Brief description
This data package contains interpretations of airborne electromagnetic (AEM) conductivity sections in the Exploring for the Future (EFTF) program’s Eastern Resources Corridor (ERC) study area, in south eastern Australia. Conductivity sections from 3 AEM surveys were interpreted to provide a continuous interpretation across the study area – the EFTF AusAEM ERC (Ley-Cooper, 2021), the Frome Embayment TEMPEST (Costelloe et al., 2012) and the MinEx CRC Mundi (Brodie, 2021) AEM surveys. Selected lines from the Frome Embayment TEMPEST and MinEx CRC Mundi surveys were chosen for interpretation to align with the 20 km line-spaced EFTF AusAEM ERC survey (Figure 1).
The aim of this study was to interpret the AEM conductivity sections to develop a regional understanding of the near-surface stratigraphy and structural architecture. To ensure that the interpretations took into account the local geological features, the AEM conductivity sections were integrated and interpreted with other geological and geophysical datasets, such as boreholes, potential fields, surface and basement geology maps, and seismic interpretations. This approach provides a near-surface fundamental regional geological framework to support more detailed investigations.
This study interpreted between the ground surface and 500 m depth along almost 30,000 line kilometres of nominally 20 km line-spaced AEM conductivity sections, across an area of approximately 550,000 km2. These interpretations delineate the geo-electrical features that correspond to major chronostratigraphic boundaries, and capture detailed stratigraphic information associated with these boundaries. These interpretations produced approximately 170,000 depth estimate points or approximately 9,100 3D line segments, each attributed with high-quality geometric, stratigraphic, and ancillary data. The depth estimate points are formatted for compliance with Geoscience Australia’s (GA) Estimates of Geological and Geophysical Surfaces (EGGS) database, the national repository for standardised depth estimate points.
Results from these interpretations provided support to stratigraphic drillhole targeting, as part of the Delamerian Margins NSW National Drilling Initiative campaign, a collaboration between GA’s EFTF program, the MinEx CRC National Drilling Initiative and the Geological Survey of New South Wales. The interpretations have applications in a wide range of disciplines, such as mineral, energy and groundwater resource exploration, environmental management, subsurface mapping, tectonic evolution studies, and cover thickness, prospectivity, and economic modelling. It is anticipated that these interpretations will benefit government, industry and academia with interest in the geology of the ERC region.
Lineage
Maintenance and Update Frequency: asNeeded
Statement:
This study interpreted almost 30,000 line km of nominally 20 km line-spaced AEM conductivity sections across an area of approximately 550,000 km2 up to a depth of 500 m. The AEM data were acquired as part of the EFTF AusAEM ERC (Ley-Cooper, 2021), the Frome Embayment TEMPEST (Costelloe et al., 2012) and the MinEx CRC Mundi (Brodie, 2021) AEM surveys, and were inverted using Geoscience Australia’s (GA) Layered Earth Inversion Sample-By-Sample Time Domain Electromagnetics inversion (Brodie, 2015). Horizontal resolution of the conductivity sections is 12.5 m. The vertical resolution varies exponentially with depth, with the cell sizes increasing from 4.0 m at the surface to approximately 55 m at the bottom cell, approximately 500 m below the surface. Consequently, the resolvability of fine detail decreases with depth. The depth of investigation (Hutchinson et al., 2010) varies depending on the bulk electrical conductivity of the Earth, and averages approximately 250 m across the survey, although the depth of signal penetration is estimated to be greater than 500 m in electrically resistive terrain. Refer to Ley-Cooper & Brodie (2020) and Ley-Cooper et al., (2020) for more details on the AusAEM survey.
This interpretation was undertaken in 2021-23 as part of GA’s EFTF Australian Resources Framework and Darling-Curnamona-Delamerian projects. The interpretations were in-part made to support stratigraphic drillhole targeting, as part of the Delamerian Margins NSW National Drilling Initiative campaign, a collaboration between GA’s EFTF program, the MinEx CRC National Drilling Initiative and the Geological Survey of New South Wales.
This study uses methodologies from GA’s multilayered chronostratigraphic AEM interpretation workflow (Wong et al., 2022). Utilisation of this workflow ensures that all stratigraphic unit information is consistent with GA’s Australian Stratigraphic Units Database (https://asud.ga.gov.au), multidimensional exports are in non-proprietary formats, and exports meet the data standards for the EGGS database (Mathews et al., 2020; accessible through GA’s Portal https://portal.ga.gov.au). The workflow used for this interpretation is the same as used in the Canning Basin AusAEM Airborne Electromagnetic Interpretation (Connors et al., 2022; Vilhena et al, 2023), and is an evolution of that used in GA’s earlier regional AusAEM interpretations (Wong et al., 2020; Wong et al., 2021).
This interpretation produced approximately 170,000 depth estimate points or approximately 9,100 3D line segments, each attributed with high-quality geometric, stratigraphic, and ancillary data. These points are formatted for and intended to be uploaded to GA’s EGGS database. This interpretation, alongside other multidisciplinary depth estimate available from the EGGS database, have applications in a wide range of investigative, modelling and analytical uses.
Notes
PurposeThe interpretation of AEM conductivity sections in the ERC study area delineates the geo-electrical features that correspond to major chronostratigraphic boundaries and other geological features of interest. The geological era chronostratigraphic resolution was used when interpreting chronostratigraphic boundaries, specifically the contacts between Cenozoic, Mesozoic, Paleozoic, Neoproterozoic, Mesoproterozoic and Paleoproterozoic stratigraphic units. Non-chronostratigraphy-related interpretations were also collected, such as faults, the base of weathering, and discrete electrical conductors. Regional interpretation of the AEM conductivity sections was made to support GA’s EFTF Australian Resources Framework project. This regional interpretation contributes to the national-scale multilayered interpretation of AEM conductivity sections. Interpretations of the chronostratigraphic boundaries were also in-part made to support stratigraphic drill hole targeting in the Loch Lilly-Kars Belt area of interest, 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 project, the MinEx CRC National Drilling Initiative and the Geological Survey of New South Wales.The chronostratigraphic and non-chronostratigraphic feature types (in the “TYPE” field) form the parent-level categories in the interpretations. These are the categories that were digitised during the interpretation; they are related to the geometry of each line segment, and are the symbolised categories displayed by the 3D GOCAD objects. All other (child) attributes are attached to the lines or points as ancillary data. Moreover, each interpretation line or point is attributed with interpretation-specific metadata, including geometry, chronostratigraphic relationship, geological contact type, stratigraphy, confidence, basis of interpretation, comments, new observations, interpreter’s details and interpretation date. The geometry data and pixel coordinates allow interpretations to be plotted in multidimensional spaces. Segment and vertex identifiers are provided to maintain polylines when converting between multidimensional spaces. The ground surface elevation directly above each vertex, derived from a digital elevation model acquired during AEM data acquisition, is provided (in the “AEM_DEM” field).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. This information is complemented by the contact type field, which describes if contacts are conformable, unconformable, intrusive, faulted, etc. The stratigraphic unit fields capture the stratigraphic unit names and numbers for the units above and below the interpretation (if the interpretation occurs at an era boundary) or the stratigraphic unit name and number of the unit the interpretation occurs within (if the interpretation line occurs entirely within one unit). The interpreter’s confidence levels of the interpretation placement, and for the stratigraphic units occurring in the locations in which they are interpreted, are provided. All stratigraphic names and numbers are consistent with GA’s Australian Stratigraphic Unit Database, with all interpreted stratigraphic units being current at the time of the interpretation.The interpretations were performed by integrating the AEM conductivity sections with supporting multidisciplinary datasets. The types of datasets that support the interpretation are captured in the attributes of each line or point, in the basis of interpretation field. In addition to this, a field that refers to specific datasets that informed the interpretation, including bibliographical references, is also provided. A comments field provides further information about the interpretation. A field that captures any new observations made during the interpretation provides insight into features that were previously unknown. The names of the interpreter and the date of the interpretation for each line or point are also provided.Interpretation of potentially newly-discovered geological faults observed in the AEM conductivity sections, and known faults from the integrated supporting information, have been included in the dataset. Where the attitudes of faults were either indiscernible in the conductivity sections or were otherwise unknown, the faults have been interpreted as vertical. Although not performed consistently across the entire dataset, a visual assessment was also performed on features that displayed anomalously high electrical conductivities, in contrast to the background electrical conductivity; these were delineated using the ‘Major_conductor’ category. These assessments were made with reference to the inversion multi-plots, infrastructure datasets, aerial photography, etc., to ensure the anomalous electrical conductors were not originating from model misfit, lightning events, anthropogenic sources, etc. In some cases, these observations and interpretations were based on integration of the AEM data and models with additional information and supporting datasets including interpreter local area knowledge, literature, surface and subsurface geological maps, boreholes, magnetics and gravity. The anomalously high conductivities interpreted in this dataset could be from a range of sources, including electrically conductive black shale horizons and other conductive lithologies, and saline groundwater. Despite care taken to ensure that these features were of geological origin, the possibility remains that some features interpreted with this class could be from anthropogenic or inversion artefact sources.In addition to the data in this data package, this interpretation is also available for visualisation on Geoscience Australia’s Portal
Created: 15 06 2023
Issued: 26 06 2023
text: westlimit=138; southlimit=39; eastlimit=145.5; northlimit=27; projection=GDA94 / MGA zone 54 / projected (EPSG: 28354)
text: uplimit=-1500; downlimit=0; projection=Australian Height Datum / vertical (EPSG: 5111)
Subjects
ARF |
Adelaide Fold Belt |
Airborne electromagnetics |
AusAEM |
Australia's Resources Framework |
Basins |
Cartography and digital mapping |
Cenozoic |
Cover thickness |
DCD |
Darling-Curnamona-Delamerian |
Delamerian Orogen |
Depth to basement |
EFTF – Exploring for the Future |
ERC |
Earth Sciences |
Earth system sciences |
Eastern Resources Corridor |
Electrical and electromagnetic methods in geophysics |
Energy |
Geomorphology and earth surface processes |
Geophysical interpretation |
Geophysics |
Geoscience data visualisation |
Geospatial information systems and geospatial data modelling |
Groundwater |
Groundwater hydrology |
Lachlan Orogen |
Lake Eyre Basin |
Mesoproterozoic |
Mesozoic |
Minerals |
Murray Basin |
Natural hazards |
Neoproterozoic |
New South Wales |
Otway Basin |
Paleoproterozoic |
Paleozoic |
Published_External |
Queensland |
Regolith and landscape evolution |
Resource geoscience |
Sedimentology |
South Australia |
Stratigraphy (incl. biostratigraphy |
Structural geology and tectonics |
Thomson Orogen |
Victoria |
geoscientificInformation |
sequence stratigraphy and basin analysis) |
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Other Information
Download data package (zip) [18.42 MB]
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https://d28rz98at9flks.cloudfront.net/147992/147992_00_0.zip
Download metadata statement (pdf) [1.1 MB]
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https://d28rz98at9flks.cloudfront.net/147992/147992_01_1.pdf
Identifiers
- DOI : 10.26186/147992
- URI : pid.geoscience.gov.au/dataset/ga/147992
- global : ea873fbe-a357-4daf-8df3-70ae3b127bf3
