Shifting sands on the edge: wave-influenced deposits on the narrow shelves of volcanic ocean islands (Azores; PLATMAR project)

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Project PLATMAR has been funded by the Portuguese Science Foundation (FCT, equivalent to NERC) to collect new geological and geophysical data around Santa Maria Island of the Azores providing a unique dataset that is unrivalled globally, even in comparison with the well-studied Big Island of Hawai’i. In the project, an international multidisciplinary group of researchers will be brought together to study how the island’s shelf and slope have developed. PLATMAR will begin in 2016 and the successful student attached to this PhD project will have the opportunity to join the marine fieldwork in 2016 and 2017 in the Azores to help collect geophysical, geological and oceanographic data. He/she will contribute to processing of the geophysical data collected on those expeditions and/or perform grain size and geochemical analyses of the collected seabed samples (a dense grid of grab samples will be collected on the island shelf). Depending on the interests and aptitudes of the student, the project will focus on physical aspects of sand deposition, on their geochemical characteristics or a combination of these scientific areas.

An extensive dataset of multibeam sonar, chirp and boomer seismic data and seabed samples has been accumulated for the shelves of the central Azores islands Faial, Pico, Terceira and São Jorge (Mitchell et al., 2008; Quartau et al., 2010, 2014, 2015). In addition to the new data from Santa Maria, these will allow a general assessment of the effects of varied waves on sand body depths (by characterising the clinoform rollovers; Mitchell et al., 2012). Variations in wave properties will be derived from the ERA-40 meteorological reanalysis grids and other sources, while sand threshold of motion stresses will be derived based on the grain size data. From these basic results and depending on the aptitude and interests of the student, the project could then develop in one or more directions, such as, to look into the effects of waves on varied coastal erosion, the geochemical record of past erosion and ocean water properties and controls on smaller bedform morphology.

If focused on geochemistry, this project will involve a diverse array of analytical techniques supported by the multi-disciplinary specialist experience of researchers in SEAES. The student will have access to the world-class facilities available in the Williamson Research Centre for Molecular Environmental Sciences (WRC) at the University of Manchester. Techniques to be used in this project will include (organic) geochemical techniques such as Liquid Chromatography Mass Spectrometry (LCMS) and (Pyrolysis) Gas Chromatography MS, (compound specific) stable isotope analyses and X-Ray fluorescence. A combination of elemental and isotopic analyses of selected samples collected as part of PLATMAR will be used to reconstruct the depositional history of these sediments. Questions to be addressed could include how the mobility of the sand implies varied over-turning and exposure to oxic ocean waters. A broad approach to analysis should also address whether the varied composition of volcanic lava and other eroded materials affects the bioclastic component of the sand.