26Al/10Be dating of an aeolian dust mantle soil in western New South Wales, Australia

Fisher, A; Fink, D; Chappell, JMA; Melville, MD

26Al/10Be dating of an aeolian dust mantle soil in western New South Wales, Australia

Date

2012-08-05

Authors

Publisher

Australian Geosciences Council

Abstract

Aeolian dust mantle soils are an important element of many landscapes in southeastern Australia, though the age of the aeolian deposits has rarely been determined. Measuring 26Al and 10Be in rocks and cobbles buried by an aeolian dust mantle soil at Fowlers Gap in western New South Wales, and modelling their exposure history has revealed the age of the deposit to be 1.1 ± 0.2 Ma, placing increasing aridity at least back to MIS 22, many stages before the MIS 10 increase in aeolian dust observed within Tasman Sea cores. The aeolian age of 1Ma coincides with initiation of the Simpson Desert dunefields and deflation of lakes in central Australia, which likely responded to the shift to longer-wavelength larger-amplitude Quaternary glacial cycles at the mid-Pleistocene Transition. Modelling the 26Al and 10Be exposure history of samples from the surface stone pavement has shown that they have experienced periods of prolonged burial. The simplest explanation for this burial is that the surface cobbles were buried, perhaps episodically, during periods of aeolian deposition, before travelling upwards through the soil to be re-exposed at the new ground surface. Vertical stone movement may have occurred through soil heaving as clay minerals swell and shrink upon wetting and drying, evidence of which is visible in the gilgai-microtopography and horizontal stone sorting (patterned ground) at the site.

Keywords

Dusts, Isotopes, Aluminium 26, Beryllium 10, Deserts, New South Wales, Australia, Quartz, Quaternary period

Citation

Fisher, A., Fink, D., Chappell, J., & Melville, M. (2014). 26Al/10Be dating of an aeolian dust mantle soil in western New South Wales, Australia. Paper presented to the 34th International Geological Congress 2012, "Unearthing our Past and Future - Resourcing Tomorrow", Brisbane, Australia, 5-10 August 2012, (pp. 2274).