Utilizing meteoric 10Be to define the mobile-stable regolith boundary within unconsolidated sediment
Mr Nicholas Patton1,2, Professor James Shulmeister1,2, Dr. Toshiyuki Fujioka3,4, Dr. David Fink4, Krista Simon4, Dr. Klaus Wilcken4
1University of Canterbury, Christchurch, New Zealand, 2University of Queensland, St. Lucia, Australia, 3 Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Burgos, Spain , 4Australian Nuclear Science and Technology (ANSTO), Lucas Heights, Australia
Understanding the physico-chemical properties of soil profiles are fundamental to evaluate long-term landscape evolution in response to climate, tectonic and human activities. The thickness of the mobile regolith; the portion of the soil profile that is experiencing down slope movement, is a key parameter controlling soil production and erosion rates on hillslopes. However, delineating the interface between the mobile and stable boundary is difficult, specifically in thick (>1 m) unconsolidated sediment profiles. In this study we evaluate the utility of in situ and meteoric 10Be depth profiles to define the mobile-stable regolith boundary at the Cooloola Sand Mass coastal dune fields, Australia. Our results indicate a fairly uniform profile for in situ 10Be concentrations, suggesting the profile is largely dominated by inheritance thus not appropriate for this application. In contrast, meteoric 10Be concentration displays a humped profile, where the concentration significantly increases near the boundary of A(E)- and B-horizons. This observation is largely consistent with the qualitative field observation of the mobile-stable boundary. Despite these positive outcomes, however, it is still uncertain whether the observed meteoric 10Be soil profile reflects the mobile-stable boundary or other changes in physiochemical characteristics (e.g., bulk density, bioturbation, zone of illuviation). Consequently, work is being undertaken to test this approach on other dunes of varying ages (0.5, 2, 5, and 10 ka) in the same area that represent different soil maturity stages and thus variable degrees of physical/chemical evolution of soil profiles. If successful, the development of this new method will be utilized to quantify the mobile regolith layer, which can then be used to create mass balance models of soil erosion and deposition in landscape evolution studies. It will control an important, previously difficult to define parameter in soil production and erosion studies.
I am a watershed scientist who is interested in the interaction between biotic and abiotic processes that drive landscape, climate, and ecosystem evolution. My work tends to be at the interface between multiple disciplines and as a result, has motivated me to become a voice for the scientific community and an advocate of science literacy and communication.
Currently, I am in my 3rd year of my PhD working within the Great Sandy Region National Park QLD, AUS to understand its evolution over the Quaternary.