Contributions to late Ediacaran geobiology in South China and southern Namibia

The Ediacaran, particularly the late Ediacaran-Cambrian (E-") boundary (551-541 Ma), has been noted as a major time of biological and biochemical transition, including: the rise of predators, the emergence of skeletons, the radiation of bioturbators, and large fluctuations in oceanic chemical conditions (e.g. anoxia/euxinia/ferruginia) with emerging data  suggesting that it is not until the late Ediacaran Period (551-542 Ma) when pervasive oxidation of the deep oceans occurred. In addition, the study of Ediacaran paleobiology involves numerous factors, including but not limited to, restricted amount of outcrops, taphonomic biases, metamorphism, enigmatic phylogenetic affinities, non-actualistic atmospheric and oceanic conditions, and unusual taphonomic windows, making it difficult to assign order to the myriad types of fossils (both body and trace) found during this time . It is with these problems in mind that my dissertation focuses on taphonomic questions in the late Ediacaran. We observe fossil through the taphonomic window and thereby colors all aspects of the study of that organism. By understanding how an organism was preserved we can learn about other factors affecting it, such as their taxonomic affinities, paleoecology, and morphology.

All of these factors were examined through taphonomic investigations and this can be seen in the analytical path through my chapters. In chapter two I examined the preservation of trace fossils in the late Ediacaran. In chapter three I analyzed the taphonomy of an exceptionally preserved Ediacaran fossil to solve its affinity, tubular trace or tubular soft-bodied fossil. In chapter four, understanding the nature of exceptional preservation, I investigated the taphonomy of an Ediacara fossil in coarse grained sediments. In chapter five, I combined the findings of the previous chapters and applied that knowledge to analyze the in situ three dimensional morphology of an Ediacara fossil. Each of the projects presented pairs new technologic methodologies (SEM, BSE-Z, EDS, Raman, microCT) with traditional paleontological and petrologic investigations (field work, hand sample, and petrographic thin-section analysis). The result of this union of Old and New are findings that expand our understanding of these earliest multicellular organisms, their modes of life, and their biological affinities.