Structural Inheritance in active and ancient extensional regimes

Structural inheritance is a characteristic of continental lithosphere deformation controlled by dynamic and long-term weakening of fault zones. Many extensional basins and continental margins show evidence for a strong influence by pre-existing structures and fabrics (structural inheritance) during their early phase that then declines as basin boundary faults grow and interact and rifting matures. How this reorganisation occurs, the controlling mechanism(s) and effects on basin fills and seismicity patterns in active regions is not well under understood and is the topic for this PhD research project.

Structural inheritance in sedimentary systems has been attributed to 1) direct reactivation of pre-existing faults and fabrics, 2) local perturbations of regional stress fields which causes faults to form or reactivate in non-optimal orientations, (transverse or - off-axial trend faults) and 3) segmentation and retardation of normal fault array growth either by basement blocks or magmatic sectors in basins.

The aim of this project is to investigate what controls the transition from inheritance-dominated to far-field stress-dominated deformation in extensional basins using a combined structural, geophysical and modelling approach. The specific focus will be on examples that represent systems in the structural reorganisation phase or where the axis-parallel faults and off-axis basement-influenced structures are superimposed but remain visible. Candidate faults (with off-axis orientations) are located in the West Greenland, East Africa Rift in Tanzania, the Ordos rifts in NW China and the Italian Apennines, which form the main study areas, however these features are common to most margins and basins.

The study objectives are to:-
1. Constrain the nature of basement inheritance components in active extensional basins using geophysical, geodetic and field-observation derived datasets.
2. Build interpolations of syn-rift basin fills using available seismic reflection data to constrain the nature and timing of structural reorganisation processes.
3. Investigate the controls and seismic hazard implications from structural reorganisation at mantle lithosphere to crustal scales using numerical simulations.

The project will give the student an opportunity to gain skills in field-based structural geology, active tectonics, seismic interpretation and numerical modelling.