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The tectonic and volcanic history of Northern Zealandia

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Wednesday, July 17, 2024

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Title: The tectonic and volcanic history of Northern Zealandia

Presenter: Maria Seton, Associate Professor and Associate Head of Research in the School of Geosciences, University of Sydney

Date and time: Wednesday, 17th July 2024 at 1800



A defining characteristic of the southwest Pacific is the significant amount of continental crust and volcanism distributed throughout the region. This includes the world’s largest submerged continent, Zealandia, which separated from eastern Australia and Antarctica in the Cretaceous during the final phase of Gondwana break-up. A large knowledge gap in the tectonic and volcanic history of Zealandia has been the location and continuity of the Mesozoic subduction related magmatic arc and the Late Cretaceous to Eocene rift-related volcanics. In addition, widely distributed, intraplate Cenozoic volcanism, which appears to pockmark much of Zealandia, has been difficult to explain via existing models. To address these gaps in our understanding, we conducted several research voyages on the RV Investigator and its precursor, the RV Southern Surveyor. We undertook a series of dredges, informed by seismic reflection profiles, to target places where basement outcrops at the seabed. We performed detailed geochronological and geochemical analysis of these samples and combined this with regional geophysical data interpretation to determine the location and orientation of the Mesozoic Gondwana magmatic arc axis (Median Batholith) from New Zealand through to the northern reaches of Zealandia. We further mapped the extent of Late Cretaceous to Eocene rift-related volcanics and their relationship to strong positive magnetic anomaly signatures in the region as well refining the age and extent of plume related volcanism within Zealandia. Our work has provided the first offshore reconnaissance geological mapping of the Zealandia continent, of critical importance for understanding the Mesozoic geological history of pre-breakup Australia, New Zealand and New Caledonia, which in turn is the basis for exploring the mineral potential hosted within these regions.



Maria Seton is an Associate Professor and Associate Head of Research in the School of Geosciences, University of Sydney, and a former ARC Future Fellow and Australian Postdoctoral Fellow. Her research focusses on using the marine record to understand global to regional plate motions, the relationship between deep Earth processes and those happening at the surface and the role of tectonics in modulating Earth's long-term climate. She has been involved in several marine expeditions and leads research projects with university, government and industry partners. Maria has a passion for science communication and has received extensive coverage for her research in the media. She also has a passion for changing the public perception of the Australian continent, from one that ends at the coastline to one that extends hundreds of kilometres offshore, and where vital information about the evolution of our continent can be found.