The title of my PhD is 'The Timing and Controls of Structural Inversion in the NE Atlantic Margin'. I started my PhD project in September, 2005 and I am sponsored by the ORSAS (Overseas Research Studentship Award Scheme), the School of Geosciences, University of Edinburgh and the British Geological Survey. My supervisors are Prof. John Underhill and Dr. Roger Scrutton of the University of Edinburgh and Derek Ritchie, Howard Johnson and Ken Hitchen of the British Geological Survey.
Continental margins were once considered passive in nature. However, seismic data across the Rockall-Faroe area, in the NE Atlantic Margin, has revealed the presence of numerous compression-related Cenozoic folds, such as the Hatton Bank, Lousy Bank, Alpin and Wyville Thomson Ridge anticlines, suggesting that active deformation is often pervasive along such margins. The presence, timing and nature of compressional structures have provided new insights into the controls and effects of contractional deformation in the region.
The Rockall-Faroe study area is located withing the NE Atlantic volcanic continental margin between the UK and Iceland. Use has been made of 40,000 km of 2-D seismic data (line-length) acquired over the past twenty years extending from the Rockall Plateau to the Faroe Shelf. Seismic data has been provided by BGS, Fugro, Veritas and GEUS. Seismic images have been crucial to the mapping of folds and unconformities which define compression. Unconformities have been dated, using well data, to constrain the ages of compressional structures. The ages of folding are compared to regional events to establish possible driving mechanisms for compression. Potential driving mechanisms affecting the NE Atlantic Margin include hotspot-influenced ridge push, and stresses from the Alpine and Pyrenean orogenies.
New Seismic Data
In May-June, 2006 I had the opportunity, as part of my study, to participate in a seismic acquisition cruise in order to collect new seismic data over my study area. Seismic lines were selected by myself and my supervisors to image areas which lacked seismic data, viz. the Lousy, Bill Bailey's and Faroe Banks. Seismic acquisition was aboard the RRS Charles Darwin.
In this study, BGS gravity data has been used to contruct gravity models (using the software, GravMag) to discern the potential underlying structures of folds not imaged on seismic data. This was essential to determine the role of underlying basin morphologies in controlling the orienation of compressional structures.
SAVFEMTM (Structural Analysis Via Finite-Element Methodology) (Applied Mechanics Inc.) was used to build a model to determine the forces required for the inversion of a basin. The model consists of a sediment-filled graben (bounded by normal faults), basement rock (upper crust), lower crust and lithosphere. The software allows properties to be assigned to elements or grids and simulates their behaviour under compressed. The modelling results of the inversion of a basin suggests that the observed amplitudes of structures are not solely the result of the reversal of normal fault movement but were most likely achieved by the flexural folding of sediment.
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