The breakup of continents to form ocean basins is a first order tectonic process. Key discussions centre on the mechanism for hyper-extension of the crust, thinning it from ~ 30 km to zero, the role of detachment faulting and mantle serpentinization in mantle unroofing, and the symmetry/asymmetry throughout the rifting process. Studies at rifted margins such as Galicia (west of Spain) see the final result on one side of the ocean and so cannot address these crucial questions, but studies across V-shaped rifts (e.g. Porcupine Basin) can address the effect of increasing extension by using different sections across the basin to reveal the structure at different stages in the rifting process, in effect using the spatial variation as a proxy for temporal evolution, and studies across narrow failed oceans (Rockall Trough) can address the asymmetry of final breakup, as both sides of the “ocean” are still geographically close and imaged by the same seismic surveys.
The project will build on previous work on the crustal structure of the Porcupine Basin (using older reflection and refraction data: Reston et al., 2004; Prada et al., 2018), and on the tectonic evolution of the Galicia margin as revealed by an NSF-NERC funded 3D seismic volume (Lymer et al., 2019) by comparing the Galicia rifted margin west of Spain to the failed rifts of the Porcupine Basin and Rockall Trough (both west of Ireland), both of which have been extended to crustal separation and likely mantle unroofing without forming a fully-fledged ocean basin. Both Porcupine and Rockall are covered by extensive recent 2D seismic survey kindly donated for this study by the Irish Petroleum Affairs Division. Preliminary work has focused on the postrift section but has shown that the data is of excellent quality, with clear image of faulting and of crustal structure.
The study of rifting to breakup has strong connections to ongoing work at the Galicia margin, where the NSF-NERC 3D volume (at Birmingham) underpinned the Birmingham-led IODP Proposal 943-Full (Reston et al., 2018), which is currently awaiting scheduling.
CENTA studentships are for 3.5 years and are funded by the Natural Environment Research Council (NERC). In addition to the full payment of their tuition fees, successful candidates will receive the following financial support.
• Annual stipend, set at £15,009 for 2019/20
• Research training support grant (RTSG) of £8,000
Lymer, G., Cresswell, D., Reston, TJ., Bull, JM, Sawyer, DS, Morgan, JK, Stevenson, C, Causer, A., Minshull, TA, Shillington, DJ, 2019. The development of detachment faulting and asymmetry during 3D continental breakup. Earth Planetary Science Letters, v 515, p 90-99
McDermott, K, Reston TJ, 2015. To see, or not to see? Rifted margin extension. Geology, 43, 967–970
Prada M, Watremez L, O’Reilly B, Minshull TA, Chen C, Reston TJ, Shannon P, Klaeschen D, Wagner G, Gaw V, 2017. Crustal strain-dependent serpentinisation in the Porcupine Basin, offshore Ireland. Earth and Planetary Science Letters, 474, 148-159
Reston, TJ, Gaw, V, Pennell, J, Klaeschen, D, Stubenrauch, A, Walker, I, Extreme crustal thinning in the south Porcupine Basin and the nature of the Porcupine Median High: Implications for the formation of non-volcanic rifted margins. J Geol Soc London, 161, 783-798, 2004
Reston TJ et al., 2018. The case for scientific drilling west of Galicia, Spain. IODP Proposal 943-Full.