No abstract available

No abstract available

The greater Eromanga Basin is an intracratonic Mesozoic basin covering an area of approximately 2,000,000 km2 in central and eastern Australia. The greater Eromanga Basin encompasses three correlated basins: the Eromanga Basin (central and western regions), Surat Basin (eastern region) and the Carpentaria Basin (northern region). The greater Eromanga Basin hosts Australia's largest known resources of groundwater as well as major onshore hydrocarbon resources, including significant coal bed methane (CBM) that has been discovered in recent years, and also contains extensive hot-sedimentary aquifer geothermal energy systems. Additionally, the basin has potential as a greenhouse gas sequestration site and will likely play a key role in securing Australia's energy future. Finally, although no major metallic mineral deposits are currently known in the greater Eromanga Basin, there is significant potential for undiscovered uranium mineralisation. A 3D geological map has been constructed for the greater Eromanga Basin using publicly available datasets. These are principally drilling datasets (i.e. water bores; mineral and petroleum exploration wells) and the 1:1,000,000 scale Surface Geology Map of Australia. Geophysical wireline logs, hydrochemistry, radiometrics, magnetic and gravity datasets were also integrated into the 3D geological map. This study has highlighted the potential of the southwest margin of the Eromanga Basin and the Euroka arch region to contain sandstone-hosted uranium mineral systems. The report demonstrates how incorporating disparate datasets in a 3D geological map can generate an integrated mapping solution with diverse applications: 1. Provide new insights into the geology and geodynamic evolution of the basin. 2. Identify hydrocarbon resource plays. 3. Assess the basin's mineral potential (e.g., sandstone-hosted uranium mineral systems). 4. Assess the basin's geothermal potential (e.g., hot-sedimentary aquifer geothermal systems). 5. Provide resource management information (e.g., groundwater). 6. Identify potential contaminants in groundwater.

A PowerPoint presentation showing regional interpretations of data from the Frome airborne electromagnetic survey, presented at a workshop on 30 November 2011 at the University of Adelaide, South Australia

Geoscience Australia conducted a survey of lakebed (benthic) nutrient fluxes in St Georges Basin, November 2003. The objectives were to: 1. determine the nature of nutrient cycling between the sediment and overlying water; and 2. determine the implications of benthic nutrient fluxes for water quality in the estuary. The relevance to management of this work is that it gives an indication of the susceptibility of the estuary to eutrophication from increased nutrient loads from the catchment. The key findings of the study were: - St Georges Basin was mesotrophic to eutrophic at the time of the survey (spring) based on relatively high respiration rates and O2 demand in the sediments measured by in situ benthic chambers. - Respiration rates were linked to phytoplankton biomass (mainly diatoms) where local fluvial discharge of dissolved nutrients created enhanced primary productivity in the water column, which in turn enhanced mineralisation rates. - St Georges Basin had comparatively low denitrification efficiencies (less than 60%). - St Georges Basin is likely to be prone to eutrophication and may have little tolerance for increases in nutrient and organic matter from the catchment due to the low denitrification efficiencies.

A collaborative field trial of the Quester-Tangent View Series 5 single beam acoustic benthic mapping system was recently conducted in Wallis Lake by Geoscience Australia and Quester Tangent Corporation. The survey involved acquisition of the acoustic backscatter data from the northern channels and basins of Wallis Lake. Quester-Tangent software (IMPACT v3) was used to classify acoustic echograms that returned from the lake bottom into statistically different acoustic classes, using principal components analysis. Six acoustically different substrate types were identified in the Wallis Lake survey area. Ground-truthing was undertaken to identify the sedimentological and biological features of the lake floor that influenced the shape of the return echograms. For each sample, measurements were made of grain size, wet bulk density, total organic carbon, CaCO3 content, and mass of coarse fraction (mainly shell) material. Statistical cluster analysis and multi-dimensional scaling were utilised to identify any physical similarities between groups of ground-truthing sites. The analysis revealed four distinct and mappable substrate types in the study area. The degree of association between acoustic classes and measured sediment parameters was also quantified. Cluster and MDS analysis revealed that, based on the parameters measured, the six acoustic classes were not uniquely linked to the sediment groups, suggesting that factors other than the sediment parameters alone are influencing the acoustic signal. The spatial interpretation of the Wallis Lake Quester-Tangent data represents the first quantification of non-seagrass habitats in the deeper areas of the lake, and provides a useful indicatior of benthic habitat diversity and abundance. For future studies, a more quantitative measure of faunal burrow size and density, and also other sedimentary bedforms, is recommended.

In April 2005, Geoscience Australia (GA) conducted a field survey of the waterbodies of the Torbay catchment drainage system. The Torbay Catchment Group and the Western Australian Department of Environment commissioned this study in order to address critical knowledge gaps in their understanding of the major components of the nutrient budget. In particular, the role of benthic nutrient fluxes, their magnitude, and total benthic nutrient supply to the water column for phytoplankton growth. The waterbodies studied were Torbay inlet, Lake Powell, Marbellup Brook and Lake Manarup. The key findings of this study were: 1. the sediments are a major source of nutrients to the water column of all waterbodies; and 2. denitrification, nitrogen fixation and benthic photosynthesis are critical processes influencing overall water quality.

Geoscience Australia has conducted four surveys in the Swan River Estuary to investigate benthic nutrient fluxes and their impact on water quality. Surveys were undertaken in March 2000, March 2001, September 2001 and October 2006, and both the upper and lower sections of the estuary were sampled. This report details the findings of the most recent benthic nutrient survey (October 2006) and compares benthic fluxes at selected sites during all four surveys. During the October 2006 survey, very high nutrient fluxes were recorded in the upper estuary muddy sites. Combined with very low denitrification efficiencies, large sediment nutrient pool sizes and hypoxic bottom waters, these muds are a significant source of bioavailable nutrients to the water column. Between 2000 and 2006 there has been a significant increase in the amount of organic matter decomposition and nutrient release from the muddy sediments in the upper estuary. A similar pattern is observed in the central basin, however, the change is not as severe. The shallow sandy margins of the lower estuary are sites of photosynthetic production, however, these differ between benthic and pelagic production depending on the light attenuation. When light is available at the sediment surface benthic production is evident, when light penetration is insufficient to reach the sediment surface pelagic production is more evident.

This report presents the results of a study by Geoscience Australia of Stokes Inlet and Wellstead Estuary, located in southwestern Western Australia, based on data collected during surveys in March 2006 and May 2007. It includes the present day rates of organic matter breakdown in the sediments of these estuaries, sediment and porewater properties, sedimentation rates, and an account of the historical environmental changes to these estuaries based on the sediment record. In the report you will find: 1. Purpose and background 2. Environmental Setting 3. Methods 4. Benthic Chambers 5. Sediment Cores and Grabs 6. Results and Discussions 7. Environmental conditions during the survey 8. Present-day nutrient dynamics in Stokes Inlet 9. Palaeoenvironmental reconstruction 10. Key conclusions

Benthic nutrient fluxes from the sediments were measured at three Sites in the Bombah Broadwater of Myall Lakes during the winter (June) of 2000. Surface sediments (0-1 cm) and two cores were collected at each site and processed for measurements of carbon and nitrogen isotopic composition of the OM (organic matter), biomarkers and bulk sediment composition (OM and major cations). Pore waters were extracted from sediments and measured for both organic and inorganic metabolites. Biomarker, benthic flux data and the compositions of inorganic metabolites in pore waters indicated that Redfield OM (organic matter) was predominant in the sediments and mostly diatomaceous and probably responsible for the observed release of nutrients from the sediments to t he overlying waters. Carbon degradation rates in the sediments, during these winter month, varied between 5-47 mmol m-2 d-1 (60-564 µg m-2d-1) and were highest in the muddy sediments (mean = 21.3 +/-12.7 mmol m-2 d-1) as compared to the sandy sediments (mean = 11.6 +/-4.8 mmol m-2 d-1). DIN fluxes were less than those predicted from CO2 fluxes and Redfield stoichiometry and the `missing nitrogen' (subsequently determined by mass spectrometry as N2) was indicative of denitrification in the surface sediments. Rates of denitrification calculated from N2 directly and from `missing N' were similar and up to 5.1 mmol N m-2 d-1. There was no evidence of organic metabolite fluxes although the organic and inorganic metabolite concentrations were similar in the pore waters. Denitrification efficiencies were high (mean = 80 +/- 4%) in the sandy sediments and lower (although there was considerable variability) in the muddy sediments (mean =38% +/- 9%). Most DIP (generally > 70%) liberated to pore waters during OM degradation was not released into overlying waters but remained trapped and enriched in surface sediments. Benthic nutrient fluxes (average DIN/DIP = 131) were preferentially enriched in N compared to the OM (N/P = 16) raining into the sediments. Adjective biophysical processes (not diffusive) dominated the fluxes of metabolites across the sediment -water interface.