PhD: Ediacaran Sedimentary Environments: Anactualistic or Ambiguous?

The Ediacaran Period was a crucial interval for the evolution of metazoan life on Earth. Enigmatic fossils of originally soft-bodied organisms are well known from localities worldwide, and there is strong interest in understanding their biological affinities and the environments in which they lived. Focussed sedimentological studies of fossil-bearing Ediacaran units have yielded interpretations that are sometimes contradictory, ranging from deep-marine to non-marine palaeoenvironments (with differing degrees of acceptance), and a commonly iterated assertion that Ediacaran sedimentary environments may have been as anactualistic (without modern analogue) as the fossils themselves. The rock record provides our only window on the habitats and environmental interactions of the Ediacaran biota, and a more refined sedimentological and geological understanding of strata from this interval is essential in order to shed further light on the theatre in which these fossil organisms operated.
This project will test existing interpretations of Ediacaran palaeoenvironments and anactualism by placing equal importance, for the first time, on the sedimentary conditions of unfossiliferous Ediacaran strata, via direct comparison with similar facies in younger strata. By such methods, a holistic assessment of the environmental back-drop to Ediacaran evolution will finally be developed, unbiased by focussing only on the most exceptional (fossil-bearing) successions. The student will construct a global database of the sedimentological characteristics and outcrop bias of fossiliferous Ediacaran strata through means of meta-analysis of published literature. This will be augmented by the petrographic analysis of existing samples of fossil-bearing Ediacaran rocks in Cambridge, and fieldwork in local relevant localities. Once key sedimentological characteristics are identified, the database will be broadened to identify their recurrence in both unfossiliferous Ediacaran strata and similar facies from older and younger strata. The project is strongly field-oriented, and a main study focus will be the sedimentological analysis of unfossiliferous Ediacaran strata identified from the database, such as those in South Australia, which have previously been overlooked as focus has been directed at the nearby, more exceptional, fossil-bearing localities. Only by applying equal rigour to the sedimentological study of these ‘unexceptional' strata can the significance of the sedimentary characteristics of the fossil-bearing units be truly understood.