Overview

Project Highlights:

  • interpretation of state of the art regional seismic data and local 3D datasets
  • imaging both margins of mini-oceans, revealing the symmetry of rifting
  • comparison with Galicia (Spain), the site of Birmingham-proposed IODP drilling and a NSF/NERC 3D volume.

Overview

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 (Figure 1).  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. 

Map of the study area showing the Rockall and Porcupine Basins and the seismic coverage.  The project will mainly use the PAD data (orange), supplemented by selected lines from other datasets

Methodology

The project will focus on the interpretation and reconstruction of state-of-the-art 2D and 3D seismic data to reveal the tectonic evolution of these basins and by implication of mature rifted margins.  Software to use will include Kingdom Suite (interpretation), 3D Move (structural analysis and reconstruction), and Globe Claritas (selective reprocessing where necessary). The results will be integrated with the result of IODP drilling west of Galicia, likely to take place in 2022 at the end of the second year of the project.   Depending on other Birmingham participation in the cruise, the DR could apply to participate on the cruise.

Training and Skills

The student will take part in the seismic processing courses offered in conjunction with this project, will learn interpretation and reconstruction techniques (Kingdom and Move software) as well as courses in figure draughting, presentation skills, and suitable courses in other areas. 

Timeline

Year 1: Literature review. Initial inspection and interpretation of regional data defining areas for detailed study.   Identification of data for selective reprocessing; training in seismic processing.

Year 2: Focused interpretation and reconstruction using 3D MOVE, and selective reprocessing of data especially in the vicinity of industry drillsites to enhance well-seismic correlation.  Participation if possible in IODP drilling expedition.  Attendance at international conference.

Year 3+: Finalisation of the interpretation, incorporating structural restoration of the data.  Attendance at international conference. Publication of results and write-up.

Partners and collaboration (including CASE)

The Irish Petroleum Affairs Division (PAD), and Petroleum Infrastructure Programme (PIP).  PAD commissioned the data and have given us permission to work on it.  PIP is a consortium of industry partners exploring offshore Ireland that can both contribute data to this study and make use of results.

Rob Hardy (Tonnta, Dublin) has overseen the reprocessing of the data collected for PAD.

Proponents of IODP Proposal 943-Full (Galicia margin: Reston et al., 2018) from six countries and 15 different institutes.  The project will be running when Galicia is drilled, probably in summer 2022 and results will be integrated with those of drilling.

 

Further Details

Contact: Tim Reston, t.j.reston@bham.ac.uk