2024-BGS1 Reconstructing palaeo-Atlantic circulation from oceanic ferromanganese crusts at unprecedented resolution

Project highlights

Development of new dating methods for deep-sea ferromanganese oxide matrices
Paleoceanographic reconstruction of the equatorial Atlantic Ocean through Pb-Nd isotopic analysis
Exploration of climate and oceanographic interaction on formation, alteration, and preservation of ferromanganese mineral deposits

Overview

Constraining changes in the flow of the North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) currents is paramount to understanding past climate and oceanographic changes to inform future climate susceptibility. The evolution of these two water-masses remains poorly constrained in equatorial settings, despite distributing heat and nutrients globally. This project proposes to reconstruct these currents by using geochemical properties of oceanic ferromanganese (Fe-Mn) crusts. These Fe-Mn crusts form by the accumulation of Fe and Mn oxyhydroxides precipitated from ambient seawater on any indurated substrate of the ocean floor. As one of the slowest processes on Earth (a few mm/Ma) and given the high reactivity of these colloids, Fe-Mn oxides efficiently scavenge and accumulates trace metals from seawater over millions of years. Fe-Mn crusts are thus considered as reliable archives of the distribution and changes in oceanographic currents throughout the Cenozoic. The composition of Fe-Mn crusts is influenced by evolving continental weathering rates through changes in climate, oceanic gateways, and latitudinal oceanography, yet remains poorly constrained and understood.

This project uses unique samples from the Sierra Leone Rise in the equatorial eastern Atlantic Ocean (Study Area, Figure 1), aiming to produce a harmonised temporal framework of isotopic and compositional records of Fe-Mn crusts. These ultra-high-resolution records form the foundation of reconstructing the provenance, distribution, intensity, and interaction of ocean water masses in this region over the Cenozoic and also to characterise the influence of the African continent on the composition of deep-sea minerals.

With samples distributed within a 2000-5200 m depth range, this set is ideally located to characterise both intermediate and deep-water properties through the major climatic, tectonic, and oceanographic changes of the Cenozoic, something which cannot always be achieved with deep-sea sediment cores. The project aims at integrating the equatorial Atlantic basin tectonic evolution with climate change to produce a high-resolution long-term paleoceanographic record of NADW and AABW. Some samples ideally located close to the Vema equatorial fracture zone complement the set to characterise exchanges of deep-water current between the western and eastern equatorial basins.

Figure 1: Modern oceanographic circulation in the Atlantic Ocean showing the main intermediate and deep-water masses with the study site indicated (yellow star): (modified from Josso et al., 2020)

Host

British Geological Survey

Theme

Climate and Environmental Sustainability
Dynamic Earth

Supervisors

Project investigator

Dr. Pierre Josso (BGS) [email protected]

Co-investigators

Dr. Tim van Peer (University of Leicester) [email protected]
Dr. Matthew Horstwood (BGS) [email protected]
Prof. Jens Zinke (University of Leiceste) [email protected]
Dr. Hannah Grant (BGS) [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

This research will use existing data complemented by the latest developments in high-resolution laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to establish the temporal framework of the samples focusing on lead (Pb) isotopes stratigraphic correlation (Josso et al., 2020). Age modelling will be developed through multi-proxy modelling including Osmium (Os) and Beryllium (Be) isotopes, and Pb cyclostratigraphy (Josso et al., 2019, 2021). Comparative analysis of these methods with the less robust, but widely employed Cobalt Chronometer will provide a critical review of dating methods.

Paleoceanographic reconstructions will rely on a combined approach of isotopic data using Pb and Neodymium (Nd) isotopes analysis, and geochemical and mineralogical data obtained by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ICP-MS measurements.

Data analysis, processing, and modelling will be done through R and MATLAB. This will notably involve Bayesian statistical techniques and advanced time series analysis with tuning to astronomical solutions.

Training and skills

Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2-provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.

Laser-ablation MC-ICP-MS analysis, clean laboratory procedures, chromatographic separation. Geochemical data quality assessment and quality check. Uncertainty in isotope and geochemistry analysis. Scanning electron Microscopy (SEM).

Paper-writing skills. Paper and proposal writing skills, oral presentation at conferences and public engagement combining both education and outreach activities.

Advanced data management and visualisation in R or Matlab. Statistical and data analysis in R or Matlab. Python and Quarto analysis such as Bayesian Regression modelling. Geochronology

Further details

Further details on how to contact the supervisor for this project and how to apply for this project can be found here:

For any enquiries related to this project please contact Dr. Pierre Josso, [email protected].

The successful applicant would be registered at the University of Leicester and will need to apply via the University of Leicester application portal.

To apply to this project:

You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2024.
You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.
The project is hosted by the British Geological Survey, but the student will need to register at the partner university. Please submit your application and complete the University of Leicester application process via: https://le.ac.uk/study/research-degrees/funded-opportunities/centa-phd-studentships. Please scroll to the bottom of the page carefully read through the ‘How to Apply’ section before selecting the “Apply for NERC CENTA Studentship” button. Your CV can uploaded to the Experience section of the online form, the CENTA application form 2024 can be uploaded to the Personal Statement section of the online form. Please quote CENTA 2024-BGS1-CENTA2-SGGE9-JOSS when completing the application form.

Applications must be submitted by 23:59 GMT on Wednesday 10th January 2024.

Possible timeline

Year 1

Literature review for familiarisation with topics of deep-sea mineral deposits, oceanographic studies, age modelling and isotope systems. Familiarisation with samples and existing dataset. Development of NEIF proposal for acquisition of Pb and Be isotope data at SUERC, Glasgow and BGS. Training to work in clean lab environments. Ultra-high resolution Pb isotope data acquisition and development of sample correlated stratigraphy. Training on R, Matlab, Python, and time series analysis. Training on SEM and methodology development for acquisition and extraction of quantitative datasets. Active participation in public engagement.

Year 2

SEM dataset acquisition. Comparative age modelling study on Os, Be, Pb cyclostratigraphy and Co-Chronometry. Acquisition of Nd isotope, bulk geochemical and mineralogical data on Sierra Leone Rise samples. Preparation of manuscript(s) and dissemination of results at conference(s). Active participation in public engagement.

Year 3

Paleoceanographic reconstruction of water-mases interactions over the Cenozoic in equatorial Atlantic setting. Characterisation of evolving detrital input from Africa desertification and its impact on the geochemistry and mineralogic textures of deep-sea deposits. Preparation of manuscript(s) and dissemination of results at conference(s). Active participation in public engagement.