• Researcher: Nahin Rezwan
• Host institution: Imperial College
• Supervisor: Alex Whittaker

Objectives:

The sedimentary archive is the only physical record we have of mass transfer across the Earth’s surface in response to tectonic or climatic boundary conditions. The fluxes and grain size characteristics of this sediment ‘cascade’ are therefore crucial observables for understanding the sensitivity of sediment routing systems to perturbation over a range of temporal and spatial scales. The objective of ESR8 is to improve our understanding of how fluvial grain size distributions record the climatic and tectonic signals using self-similarity models and well-calibrated field examples. The researcher will:

• improve existing self-similarity models of gravel grain size fining in fluvial systems by implementing sand-fraction fining
• drive the models with field calibrated estimates of hillslope input grain size distributions
• evaluate the sensitivity of grain size fining predictions to changing supply and tributary inputs for a range of sediment accommodation generation scenarios and
• compare model outputs to field/sub-surface examples of grain size fining, where boundary conditions are independently constrained.

 

The student will gain experience of numerical modelling of grain size, field sedimentology and techniques for measuring sediment calibre and GIS techniques.

 

Expected Results:

• An improved self-similarity model of grain size fining for sand and gravel fractions;
• New constraints on the extent to which the sediment cascade in source to sink systems is sensitive to short-term sediment supply variations for a range of accommodation generation scenarios and
• Calibration examples of the model with data in which sediment supply and tectonics are independently constrained.

 

The model outputs will also link with WP4 on modelling process and response in source to sink systems.

 

Secondments:

• Université de Genève (S. Castelltort) - Comparison with known grain size data and sediment input (2 months)
• EQUINOR (T. Somme) - Comparison with subsurface data (2 months)
• GFZ – Helmholtz Centre Potsdam (J. Braun) - Integration of numerical experiments of S2S perturbations, link with WP4 (same timing as ESR 9 for cross-collaboration) (2 months)