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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
Brief summary: 
Ejecta from extra-terrestrial impacts often go unrecognised in palaeoclimatic archives, yet may offer unique chronological controls to definitively tie records across broad spatial and environmental settings.
Importance of the area of research concerned: 
Ice, marine and terrestrial sediment archives offer invaluable insights into Earth System processes and climate teleconnections. Precise tie-points between palaeorecords are essential to determine phasing and drivers of inter-hemisphere climate variability. Globally this can be done through the correlation of infrequent palaeomagnetic shifts. On a regional scale, volcanic ash (tephra) layers give time-synchronous marker horizons. Tephrochronology can validate orbitally-tuned age models and reveal time-transgressive climate changes on continental scales. Microscopic ejecta from extra-terrestrial impacts, microtektites, provide similarly instantaneous marker horizons to tephra, yet have the potential to correlate records over a greater area. Microtektites formed by the ~780 ka Australasian impact microtektites are a stratigraphical marker in the Indian Ocean, yet their presence further afield is poorly constrained. This project is inspired by candidates for Australasian microtektites found in the South Atlantic, well outside the currently defined strewn field for this impact, suggesting that certain impacts may provide near globally synchronous marker horizons.
Project summary : 
Microtektites are glassy spheroids (<1 mm). High temperatures and pressures during extra-terrestrial impacts vaporise the earth’s crust, producing clouds of molten silicate droplets that quickly cool to form microtektites and fall back to earth. Due to their near-instantaneous deposition, microtektite-rich horizons from known impact events are invaluable stratigraphical makers in marine sediments. However, the geographical range of specific microtektite strewn fields remain poorly constrained in the marine realm and largely unstudied within the lacustrine and cryosphere. This project will investigate the spatial distribution of microtektite horizons associated with a number of extra-terrestrial impact events. The ultimate outcome of this project will be a novel microtektite-based chronology for the Neogene tying marine, terrestrial and cryosphere environments.
What will the student do?: 
Working between BAS, the Departments of Geography and Earth Sciences the student will select a number of well-dated extra-terrestrial impact events and systematically refine their strewn field extent by targeting existing marine and lacustrine sediments that span the time interval of the impact. The student may exploit a range of sediment archive collections including those held at BAS and Cambridge University, IODP, ICDP and other international collections as they determine appropriate. The student will develop novel morphological and geochemical approaches to characterise impact-specific microtektites. Careful chemical analysis and inter-comparisons, in conjunction with stratigraphic information, will be used to correlate microtektite horizons and reveal their value as time-stratigraphic marker horizons in diverse sediment records. In addition, the student may consider spatial analysis of these morphological and geochemical parameters to better constrain the site of the impact in cases where a crater has not been identified. The student will be able encouraged to evolve and direct the project themselves.
References - references should provide further reading about the project: 
Folco, L. et al. 2016. Stretching out the Australasian microtektite strewn field in Victoria Land Transantarctic Mountains. Polar Sci., 10, 147-159.
Van Ginneken M. et al. 2018. A new type of highly‐vaporized microtektite from the Transantarctic Mountains. Geochimica et Cosmochimica Acta 228, 81–94.
Valet, J.‐P. et al. 2014. Geomagnetic, cosmogenic and climatic changes across the last geomagnetic reversal from Equatorial Indian Ocean sediments. Earth Planet. Sci. Lett. 397, 67–79.
You can find out about applying for this project on the British Antarctic Survey (BAS) page.
Dr Victoria Peck
Professor Christine Lane
British Antarctic Survey Graduate Administrator