Regional magnetic depth estimates for Eastern Resources Corridor (ERC), Officer Basin, Tasmania and Northeast Queensland - Interpretation Data Package

Brief description

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Maintenance and Update Frequency: asNeeded

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Purpose
The interpretation of magnetic depth estimates in the four key study areas provides information about both the chronostratigraphic meaning of and depth to top of magnetisation sources across Australia. This information is useful for mapping both the horizontal and vertical distribution of magnetic stratigraphic units that are dated as Cenozoic, Mesozoic, Paleozoic, Neoproterozoic, Mesoproterozoic and Paleoproterozoic in age. In some instances, these boundaries denote post-depositional intrusive units, for example the Cenozoic, Mesozoic and Paleozoic dolerites in Tasmania, which intrude into older rocks or where aging relationships have been inverted as a result of structure. The regional interpretation of the magnetic depth estimates was made to support GA’s Exploring for the Future (EFTF) Australian Resources Framework (ARF) project. The four regional interpretations also contribute to national coverage of TMIM estimates, complimenting work carried out in the North Australian Craton (Matthews et al, 2020), in the Thomson Orogen (Goodwin et al., 2017), and over the Murray Basin in southeast Australia. The magnetic depth estimates also provided a preliminary estimate of cover thickness to support stratigraphic drill hole targeting in the Loch Lilly-Kars Belt area as part of the Delamerian Margins NSW National Drilling Initiative campaign. This stratigraphic drilling campaign was conducted as a collaboration between Geoscience Australia’s EFTF program’s Darling-Curnamona-Delamerian (DCD) project, the MinEx CRC National Drilling Initiative and the Geological Survey of New South Wales.Each interpretation point is attributed with interpretation-specific metadata, including location, depth, elevation or height of the magnetometer and elevation of ground level, chronostratigraphic relationship, stratigraphy, confidence in both the stratigraphic interpretation and 3D location of the point, the basis of interpretation, any further supporting comments regarding the interpretation, and the interpreter’s details. Chronostratigraphic relationships are captured by the eras of the units above and below the interpretations, which identify if the high-level chronostratigraphic order is continuous or discontinuous. The stratigraphic unit fields capture the stratigraphic unit names and numbers for the units above and below the depth estimate (if the interpreted depth estimate occurs at an era boundary) or the stratigraphic unit name and number of the unit within which the depth estimate is located (if the estimate sits entirely within one unit). The interpreter’s confidence in the point depth and in stratigraphic units occurring in the locations in which they are interpreted, are also provided. All stratigraphic names and numbers are consistent with GA’s Australian Stratigraphic Unit Database (ASUD), with all interpreted stratigraphic units being current at the time of the interpretation.The interpretations were performed by integrating the magnetic depth estimates generated by CSIRO with supporting multidisciplinary datasets. The types of datasets that support the interpretation are captured in the attributes of each point, in the basis of interpretation field. In addition to this, the reference field includes a link to the magnetic depth estimates data package and summary report. The comments field provides further information about the interpretation (if required). The names of the interpreter(s) for each point are also provided.Interpretation of the magnetic depth estimates was made by integrating the modelled estimates with additional information and supporting datasets including interpreter local area knowledge, literature, surface and subsurface (basement geology, solid geology) geological maps, boreholes, magnetics, airborne electromagnetic interpretation, and other geophysical datasets (including gravity and seismic). Generating depth to magnetic sources is a non-invasive and cost-effective way to quickly estimate the thickness of largely non-magnetic sedimentary cover over magnetic rocks. The attribution of these depth estimates with stratigraphic unit information, consistent with the Australian Stratigraphic Units Database (ASUD), adds value and utility to the depth estimates. In addition to the data in this release, this interpretation is also available for visualisation on Geoscience Australia’s Data Delivery Portal and is stored in, and retrievable from, the Estimates of Geological and Geophysical Surfaces (EGGS) database, also accessible through the Portal. Delivery through the EGGS database means that these depth estimate will have enduring value to a wide range of users in academia, government and industry.