(a) Upland airborne K pixel values for boreholes versus the average EC 1:5 for the cover including the top 15m of saprolite for nearest value and averaged upslope from the borehole (b) same for airborne Th. 

Contexts in source publication

Context 1

... order to avoid errors in calibration between AGS data-sets at this stage, only the boreholes from a single radiometrics data-set (at Billabong Creek) were analysed. Pixel values for gamma-element concentrations and upslope averages relating to the representative Billabong Creek boreholes and for all elements, are shown in Figure 3. These values are compared with the average EC 1:5 (soil extract) for the cover combined with the top 15m of saprolite. ...

Context 2

... that salt in deep boreholes is likely to be sourced from materials that are upslope from the site, regions of interest were drawn to include up-slope colluvial sediments with a maximum distance of 1km. The upslope values of K corresponding to each hole can be compared with insitu values (Figure 3). The upslope relationship is generally improved and these results indicate that upland salt storages can broadly be estimated using the airborne K and Th data. ...

Context 3

... one site with low salinity in metasediments (BC 11) has a similar Th signature to aeolian soils but a contrasting K signature. With the data trends in Figure 3, it appears possible to derive an index from both K and Th that might differentiate saline aeolian soils. Generating a salt source model A simple model is achieved by calculating the Euclidean distance (ED): ...

Context 4

... to this calculation, the K data was transformed so that the mean and standard deviation equalled those for the Th data. A target value of 0.7% K and 10ppm Th for saline aeolian soils were obtained from Figure 3. Using equation 1 above, ED was calculated and pixel values extracted for upland boreholes for both the Billabong Creek and Billabung Creek areas (see Figure 2 for location). ...

Context 5

... were plotted against EC 1:5 (soil extract) data which were averaged for the cover material including the top of the saprolite (Figure 4). In general there is a much better correlation between ED and upland salinity than for the individual elements K and Th, as depicted in Figure 3. Apart from the borehole BC1, whose distance appears to be still influenced by the gamma-ray signature of sandstone soils, pixels with a Euclidean distance (to the target signature) of less than 1 generally have an EC 1:5 (soil extract) > 400 uS/cm, a value that, although not quite a saline soil, represents a substantial salt-source. ...