The thermal structure of the Sydney Gunnedah Bowen Basin Eastern Australia

The Earth's upper crust hosts many important economic resources and understanding its geometry and thermal structure is critical for resource development and management, and scientific research. In Australia subsurface structure is currently understood through deep seismic reflection surveys, gravity profiles and small scale integrated geological models and the subsurface thermal profile from extrapolated borehole temperature measurements and heat flow measurements. This style of approach has inherent limitations, including the inability to account for 3D effects on subsurface temperatures and heat flow. -- The Sydney-Gunnedah-Bowen Basin (SGBB) system is the largest sedimentary basin on the east coast of Australia, and is host to many energy rich resources. Thermal structure is controlled principally by geology and basin architecture, which is characteristic of an extensional rift origin. Through integrated geophysical methods and a novel approach to 3D thermal modelling both the geometry and thermal structure of the upper crust of the SGBB is characterised. The ability to calibrate and constrain thermal models with real world observables is critical to understanding uncertainties and providing representative estimates of temperature. By constructing the thermal model on an upper crustal scale the thermal field is self consistent with detailed 3D geological structures and physical rock properties. This model is also scalable and able to focus on smaller, detailed areas. -- The 3D geological and thermal model of the SGBB provides the first integrated framework from which to assess the thermal structure and build the next generation of detailed models for future research. By characterising the thermal structure new resource exploration in geothermal energy is possible, with the estimated temperature at depth over 150°C in most parts of the Sydney and Bowen basins.