and function has far-reaching implications for studies of astrobiology, global environmental change, and most importantly, our understanding of the early Earth. Although thrombolitic microbialites have been investigated for over forty years, we still understand relatively little about how they form, specifically what causes the differentiation between fabric types.;In Highborne Cay, the thrombolitic microbialites growing in close proximity to the well-studied stromatolites allow for a comparison of microbial community composition and biogeochemistry. The thrombolitic microbialites were much more productive, with respect to DO and DIC, than the stromatolitic mats and contained several major differences in dominant micro-organisms. Specifically, the presence of heterocystous cyanobacteria, Nostocales, and a coccoid cyanobacteria, Synechocystis spp. suggest that fabric differences may, in part, be determined by microbial community composition.;The historical perspective on microbialitic fabrics and how they are defined and categorized, in conjunction with an analysis of patterns of abundance and both global and environmental distribution, illuminates the potential for using modern microbialites as analogs for their fossil counterparts, while also providing a window into the early Earth. Integrating methodologies from a variety of scientific fields within one structure, while also communicating through detailed descriptions and multi-scaled photographs, will allow for more efficient and thorough analyses of microbialitic fabrics, in both the modern and ancient. |
