Dr Faye E. Nelson
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Email: faye.nelson (a) otago.ac.nz PhD title: Supervisor: Gary Wilson (graduated August 2011) |
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Current Research Focus
I am an Assistant Research Fellow (Marine Science). My current research focus is the paleomagnetism and environmental magnetism of piston cores from southern New Zealand and the NZ subantarctic islands.
Research Interests
My research interests lie in the geological record of Quaternary climate change and the application of paleomagnetic methods to dating and correlation and as proxies for environmental change.
Specifically,
- Marine records of early Pleistocene terrestrial glaciation.
- Are Southern Alps events synchronous with Northern Hemisphere (N.H.) glaciations?
- Is there a hemispheric lead/lag in the onset or termination of glaciations?
- What is the role of insolation forcing?
- Last Glacial Maximum (LGM) and deglacial signals in the marine record.
- Oceanographic or atmospheric linkages between NZ and Antarctica?
- Is the timing of abrupt climate events synchronous or asynchronous with N.H. events?
- Developments of techniques that better remove the environmental signal from relative paleointensity records.
- Hydrodynamic sorting of magnetic minerals; implications for current speed and near-shore paleobathymetry.
- Magnetic grain-size; comparison of magnetic and other methods of determination, relationship between magnetic grain-size and mean sortable silt/whole sediment distribution.
PhD Research
New Zealand and its continental shelf are situated in a unique position to track changes in the global ocean and climate system. New Zealand spans the subtropical and subantarctic currents and intercepts and deflects both westerly winds and the westerly Antarctic Circumpolar Current (ACC). The ACC influences global ocean circulation and is considered to be a major climate driver. Furthermore, the New Zealand landmass presently contributes almost two percent of the global ocean sediment load per year. Rain and wind erosion (heightened by New Zealand’s position as a barrier in the South Pacific) and tectonics (e.g., uplift caused by collision of the Pacific and Australian plates) contribute to New Zealand’s high sedimentation rates. As a result, ocean sediment in the New Zealand sector of the South Pacific have the potential to record very high resolution records of both terrigenous and marine input that forms a globally relevant, Southern Hemisphere paleoclimate record.
Long sediment cores were collected from the banks of submarine Hokitika Canyon off New Zealand’s West Coast during the MD152 MATACORE research cruise (Figures 1 & 2). Three cores (30-45m long) from the MATACORE cruise form a transect along Hokitika Canyon at various depths (1000->3000m) and record up to one million years of earth’s geological and climatic history (Figure 3). In addition, shorter cores were collected during NIWA’s West Coast Canyons II cruise. The paleomagnetic laboratory at Otago is equipped with a high-sensitivity, high-resolution cryogenic magnetometer suitable for long core samples. During the cruises, I assisted in collecting u-channel samples from the cores for a range of paleomagnetic and environmental magnetic analyses, including automated closely spaced measurements of natural remanent magnetism, alternating field demagnetisation, anhysteretic remanent magnetism and magnetic susceptibility. Remanent magnetism can provide a high-resolution (sub-millennial) chronology for the climate records through the determination of secular variation and paleointensity changes as well as the application of the more traditional magnetic polarity reversal stratigraphy.
Magnetic susceptibility (the magnetisability of a substance) can indicate changing types and concentrations of magnetic minerals, which in turn indicates the source of the minerals and/or the type of weathering the minerals underwent. Glacial conditions in the Southern Alps contributed non-oxidized, physically weathered minerals. Fieldwork in the Southern Alps aided in identifying the signatures of terrestrially-derived minerals in the cores.
New Zealand’s offshore sediment record is an ideal matrix for environmental magnetic proxy indicators of paleoclimate. Magnetic properties of sediment cores can be used to better understand the dynamics of New Zealand’s continental margin (e.g., catchment and canyon evolution through time) and its record of climate change. Hokitika Canyon provides an opportunity to understand the continuum of processes that affect paleomagnetism and environmental magnetism off New Zealand’s South Island West Coast on sub-millennial timescales.
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Figure 1: R/V Marion-Dufresne II about to embark on the MD 152/MATACORE "Tectonic and climatic controls on sediment budget" cruise (Hobart, Tasmania – Auckland, NZ) (January 24-February 6, 2006). |
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Figure 2: Calypso piston coring system. The lead weight (up to 10 tonnes) drives the core pipe into marine sediment. The longest core recovered on this cruise was over 39 m long (MD06-2987). |
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Publications
Peer-reviewed journal publications (submitted/in review)
Nelson, F.E., Wilson, G.S. and Neil, H.L. Marine magnetic signature of the last glacial cycle in South Westland, New Zealand. Earth and Planetary Science Letters.
- South Westland marine cores comprise enviromagnetic climate and sea level signals. The LGM signal is characterised by Heinrich event-related pulses of sediment. The onset of deglacial (cessation of fine material) signal is constrained at 18.6 cal ka BP. The transition to the Holocene is defined by a steady increase in fine magnetic minerals. There is no apparent Younger Dryas signal. Increased ENSO frequency from mid to late Holocene is inferred from the magnetic grain-size record.
Peer-reviewed journal publications
Jackson, L.E., Jr., Nelson, F.E., Huscroft, C.A., Villeneuve, M., Barendregt, R.W., Storer, J. E. and Ward, B.C., 2011. Pliocene and Pleistocene volcanic interaction with Cordilleran ice sheets, damming of the Yukon River and vertebrate Palaeontology, Fort Selkirk Volcanic Group, west-central Yukon, Canada. Quaternary International. doi:10.1016/j.quaint.2011.08.033
Nelson, F.E., Barendregt, R.W. and Villeneuve, M., 2009. Stratigraphy of the Fort Selkirk Volcanogenic complex in Central Yukon, and its paleoclimatic significance: Ar/Ar and Paleomagnetic Data. Canadian Journal of Earth Sciences: 46(5), 381-401.
- My MSc research focussed on Quaternary glacial limits at the eastern edge of ‘Beringia’ --- the subarctic region that remained ice-free during recent glaciations. At Fort Selkirk, Yukon Territory (~63°N), glacial material is preserved between lava flows exposed in palisades along the mighty Yukon River. Both the lava and glacial till yielded reliable directional records of Earth’s magnetic field at the time of deposition.
- Recently, I have been able to assign early Pleistocene (Porikan) glacial events in NZ to the same Marine Isotope Stages as glaciations identified at Fort Selkirk (article in preparation).
Nelson, F.E.N. and Jackson, L.E., Jr., 2004. High-level terraces, Indian River Valley, Yukon. In: Yukon Exploration and Geology 2003, D.S. Emond and L.L. Lewis (eds.), Exploration and Geological Services Division, Yukon Region, Indian and Northern Affairs Canada, p. 177-190.
- Differential GPS and sedimentological study of river terraces in the Klondike goldfields (Yukon), and possible implications of Quaternary events for placer gold exploration.
Nelson, F.E.N. and Jackson, L.E., Jr., 2003. Cirque forms and alpine glaciation during the Pleistocene, west-central Yukon. In: Yukon Exploration and Geology 2002, D.S. Emond and L.L. Lewis (eds.), Exploration and Geological Services Division, Yukon Region, Indian and Northern Affairs Canada, p. 183-198.
- I used cirque-floor elevation as a proxy for equilibrium line altitude (and further, summer mean temperature) during glaciations. Degree of symmetry of cirque aspect (using cumulative vector technique) was used as a proxy for intensity of glaciation (moisture availability), with asymmetric cirque aspects inferred to belong to marginal glaciations and symmetric cirque aspects to more extensive Pleistocene glaciations. Changes in moisture availability in Yukon Territory has variously been linked to changes in sea ice cover in the Bering Sea/Arctic Ocean, uplift of the St. Elias Mountains and atmospheric circulation changes related to massive ice sheets.