Ocean oxygenation and the rise of Metazoans

Rationale: Animals require oxygen, and therefore the first appearance of metazoans during the later Ediacaran (580-543 million years ago) and calcified skeletons from ~550 million years ago has been linked to the widespread development of oxygenated oceanic conditions. Likewise, increased biodiversification and carbonate saturation state of surface waters facilitating the
radiation of heavily skeletonised biota has been linked to rising oxygen levels in the late Cambrian to early Ordovician. However, the global nature of ocean redox chemistry throughout this period has been shown to be complex, with deeper water anoxia persisting in certain areas. Furthermore, few studies have directly documented the nature of ocean chemistry at locations that coincide with palaeontological evidence for major biological innovation. Thus, the precise environmental context for early animal evolution remains unclear. Chemical tracers reveal a profound change in oceanic composition for this time interval. Significant perturbations to major biogeochemical cycles occurred which may be linked to either the oxidation of a substantial reservoir of organic carbon suspended in the deep ocean, or to a large flux of methane clathrates, or may be as a result of diagenetic phenomena. One inference that has been drawn from detailed reconstructions of ocean chemistry is that a globally anoxic and ferruginous deep ocean state existed to at least ~580 Ma (and beyond in certain areas), whereas surface-water oxygenation is thought to be a near-continuous feature through the latter half of the Ediacaran. But there is also growing evidence to suggest that mid-depth euxinia (freesulphide in the water column) may have been a feature (but possibly temporally-restricted) along some continental shelves. There is also some evidence for unstable oxygenation of surface waters at some times, but this is far from clear. Thus, perturbations of the iron and sulphur cycles, and the global carbon budget, all imply strong environmental controls on evolution during this period.

This project will explore the spatial and temporal reconstruction of carbon isotope and ocean redox dynamics, as recorded in sedimentary rocks deposited from the beginning of the Cambrian, some ~543 million years ago, through to the middle Cambrian, a time period encompassing most of the so-called ‘Cambrian Explosion’. Carbonate and clastic sediments will be analysed from a
number of localities including Siberia and Australia. These successions span deep distal to shallow proximal settings, which coincide with the appearance of many new types of body plans and skeletons.

For full project detail please see link:
http://www.ed.ac.uk/schools-departments/geosciences/postgraduate/phd/programmes-supervisors/physical-sciences/phd-projects?NotHG=1&cw_xml=index.html