Using radiometric data to identify æolian dust additions to topsoil of the Hillston district, western NSW

Abstract

The identification and characterisation of æolian dust additions to Australian soil profiles has been attempted using a wide range of analytical techniques. Such techniques are often reliant on specialised equipment and operator expertise, but do not necessarily yield information on the spatial distribution of deposited dust across the landscape. An airborne geophysical technique which measures naturally occurring gamma-rays may now assist in the rapid assessment of dust accumulation sites at the catchment scale. This technique, known as gamma ray spectrometry or radiometrics, assesses the potassium (K), uranium (U), and thorium (Th) contents of the Earth's surface, and may potentially distinguish æolian sediments from the underlying rock or in situ developed soil profile by their differing K, U, and/or Th-bearing mineral suites. This paper summarises a study of this technique for identifying æolian dust in topsoils of the Hillston district in western New South Wales. Using airborne with follow-up ground-based radiometric data, a variable relationship was established between large K signatures and apparent topsoil dust accumulations, which were identified as containing appreciable feldspar and illite. The previously established correlation between topsoil clay content and eTh (equivalent Th) concentration was also observed in this region, indicating that the technique may allow for rapid identification of landform features with significant clay and silt enrichment, as often occurs with dust accession. Despite the ubiquity of æolian sediments in this region, the radiometric data were moderately effective in discriminating different dune systems and may therefore represent a useful initial technique for discerning likely areas of dust accumulation in this environment. However, in areas influenced by fluvial sediments, the radiometric signatures were not necessarily indicative of the topsoil dust content.

Mapping soil clay contents in Dutch marine districts using gamma-ray spectrometry

“…The models with the smallest RMSE were those that used 40 K and/or 232 Th or TC. Within soils, 40 K content is related to secondary minerals such as illite, whereas 238 U and 232 Th contents are related to Fe‐ and Ti‐oxides (Cattle et al , 2003). The clay deposited in the SMD originates from the southern rivers such as the Meuse and the Rhine.…”

Mapping Water Table Depth Using Geophysical and Environmental Variables

“…In the field of soil science, gamma radiometric data have been used to assess the spatial extent of Aeolian deposits (Dickson and Scott 1992), soil map units (Wilford 1997), and clay content estimation (Cattle et al 2003). It has also been used to infer soil physical properties that have a significant bearing on water table depth, including the determination of soil moisture (Carol 1981), locating sands in water channels (Wilford 1997), and also in delineating soil and landforms that act as water table recharge beds (Bierworth and Welsch 2000).…”

A weathering intensity index for the Australian continent using airborne gamma-ray spectrometry and digital terrain analysis

“…Gamma-ray survey data was used initially for uranium exploration and geological mapping but in the last two decades has been used more broadly in conjunction with other datasets for mapping soils and regolith (Wilford and Minty, 2007). Once calibrated with field data, gamma-ray imagery can often provide information on quite specific soil/regolith properties (Bierwirth, 1996;Cattle et al, 2003;Cook et al, 1996;Dauth, 1997;Dickson and Scott, 1997;Gessler et al, 1995;Lahti and Jones, 2003;Martz and de Jong, 1990;McKenzie and Ryan, 1999;Rawlins et al, 2009Rawlins et al, , 2007Ryan et al, 2000;Roberts et al, 2002;Taylor et al, 2002;Thomas et al, 2009;van Egmond et al, 2010;Wilford et al, 1997) and in understanding erosion and weathering processes (Erbe et al, 2010;Pickup and Marks, 2000;Wilford, 1995).…”