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Competition Funded PhD Project (European/UK Students Only)
Despite being stable across a range of grain sizes and flow conditions, the dune cross-stratification bedform is generally rare in deepwater turbidite sands and gravels. There are a number of potential reasons for the paucity of this ‘missing’ bedform from turbidite successions, linked to near bed conditions beneath parental turbidity currents, including sediment concentration, turbulence modulation and the temporal scales of flow (e.g., Arnott, 2012). Whilst dunes are indeed scare, their presence is noted in many ancient turbidite systems at outcrop, from the modern sea floor and in subsurface hydrocarbon reservoirs. Given their scarcity, when dunes are developed they form a distinctive facies. However, the controls on their ability to form (when normally they cannot) their patterns of spatial occurrence within turbidite systems, and their significance in a hydrocarbon exploration and development context remain poorly understood. The goal of this project is to characterise the different types of dunes and their association with different sub-environments, especially differences between channelized and frontal splay/lobe sequences that may look similar in cored sequences, and to develop hydrodynamic models for their development, linked to the dynamic evolution of the host turbidite systems.
The student will collect field data from the Peïra Cava ponded minibasin (Eo-Oliogocene, SE France) and the Marnoso Arenacea foredeep basin (Miocene, Italy) where bed-to-bed correlations have been established that allow analysis of depositional trends in events bed over scale of 10-100 km. The data will be used to test and advance current models describing dune formation in terms of their hydrodynamic processes and environment of formation. One influential model is that dunes may be developed at times of lower sediment concentration near the bed (Kneller & McCaffrey (2003), with dune cross-stratified intervals arising from reworking after initial sedimentation. This model suggests that dunes could be relatively widely distributed in systems. Another prominent model suggests that dunes are principally formed in the channel-lobe transition of submarine fans as a consequence of locally enhanced turbulence and reduced sediment concentration as flows experience a hydraulic jump (Mutti & Normark, 1991; Wynn et al., 2002). Other workers place emphasis on the occurrence of cross-stratification at the tops of lobes/frontal splays during phases of element abandonment and reworking and sediment bypass by subsequent flows (e.g., Stephenson et al., 2015). Whilst these models may all be valid, cross bedding is also noted more widely in systems including within the axis of incised-channels (e.g., Brunt et al., 2007), in proximal part of sheet systems (e.g., Kneller and McCaffrey, 2003) and in unchannelised distal sheet systems (e.g., Sumner et al., 2012).
Potential for high impact outcome
The work has the potential to develop models for dune formation which can be used as a tool to assess the large scale dynamic evolution and stratigraphic architecture of turbidites systems. It would also provide new insights into the degree to which the latter parts of flows (i.e., body and tail) can rework its own deposit and redistribute sediment: an aspect poorly constrained in existing depositional models. These results will provide useful insights for the petroleum industry specifically in terms of the prediction of reservoir location and character and potential production behaviour. The successful delivery of such insights would permit publication of high-impact papers both in academic and applied journals.
The student will work within the inter-disciplinary Turbidites Research Group, which itself is part of a wider Sedimentology group and has a number of on-going research projects related to deep-marine clastic sedimentology via field studies, physical and numerical modelling and seismic studies. This project provides specialist scientific training in: (i) field-based techniques for the sedimentological and architectural analysis of clastic successions; (ii) geological interpretation of seismic datasets; (iii) relational-database theory and practice and SQL coding; (iv) statistical analysis. In addition, the successful PhD student will have access to a broad spectrum of training workshops provided by the Faculty that include an extensive range of training workshops in statistics, through to managing your degree, to preparing for your viva (http://www.emeskillstraining.leeds.ac.uk). The successful candidate will be strongly encouraged to publish their research in leading international journals.
The student will be attached to the industry-funded Turbidites Research Group (TRG) project. The appointed student will engage with sponsor companies at regular update meetings, and will be encouraged to undertake an internship with a company during the PhD period.
Please visit our LARS scholarship page for more information and further opportunities: https://www.environment.leeds.ac.uk/study/postgraduate-research-degrees/lars-scholarships/
Arnott, R.W.C., 2012. Turbidites, and the case of the missing dunes. Journal of Sedimentary Research, 82, 379-384.
Brunt, R. L. & McCaffrey, W. D., 2007. Heterogeneity of fill within an incised channel: The Oligocene Gres du Champsaur, SE France. Marine and Petroleum Geology, 24, 529-539.
Kneller, B. C. & McCaffrey, W. D., 2003. The interpretation of vertical sequences in turbidite beds: The influence of longitudinal flow structure. Journal of Sedimentary Research, 73, 706-713.
Mutti, E. & Normark, W.R., 1991. An integrated approach to the study of turbidite systems. In Seismic facies and sedimentary processes of submarine fans and turbidite systems, eds. P. Weimer and H. Link: Springer, New York, p. 75-106.
Stevenson, C. J., Jackson, C. A. L., Hodgson, D. M., Hubbard, S. M. & Eggenhuisen, J. T., 2015. Deep-Water Sediment Bypass. Journal of Sedimentary Research, 85, 1058-1081.
Sumner E.J., Talling, P.J., Amy, L.A., Wynn, R.B., Stevenson, C.J. and Frenz, M., 2012. Facies architecture of individual basin-plain turbidites: Comparison with existing models and implications for flow processes. Sedimentology, 59, 1850-1887.
Wynn, R.B., Kenyon, N.H., Masson, D.G., Stow, D.A.V. & Weaver, P.P.E., 2002. Characterization and recognition of deep-water channel-lobe transition zones. AAPG Bulletin, 86, 1441-1462.
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