Depositional architecture of a deep-water apron system: Unit 5, Skoorsteenberg Fm., Tanqua Depocentre, Karoo Basin, South Africa
Prof David Hodgson
Prof S Poulton
No more applications being accepted
Competition Funded PhD Project (European/UK Students Only)
Submarine fans are the largest sediment accumulations on the planet and provide a rich, if cryptic, record of environmental change. The depositional architecture of a submarine fan is controlled by the interplay of various parameters, such as the bathymetric template of the basin, grain-size range, and the climatic and tectonic setting. One parameter that is poorly constrained is the physiography of the submarine supply slope, which can range from point-sourced, with a single feeder system, to line-sourced, with multiple coeval entry points. Systems with multiple feeder channels supply lobe complexes that coalesce to build laterally extensive aprons, and have been identified in seismic datasets (e.g. Gulf of Mexico offshore West Africa), and in modern systems (e.g. offshore California and Lake Baikal). Outcrop examples of apron deep-water systems, however, are rare.
Previous work has indicated that the latest Permian Unit 5 (~100m thick) in the Skoorsteenberg Fm., Tanqua Depocentre, was fed by multiple channel-levee systems along strike that were active at different times (van der Werff and Johnson 2003; Wild et al. 2005; Hodgson et al. 2006). Detailed aspects of the stratigraphy and evolution of the Unit 5 system have been addressed by previous workers (e.g. Wild et al. 2005; Oliveira et al. 2009); however, there has not been a synthesis study of the entire Unit 5 stratigraphy. This is despite the system having been active around the Permo-Triassic boundary, which is one of the most significant periods of environmental change, and mass extinction, in the Phanerozoic.
Key aspects of Unit 5 to be constrained and evaluated against the underlying point-sourced systems include the range of sedimentary facies, the geometry of depositional elements, the transition from channels to lobes, and the distal fringe facies associations. In addition, the sequence stratigraphic context of Unit 5 will be reassessed with analysis of the system. The control provided by extensive outcrops will be supported by integration of core and well logs from 7 research boreholes (3 NOMAD, 1 Slope, and 3 LOBE2) that intersect Unit 5 and provide unique 3D constraints. In mature hydrocarbon systems, such as the North Sea, deep-water stratigraphic traps are commonly identified as prospects although the resolution of data means that these are typically deem high risk. Furthermore, an additional business impact for this project is that similar deep-water systems as also being considered as potential carbon capture and storage sites.
The interdisciplinary nature of this studentship means that the student will be trained in process sedimentology and stratigraphy, and geochemical techniques to constrain environmental change. The student will fully participate in the School and University postgraduate training programme and will be encouraged to attend and present at national and international conferences, and will be strongly encouraged to write their thesis as a collection of manuscripts.
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