Depositional and preservational environments of the Ediacara Member, Rawnsley Quartzite (South Australia): Assessment of paleoenvironmental proxies and the timing of 'ferruginization'

The paleoenvironmental setting in which the Ediacara Biota lived, died and was preserved in the eponymous Ediacara Member of the Rawnsley Quartzite of South Australia is an issue of longstanding interest and recent debate. Over the past few decades, interpretations have ranged from deep marine to shelfal to intertidal to terrestrial. Here we examine the evidence in support of and against various paleoenvironmental interpretations of the fossiliferous Ediacara Member, as well as exploring in depth a range of paleoenvironmental proxies that have historically been employed in such studies. We emphasize the importance of reconciling paleoenvironmental analysis with an understanding of sedimentological processes and outline which proxies are consistent with this approach. A careful assessment of paleoenvironmental parameters is essential to the reconstruction of the depositional and early diagenetic history of the Ediacara Biota and thus the physical, chemical and biological factors that shaped the development and the fossilization of these earliest examples of complex life. We find no compelling evidence for a terrestrial setting for the Ediacara Member and strong support for a shallow marine depositional environment.