Subsurface sequence stratigraphy of Devonian carbonates, Canning basin, Western Australia

The Canning basin of Western Australia is best known for its Devonian reef complexes. in 1990 the Australian Bureau of Mineral Resources (BMR) began a sequence stratigraphic study of key parts of the basin. This work integrates industry seismic and well data with two deep-crustal, regional seismic lines acquired by BMR in 1988. Initial work on the Lennard Shelf and adjacent Fitzroy trough has established a new sequence stratigraphy. At the margin of the Fitzroy trough, the most prominent features on seismic sections are alternating wedge-shaped and tabular bodies up to 150 m and 50 m thick, respectively. Internal reflections in the wedge-shaped bodies show downlap toward the basin and onlap toward the platform margin. On strike lines these wedges exhibit complex lensoidal geometries. Drillcore indicates that the wedges comprise basement-derived conglomerates with a sandy calcareous matrix. Seismic and well data suggest five Late Devonian sequences. The wedges and oblique prograding units are thickest and most easily recognized in the upper three sequences (Late Frasnian-Famennian ). The underlying thinner sequences probably correlate with the classic back-stepping Frasnian reefs identified in outcrop by Playford. Recognition of lowstand deposits in the Devonian reef complexes represent a new hydrocarbon exploration play.