The Surat Basin of eastern Australia contains 2500 m of Jurassic and Cretaceous sediments, terrestrial during the Jurassic, but showing two marine incursions during the Early Cretaceous. The sequence is almost flat-lying; the gentle basinward dip is modified by a few drape or compaction folds and faults. Deposition during the Jurassic was dominantly fluviatile and consisted of fining-upward megacycles, each more than 100 m thick. Volcanic debris suggests contemporaneous volcanism in both the Jurassic and the Early Cretaceous. Sedimentation gave way to erosion during the Late Cretaceous and Early Tertiary, and the rocks were deeply weathered. In the Oligocene and Miocene, basin volcanicity around the margins of the Basin accompanied epeirogenic basinward tilting; since then the basin has been stable. Petroleum reserves in the basin in 1974 were estimated as 51 billion m3 of gas and 31 million m3 of oil. The Walloon Coal Measures hold considerable reserves of bituminous coal and some of oil shale.