Continental Margin Process Analysis, Structures & Stratigraphy
Seafloor Depth through Time in the South Atlantic
Supervisor: Dr Graeme Eagles
Our knowledge of the tectonic plate motions that resulted in the growth of the South Atlantic ocean has recently increased dramatically in detail (Eagles, 2007; Eagles and König, 2008). The map form of this iconic ocean basin, and of the regions where it connects to the Pacific and Indian oceans, can consequently be modelled with much improved accuracy and confidence for times since the onset of its growth around 150 million years ago. This forms a good basis for modelling the shape of the ocean throughout this time, an essential task if its role in paleoclimate change is to be properly understood, either in terms of outcrop geology at its margins, or using paleoclimate simulation experiments. But for a fuller understanding, the bathymetric evolution also needs to be understood. At first order, plate tectonics controls this by the mechanism of thermal subsidence, and knowledge of past plate motions provides the keys for modelling this by allowing us to accurately define the age of the seafloor. One of the student’s initial tasks will be to generate age grids and use them to model the thermal evolution of the South Atlantic. However there are numerous other factors that affect bathymetry at smaller scales, both within oceans and at their margins. Examples are sedimentation, volcanism, subduction, intraplate tectonics, mantle dynamics, and eustatic fluctuations such as those caused by ice sheet fluctuations. Some of these processes are well quantified from observational evidence (for example the uplift of Southern Africa), without there necessarily being any agreement on their causes, some others have both a sound theoretical and observational basis (sedimentation and the subsidence it produces), and some may exist largely in theory or from indirect evidence only (mantle dynamic topography). The student will need to assess and quantify all of these processes in order to increase the resolution of paleobathymetric maps. A final strand of the project will be to iteratively improve the modelling process by tuning it to observations of paleobathymetry in drill core data.
Specific deliverables of PhD project 6 are:
- High resolution seafloor age maps of the South-Atlantic Basin
- Sediment thickness maps of the South-Atlantic Basin
- Animated tectonic reconstruction of the South-Atlantic Basin.
Paleo-bathymetric sea floor reconstruction during the early opening of the South Atlantic.