2025 PESA WEBINAR SERIES: Mega-Intrusions and Volcanic Ruins: A Tour of Magmatism in the Carnarvon Basin

The Northern Carnarvon Basin formed as a result of Late Jurassic rifting, and Early Cretaceous breakup of Greater India from the Australian continent. Magma was emplaced into the Exmouth Plateau and Exmouth Sub-Basin over an area of ~50,000 km2. Until recently the spatial distribution of this igneous system, and hence its potential impact on regional petroleum systems, was relatively unknown. The only references to the magmatic system were 1990s ‘blob’ maps created using 100+ km spaced 2D seismic, magnetic and gravity data, and references of penetrations of igneous rocks in well completion reports from ~8 wells and boreholes.

New interpretive work (the essence of my PhD), utilising SLB & TGS ultra-broadband 3D seismic data covering much of the Exmouth Plateau and Exmouth Subbasin, reveals the igneous system in all its glory! In this talk we will tour both its intrusive and extrusive components, asking why it is the way it is and what its current configuration might have meant for the development of Carnarvon Basin petroleum systems. We will attempt to answer why some intrusions are of record-breaking proportions (170+ km long), while others nearby are much much smaller (3 to 5 km diameter). We’ll also look at the eroded ruins of volcanoes (that until recently hadn’t been known to exist at all) and consider the original size of the volcanic complex, and the implications of volcano erosion on regional reservoir quality.