Experimental Approaches to Understanding Fossil Organisms

Abstract

Microbialites dominated the biosphere throughout the Proterozoic, becoming relatively rarer into the Phanerozoic. Microbialites are potential analogs of life on the early Earth; therefore, understanding how they form and function can provide a window to the past. Much of what we know about early life and environments derives from investigations of modern microbialites, making studies of these structures critical to interpreting the ancient fossil record. Creating a database of worldwide microbialite specimens, both modern and fossil, to be used for analyzing patterns in modern microbialite distribution, both in space and time, along with environmental characteristics and concurrence with grazing and/or boring organisms, can offer understanding into ancient microbialites, specifically the processes impacting their formation, persistence, and preservation. Additionally, analyzing the composition and structure of modern microbialites may allow for connections to patterns of the past, and also provide a clearer understanding of what is seen (or not seen) in the fossil record. A sample database of microbialites reported from the Phanerozoic was analyzed for characteristics such as distribution in time, space, and across different environments, as well as the alignment of distribution with mass extinctions, global sea level curves, and association with grazing/burrowing organisms. We find microbialite distribution is widespread worldwide and abundance fluctuates over the Phanerozoic with increases often corresponding to mass extinctions. Contrary to previous interpretations, fossil microbialites do not appear to prefer open marine environments, with data showing broad distribution in a variety of environments. Modern microbialites, however, primarily form in restricted environments. Data show that grazers/borers are commonly found in association with microbialites throughout the Phanerozoic, though it is difficult to discern if they did or did not impact microbialite formation.