Development and evolutionary patterns in Cambrian eukaryotic primary producers and their relationship to perturbations in the carbon cycle

Eukaryotic phytoplankton provide an important record of environmental change and are indeed a driving force in global change. Stable isotopes studies have recently lead to recognition of a major global change event in the early Late Cambrian (SPICE event). Intriguingly the SPICE event is broadly correlative with a major diversification in acritarchs (the dominant group of Palaeozoic eukaryotic phytoplankton). This PhD project is designed to provide the first detailed examination of the Middle to Late Cambrian phytoplankton record of Laurentia across the SPICE event. It will test the hypotheses that the SPICE event and the Middle-Upper Cambrian phytoplankton evolutionary turnover are causally linked, with enhanced phytoplankton production a key factor in producing the carbon isotope excursion. The project will be based on new collections of palynological and isotope samples from Middle-Upper Cambrian sequences for the oceans bordering the palaeocontinent Laurentia. Samples will be collected from the Steptoean sequence of the eastern Great Basin, USA, where the SPICE event was originally identified. Samples will also be collected from outcrop and borehole (e.g. JOY-2 core) material from the Middle-Upper Cambrian Conasauga Group and Knox Group from the eastern margin of Laurentia (cropping out along the Appalachian Belt of eastern USA), where the SPICE event has also been reported. These strata are known to yield diverse assemblages of acritarchs that are well preserved and of low thermal maturity. The acritarchs will be analysed using a variety of observational techniques (including novel techniques such as confocal laser-scanning microscopy) and systematically described. A database of occurrences, biodiversity and disparity will be compared with the SPICE event to test the hypothesis. The SPICE event has previously been reported from a few individual sections in both areas. Isotopic data will be obtained to determine the SPICE signal in the newly sampled sections, to achieve geochemical background information and to enable worldwide correlations with all other occurrences of the SPICE signal. The fieldwork will provide the student with training in geological and palaeontological research skills, complementing the intensive research specialisation, which will be gained from the detailed study of the acritarchs. Both the University of Sheffield and the CASE partner (Natural History Museum) will provide access to state of the art facilities for palynological study, a wide body of complementary expertise and integration into active research groups investigating the evolution of organic-walled phytoplankton and its links to global environmental change. This is primarily an academic study leading to a deeper understanding of global climate change and development of biosphere-geosphere interactions on long geological timescales. However, the student will also be trained in biostratigraphical palynology, and can thus expect to find employment in either academia or industry (e.g. as an exploration palynologist). Results will be published in the peer-reviewed scientific literature and presented at international conferences. Opportunity for additional presentations to the general public is provided through collaboration with the Natural History Museum's Education Department and particularly the Darwin Centre Live programme.