New geophysical data acquired by Geoscience Australia during the Southwest Margins 2D seismic survey in 2008-09 has been used to interpret the tectonic and depositional history of the Mentelle Basin. The Mentelle Basin is a large, potentially prospective frontier basin located between the Yallingup Shelf and the Naturaliste Plateau. It comprises several shallow water depocentres (500-1500 m) in the east (eastern Mentelle Basin) and a large ultra deep-water depocentre (3000-3500 m) in the west (western Mentelle Basin).
Interpretation of the new data revealed that initial rifting in the Mentelle Basin occurred in the Early Permian as part of the Perth Basin extensional system. This was followed by Late Permian to Early Jurassic thermal subsidence. Half-graben structures with Permo-Triassic fill have been mapped in the eastern Mentelle Basin. The main depositional phase in the western Mentelle Basin has been interpreted to correlate with Late Jurassic to Early Cretaceous extension in the Perth Basin and on the Southern Margin. New structural interpretation shows that in the northern part of the western Mentelle Basin, major structures are trending N-S similar to the Perth Basin, whereas in the south most structures are trending SW-NE, which is consistent with the orientation of the extensional basins on the Southern Margin. The proximity of the Southern Margin rift system not only affected the structure of the Mentelle Basin but also resulted in major fault reactivation, inversion and margin collapse in the Eocene corresponding to the onset of fast spreading in the Southern Ocean.
