Investigating the North America/South America plate boundary with marine geophysical data

Project Rationale:

Continental plates are well-known to deform over broad areas but oceanic plates are often thought of as rigid blocks with narrow boundaries. However there is increasing evidence for broader-scale deformation within oceanic plates. One example is within the central western Atlantic, where there is a diffuse boundary between the North American and South American plates. Some of the relative motion is expressed in changes in the trends of Atlantic fracture zones, but some of the motion is taken up by individual areas of shortening that has formed elevated ridges on the seafloor in the central Atlantic, such as Barracuda Ridge and Tiburon Rise. This project will aim to constrain the timing and amount of shortening that has occurred, and how it is accommodated. Potentially the ridges represent overthrusting of the oceanic crust, and thus the initiation of a new subduction zone. The ridges are also partly subducted beneath the existing Antilles subduction zone, changing regional sediment transport from south to north and possibly controlling the size and location of major earthquakes.

Methodology:

The student will use high-quality multichannel seismic reflection data and high-resolution sub-bottom profiler data collected in 2017 to study the timing of uplift of the ridges, and evidence at the seabed for present-day deformation. He/she will also use seismic refraction data together with gravity and magnetic data to investigate the deeper structure of Barracuda Ridge. The student will process the seismic reflection data in ProMAX, and complete a stratigraphic interpretation in Petrel linking to other published data and ODP core sites to provide timing. The seismic reflection data will be used to provide evidence for shortening from faulting and sedimentary package structure, and measure this shortening as a constraint on the relative plate motion. The deep structure of the ridges will be investigated by constructing density models constrained by the seismic reflection data and coincident seismic refraction velocity models to investigate how the crustal thickness varies, and thus how the elevation of the ridge is supported, giving additional information on regional shortening. The student will combine these results with regional gravity and magnetic anomalies, and plate kinematic models, to generate an updated framework for western central Atlantic tectonics, and compare this with present-day deformation in the shallow sediments.

Training:

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at Southampton.

Specific training will include:
Seismic reflection processing using ProMAX software
Seismic interpretation and use of Petrel interpretation package
Quantitative interpretation of gravity and magnetic anomalies
Scripting and use of GMT and ArcGIS for geographical data processing and manipulation
Programming in relevant languages such as Python

The student will join a highly active group of marine geophysicists and will have opportunities to participate in crustal-scale seismic data acquisition at sea.