James Campbell
Dust deposition and climate records in South-Eastern Australia.
Research Interests:
Landscape evolution, Aeolian processes, slope processes, optically stimulated luminescence dating and geochronology
Current Project: A Record of Quaternary Dust Deposition in South
Eastern Australia
The loess deposits of China and Europe have formed from the deposition of aeolian dust over hundreds of thousands and in many cases millions of years. They contain within them a wealth of information for the palaeoclimate researcher. The study of fossil assemblages, loess morphology, particle grain size, loess geochemical properties and palaeomagnetic properties has allowed the development of a vast continental palaeoclimate archive based on loess deposits.
An important question is whether we can do the same in Australia?
In 1999 in the central tablelands near Carcoar, NSW, a loess deposit up to four metres thick was been located, to date, this is the deepest known primary loess deposit in Australia. This project will use a range of techniques to answer important questions about Australia’s late Quaternary history from this loess profile and then compare the results with a similar though smaller deposit at Young, NSW.
Questions of interest include:
1.How long has it been accumulating? Did it start at the LGM or is it a much longer record.
2. How has the dust deposition rate varied over the late Quaternary? Was the LGM aridity accompanied by increased dust activity?
3. How has the profile been altered? Has bioturbation of the soil particles over time led to large changes in morphology?
4. What techniques are capable of dating bioturbated profiles? Is Single grain optically stimulated luminescence the answer?
5. What are the geomorphologic controls on the development of these deep loess profiles?
6. What are the future options for researching Loess in South-eastern Australia
7. Does dust and loess have a role in the development of soil salinity?
Techniques used:
The primary technique I have used with the loess is single grain optically stimulated luminescence (OSL) dating at the CSIRO in Canberra. This involves the dating of thousands of individual sand grains to develop a population of age estimates for each sample depth. The technique may allow us to decode the depositional history of the loess.
This work commenced in December 2003 and has uncovered a complex profile of bioturbated grains that mask the deposition date signal. Statistical techniques have been adapted to create a mixture model capable of defining separate components in the OSL dating results in an attempt to separate the bioturbation signal from any deposition date signal that may be present. Questions remain however, especially in deciding whether the mixture model components represent the time since deposition or the time since bioturbation.
Confirmation of these results will be made using cosmogenic isotope analysis at ANSTO to determine the Beryllium-10 variation down-profile, this will vary according to the depositional history and an age-model will need to be created to match the beryllium concentrations with the OSL depositional history.
Contact me:
James Campbell
Macquarie University
Ph (02) 9850 8396
Email: jacampbe@els.mq.edu.au
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