Spatial and temporal variations in lithospheric strength along the Louisville Seamount Chain
Lead Research Organisation:
University of Oxford
Department Name: Earth Sciences
Abstract
The first phase of this proposal focuses on developing new techniques and software to process and display data collected on the rock cores' physical properties, including density, porosity, colour properties, and concentration of potassium, thorium, and uranium in the rock. These tools will enable us to better identify and quantify real changes in these properties, rather than spurious variations caused by the breaks and fractures in the rock, and will enable future expeditions to do these analyses in real time, which provides valuable information for geochemical and petrological studies both during and after the expedition.
The second phase of this proposal is directed at determining the vertical movements of the Louisville seamounts, which were once at or above sea level, but now lie over a kilometer under water, and how these movements reflect the strength of the outer part of the Earth, the lithosphere, underlying each seamount. We will be looking at how this strength varies over time at an individual seamount, as the lithosphere 'relaxes' under the load of the volcano, and also how it varies along the length of the Louisville Seamount Chain. This along-chain variation should predominantly reflect the variations in the age of the lithosphere when each volcano formed, but may also contain information about the impact of the hotspot that formed the seamounts and the geochemistry of the volcanoes themselves.
The second phase of this proposal is directed at determining the vertical movements of the Louisville seamounts, which were once at or above sea level, but now lie over a kilometer under water, and how these movements reflect the strength of the outer part of the Earth, the lithosphere, underlying each seamount. We will be looking at how this strength varies over time at an individual seamount, as the lithosphere 'relaxes' under the load of the volcano, and also how it varies along the length of the Louisville Seamount Chain. This along-chain variation should predominantly reflect the variations in the age of the lithosphere when each volcano formed, but may also contain information about the impact of the hotspot that formed the seamounts and the geochemistry of the volcanoes themselves.
Planned Impact
At this stage, the proposed research of this UKIODP post-cruise support proposal is blue-sky academic research with no immediately identifiable non academic end-users. 'Downstream', however, the research is likely to have wide-ranging impacts. Lithospheric strength is an input parameter for a wide range of geological/geophysical models, and may, eventually, deliver impact when these models are used to underpin fossil fuel exploration and exploitation, or in the assessment of natural hazards from phenomena such as earthquakes and tsunamis.
Naturally all research outputs will be available for the whole UK earth system science and IODP communities, and therefore feed into the formulation of advice to public and policy makers in support of the overall NERC mission and UK Government policy.
The most immediately accessible of these outputs will include a suite of 'freeware' code modules and software for the filtering, processing, and display of physical properties data arising from the project. The suite will be hosted on, and freely downloadable from, a project webpage, which will also host lithospheric strength models.
Routine dissemination of research outputs from the project will include the publication of peer reviewed scientific papers and the presentation of research results at international conferences.
Naturally all research outputs will be available for the whole UK earth system science and IODP communities, and therefore feed into the formulation of advice to public and policy makers in support of the overall NERC mission and UK Government policy.
The most immediately accessible of these outputs will include a suite of 'freeware' code modules and software for the filtering, processing, and display of physical properties data arising from the project. The suite will be hosted on, and freely downloadable from, a project webpage, which will also host lithospheric strength models.
Routine dissemination of research outputs from the project will include the publication of peer reviewed scientific papers and the presentation of research results at international conferences.
Organisations
Publications
Koppers A
(2012)
Erratum: Limited latitudinal mantle plume motion for the Louisville hotspot
in Nature Geoscience
Koppers A
(2013)
IODP Expedition 330: Drilling the Louisville Seamount Trail in the SW Pacific
in Scientific Drilling
Valentine A
(2013)
Discovery and analysis of topographic features using learning algorithms: A seamount case study
in Geophysical Research Letters
| Description | - Te is moderately high along the chain, typically 12-18 km (I think these are 'uncorrected' for windowing, and it goes up to low 20 kms when corrected, but unfortunately, I'm doing these from Newcastle without my lab notebook for reference.) This corresponds to a 'flank' to off-ridge setting. - Most parameter settings show quite a consistent Te along the chain, with no clear trend from one end to the other (from trench to the Wishbone Scarp; I didn't look farther east). A few combinations of settings show a moderate trend from higher Te near the trench (18-20 km) to lower near Wishbone (12-13 km). This suggests little variation in the age of the lithosphere at the time of loading, which is particularly significant for the Louisville Seamount Chain because the underlying lithosphere formed in the Cretaceous Quiet Zone and cannot be dated magnetically. - Many parameter settings showed a brief spike in Te (2-3 seamounts wide) centred around 187.5 deg lon, typically an increase of about 5 km compared to the neighbouring seamounts. The feature is surprisingly robust, but has no obvious geophysical/tectonic explanation. - Methodologically, median depth & density parameter space searches showed that admittance RMS consistently underestimates the median depth, perhaps indicating an inherited bias from the input gravity/bathymetry. There is a strong correlation between depth and density in the RMS, so the density is also biased slightly low compared to MAD measurements aboard ship (and compared to commonly inferred values for seamounts). However, our depth/density fitting algorithm is excellent at determining a depth/density combination very close to the global RMS minimum. - The Te impact of the above bias is to generally shift the RMS minimum Te a couple of km lower than would be favoured using the median depth from Sandwell & Smith and a density of 2900 kg/m^3 (which was the average for flows we drilled, if I recall correctly). (I did also check observed median depth and a density of 2500 kg/m^3, which was, I think, the average for all volcanics we drilled - but is presumably biased low by virtue of being only the top portion of the seamount. That would give a Te typically a couple of km lower than the RMS minimum Te.) |
| Exploitation Route | Scientific Ocean Drlling is of benefit to a wide community of scientists in the Earth Sciences. It is essential to our understanding of the oceans and how they interact with the solid-Earth. |
| Sectors | Education,Environment |