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The Upper Jurassic Walloon Coal Measures of the Surat Basin is one of Australia’s largest and most productive gas provinces. Despite the drilling of over 8500 wells and numerous publications, the stratigraphic framework is poorly defined. The laterally discontinuous nature of the sedimentary facies, including coals and fluvial channel sandstones, makes correlation difficult. The abundance of volcanic air-fall tuff beds within strata across the basin provides a unique opportunity to independently verify existing stratigraphic frameworks. Using the high-precision chemical abrasion thermal ionisation mass spectrometry technique, zircon grains from 28 tuff beds have been successfully dated within an error margin of less than 100 kyr. These dates substantially revise biostratigraphic and lithostratigraphic frameworks. Lithostratigraphic units are diachronous across the basin. In addition, the sparsity of key spore–pollen taxa limits the application of biostratigraphy. The complex interplay of climate and subsidence on facies distributions can now be documented over a time frame of ~4 Ma. Syntectonism played an important role in variable palaeodrainage patterns across the basin, the frequency of fluvial avulsions and preferential sites of peat accumulation through time. The new stratigraphic framework should aid in future exploration for coal seam gas in the area. Dating tuff beds using high-precision dating techniques should also assist in correlation of non-marine strata elsewhere in the world.
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