IAP-26-097

A Comparative Investigation of Strain Localisation, Deformation and Remobilisation in Biogenic and Fine-Grained Marine Sediments.

The deep-sea floor accounts for more than 60% of the Earth’s surface and is dominated by biogenic and fine-grained sediments, including calcareous sediments, siliceous oozes and clay-rich deposits (Diesing, 2020). Recent assessments of global burial fluxes indicate that deep-marine sediments experience far more variable accumulation and preservation histories than previously recognised, reflecting the combined influences of productivity, sediment focusing, bottom-current reworking and preservation (Hayes et al., 2021). This variability is likely to influence rates of compaction, pore-fluid expulsion, diagenesis and strain localisation during burial. In these environments, conventional models of sediment behaviour developed from more rapidly deposited continental-margin successions may not always be applicable. During early burial, deep-marine sediments occupy a transitional state between deposition and lithification, behaving as partially consolidated materials whose evolution is governed by compaction, deformation, fluid migration and early diagenetic processes.

Over the past 25 years, seismic reflection imaging has revealed a remarkable diversity of deformation and remobilisation structures within these shallowly buried sedimentary successions. These include folds, faults, polygonal fault systems, remobilised sediment bodies, fluid-escape structures, furrows and other forms of strain localisation (see Huuse et al., 2010 for a review). Such features have been documented across a wide range of sedimentary basins and lithologies, including carbonate and siliceous oozes, chalks and fine-grained marine sediments. The unusual physical, mechanical and diagenetic characteristics of carbonate and siliceous oozes may drive distinctive styles of strain localisation and remobilisation during burial.

Existing work indicates that apparently weak, unlithified sediments can accommodate significant deformation. For example, large-scale folding and thrusting have been documented within biosiliceous sediments offshore Norway, highlighting the capacity of highly porous sediments to develop organised deformation structures prior to lithification (Ireland et al., 2011). Other studies have linked deformation in fine-grained sediments to burial-related processes including compaction, fluid migration and diagenetic evolution, suggesting that many structures traditionally considered as separate phenomena may instead represent different responses to common subsurface processes (Davies et al., 2009). More recently, kilometre-scale mounds and associated sink structures formed through buoyancy-driven stratigraphic inversion have demonstrated that substantial post-depositional deformation can arise from contrasts in sediment properties and density, even in the absence of significant tectonic forcing (Rudjord & House, 2025). Together with the widespread occurrence of polygonal fault systems, remobilised sediment bodies and fluid-expulsion structures, these observations raise fundamental questions regarding how sediments accommodate strain during burial and what the common mechanisms are across the diversity of structures observed.

This project will investigate the question: Why do partially consolidated marine sediments develop such diverse styles of strain localisation, deformation and remobilisation during burial?
Using a comparative approach, the research will examine examples from biogenic and fine-grained marine sedimentary systems, including carbonate-rich and siliceous successions alongside more conventional fine-grained sediments. The project will integrate seismic interpretation, sedimentological observations, physical property data and published geomechanical constraints to evaluate how sediment composition, burial history, fluid migration and diagenetic evolution influence deformation style.

The research will develop a process-based understanding of sediment behaviour during the transition from deposition to lithification. By comparing contrasting sediment types and geological settings, the project will assess whether common mechanisms underpin apparently diverse structures and determine whether biogenic sediments exhibit characteristic modes of strain localisation and remobilisation. The outcomes will provide new insights into sediment deformation during burial and contribute to broader understanding of basin evolution, fluid flow, geohazards and the evolution of the shallow subsurface.

The project will combine seismic interpretation, sedimentological analysis and burial-history reconstruction to investigate the development of strain localisation, deformation and remobilisation structures within biogenic and fine-grained marine sediments.

A range of case studies will be selected from contrasting geological settings and utilise extensive existing 2D and 3D seismic reflection datasets. These data will be used to identify and characterise deformation structures, including faults, folds, remobilised sediment bodies, fluid-expulsion structures and other manifestations of strain localisation. Structural analysis will be undertaken to quantify the geometry, spatial distribution and evolution of deformation features and to compare deformation styles between different sediment types.

Seismic observations will be integrated with sedimentological and petrophysical data with an emphasis on understanding how sediment composition, porosity, grain fabric and diagenetic evolution influence deformation behaviour.

Burial-history analysis will be used to reconstruct depositional, burial and diagenetic histories for selected case studies. This will allow assessment of how sediment accumulation rates, compaction, fluid migration and evolving material properties influence the timing and style of deformation. Comparisons between contrasting sedimentary systems will be used to identify common controls and evaluate whether apparently diverse structures arise from similar underlying processes.

The end goal is to develop a process-based framework for describing how partially consolidated marine sediments accommodate strain during burial and transition towards lithification.

Year 1

Complete a systematic review on deformation, strain localisation and remobilisation in shallowly burried marine sediments.
Undertake training in seismic interpretation, structural geology, sedimentology and petrophysical interpretation.
Compile a global database of deformation and remobilisation structures in biogenic and fine-grained marine sediments.
Identify and quality-check relevant 2D and 3D seismic datasets and supporting petrophysical and sedimentological data for case studies.

Year 2

Undertake detailed interpretation of selected 2D and 3D seismic datasets.
Characterise deformation styles, remobilisation features and strain localisation patterns within contrasting sedimentary systems.
Integrate available sedimentological, petrophysical and physical property datasets.
Undertake detailed structural and geometric analysis of deformation features.
Begin burial-history reconstruction and assessment of sediment accumulation, compaction and diagenetic evolution.
Submit first manuscript

Year 3

Complete comparative analysis of carbonate-rich, siliceous and fine-grained sedimentary systems.
Refine burial-history and process-based interpretations.
Develop a conceptual framework linking sediment properties, burial evolution and strain localisation.
Prepare additional publications.
Develop detailed thesis completion plan.

Year 3.5

Finalise process-based model for deformation and remobilisation in partially consolidated marine sediments.
Submit remaining journal manuscripts.
Complete thesis writing and submission.
Archive project data and outputs in appropriate NERC data repositories.

The student will receive interdisciplinary training spanning marine geophysics, sedimentology, structural geology and quantitative Earth science, including:

2D and 3D seismic reflection interpretation.
Seismic geomorphology and seismic attribute analysis.
Structural geological analysis and strain interpretation.
Marine sedimentology and deep-marine depositional systems.
Biogenic sediment systems, including carbonate and siliceous sediments.
Burial history reconstruction and basin analysis.
Petrophysical data interpretation and integration.
Geographic Information Systems (GIS) and spatial analysis.
Scientific programming and data analysis (e.g. Python).
Statistical methods and quantitative geological analysis.

The student will develop expertise in integrating geological, geophysical and petrophysical datasets to investigate the evolution of marine sediments between deposition and lithification.

Through participation in Iapetus training events, conferences and potential external placements, the student will also develop transferable skills.