Earth’s Great Oxidation: Redox and nutrient controls on the transition to a permanently oxygenated atmosphere

Earth’s Great Oxidation: Redox and nutrient controls on the transition to a permanently oxygenated atmosphere

Quick Decision

Strong but verify fit. This is a well-defined early-Earth biogeochemistry project for applicants who want to combine marine-shale geochemistry with quantitative Earth-system interpretation. The advertised work targets the poorly constrained final ~150 million years of the Great Oxidation Event (GOE), including the Lomagundi carbon-isotope excursion, and links ocean redox and nutrient availability to oxygenation. Leeds names Simon Poulton as primary supervisor and Benjamin Mills as academic supervisor; their recent work overlaps phosphorus cycling, redox reconstruction and modelling. YES-DTN advertises a 3.5-year stipend and tuition award, with international applicants eligible in principle but limited to up to 30% of full awards. Check the application portal now: official pages disagree whether applications opened on 2 or 12 November 2026. They agree on a deadline of 13:00 GMT, 12 January 2027. Exact sample sets, isotope platforms, model, fieldwork and the external partner’s role remain unconfirmed.

Research Problem and Doctoral Work

What Is Unsolved and Why It Matters

The project starts from a specific gap: oxygenation during the GOE was not one smooth event. It spanned hundreds of millions of years, with oxygen rising and falling, and the final interval through the Lomagundi excursion remains poorly constrained. The project asks what controlled ocean redox and nutrient cycling during that interval, whether changing phosphorus and trace-metal availability helped drive the excursion, how high oxygen rose, and whether those levels persisted. These questions matter because nutrient supply and recycling affect productivity, organic-carbon burial and oxygen release. The official project description frames phosphorus bioavailability and trace-metal cycling within both water-column redox and sediment diagenesis, rather than treating a single sediment proxy as a direct measure of atmospheric oxygen. Official project description

Work, Methods, and Potential Outputs

The advertised research object is marine shale deposited during approximately the final 150 million years of the GOE/Lomagundi interval. The project proposes to examine phosphorus speciation in those shales while reconstructing redox conditions of the overlying water and the sediment during diagenesis. Named methods include C-S-Fe systematics, phosphorus speciation, trace-metal analyses, advanced isotope techniques and global-scale biogeochemical modelling. Existing low-grade metamorphic, unweathered sample collections are available from South Africa, Botswana, Brazil and North America; further field sampling may be added. The stated goals include testing nutrient-availability and oxygenation hypotheses and using models to scale local geochemical observations toward global explanations. The page does not give sample formations or counts, identify each isotope system or model, or promise a field campaign. Project methods and scope

This mix of proxies is valuable because iron, sulphur, carbon, phosphorus and trace metals can constrain different parts of the redox and nutrient system. The challenge is that each proxy records local chemical and depositional processes; diagenesis, preservation and model boundary conditions affect how confidently local records can be extended to the global ocean or atmosphere. A useful thesis could test competing nutrient-recycling explanations by comparing records and model scenarios, but the project description does not specify a preferred hypothesis or guarantee a particular result.

School, Programme and Field Context

The University of Leeds is the named host and degree-awarding institution. Its Geochemistry PhD research area describes work across sedimentary geochemistry, phosphorus/iron/sulphur cycles, oxygenation proxies, laboratory and field research, and modelling. The Cohen Geochemistry Laboratory page lists facilities and analytical capabilities relevant to sediment extracts, Fe/P/S speciation, stable isotopes and trace-element analysis; this is local capacity, not confirmation that every technique will be assigned to this student. Leeds Geochemistry PhD area · Cohen Geochemistry Laboratory

The School reported that 96% of its REF 2021 UoA 7 Earth Systems and Environmental Sciences activity was world-leading or internationally excellent, with separate reported shares of 95% for outputs and 94% for impact. This is a useful but dated research-quality signal; it is not a current subject league-table position, a teaching rating or a project-level supervision outcome. I did not verify a current Earth Science subject ranking. Leeds School REF 2021 outcome

The project page identifies Andrey Bekker at the University of California, Riverside as a project partner and describes training across Leeds and UCR. It also explicitly marks the project “CASE: No” and “Collaborative Project: No.” Treat UCR as a named research contact/network unless the supervisors confirm a concrete visit, placement or work package; there is no evidence of a joint or double degree. Project team and training · UCR Earth and Planetary Sciences faculty

Leeds says a full-time PhD normally takes three years, while YES-DTN provides a 3.5-year award for this competition. Ask how the funded period aligns with registration, submission and writing-up. The official YES-DTN training page describes postgraduate research training; the project-specific plan and balance between research, fieldwork and cohort training should be confirmed. Leeds research-degree types and duration · YES-DTN research training

Supervisor and Lab Assessment

Supervisor Research Directions

Simon Poulton’s Leeds profile describes research in biogeochemistry and Earth history, with geochemical and isotope approaches to redox conditions and nutrient availability. Benjamin Mills works on Earth-system evolution and numerical biogeochemical modelling and leads the Earth Evolution Modelling group, which maintains the SCION model. This makes the listed supervision intellectually complementary: sedimentary and proxy geochemistry on one side, long-term Earth-system model synthesis on the other. Exact day-to-day supervision allocation is not public. Simon Poulton profile · Benjamin Mills profile · SCION model code and documentation

Recent Important Publications

• Alcott et al. (2026), “A nutrient control on oxygenation dynamics during Earth’s Great Oxidation Episode.” This study combines phosphorus-phase partitioning, redox proxies and C-O-P-S modelling of South African core material to argue that phosphate recycling and redox/sulphur cycling help explain oxygenation variability. It is a close precedent for the advertised P-speciation and modelling combination, but the PhD is not guaranteed to use the same core or model, and interpretations depend on proxy preservation and model assumptions. Nature Communications paper
• Dodd et al. (2025), “Marine phosphorus and atmospheric oxygen were coupled during the Great Oxidation Event.” The paper uses a carbonate-associated phosphate proxy across multiple records and modelling to support covariation between phosphorus availability/productivity and atmospheric oxygen. It provides a direct comparison for a shale-based project, but coupling does not prove phosphorus was the sole driver. A 2026 correction replaced an incorrectly dated fossil illustration; the journal says this did not alter data or conclusions. Nature Communications paper · Author correction
• Zhao, Mills, Poulton et al. (2024), “Drivers of the global phosphorus cycle over geological time.” This review synthesizes how weathering, nutrient supply, burial and redox-dependent recycling shape long-term phosphorus cycling. It provides a framework for distinguishing the project’s competing supply and recycling mechanisms; it does not resolve the Lomagundi record. Nature Reviews Earth & Environment review
• Song, Bowyer, Mills, Poulton et al. (2023), “Dynamic redox and nutrient cycling response to climate forcing in the Mesoproterozoic ocean.” The study combines iron speciation, trace elements, sulphur isotopes, weathering indicators, phosphorus partitioning and modelling. It demonstrates a multiproxy approach within the supervisory network, although its Mesoproterozoic interval differs from the GOE. Nature Communications paper
• Alcott, Mills, Bekker and Poulton (2022), “Earth’s Great Oxidation Event facilitated by the rise of sedimentary phosphorus recycling.” This paper proposes that rising sedimentary phosphorus recycling helped facilitate GOE oxygenation. It is a direct hypothesis antecedent; the new project’s later interval can test how such mechanisms behaved through the Lomagundi excursion and its termination. Nature Geoscience paper
• Mills et al. (2025), “Exploring Neoproterozoic climate and biogeochemical evolution in the SCION model.” This work applies SCION to a later interval and reports broad pattern reproduction while leaving major climate and oxygenation transitions unresolved. It illustrates model capability and limits, and is a reason to ask how this PhD will choose, calibrate and constrain a model. It does not establish that SCION will be used here. Global and Planetary Change paper

Lab, Resources, and Collaboration Environment

Leeds’s Cohen Geochemistry Laboratory and SCION documentation suggest local capacity relevant to the advertised laboratory/model combination. The project page says samples are already available and that field sampling may be added. Confirm which instruments and protocols are accessible, whether the named model will be used, how much training is provided, and whether the student is expected to collect additional material. The external partner listing is useful evidence of a research connection, but the explicit non-collaborative flag means a formal placement or regular UCR visit should not be assumed.

Funding, Application, and Living Cost

YES-DTN advertises a 3.5-year stipend at Research Council rates, tuition fees and generous research, fieldwork, training and conference support. Its FAQ says the full award covers tuition including the home/international difference and that up to 30% of full awards can go to international applicants. It does not cover relocation, visa fees, immigration health surcharge or travel to the UK. The optional 3.75-year route depends on a three-month industry placement; this project is marked non-CASE and non-collaborative, so do not assume that extension applies. YES-DTN studentship and date page · Funding and eligibility FAQ

Opening-date conflict: the Join Us overview says applications opened at 10:00 on 2 November 2026, while the detailed How To Apply page and 2027 roster say 12 November 2026. As checked on 5 November, one official page implies the window should already be open and two say it is still pending. Verify directly whether the forms are currently live and whether this project remains selectable. All sources agree on the deadline: 13:00 GMT, 12 January 2027. The detailed application instructions require both a Leeds online application and a YES-DTN form; the Leeds student ID can take over 24 hours to arrive, so do not leave the first form until the deadline day. Detailed application steps · 2027 project roster and schedule

For scale only, UKRI’s 2026/27 minimum stipend is £21,805 a year; the 2027/28 rate has not yet been confirmed. Leeds estimates 2026/27 living costs for a single student over 52 weeks at an average £16,640 (low £8,890; high £24,230). The simple average-budget remainder against today’s stipend comparator is about £5,165 before visa/IHS, international travel, relocation, setup costs, any home-country tax and future rate changes. This is not a personal budget or a guaranteed 2027/28 award calculation. Leeds’s published 2027/28 international research fee comparator for this subject area is £33,000 per year; the DTP says tuition is covered, while the home fee and any project bench fees should be confirmed. UKRI studentship rates · Leeds living-cost guidance · Leeds PGR fee schedule

Applicant Fit and Preparation

Required Background and Skills

The project page names Earth sciences, geochemistry, geology, environmental science and Earth-system science among relevant degree areas. Leeds requires a related 2:1 or a good relevant master’s for this research area; the DTP says a first-class degree is usually competitive. DTP guidance emphasizes relevant skills over an exact prior topic and says publications are not required. English-language evidence must be in place before registration, and formal qualification equivalency should be checked directly. Relevant project degrees · YES-DTN FAQ · Leeds entry requirements

Preferred Experience and Suggested Preparation

The opportunity does not publish an individual scoring rubric. An applicant can strengthen their case by showing careful laboratory practice, sample handling/QA-QC, geochemical data interpretation, quantitative or coding experience, and the ability to explain how proxy evidence supports or limits a larger environmental inference. These are analyst-suggested ways to evidence readiness, not extra official requirements. Prepare a concise explanation of how phosphorus availability, redox and oxygenation may interact, and where proxy-based inference is uncertain. Check the candidate resources for interview format and selection details. YES-DTN candidate resources

Next Actions and Questions to Verify

Before Applying

1. Ask YES-DTN whether the application forms are live and whether YES-27-D-20 remains selectable; reconcile the 2 November/12 November schedule discrepancy.
2. Confirm the 2027/28 stipend, home/international fee coverage, bench fees and which visa, IHS, relocation or travel costs remain uncovered.
3. Check formal qualification equivalency and English-language evidence requirements for your country and degree history.
4. Follow the two-form process and apply early enough to receive the Leeds SID before submitting the YES-DTN form.

At Interview

1. Which formations and sample sections are core, and what are the collection sizes, provenance and preservation limitations?
2. Which isotope systems, trace-metal protocols, phosphorus-speciation methods and instruments are expected, and what training/access is available?
3. Which model will the student use—SCION, COPSE, another model or a new implementation—and what quantitative/programming preparation is expected?
4. How is supervision divided between Poulton and Mills? What practical training, visit or task is planned with Andrey Bekker/UCR despite the non-collaborative project flag?
5. How much work is planned in the laboratory, modelling and field, and what field locations, timing and expenses are anticipated?

Before Accepting an Offer

1. Do the 3.5 funded years align with Leeds registration, submission and writing-up dates? What happens if the thesis is not submitted by the end of funding?
2. What is the annual project research/fieldwork budget, how are bench fees and sample access handled, and what conference support is available?

Evidence and Sources

Core Institutional and Programme Sources

• YES-27-D-20: Earth’s Great Oxidation
• YES-DTN 2027 studentship roster and schedule
• Geochemistry PhD research area at Leeds
• Cohen Geochemistry Laboratory
• University of California, Riverside Earth & Planetary Sciences faculty
• University of Leeds research-degree types and duration
• Leeds School REF 2021 outcome
• University of Leeds contact and address

Supervisor and Publication Sources

• Professor Simon Poulton profile
• Professor Benjamin J. W. Mills profile
• Earth Evolution Modelling: SCION and related model code
• Author Correction: Marine phosphorus and atmospheric oxygen were coupled during the Great Oxidation Event
• A nutrient control on oxygenation dynamics during Earth’s Great Oxidation Episode
• Marine phosphorus and atmospheric oxygen were coupled during the Great Oxidation Event
• Drivers of the global phosphorus cycle over geological time
• Dynamic redox and nutrient cycling response to climate forcing in the Mesoproterozoic ocean
• Earth’s Great Oxidation Event facilitated by the rise of sedimentary phosphorus recycling
• Exploring Neoproterozoic climate and biogeochemical evolution in the SCION model

Training, Funding, Application, Cost And Market Sources

• Join us: studentship award and application dates
• How To Apply: 2027 application steps
• FAQ: funding, eligibility, selection and interviews
• Candidate resources and interview format
• Research training for postgraduate researchers
• Earth, Environment and Sustainability PhD entry requirements
• Geological Society of London: careers in geology
• Leeds research-degree fees: 2027/28
• UKRI studentship guidance: current stipend and fee rate
• Leeds living costs and budgeting: 2026/27