2025-BGS1 Palaeo-environmental characterization of Triassic–Jurassic lower strength sedimentary rocks, potential hosts for a geological disposal facility

Project highlights

Investigate the organic fraction of potential host rocks for one of the largest environmental projects ever undertaken in the UK: the construction of a deep geological disposal facility for nuclear waste.
Generate a unique, integrated organic geochemistry-palynological dataset to help understand changes during the Triassic–Jurassic recovery phase following the “Phytoplankton Blackout”.
Training in a scientific growth area aligned with the strategy of governmental and higher education institutes and consultancies offering excellent career opportunities.

Overview

This project evaluates the nature of organic matter in the Mercia Mudstone (Triassic), Ampthill Clay, Oxford Clay and Kimmeridge Clay formations (Jurassic). The PhD candidate will combine (1) palynofacies analysis, the study of organic matter utilising transmitted light microscopy and (2) organofacies analysis, organic chemistry at the bulk and molecular level. A same-sample methodology will allow the precise correlation of the palynofacies and organofacies analyses which will be processed in the R environment. The project aims to address two topical geoscience issues:

The study materials are classed as Lower Strength Sedimentary Rocks (LSSRs); the main candidate host rocks for a deep Geological Disposal Facility (GDF) for the storage of nuclear waste. The construction of a GDF is one of the largest environmental projects undertaken in the UK and will be a focal point of investments in the UK subsurface offering excellent career prospects for early career geoscientists (Turner, 2020). The safe underground storage of radioactive waste requires accurate and precise assessment of borehole sedimentary organic matter to determine amount, type, distribution and reactivity to inform the design of a GDF. By combining palynology (palynofacies analysis) and organic geochemistry (Rock-Eval, GC-MS) the PhD candidate will generate a unique, invaluable dataset through key geological formations.

Modern phytoplankton assemblages emerged in the Triassic and Jurassic in a Regeneration Phase following an enigmatic absence in the geological record, dubbed the “Phytoplankton Blackout” (Riegel, 2008). A change in the C₂₈/C₂₉ sterane ratio was recorded near the start of the Phytoplankton Blackout (Schwark and Empt, 2006), but accurate records for the Triassic and Jurassic, when dinoflagellate cysts start to diversify (MacRae et al., 1996; Wiggan et al., 2017) are currently lacking. Modern phytoplankton produce half of the global annual oxygen (e.g., Baumert and Petzoldt, 2008) and are responsible for half the carbon fixation in the carbon cycle (Field et al., 1998). Understanding their establishment in the oceans will advance understanding of their resilience in a changing climate.

Figure 1: General workflow envisaged for this project. A same-sample methodology will be used for palynological processing, GC-MS and Rock-Eval analysis. Results will be processed in the R environment and will establish the primary depositional environment of the studied Lower Strength Sedimentary Rocks (LSSRs). The characterisation of the organic matter in these Triassic–Jurassic is fundamental in informing the siting of a deep Geological Disposal Facility (GDF). Moreover, the time of deposition of the LSSRs is co-eval with the establishment of modern phytoplankton assemblages, which are currently responsible for half of the global oxygen production and carbon fixation.

Host

British Geological Survey

Theme

Climate and Environmental Sustainability

Supervisors

Project investigator

Jan Hennissen (BGS, [email protected])

Co-investigators

Christopher Vane (BGS, [email protected])
Tom Harvey (University of Leicester, [email protected])

How to apply

Each host has a slightly different application process.
Find out how to apply for this studentship.
All applications must include the CENTA application form.
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Methodology

Access boreholes proving LSSRs from the National Geological Repository; design sampling strategy. Borehole materials can be supplemented with outcrop materials. Approximately 300 samples (50–100g each).
Crush samples and utilise sample riffler to create representative sub-samples for organic geochemistry and palynology.
Palynologically prepare using the standard preparation protocol in the Biostratigraphy and Palaeontology Laboratories (BPL).
Run the samples on the Rock-Eval 6 in the Organic Geochemistry Laboratories to investigate the influence of organic matter Type mixing on Rock-Eval van Krevelen plots.
Microscopy of the palynological samples using transmitted light microscope equipped with an automated stage.
Assessment of caving (if present), drill fluids and evaluation of particle size on Rock-Eval chemistry and pyrograms.
Interrogate datasets including multivariate statistics and data visualisation in R.
Isolate n-alkanes to inform organic/biological source and obtain C₂₈/C₂₉ sterane ratios.
Contrast kerogen isolates and whole rock Rock-Eval data.

Training and skills

DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.

Palynological preparation protocol: (estimated 3 days = ~23 hours). Laboratory based training in preparing microscopy studies. Microscopy training (estimated 1 week = ~ 37 hours).
Palynofacies analysis: recognising organic components on a microscopic scale in the 10–250 µm fraction.
Statistics in the R environment (estimated 3 days): includes data visualization, integration of geochemical and palynological datasets and basic multivariate statistics.
Rock-Eval(6) pyrolysis: Training and maintenance (1 week = ~ 37 hours).
Molecular geochemistry: Training in measurement of selected compound classes using Gas Chromatograph–Mass Spectrometer (GC, GC-MS) (3 weeks = ~ 111 hours).

Further details

For any enquiries related to this project please contact Jan Hennissen (BGS, [email protected]).

The successful applicant would be registered at the University of Leicester. 

To apply to this project: 

You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2025.

You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.

Please submit your application and complete the host institution application process via: CENTA PhD Studentships | Postgraduate research | University of Leicester.  Please scroll to the bottom of the page and click on the “Apply Now” button.  The “How to apply” tab at the bottom of the page gives instructions on how to submit your completed CENTA Studentship Application Form 2025, your CV and your other supporting documents to your University of Leicester application. Please quote CENTA 2025-BGS1 when completing the application form.

  Applications must be submitted by 23:59 GMT on Wednesday 8th January 2025. 

Possible timeline

Year 1

Literature review: familiarisation with GDF development, the already available organic geochemical and palynological datasets. Chart knowledge gaps.
Sample selection: create overview of available core materials in National Geological Repository and outcrop sites. Sample (n = ~300) the LSSRs.
Palynological preparation: commence palynological preparation (n = 100 samples).
Geochemical analyses, Rock-Eval bulk rock core material (n=200 samples)
Year 1 Residential trip

Year 2

Finish palynological preparation.
Microscopy of ~300 samples
Rock-Eval optimisation and organic matter type mixing experiments (n=40 samples)
Molecular geochemical analyses (GC, GC/MS), concentrations and ratios

Year 3

Integrate geochemical and palynological data for visualization in R
Conduct statistical analysis in R
Write up