Gammidge, Larissa1; Xu, Min1
1Geological Survey of New South Wales, Department of Regional NSW, Maitland, Australia
The late Silurian to Devonian Darling Basin in western New South Wales is one of the least explored sedimentary basins in the state and is prospective for petroleum. It comprises many sub-basins that share, or partially share, a similar depositional history. The location of the boundaries of some of the sub-basins have recently been revised as more data have been acquired and new modelling completed.
Limited seismic and drilling data across the Darling Basin, particularly near the margins of the sub-basins, and extensive shallow cover required a reliance on gravity and aeromagnetic data to interpret the boundaries of the sub-basins. The most widely used dataset to interpret sub-basin boundaries is the 2006 Murray-Darling-Eromanga SEEBASE™ model, created by Frogtech.
The SEEBASE™ model for the Yathong and Ivanhoe troughs shows that they are contiguous, but they were interpreted as two troughs based on their different orientations and slightly different structural histories. However, the interpretation and modelling of seismic survey data acquired in 2009 and 2013 show that there is continuity of strata across the Yathong and Ivanhoe trough boundaries. Therefore, there is no justification for two separate troughs and a single trough is more consistent with the current data. The revised trough is named the Yathong–Ivanhoe Trough.
The Yathong–Ivanhoe Trough boundary has been defined based on the extent of outcropping Devonian sedimentary rocks and the interpreted pre-Devonian basement rocks. Additionally, the SEEBASE™ and aeromagnetic data were used to define the boundary in areas of no outcrop. The former Yathong Trough has been shortened in the north–south direction by almost half. In contrast, the former Ivanhoe Trough is revised to be larger.
The revised boundary for a combined Yathong–Ivanhoe Trough is a more geologically robust interpretation than previous ones. This has implications for petroleum exploration targets within the trough. Recent work has highlighted areas where petroleum systems may be located and gives a greater understanding of the development of the Darling Basin over time.
Larissa is part of the Geological Survey of NSW, in the Petroleum and Renewables team. She has helped produce data packages for the Darling Basin, soil gas surveys and validated location information. Prior work includes supporting Coal Innovation NSW’s CO2 storage program, drilling two wells in the Darling Basin.