Academic literature on the topic 'Geochemistry – New South Wales – Coleambally'

If management decisions are based on geospatial data that have not been assessed for spatial accuracy, then debate about both the measurements and the decisions themselves can occur. This debate, in part, can be avoided by evaluating the spatial accuracy of geospatial data, leading to heightened confidence in both the data and the decisions made from the data. To increase the effectiveness of environmental compliance monitoring, the spatial accuracies of 2 Geographic Information System datasets were estimated at the Coleambally Irrigation Area, New South Wales. The first, high-resolution digital aerial photography acquired in January 2000, is the Geographic Information System baseline data for Coleambally Irrigation Area. The second, Digital Topographic Data Base roads data, although not a reference dataset at Coleambally Irrigation Area, is often used as a baseline dataset across Australia. Neither dataset met the National Mapping Council of Australia’s standard of map accuracy, so a new version of the digital aerial photography was created that did. The positional accuracy of the improved dataset was over 4 times more accurate than the Digital Topographic Data Base roads dataset and over 2.5 times more accurate than the original digital aerial photography. It was also found that the overall areal error of paddocks measured from the improved dataset decreased as more paddock areas were added together; a finding that has a direct impact on management decisions at Coleambally Irrigation Area. This study both provides a demonstration of how to assess and improve spatial accuracy and shows that this process is not unduly complicated.

Irrigation farmers in the Murray–Darling Basin of Australia are under considerable pressure to reduce the amount of water they use for irrigation, while sustaining production and profitability. Changing from surface to pressurised irrigation systems may provide some or all of these outcomes; however, little is known about the performance of alternative irrigation methods for broadacre annual crops in this region. Therefore, a demonstration site for comparing furrow, subsurface drip and sprinkler irrigation was established on a representative clay soil in the Coleambally Irrigation Area, NSW. The performance of maize (Zea mays L.) under the three irrigation systems was compared during the 2004–05 season. Subsurface drip irrigated maize out-performed sprinkler and furrow irrigated maize in terms of grain yield (drip 11.8 t/ha, sprinkler 10.5 t/ha, furrow 10.1 t/ha at 14% moisture), net irrigation water application (drip 5.1 ML/ha, sprinkler 6.2 ML/ha, furrow 5.3 ML/ha), net irrigation water productivity (drip 2.3 t/ML, sprinkler 1.7 t/ML, furrow 1.9 t/ML) and total water productivity (drip 1.7 t/ML, sprinkler 1.4 t/ML, furrow 1.3 t/ML). Thus, subsurface drip irrigation saved ~30% of the total amount of water (irrigation, rain, soil water) needed to produce the same quantity of grain using furrow irrigation, while sprinkler irrigation saved ~8% of the water used. The higher net irrigation with sprinkler irrigation was largely due to the lower soil water content in the sprinkler block at the time of sowing. An EM31 survey indicated considerable spatial soil variability within each irrigation block, and all irrigation systems had spatially variable water distribution. Yield variability was very high within all irrigation systems, and appeared to be more strongly associated with irrigation variability than soil variability. All irrigation blocks had large patches of early senescence and poor cob fill, which appeared to be due to nitrogen and/or water deficit stress. We expect that crop performance under all irrigation systems can be improved by improving irrigation, soil and N management.

AbstractSpecimens of honey-brown to pinkish-brown globular carbonates encrusting concretionary goethite–coronadite from the oxidized zone at Broken Hill, New South Wales, have compositions in the rhodochrosite–smithsonite series. This may be the first extensive natural occurrence of this solid-solution series. Growth of the carbonates occurred in zones which have near uniform composition. The ratio MnCO3/(MnCO3 + ZnCO3) for each zone bears a linear relationship to the measured d spacing for the 104 X-ray reflections. Because cerussite is the only other mineral associated with the Zn-Mn carbonates and because of an absence of detailed locality information, the paragenetic significance of these minerals cannot be determined. The solutions depositing them may have been derived from the near-surface equivalents of the Zinc Lode horizons.

AbstractThe paper discusses the mineralogy of eruptives from the Nandewar Volcano, which range in composition from hawaiite and trachyandesite to comendite via tristanite and mafic and peralkaline trachyte. Olivine, Ca-rich pyroxene, and amphibole display marked decreases in 100 Mg/(Mg + Fe) ratios in the sequence trachyandesite to comendite, reflecting variation in host rock compositions. The presence of tscher-makitic subcalcic pyroxene and aluminous bronzite megacrysts in several trachyandesites indicates that these experienced intratelluric crystallization at elevated pressures (6–8 kbar). Some titanomagnetite and plagioclase phenocrysts in trachyandesites may also be moderate pressure cognate precipitates. Groundmass pyroxenes of some trachytes and comendites are strongly acmitic. The presence or absence of coexisting alkali amphiboles and aenigmatite appears to reflect stability over a relatively broad range of fO2 conditions. Aenigmatite rims on titanomagnetite and ilmenite microphenocrysts in several peralkaline eruptives provides support for a ‘no-oxide’ field in T-fO2 space. The Fe-Ti oxide compositional data indicate that magmas spanning the spectrum trachy-andesite-comendite crystallized under conditions of decreasing T and fO2 which broadly coincided with the FMQ synthetic buffer curve. However, a voluminous group of slightly older associated rhyolites appear to have crystallized under significantly more oxidizing conditions.

Discriminating crops by remote sensing remains reasonably complex and expensive for many agricultural land managers. The current study was conducted to facilitate the operational use of remote sensing for field-level rice monitoring in Australia by determining (i) whether existing methods relating to simple moisture-based rice classification could be further simplified, and (ii) whether the high accuracies resulting from that moisture-based methodology could be further increased. First, the impact of removing the most complicated processing step, atmospheric correction, on rice classification accuracies was assessed for the 2000–01 summer growing season at the Coleambally Irrigation Area, New South Wales. The primary error sources of rice classification were then identified and simple rules developed in an attempt to reduce errors associated with confusion between unharvested winter cereals and flooded rice paddies early in the summer growing season. These newly defined rules were then used on imagery acquired in the subsequent summer growing season (2001–02) in order to assess their repeatability. The assessment of atmospheric correction showed that during the critical time frame associated with high rice identification (October–November), using non-atmospherically corrected data increased overall accuracy, although the improvement was small (about 1%). Overall accuracy also increased for every case tested for both growing seasons as a result of the rule-based classification (ranging from about 1 to 14%), revealing that the methods were sufficiently repeatable. This study moves per-field rice monitoring at the Coleambally Irrigation Area closer to an operational application and shows that simple rule-based remote sensing classifications can be very effective when site practices are known.

Within the last 10 years throughout south-eastern Australia, there has been a rapid expansion of modernisation efforts by irrigation companies that has included installation of automatic control structures, the so-called total channel control (TCC) technology. TCC includes supervisory control and data acquisition technology, which results in production of integrated databases utilising real time measurements of flow and water depth throughout the whole system. Pondage tests are acknowledged as the best direct method for seepage measurement and the recorded water level data from automated systems during periods of gate closure can be treated as pondage test data. This paper presents the development and operation of a new computer model that applies pondage test methodology to automated channel control data during periods of shut down in order to estimate seepage rates in different channel reaches. The Coleambally Irrigation Area (CIA) in southern New South Wales was chosen as the case study, as it is one of the first irrigation districts in the world to be automated. The methodology was tested using the TCC data of the entire CIA during the 2010–11 season and was demonstrated to be successful in identifying all pondage conditions throughout the entire network as well as estimating the seepage rates for each gauge, pondage and pool.

The Quaternary alluvial and aeolian sediments underlying the eastern portion of the Riverine Plain have been examined to assess their impact on groundwater access and movement in the Coleambally district. Over 9800 borehole logs from the Coleambally Irrigation Area (CIA) and surrounding districts were digitized using GIS and database software and supplemented with 632 borehole logs from the Department of Land and Water Conservation (Leeton) to form the platform for stratigraphic and groundwater investigations conducted in this study. The borehole data were summarised into two sediment classification schemes, the first to delineate the distribution of palaeochannel sediments and the second to assess to spatial distribution of aquitards and aquifers. A series of detailed cross-sections differentiated between at least four distinct palaeochannel sequences identified within the Upper Shepparton Formation overlying the clay-dominated Lower Shepparton Formation. The two deepest sequences, the new Gumblebogie and Ugobit members, comprise thick (3-10 m), laterally extensive (up to 25 km wide) sheets of coarse sandy alluvium that occur to the north of the CIA at depths between 12 to 35 metres below the surface. These deposits are evidence of highly active alluvial phases on the plain, more vigorous than any since. Slightly higher in the sequence (typically 10-20 m depth) is a thick (2-15 m), laterally extensive (up to 10 km wide) mixed-load sequence (the new Duderbang member), which is stratigraphically disconnected from the deeper sanddominated units. Near-surface palaeochannel deposits, which consist of less extensive (up to 3 km wide) coarse sandy alluvium at depth and a combination of mixed- and bedload sequences closer to the surface, make up the youngest palaeochannel deposits in the area. The size and extent of reserved palaeochannel sequences beneath the study area have decreased markedly since what is interpreted as the mid Quaternary and is probably symptomatic of declining fluvial activity on the Riverine Plain through to the present. The development of source-bordering dunes associated with belts of palaeochannel material in the area was examined using shallow geophysics (GPR), topographic surveys, laser particle size analysis and thermoluminescence dating. Dune building in Contents the area occurred in conjunction with channel activity during the Kerarbury (55-35 ka) and Coleambally (105-80 ka) palaeochannel phases (Page et al., 1996) when sediment supply conditions were favourable, probably due to strongly seasonal discharges draining the southeastern highlands. The presence of stabilising vegetation on the channel margins is believed to have played a key role in the development of dunes in the area, which show poorly developed internal structure. The increased precipitation that enhanced channel discharges must also have sustained dune vegetation. Increased aridity and reduced vegetation approaching and during the LGM appears to have caused the widespread remobilization of dune crests. The complex alluvial and aeolian stratigraphy of the Shepparton Formation strongly influences groundwater movement in the Coleambally district. Piezometric levels show that deeper, highly permeable units (e.g. Ugobit member) in the northern part of the study area act as conduits for the discharge of groundwater, helping to maintain much lower watertables in the north as well as induce groundwater flow from the CIA. ‘Sediment vs depth’ analysis demonstrates that there is limited vertical connection through the thick, clay-dominated sequence of the Lower Shepparton Formation to the highly transmissive sands and gravels of the underlying Calivil Formation. The tendency of the Lower Shepparton Formation to restrict downward leakage is likely to both contribute to the problem of shallow irrigation-induced watertables in the CIA as well as impede efforts to lower watertables by pumping from deeper aquifers. The upper 3 metres of the Shepparton Formation are clay-dominated with a low water storage capacity, causing near-surface watertables to be highly responsive to recharge by surface water. The available data indicate that when piezometric levels fall below this clay-rich zone they are able to absorb short-term increases in recharge due to the higher proportion permeable alluvium in the unsaturated zone.

The Monaro Volcanic Province (MVP) is an Oligocene-Eocene intraplate basaltic lava field situated in the Southern Highlands of New South Wales between the towns of Cooma and Bombala. The lava pile of the MVP consists of basal sub-alkali rocks (olivine tholeiite, transitional basalt) capped by a number of thick ankaramite lavas, above which lie less numerous alkali rocks including alkali olivine basalt, nepheline basanite and olivine nephelinite. Intercalated with the lava flows are massive and matrix-supported alkali and ankaramitic hyaloclastites, alkali pillow basalts, rare tuffs, bauxitic weathering profiles, lacustrine sediments and reworked late Cretaceous to early Tertiary river gravels. The lava pile is intruded through by numerous volcanic plugs and dykes and rare maars. Volcanic centres are principally concentrated in two NW-SE trending zones parallel to major crustal-scale fractures in the Palaeozoic basement. Centres almost always lie over the intersections of two or more conjugate strike-slip or transverse fractures. The stratigraphy, whole-rock geochemistry and Sr and Nd isotopic signatures of rocks from the MVP indicate magma-genesis initially from an asthenospheric source with EM1 characteristics, gradually becoming more lithospheric with DM source characteristics. The long-lived nature of the MVP rules out a mantle plume-type source for magmas. Instead, a diapiric source is envisaged. The MVP mantle xenolith suite appears to have equilibrated at slightly higher temperatures for given pressures than the Newer Volcanics Province suite suggesting the palaeogeotherm for the MVP was slightly hotter than the "South East Australian" geotherm. Large amounts of amphibole (pargasitic hornblende, pargasite, ferroan pargasite and kaersutite) occuring within the more silica-undersaturated rocks of the MVP, and rarely within Iherzolitic xenoliths, are interpreted to have formed as selvages on mantle veins in contact with peridotite beneath the MVP. Amphiboles were later sampled by magmas rising through the same conduits and were brought to the surface. MVP ankaramite lavas feature < 2cm clinopyroxene porphyrocrysts, the cores of which are shown to have crystallised at ca. 18 kb pressure or ca. 54 km depth. This defines the base of the local crust within the MVP region. Data from the MVP support a landscape evolution model based on the isostatic rise of the Southern Highlands due to voluminous magmatic underplating since the Cretaceous. Data further support limited denudation since the Early Tertiary based on a pulsatory but high palaeogeotherm.

The three-dimensional thermal maturity pattern has been investigated and the hydrocarbon generation potential assessed for the Permian and Triassic sequences of the southern Bowen and northern Gunnedah Basins and the lower part of the overlying Jurassic Cretaceous Surat Basin sequence in northern New South Wales. An oil-source rock correlation also has been investigated in the Gunnedah Basin. Vitrinite reflectance measurements were conducted on 256 samples from 28 boreholes. A total of 50 of these samples were subjected to Rock-Eval pyrolysis analysis, and 28 samples extracted for additional organic geochemical studies (GCMS). A re-evaluation of the stratigraphy in the southern Bowen Basin and a stratigraphic correlation between that area and the northern Gunnedah Basin was also included in the study. An overpressured shaly interval has been identified as a marker bed within the lower parts of the Triassic Moolayember and Napperby Formations, in the Bowen and Gunnedah Basins respectively. Suppressed vitrinite reflectance in the Permian sequence was used as another marker for mapping the stratigraphic sequence in the southern Bowen Basin. The Permian sequence in the Bowen Basin thins to the south, and probably pinches out over the Moree High and also to the west. The coal-bearing Kianga Formation is present in the north and northeastern parts of the study area. A disconformity surface between Digby and Napperby Formations in the Gunnedah Basin is probably time-equivalent to deposition of the Clematis Group and Showgrounds Sandstone in the Bowen Basin. The Clematis Group is absent in the study area, and the Moolayember Formation considered equivalent to the Napperby Formation. Although in many cases core samples were not available, handpicking of coal or shaly materials from cuttings samples where geophysical log signatures identify these materials helped in reducing contamination from caved debris. Histogram plots of reflectance also helped where the target and caved debris were of similar lithology. Vertical profiles of the vitrinite reflectance identified suppressed intervals in the study area due to marine influence (Back Creek Group and Maules Creek Formation) and liptinite rich source organic matter (Goonbri Formation). The suppression occurs due to the perhydrous character of the preserved organic matter. High reflectance values were noted within intrusion-affected intervals, and two types of igneous intrusion profiles were identified; these are simple and complex profiles. An isoreflectance map for the non-suppressed interval at the base of the Triassic sequence in the southern Bowen Basin shows that the organic matter is mature more towards the east close to the Goondiwindi Fault, and also towards the west where the Triassic sequence directly overlies the basement. High values also occur over the Gil Gil Ridge in the middle, to the south over the Moree High, and to the north where the sequence is thicker. The reflectance gradient in the suppressed intervals is higher than in the overlying non-suppressed sequences, especially when the rank has resulted from burial depth. Tmax from Rock-Eval pyrolysis was found to be lower in the perhydrous intervals, and was high in mature and igneous intrusion-affected intervals. Based on the source potential parameters, the Permian Back Creek Group is a better source than the Kianga Formation, while the Goonbri Formation is better than the Maules Creek Formation. The Triassic Napperby Formation has a fair capacity to generate oil, and is considered a better source rock than the equivalent Moolayember Formation. The Jurassic Walloon Coal Measures is a better source than Evergreen Formation, and has the best source rock characteristics, but is immature. The Rock-Eval S1 value shows better correlation with extracted hydrocarbon compounds (saturated and aromatics) than the total extractable organic matter. This suggests that solvent extraction has a greater ability to extract NSO compounds than temperature distillation over the Rock-Eval S1 interval. Terrestrial organic matter is the main source input for the sequences studied. This has been identified from organic petrology and from the n-alkane distributions and the relatively high C29 steranes and low sterane/hopane ratios. The absence of marine biomarker signatures in the Permian marine influenced sequence, could be attributed to their dilution by overwhelming amounts of non-marine organic matter. A mainly oxic to suboxic depositional environment is inferred from trace amounts of 25-NH, BNH and TNH. This is further supported by relatively high pr/ph ratios. Although C29/C30 is generally regarded as an environmental indicator, high values were noted in intrusion-affected samples. The 22S and 20S ratios were inverted ????reaches pseudo-equilibrium???? in such rapidly heated, high maturity samples. The ratio of C24 tetracyclic terpane to C21-C26 tricyclic terpanes decreases, instead of increasing, within the Napperby Formation close to a major igneous intrusive body. The 22S ratio, which is faster in reaction than the other terpane and sterane maturity parameters, shows that the Permian sequence lies within the oil generation stage in the Bowen Basin, except for a Kianga Formation sample. The Triassic sequence is marginally mature, and the Jurassic sequence is considered immature. In the Gunnedah Basin, the Permian sequence in Bellata-1 and Bohena-1, and the Triassic sequence in Coonarah-1A, lie within the oil generation range. In the intrusion-affected high maturity samples, the ratio is reaches pseudo-equilibrium. This and other terpane and sterane maturity parameters are not lowered (suppressed) in the perhydrous intervals. The ???????? sterane ratio, however, is slowest in reaction to maturity, and variations in low maturity samples are mainly due to facies changes. Diasterane/sterane ratios, in the current study, increase with increasing TOC content up to 5% TOC, but decrease in rocks with higher TOC contents including coals. Highly mature samples, as expected, in both cases are anomalous with high ratios. Calculated vitrinite reflectance based on the method of Radke and Welte (1983), as well as MPI 1 and MPI 2, shows the best comparison to observed values. These aromatic maturity parameters are lowered within the reflectance-suppressed intervals. Oil stains in the Jurassic Pilliga Sandstone in the Bellata-1 well have been identified as being indigenous and not due to contamination. The vitrinite reflectance calculated to the oil stain suggests that the source rock should be within a late mature zone. Such high maturity levels are only recognised within intrusion-affected intervals. A close similarity between the oil stain sample and the intruded interval of the Napperby Formation is evident from the thermal maturity and biomarker content. Hydrocarbon generation and expulsion from the lower part of the Napperby Formation as a result of igneous intrusion effects is suggested as the source of the oil in this particular occurrence. Terpane and sterane maturity parameters increase with increasing burial depth in the intervals with suppressed (perhydrous) vitrinite reflectance. The generation maturity parameters also increase through intervals with perhydrous vitrinite, which suggests that hydrocarbons continue to be generated and the actual amount is increasing even though traditional rank ????????????stress???????????? maturity parameters are lowered. Accordingly, the Permian sequences in the lower part of the Bowen Basin are at least within the peak oil generation zone, and probably within late oil generation in the north and northeast of the study area. To generate significant amounts of hydrocarbon, however, the thickness of the shaly and coaly intervals in the Permian sequence is probably a critical parameter. In the Gunnedah Basin, a significant amount of hydrocarbon generation is probably only possible as a result of igneous intrusions.

Salinisation of the shallow groundwater system has occurred coincident with the development of irrigation in the Coleambally Irrigation Area. Salinisation in irrigation areas has previously been attributed to the evaporative concentration of the water table; however, there are other sources of salt such as the accumulation of rainfall by vegetation and the dry deposition of salt-laden dusts. A significant store of crystalline gypsum, together with high concentrations of Na, Mg and Confidence limit, was found within the previously unsaturated zone of the Upper Shepparton Formation. The salt store was identified both within and outside of the groundwater mound; therefore evaporative concentration of the water table cannot be the source of salt. The transition from regional groundwater quality, as applied as irrigation to the ground surface, to shallow groundwater quality is simply explained by solubilisation of this salt store in the presence of soil CO2. Dating of basal palaeochannel sands indicates that the identified salt store, a profile of only 20 m, was accumulated during the last glacial cycle. Radiocarbon dating indicates that the peak in eluate salinity, at approximately 2 m below ground surface, is between 15,000 and 25,000 years old, coincident with the Last Glacial Maximum. The Last Glacial Maximum was a period of significantly enhanced aridity on the Australian continent. It was also found that the peak in eluate salinity coincided with a bi-modal particle size distribution. The bi-modal signature implies that these sediments were subject to the aeolian accession of dusts. It was found that the contribution of salt from dry deposition of dusts exceeded the contribution from rainfall by at least 1.9 to 11 times during the last glacial cycle. The results of this study imply that salt-laden dusts have, and continue to play an important role in the salinity and sodicity of soils in the Coleambally Irrigation Area and beyond.

Transported regolith has the capacity to mask underlying mineralisation by restricting the migration of most trace elements to the surface. Oxidation of sulphides generates highly mobile H+ which may migrate to surface, resulting in alteration of minerals and redistribution of elements within transported regolith cover. A detailed geochemical and geophysical study has been conducted at the Mandamah Cu-Au deposit in central-western New South Wales, where sub-economic mineralisation is covered by ~50 m of transported regolith and ~30 m of in situ regolith. A shallow-penetration electromagnetic survey was undertaken on nine transects and detailed mineralogical and selective extraction/ICP-MS geochemical analysis performed on regolith samples obtained from 107 soil cores and 16 pits spanning three extensive traverses across buried mineralisation. The selective extractions used were ammonium acetate, hydroxylamine.HCl and aqua regia. A distinct vertical zonation exists in the upper two metres of the transported regolith cover across the site and is related to soil mineralogy, soil pH, electrical conductivity and the amount of selectively extractable elements using the different geochemical extractions. The upper zone of near-neutral soil pH contains organic material but little carbonate; the intermediate high-pH zone has up to 2% Mg-calcite; the underlying low-pH zone displays Fe mottling. This zonation results from precipitation of salts due to evaporation, changes in redox potentials and accumulation of organic materials, in an otherwise relatively homogeneous quartz-clay alluvium. Ground conductivity measurements and selective extraction geochemistry display a strong response to parts of the underlying mineralisation. The principal signature is the depletion of Ca, S and Na, a reduction in the cation exchange capacity, the presence of non-carbonate alkalinity and a low electrical conductivity. A model to account for these patterns has been developed and involves a "prograde" stage of alteration of clay mineralogy and a redistribution of carbonates and various trace elements due to the development of an "acid chimney" above the oxidizing mineralisation during a period of elevated water tables and a "retrograde" stage involving a redistribution of some mobile elements back into the former acid chimney zone following the onset of more arid conditions. The results of this research demonstrate that the effects of sulphide mineralisation on the upper transported regolith at Mandamah can be detected using a combination of selective extraction geochemistry and shallow depth conductivity measurements. This technique has potential application in similar arid to semi-arid terrains.