P024-0006
Recognizing the Textures of Life: Implications of Diverse and Ubiquitous Ediacaran Organic Surfaces for the Detection of Microbial Structures on Other Planets
Wednesday, 9 December 2020
Poster
Mary Droser, University of California Riverside, Riverside, CA, United States, Lidya Tarhan, Yale University, Department of Earth and Planetary Sciences, New Haven, CT, United States, Scott Evans, The Smithsonian Institution, National Museum of Natural History, Department of Paleobiology, Washington, D.C., United States, James Gehling, South Australian Museum, Department of Palaeontology, Adelaide, Australia and Rachel Surprenant, University of California, Riverside, Earth and Planetary Sciences, Riverside, CA, United States
Abstract:
The Precambrian seafloor was covered in widespread organic matgrounds. The greatest diversity and complexity of organic mat textures occur in the Ediacaran fossil record, as exemplified by the Ediacara Member of the Rawnsley Quartzite, which crops out in and around the Flinders Ranges of South Australia. This succession demonstrates that heterogenous mats coexisted with and were central to the ecology, biology and taphonomy of the Ediacara Biota. The Ediacaran occupies a critical time in Earth’s history when we can observe the emergence of complex life forms in environments containing ubiquitous mat textures. Among these are microbially induced sedimentary structures (MISS), which include microbial laminations, bed-plane organosedimentary textures and stromatolites. The Ediacaran record is further characterized by textured organic surfaces (TOS), which likely included both populations of microorganisms and densely aggregated communities of macroscopic, multicellular eukaryotic organisms, including algae and ‘thickets’ of organisms such as tubular fossils that first occur in this time interval.
Distinct sedimentary features indicative of mats are particularly pervasive, demonstrating that the organically stabilized substrate not only mediated community ecology, but also shaped the sedimentology and stratigraphy of Ediacaran successions. Organic binding of sediment inhibited reworking, erosion and amalgamation of adjacent beds of similar texture, facilitating preservation of extremely thin event and background deposits as discrete beds and ultimately, the capture of an unusually complete sedimentary and stratigraphic record. As a result, unique mat signatures are preserved on discrete bedding planes and, importantly, in cross-section, as repeated and readily identifiable sedimentary structures that could potentially serve as biosignatures in the search for life on other planets.
