- Contribute to the scientific debate on the duration and timing of the most voluminous sub-aerial magmatism of the Cenozoic
- Develop robust methodologies for determining ages on basalt using 40Ar/39Ar dating
- Work with eminent US field geologists in spectacular regions of Washington and Oregon
The Columbia River Basalts, USA, erupted in the mid-Miocene and represent the youngest large igneous province on Earth. At the time of the eruptions, the Columbia River Basalt (CRB) lavas likely profoundly effected the Miocene climate. However, the timing of their most voluminous eruptive phase, the Grande Ronde Basalts, remains notoriously elusive (eg. Barry et al., 2013). This project seeks to generate a high resolution time framework that connects with the palaeomagnetic timescale and enables investigation of the links between Miocene eruptions and key climatic excursions.
The Grande Ronde Basalts are aphyric and glassy and as a consequence have hindered 40Ar/39Ar dating methods (Barry et al., 2010). This is in contrast to other major units in the CRB, such as the Steens Basalts (Camp & Hanan, 2008), for which it has been possible to achieve high quality Ar-dating (e.g. Jarboe et al., 2008). The Picture Gorge Basalts of northern Oregon are interbedded with the Grande Ronde Basalts, and are petrologically similar to the Steens Basalts. As such they seem to be an ideal target for 40Ar/39Ar dating. Furthermore, the Picture Gorge Basalts contain abundant feldspars, which should aid high quality Ar-dating. The PhD will therefore focus on dating the Picture Gorge Basalts to constrain the time interval in which the Grande Ronde Basalts erupted.
This project will undertake the first 40Ar/39Ar dating programme on the Picture Gorge Basalts, and will also assess their chemistry and eruption history to determine their detailed relationship with the Grande Ronde Basalts. The student will work in close collaboration with Prof Reidel of Washington State University (see below) and his ongoing research on the stratigraphy of the CRB.
Fieldwork The student will examine basalt exposures within northern Oregon, to establish field relationships between the Picture Gorge Basalts and the Grande Ronde Basalts and collect samples for Ar dating and geochemistry.
Analyses The student will undertake 40Ar/39Ar sample preparation and analyses. Alongside the 40Ar/39Ar dating, the student will undertake whole rock geochemistry for trace and rare earth element analyses and assess the relationship of the PGB to penecontemporaneous lavas from across the region. The student will also have the opportunity to assist US collaborator with ongoing research into the wider stratigraphy of the Columbia River Basalts including correlations with the paleomagnetic record.
Training and Skills
CENTA students benefit from 45 days training throughout their PhD including a 10 day placement. In the first year, students receive training 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.
Project specific training will include: field sampling for 40Ar/39Ar dating; XRF and ICP-MS analysis for bulk chemistry, and modelling these data to determine melt genesis, magma history and source composition. Training will be given for critical analysis of Ar-Ar data, and scientific writing.
Year 1: The project will start September 2017 with fieldwork to northern Oregon to collect samples. The successful student will learn how to prepare samples for Ar-Ar analyses and XRF whole rock analyses. The student will attend a national conference to present preliminary results.
Year 2: The student will return to Oregon early in the summer 2018, to closely examine the field relationships between the Picture Gorge Basalts and the Grande Ronde Basalts and assess any potential diachroneity of the lavas. This will be followed with sample preparation and analyses of the second field season’s samples. Whole rock geochemistry will be supplemented with additional ICP-MS analyses for rare earth elements, and the student will start to draft papers for publication.
Year 3: In the final year the student will complete the isotope analyses and conduct detailed critical analysis of the data. The student will write up papers for publication and complete thesis writing. They will present findings to a national/international conference.
Partners and collaboration (including CASE)
At Leicester, Dr Tiffany Barry has worked extensively on the timing of the Columbia River Basalts eruptions, particularly the Grande Ronde Basalts. Tiffany, along with Dr Marc Reichow, have a wealth of experience dating volcanic rocks and working on basaltic terranes including other large igneous provinces such as the Siberian Traps and the Snake River Province. At the Open University, Dr. Sarah Sherlock spearheads one of only two Ar-Ar facilities in the UK, and has leading expertise in the 40Ar/39Ar dating process. She has worked on a wide range of rock types and tectonic settings.
For the fieldwork, we will collaborate with Prof Steve Reidel (Washington State University). Prof Reidel is a leading figure in the geology of the Columbia River Basalts (CRB), and an extremely experienced field geologist with first-hand knowledge of geochemistry and 40Ar/39Ar dating. He has published extensively on the stratigraphy of the CRB (e.g. Geological Society of America Special Paper 497, 2013, The Columbia River Flood Basalt Province, edited by Reidel et al.) and has unrivalled first-hand experience of the exposures and terrane of the Picture Gorge Basalts.
Please contact Tiffany Barry (firstname.lastname@example.org) for further information.
Students should have a strong background in geological sciences, and enthusiasm for fieldwork, working in a laboratory, and trying to understand complex data. Experience of fieldwork investigating igneous geology is desirable but not essential.