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Department of Earth Sciences

 
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A collection of all the seminars going on at the Department, either on the downtown site, or out at the Bullard Laboratories
Updated: 50 min 45 sec ago

Thu 25 Feb 15:00: Volatiles in Earth’s mantle: primordial or subducted? Insights from new generation nitrogen and sulfur isotope systematics

Wed, 27/01/2021 - 10:39
Volatiles in Earth’s mantle: primordial or subducted? Insights from new generation nitrogen and sulfur isotope systematics

Hydrothermal 15N15N abundances constrain the origins of mantle nitrogen

Nitrogen (N) is the main constituent of the Earth’s atmosphere, but its provenance in the Earth’s mantle is uncertain. In this presentation, we discuss nitrogen enrichments in multiple mantle reservoirs. We show that subduction may not be as important as previously thought to account for mantle nitrogen. We use the rare 15N15N isotopologue of N2 as a novel tracer of air contamination in volcanic gas effusions. By correcting for air contributions in the gases using this tracer, we derive new estimates for mantle 15N and N2/3He ratios from multiple volcanic regions. We focus on Yellowstone, a primitive hotspot, and the central American subduction zone. We show that subduction may cause elevated 15N and N2/3He values in a mantle source, as the result of the accumulation of surface-derived components. However, our 15N15N-based analysis requires the Yellowstone plume to have some of the lowest N2/3He ratio. This is inconsistent with subducted volatiles in this mantle source, and allows plume nitrogen to be a primordial component. This result opens the possibility that the budget of mantle volatiles was at least partly established during planetary formation, rather than exclusively reflecting subduction and tectonic plate activity.

Isotopic evidence of multiple sulfur sources delivered to the Samoan islands

Like nitrogen, sulfur isotopes can be used as a tool in placing constraints on crustal recycling and the nature of volatiles in primordial mantle reservoirs. Basalts from the Samoan islands sample contributions from all classical mantle endmembers, including extreme EM II and high 3He/4He components, as well as dilute contributions from the HIMU , EM I, and DM components. The geochemical heterogeneity of the Samoan islands provides an opportunity to test whether distinct S-isotope compositions are delivered to the Samoan mantle plume and whether they are linked to the various observed mantle components. Through high precision, quadruple S-isotope analyses of Samoan Basalts we observe unique S-isotope compositions linked to the HIMU , EM II, and EM I components at Samoa. We also use relationships between sulfur and tungsten isotopes to show that the primordial S-isotope composition of the mantle is within uncertainty of the convective mantle, suggesting S isotope compositions were well mixed within 60 Ma of Earth’s accretion.

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Thu 04 Feb 15:00: Paleocene–Eocene climate and carbon cycle: tales from the 'boring background'

Tue, 26/01/2021 - 12:42
Paleocene–Eocene climate and carbon cycle: tales from the 'boring background'

The Paleocene and Eocene Epochs (~66–34 Ma) were important greenhouse periods, characterised by high frequency orbitally-paced events (e.g., hyperthermals) superimposed on long term changes in climate and the carbon cycle. Major changes in the marine and terrestrial biosphere also occurred at this time, synchronous with both high frequency and long-term changes in climate. While many detailed palaeoclimate records have been generated for the enigmatic hyperthermals, such as the Paleocene Eocene Thermal Maximum (PETM), the general background climate of this period has only been reconstructed at a much lower resolution. This poorly characterised ‘boring background’ hampers our understanding both of the overall climate state of this greenhouse world and the hyperthermals themselves. Here I’ll talk through some new data from the ancient Atlantic and Indian Oceans which help to better characterise background climate and carbon-cycle of the Palaeocene–Eocene.

Three supporting papers:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019PA003556

https://www.sciencedirect.com/science/article/pii/S0012821X20303587

https://science.sciencemag.org/content/369/6509/1383.abstract?casa_token=0BWfLrOWyjgAAAAA:AHypTjer434afTBpW43UNHxIH5lALOtLKGbNWpMUugHl3l1L8IbeTuEAKlVhkUrl5_79yL4KtIlZxEw

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Thu 25 Mar 15:00: Title to be confirmed

Sat, 23/01/2021 - 13:36
Title to be confirmed

Abstract not available

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Thu 28 Jan 15:00: Psyche: Journey to a Metallic World

Sat, 23/01/2021 - 13:35
Psyche: Journey to a Metallic World

“Psyche” is both the name of an asteroid in the main belt, orbiting out past Mars, and the name of our mission to visit that asteroid. Psyche’s density, radar, and reflected light properties indicate that it is largely made of metal. Humans have never visited a world made of metal. So if Psyche turns out to be what we think, we’ll be visiting a new kind of world.

Our spacecraft will launch in August 2022 – just 19 months away! – and in 2026 will begin orbiting Psyche and performing carefully planned scientific measurements. In this talk we’ll discuss the state of the mission and our plans, and, especially, what we each are doing on the mission and how we got here.

Psyche will surprise us. The universe always outsteps even our best imaginations. And our whole Psyche team looks forward to sharing all we discover with everyone here on Earth.

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Mon 01 Feb 17:00: Improving EDI in academic and field settings

Fri, 22/01/2021 - 16:38
Improving EDI in academic and field settings

An audit for action: strategies for change

2020 saw the geosciences community reaffirm its commitment to the development of a fairer and more equal field, especially in terms of racial equality. However, developing strategies to address the challenges of poor representation can be challenging, especially if we wish to do this in a way that does not further burden minority groups to make the changes we wish to see. Here, I will present a potential strategy for identifying barriers to inclusion and retention within academic geoscience settings, based upon work first undertaken in the Department of Earth Sciences at the University of Oxford, and now being expanded across other departments in the UK. Finally, this work will discuss how similar strategies may be replicated (or preferably improved!) at other institutions, recognising that this is only one possible avenue to achieving change.

Happy Campers; perspectives on equality, diversity and inclusivity in geoscience fieldwork

Due to the unprecedented COVID -19 pandemic and growing awareness of the need for improved equality, diversity and inclusivity in the geosciences, the role of fieldwork has increasingly been called into question in recent literature and social media. In this contribution, drawing on my own experiences of working in the Highlands of Scotland, I describe how in the right place, with supportive people, adequate provisions and thorough planning, fieldwork can be accessible, inclusive and truly rewarding.

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Mon 22 Feb 17:00: Title TBC

Thu, 21/01/2021 - 16:46
Title TBC

Abstract not available

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Mon 01 Feb 17:00: Happy Campers; perspectives on equality, diversity and inclusivity in geoscience fieldwork

Thu, 21/01/2021 - 16:45
Happy Campers; perspectives on equality, diversity and inclusivity in geoscience fieldwork

Due to the unprecedented COVID -19 pandemic and growing awareness of the need for improved equality, diversity and inclusivity in the geosciences, the role of fieldwork has increasingly been called into question in recent literature and social media. In this contribution, we recount our own experiences of fieldwork in Wyoming, USA and the Highlands of Scotland and the barriers we faced and subsequently overcame. We describe how in the right place, with supportive people, adequate provisions and thorough planning, fieldwork can be an accessible, inclusive and truly rewarding experience.

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Mon 25 Jan 17:00: Geodynamic of rifted margins: pre-rift inheritance and post-rift movements

Thu, 21/01/2021 - 16:45
Geodynamic of rifted margins: pre-rift inheritance and post-rift movements

Rifted margins host the Earth’s largest sedimentary basins, which contain important ore deposits and energy (hydrocarbon and thermal) resources and could play a pivotal role in the energy transition as ideal locations for carbon sequestration, energy and nuclear waste storage. In addition, their thick sedimentary cover constitutes a unique archive of global climate changes throughout Earth’s history and a valuable record of the dynamic processes controlling lithospheric deformation. Rifted margins form by continental rifting and the subsequent lithospheric breakup and oceanic spreading. Several key parameters influence continental rifting and the final geometry of rifted margins, including lithosphere composition and thermal state (i.e., rheology), spatial and temporal distribution of strain rate, mantle dynamics, magmatism, and surface processes (i.e., erosion and sedimentation rates). In this seminar, I will examine the role of lithosphere rheology in influencing the tectonics of continental rifting, using the Labrador Sea as a case study. I will also touch on the post-breakup life of the Atlantic NW African margin, where some intriguing post-rift vertical movements have been documented.

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Mon 22 Feb 18:00: Title TBC

Thu, 21/01/2021 - 16:27
Title TBC

Abstract not available

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Mon 25 Jan 18:00: Geodynamic of rifted margins: pre-rift inheritance and post-rift movements

Wed, 20/01/2021 - 22:10
Geodynamic of rifted margins: pre-rift inheritance and post-rift movements

Rifted margins host the Earth’s largest sedimentary basins, which contain important ore deposits and energy (hydrocarbon and thermal) resources and could play a pivotal role in the energy transition as ideal locations for carbon sequestration, energy and nuclear waste storage. In addition, their thick sedimentary cover constitutes a unique archive of global climate changes throughout Earth’s history and a valuable record of the dynamic processes controlling lithospheric deformation. Rifted margins form by continental rifting and the subsequent lithospheric breakup and oceanic spreading. Several key parameters influence continental rifting and the final geometry of rifted margins, including lithosphere composition and thermal state (i.e., rheology), spatial and temporal distribution of strain rate, mantle dynamics, magmatism, and surface processes (i.e., erosion and sedimentation rates). In this seminar, I will examine the role of lithosphere rheology in influencing the tectonics of continental rifting, using the Labrador Sea as a case study. I will also touch on the post-breakup life of the Atlantic NW African margin, where some intriguing post-rift vertical movements have been documented.

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