A new continental-scale geochemical atlas and dataset for Australia were officially released into the public domain at the end of June 2011. The National Geochemical Survey of Australia (NGSA) project, which started in 2007 under the Australian Government's Onshore Energy Security Program at Geoscience Australia, aimed at filling a huge knowledge gap relating to the geochemical composition of surface and near-surface materials in Australia. Better understanding the concentration levels and spatial distributions of chemical elements in the regolith has profound implications for energy and mineral exploration, as well as for natural resource management. In this world first project, a uniform regolith medium was sampled at an ultra-low density over nearly the entire continent, and subsamples from two depths and two grain-size fractions were analysed using up to three different (total, strong and weak) chemical digestions. This procedure yielded an internally consistent and comprehensive geochemical dataset for 68 chemical elements (plus additional bulk properties). From its inception, the emphasis of the project has been on quality control and documentation of procedures and results, and this has resulted in eight reports (including an atlas containing over 500 geochemical maps) and a large geochemical dataset representing the significant deliverables of this ambitious and innovative project. The NGSA project was carried out in collaboration with the geoscience agencies from every State and the Northern Territory under National Geoscience Agreements. .../...

pH is one of the more fundamental soil properties governing nutrient availability, metal mobility, elemental toxicity, microbial activity and plant growth. The field pH of topsoil (0-10 cm depth) and subsoil (~60-80 cm depth) was measured on floodplain soils collected near the outlet of 1186 catchments covering over 6 M km2 or ~80% of Australia. Field pH duplicate data, obtained at 124 randomly selected sites, indicates a precision of 0.5 pH unit (or 7%) and mapped pH patterns are consistent and meaningful. The median topsoil pH is 6.5, while the subsoil pH has a median pH of 7 but is strongly bimodal (6-6.5 and 8-8.5). In most cases (64%) the topsoil and subsoil pH values are similar, whilst, among the sites exhibiting a pH contrast, those with more acidic topsoils are more common (28%) than those with more alkaline topsoils (7%). The distribution of soil pH at the national scale indicates the strong controls exerted by precipitation and ensuing leaching (e.g., low pH along the coastal fringe, high pH in the dry centre), aridity (e.g., high pH where calcrete is common in the regolith), vegetation (e.g., low pH reflecting abundant soil organic matter), and subsurface lithology (e.g., high pH over limestone bedrock). The new data, together with existing soil pH datasets, can support regional-scale decision-making relating to agricultural, environmental, infrastructural and mineral exploration decisions.

Iron (Fe) oxide mineralogy in most Australian soils is poorly characterised, even though Fe oxides play an important role in soil function. Fe oxides reflect the conditions of pH, redox potential (Eh), moisture and temperature in the soil environment. The Fe oxide mineralogy exerts a strong control on soil colour. Visible-near infrared (vis-NIR) spectroscopy can be used to identify and measure the abundance of certain Fe oxides in soil as well as soil colour. The aims of this paper are to: (i) measure the hematite and goethite content of Australian soils from their vis-NIR spectra, (ii) compare these results to measurements of soil colour, and (iii) describe the spatial variability of hematite, goethite and soil colour, and map their distribution across Australia. The spectra of 4606 surface soil sample from across Australia were measured using a vis-NIR spectrometer with a wavelength range between 350-2500 nm. We determined the Fe oxide content from characteristic absorptions of hematite (near 880 nm) and goethite (near 920 nm) and derived a normalised iron oxide difference index (NIODI) to better discriminate between them. The NIODI was generalised across Australia with its spatial uncertainty using sequential indicator simulation. We also derived soil RGB colour from the spectra and mapped its distribution and uncertainty across the country using sequential Gaussian simulations. The simulated RGB colour values were made into a composite true colour image and were also converted to Munsell hue, value and chroma. These colour maps were compared to the map of the NIODI and both were used for interpretation of our results. The work presented here was evaluated using existing studies on the distribution of Fe oxides in Australian soils.

Abstract The ability of thermal infrared (TIR) spectroscopy to characterise mineral and textural content was evaluated for soil samples collected in the semi-arid environment of north-western Queensland, Australia. Grain size analysis and separation of clay, silt and sand sized soil fractions were undertaken to establish the relationship between quartz and clay emissivity signatures and soil texture. Spectral band parameters, based on thermal infrared specular and volume scattering features, were found to discriminate fine clay mineral-rich soil from mostly coarser quartz-rich sandy soil, and to a lesser extent, from the silty quartz-rich soil. This study found that there was the potential for quantifying soil mineral and texture content using TIR spectroscopy. Key Words Soil composition, quartz, kaolinite, smectite, grain size, Tick Hill

The ability of thermal and shortwave infrared spectroscopy to characterise composition and textural was evaluated using both particle size separated soil samples and raw soils. Particle size analysis and separation into clay, silt and sand sized soil fractions was undertaken to examine possible relationships between quartz and clay mineral spectral signatures, and soil texture. Spectral indices, based on thermal infrared specular and volume scattering features, were found to discriminate clay mineral-rich soil from mostly coarser quartz-rich sandy soil, and to a lesser extent, from the silty quartz-rich soil. Further investigations were undertaken using spectra and information on 51 USDA and other soils within the ASTER Spectral Library to test the application of shortwave, mid- and thermal infrared spectral indices for the derivation of clay mineral, quartz and organic carbon content. A non linear correlation between quartz content and a TIR spectral index based on the 8.62 im was observed. Preliminary efforts at deriving a spectral index for the soil organic carbon content, based on 3.4 - 3.5 im fundamental H-C stretching vibration bands were also undertaken with limited results.

Analytical data for 10 major oxides (Al2O3, CaO, Fe2O3, K2O, MgO, MnO, Na2O, P2O5, SiO2 and TiO2), 16 total trace elements (As, Ba, Ce, Co, Cr, Ga, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn and Zr), 14 aqua regia extractable elements (Ag, As, Bi, Cd, Ce, Co, Cs, Cu, Fe, La, Li, Mn, Mo and Pb), Loss On Ignition (LOI) and pH from >3500 soil samples from two continents (Australia and Europe) are presented and compared to (1) the composition of the upper crust, (2) published world soil average values, and (3) data from other continental-scale soil surveys. It is demonstrated that average upper continental crust values do not provide reliable estimates for natural concentrations of elements in soils. For many elements there exist substantial differences between published world soil averages and the median concentrations observed on two continents. Direct comparison with other continental datasets is hampered by the fact that often mean, instead of the statistically more correct median, is reported. Using a database of the worldwide distribution of lithological units, it can be demonstrated that lithology is a poor predictor of soil chemistry. Climate-related processes such as glaciation and weathering are strong modifiers of the geochemical signature inherited from bedrock during pedogenesis. To overcome existing shortcomings of predicted global or world soil geochemical reference values, we propose Preliminary Empirical Global Soil reference values based on analytical results of a representative number of soil samples from two continents (PEGS2).

This dataset was created for the National Geochemical Survey of Australia (NGSA) to help determine the location of target sites for sampling catchment outlet sediments in the lower reach of defined river catchments. Each polygon represents a surface drainage catchment derived from a national scale 9 second (approximately 250 m) resolution digital elevation model. Catchments were extracted from an unpublished, interim version of a nested catchment framework with an optimal catchment area of 5000 km2. Only catchments from the Australian mainland and Tasmania were included. In order to generate catchments approaching the optimal area, catchments with an area of less than 1000 km2 were excluded from the dataset, while other small catchments were amalgamated, and catchments much larger than 5000 km2 were split.

The Northern Australian Development Committee nominated the region of the Ord and Victoria rivers to be surveyed by the Northern Australian Regional Survey, when the Barkly Region had been completed. The immediate objectives of the Survey are "to accurately record the nature of the country, to establish a sound basis upon which the production possibilities of the Region may be appraised and to make general recommendations concerning development and further investigations." It was decided that the region should include the Army Four Mile Map Sheets of Delamere, Victoria River Downs, Wave Hill, Birrundudu, Limbunya, Waterloo, Auvergne, Port Keats, Medusa Banks, Cambridge Gulf, Lissadell, Dixon Range, and Gordon Downs, and that the field work would be commenced during the 1949 dry season. The techniques and methods used to complete this survey work are noted. The stratigraphy, pedology, and economic geology of the area are described in some detail.

This report deals with an investigation of the electrical resistivities of a variety of wet surface soils, gravels and sands. The work may be regarded as preliminary to an investigation by Mr. R.F. Thyer into the detection of electrically resistive bodies buried in wet soils at shallow depths. It was required to determine the range over which the resistivities of surface soils vary, and also the changes that may be expected in any one type of soil between measurements made within any 1 foot of each other. Measurements were made in four localities, three being in the bed or on the banks of the Molonglo River, where the surface materials are sand, gravel, silts, and in some places, clay. The fourth locality was near the head of Sullivan's Creek, where the soil is a heavy black clay.

This report deals with the problem of detecting electrically resistive bodies of small size buried at shallow depths in wet soils. Detection was attempted by means of measurements made on the surface of the soil using the electrical resistivity method. The present report can be regarded as an extension of an earlier one (No. 1943/64B). The purpose of the new tests was twofold. Firstly it was proposed to make tests of 'normal' resistivity effects using a constant electrode arrangement and measuring the resistivity at closely spaced points on water saturated soils. The second part of the testing programme was contingent on the first part proving that under saturated conditions soil resistivities were sufficiently constant to warrent an attempt being made at detection. If this condition of constancy existed, it was proposed to extend the work of the tests, reviewed in the previous report, to actual field conditions. This has been done and the present report deals with the results obtained.