Revisiting the deep structure of the Northern Carnarvon Basin: insights from new seismic reflection data

The Carnarvon Basin has long been a focus for hydrocarbon exploration and development. Many models have been proposed for the basin’s lithospheric structure, although the great thickness of the Mungaroo delta system has hampered the clear imaging of the underlying rift and break-up structure. New deep, long offset seismic reflection data acquired across the basin as a part of ION’s Westralia SPAN survey provide unique imaging of the deep basement structures and the complete overlying sedimentary section. The survey crossed the offshore terrains, from weakly stretched continental crust to oceanic crust. The margin has developed during two major events; one of Permo-Carboniferous age, prior to the Mungaroo delta system, and one of Middle to Upper Jurassic age. There is a possibility that the basement terrain under parts of the Exmouth Plateau is actually Permo-Carboniferous oceanic crust, rather than hyper-extended continental crust or exhumed continental lithospheric mantle. Deformation during the second major event in the Jurassic was focussed in the Barrow-Dampier Sub-basin and at the present day ocean-continent transition with little deformation across the Exmouth Plateau in-between. The only basement involved extension appears to be in the Barrow-Dampier system and appears to be non-volcanic. The outer margin along the northwest edge of the Exmouth Plateau includes significant volcanic input, likely underplating and emplacement of seaward-dipping reflectors.