IAP2-23-054

Getting to the core of the Great Glen Fault

The Great Glen Fault (GGF), one of the largest strike-slip faults in N Europe, lies adjacent to the Coire Glas pump storage facility at Laggan, slated to commence electricity generation in 2031. The GGF divides the Northern and the Grampian Highlands. Glacial erosion has created a geomorphological legacy of deep lochs and hanging valleys which is ideal for hydroelectricity, a vital component towards NetZero targets. However, the presence of a major fault damage zone and core and the inherent heterogeneity of fault zones present important engineering challenges related to stability and safety of hydroelectric tunnels as they cross the GGF.

The direction and magnitude of motion on the GGF and associated structures over time is poorly constrained, fostering generations of debate. It originated as an orogen-parallel strike-slip fault during the Silurian-Devonian Caledonian Orogeny, associated with extensive plutonism. The fault system has been multiply reactivated since. Onshore, the fault displaces Archaean basement, Proterozoic metasedimentary rocks, Caledonian and post-Caledonian intrusions, and the Devonian to Jurassic sedimentary cover sequences.

Thanks to collaboration between Glasgow, Durham, the British Geological Survey (BGS) and Scottish and Southern Energy (SSE), you will work with rocks obtained from the Coire Glas exploratory tunnel, a generational opportunity to study fresh material from near the core of the GGF. Analysis of these previously inaccessible rocks will be combined with fresh interrogation of the Rosemarkie-Cromarty and Ardgour sections of the GGF. Your aim is to generate structural, compositional, geochemical, and geochronological datasets to address when and how the fault moved. You will thus tackle a long-standing mystery in Scottish geology, whilst your rock characterisations will inform rock mechanics studies of the Coire Glas site. The findings will also be of relevance to future offshore activities and any further hydroelectricity schemes in the Great Glen.

Coire Glas site visits will allow characterisation and sampling of the GGF’s core and damage zone, whilst extensive field studies at Rosemarkie-Cromarty and Ardgour will update mapping and generate new samples from the extent of the on-land exposure of the GGF.

Initial analysis at Glasgow, supported by the BGS and Durham, will include optical microscopy, X-ray diffraction, whole rock geochemistry and Scanning Electron Microscopy. Outcomes include the mineralogy of the GGF system to inform rock mechanics work, qualitative assessment of fluid-flow and the depth, direction, and relative timing of fault motion. Suitable samples for geochronological analysis will be identified at this stage. Absolute geochronology will depend on the material collected, but we anticipate a combination of the following: 1) K-Ar dating of illite from fault gouges, at the Scottish Universities Environmental Research Centre (SUERC), 2) U-Pb dating of calcite, at the BGS facilities in Nottingham, 3) U-Pb dating and trace element geochemistry of zircons from Coire Glas and other fault-bounded granitoid clasts, at Glasgow or SUERC, as well as investigation of the potential for 4) Re-Os dating of sulfides, at Durham. The first two methods will place absolute age constraints on fault motion, whilst the age and geochemistry of granitoid clasts will assess the provenance and transport of material in the fault zone by matching with similar datasets from nearby plutons such as Strontian, Abriachan, Linnhe and Clunes.

SSE will guarantee access and sampling at Coire Glas site, and they or on-site contractors may be open to internship opportunities in the duration of the project. The overall workflow will be staggered to enable you to complete packages of work associated with one site whilst also efficiently progressing specific samples for analyses with longer lead times, such as illite separation for irradiation and K-Ar dating. You will exchange knowledge with Dr Audrey Ougier-Simonin at the BGS in Nottingham throughout your work to establish the foundations for rock mechanics studies, especially on the Coire Glas site.

Year 1

Literature review.
Team and stakeholder familiarisation, Coire Glas visits.
Sample characterisation from Coire Glas.
Field study 1 (Ardgour or Rosemarkie-Cromarty).
Additional funding applications.

Year 2

Prepare Coire Glas samples for geochronology, K-Ar first (long lead time).
Field study 2.
Sample characterisation from Rosemarkie-Cromarty and Ardgour.
Prepare samples for U-Pb geochronology.
Local workshop or conference and ongoing stakeholder engagement until project end.

Year 3

Geochronology data collection.
Ongoing write-up and feedback.

Year 3.5

International workshop or conference and/or opportunity for a wrap-up “Great Glen Workshop”.
Compete write-up and feedback cycle.
Ongoing planning of future directions and career opportunities.

This project suits a hard rock geology candidate willing to combine field and laboratory approaches to geological problems. Ideally, you will have extensive field experience with deformed rocks, and if possible have had access to analytical facilities to generate geological data. You should be ambitious to be involved in one of Scotland’s largest infrastructure programmes of recent years, and the range of project and geological skills that you pick up will be much valued in industry or academia.

We will encourage training in structural analysis, geochronology, communication, and project management skills, some of which will be provided by NERC and IAPETUS courses. The University of Glasgow graduate researcher programme includes >20 days of training, seminars, and public engagement activity. We anticipate that there will be sustained academic and public interest in Coire Glas and the Great Glen which will give you experience of communicating across expert and non-expert audiences. There may be an opportunity to help develop a Great Glen Workshop to bring researchers together towards the end of the PhD.

Full training will be provided for laboratory techniques, with the goal of you being able to develop interests in specific techniques. There will also be opportunities to lead or assist with funding applications, for example to local geological societies or to NERC’s environmental isotope facility steering committee.

The enthusiastic supervisory team across academia and the BGS give you the opportunity to grow from our collective >7 decades of Scottish geology expertise, as well as global perspectives across micro- to plate-scale studies of geological evolution, fault mechanics, geochronology, and magmatism. You will join a tight-knit cohort of geology-focused postgraduate researchers in Glasgow, and we are expecting hiring additional MSc by Research students at Glasgow and Durham to build a larger Great Glen team and provide mentoring opportunities.