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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 
A composite image showing an overview of a rift valley landscape, sediment cores, a rockshelter site and tephra layer within sediment section
Brief summary: 
A major contribution to the Pleistocene tephrostratigraphic record for Ethiopia, which will enable tackling questions at the interface between explosive volcanism, palaeoclimate and human evolution.
Importance of the area of research concerned: 
The potential to develop the tephrostratigraphy and chronology of widely dispersed tephra in eastern Africa has been highlighted for over two decades, yet much work remains to refine, date and connect regional records. The Main Ethiopian Rift (MER; a ~600 km section of the East African Rift System) connects the Afar rift in NE Ethiopia to the Turkana Basin in the southwest and houses regularly spaced, large Pleistocene silicic volcanic centres. Across Ethiopia, distal tephra are used as key chronostratigraphic markers in sedimentary sequences containing fossils and artefacts associated with human presence. In addition, tephra layers in lake sediment sequences in Ethiopia are increasingly playing a role in dating paleoclimate records. Whilst tephra in such settings have been described and many directly dated, limited correlations have been made to MER caldera-forming eruptions. A robust tephrostratigraphy for the MER will provide a framework to address key chronostratigraphic questions in paleoenvironmental and archaeological contexts, as well leading to a deeper understanding of the age and magnitude of past explosive volcanism in the region, of relevance to geohazard assessment.
Project summary : 
Pleistocene volcanism along the MER produced colossal pyroclastic deposits found widely as tephra layers within sedimentary archives such as lake sediments and fluvial terraces. Due to the prevalence of tephra in archaeological sequences, their correlation and dating has become fundamental to the chronology of the hominin record in Ethiopia. However, the record of past MER volcanism is far from complete and recent work combining volcanic outcrop, archaeological, fluvial and lake sediment sequences, has shown that many correlations require testing with new samples and state-of-the-art analytical protocols. In addition, there is now demonstrated potential to use cryptotephra methods to fill critical gaps in the volcanological record and increase the detection and correlation of tephra isochrons within sedimentary sequences.
What will the student do?: 
The student will contribute to the construction of a highly connected tephrostratigraphic framework for Ethiopia, thereby informing the understanding of the interrelationships between the largest explosive volcanic eruptions, paleoclimate and human evolution in the Pleistocene. They will detect, geochemically characterise and date tephra and cryptotephra within lake sediment records (e.g. the ~620 ka Chew Bahir paleolake record), archaeological sites (e.g. Melka Wakena, Mochena Borago) and outcrops near candidate volcanoes to test existing tephra correlations, confirm stratigraphic relationships and identify the sources of as of yet unprovenanced, widespread tephra layers. The project will involve field sampling of proximal and distal volcanic and archaeological sequences and sub-sampling of sediment cores during visits to other laboratories (e.g. LacCore, Minneapolis). Cryptotephra analyses will be carried out in the Cambridge Tephra Laboratory and tephra samples will be characterised using geochemical techniques (WDS-EPMA, LA-ICPMS). The student will prepare samples for Ar-dating with the expectation of obtaining new dates for critical deposits.
References - references should provide further reading about the project: 
WoldeGabriel, G., Hart, W.K., Katoh, S., Beyene, Y. and Suwa, G., 2005. Correlation of Plio–Pleistocene tephra in Ethiopian and Kenyan rift basins: Temporal calibration of geological features and hominid fossil records. Journal of Volcanology and Geothermal Research, vol. 147, pp.81-108.
Vidal, C., Lane, C., Asrat, A., Barfod, D., Tomlinson, E., Tadesse, A.Z., Yirgu, G., Deino, A., Hutchison, W., Mounier, A. and Oppenheimer, C., In Review. Age of the oldest Homo sapiens from eastern Africa. https://www.researchsquare.com/article/rs-373661/v1
Roberts, H.M., Ramsey, C.B., Chapot, M.S., Deino, A.L., Lane, C.S., Vidal, C., Asrat, A., Cohen, A., Foerster, V., Lamb, H.F. and Schäbitz, F., In press. Using multiple chronometers to establish a long, directly-dated lacustrine record: constraining >600,000 years of environmental change at Chew Bahir, Ethiopia. Quaternary Science Reviews, p.107025.
Applying
You can find out about applying for this project on the Department of Geography page.
Professor Christine Lane
Department of Geography Graduate Administrator
Professor Clive Oppenheimer