Overview

The exposure at the seafloor of broad expanses of mantle rocks at magma-poor rifted margins and ultraslow-spreading ridges (Reston, 2009; Reston and McDermott, 2011) and at slow-spreading ridges (Reston and Ranero, 2011) has challenged conventional views of rifting and seafloor spreading.  In each case, the mantle exposure appears to have been controlled by large-offset, deeply-rooted normal faults termed detachment faults.  Thus there is an apparent continuity of process from magma-poor rifting and the exposure of mantle when the crust has thinned to zero, the amagmatic spreading that occurs at some ultra-slow spreading ridges and the development of discrete “oceanic core complexes” at slow-spreading ridges. 

This project will use modern seismic data from a magma-poor rift (Porcupine Basin) where the symmetry of the process can be traced from continental rifting to incipient mantle unroofing along strike, 3D seismic data from the classic magma-poor margin (Galicia west of Spain where mantle unroofing was first recognised)and new seismic data across mantle exposures developed during slow seafloor spreading at the Mid-Atlantic Ridge at 13N. 

Top: Perspective view of the exhumed mantle represented by the striated slip surface surface at 13N (MacLeod et al., 2009), the target for the 2016 research cruise being led by Reston.  The project will compare such oceanic detachment faults with those found at magma poor rifted margins.

Methodology

The project will be based on the seismic interpretation of seismic reflection data.  Datasets include data collected by industry offshore Ireland, a large number of profiles across the magma poor margin west of Spain (including a bespoke 3D seismic reflection survey collected in 2013 by Rice, Lamont-Doherty, Birmingham (Reston) and others) and now fully processed, and data to be collected during a geophysical cruise (Jan-Feb 2016) to the Mid-Atlantic Ridge at 13°N.

Training and Skills

CENTA students will attend 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes. 

In addition to training in seismic interpretation and structural analysis, the successful candidate wil learn basic seismic processing, and should collaborate with a large group of scientists at Birmingham, Durham, Cardiff, Southampton, Paris Woods Hole and Rice (both USA), who are studying detachment faulting using a variety of data, from microearthquakes,  3D seismic, seafloor imagery, and wide-angle seismic, thus gaining experience in a wide variety of geophysical techniques. 

Timeline

Year 1: Background reading and initial interpretation of seismic profiles from the west of Ireland and of portions of the 3D volume west of Spain, focussing on mantle unroofing.  

Year 2: Continued seismic interpretation and comparison of rifted margin data with that from slow spreading ridges.

Year 3: Finalising interpretation for publication and presentation.  Presentation of results at conferences, writing of thesis.

 

Partners and collaboration (including CASE)

The geophysical cruise to 13N is in collaboration with Cardiff and Durham.  The study of the Spanish margin in collaboration with Rice University, Southampton, GEOMAR (Kiel, Germany).  The study of data offshore Ireland is in collaboration with PiP. 

 

Further Details

Contact Prof Tim Reston (t.j.reston@bham.ac.uk) for project specific information.  See CENTA web page for information on how to apply and general information (http://www.birmingham.ac.uk/generic/centa)