What is underneath? Our Members Mapped the Volcanoes Buried in the Central Offshore Otway Basin

A new paper is JUST published in Marine Geology, focusing on the magmatic and hydrothermal activtiy occured between late Eocene (~50 million years ago) to early Miocene (~10 million years ago), in the central continental shelf of the Otway Basin, SE Australia. The paper is entitled :"Post-rift magmatism and hydrothermal activity in the central offshore Otway Basin and implications for magmatic plumbing systems".

Image from Niyazi et al. (2021)


Spatially and volumetrically extensive igneous rocks are exposed onshore in southeastern Australia and provide important information about the Cenozoic evolution of the region. However, the morphology and distribution of igneous rocks are still not well constrained in the ∼70 km wide continental shelf of the central Otway Basin. Within this region, they present seismo-geomorphological characteristics of 30 volcanoes and 27 hydrothermal vents, as well as several lava flows and magmatic sills, based on 2D and 3D seismic reflection data. Hydrothermal vents formed mainly during the mid-Eocene, while igneous complexes developed between the mid-Eocene to late Miocene, both post-dating continental break-up in the basin. The distribution and morphology of igneous rocks and hydrothermal vents is influenced by rift-related faults, as most of these features are linked to the underlying faults by near-vertical zones of disruption and are elongated in an NW-SE direction that parallels the primary fault trend.


Magma for volcanoes and heat sources for hydrothermal vents within the study area are likely supplied by deep-sourced dykes, as magmatic sills only have a scattered distribution in this region. This implies a dyke-dominated plumbing system for magmatism in the Otway Basin. In comparison, the nearby Bight Basin, which has a thin basement but a relatively thick sedimentary sequence, displays magma propogation more prone to forming igneous sills. There are many lithological and tectonic similarities between the Otway and Bight basins; thus, they propose that a relatively thin sedimentary sequence over a thick basement in the Otway Basin produced sufficient magma pressure for a predominantly dyke-dictated igneous plumbing system.


This work highlights the critical role of basin structures, such as the thickness of basement and overlying strata, in the control of igneous plumbing styles and the distribution of post-rift igneous complexes along magma-poor continental margins. Their work, therefore, aids the estimation of different magmatic components within the sedimentary basins and facilitates the understanding of their diverse impacts on the exploration of frontier basins. This result also provides some constraints on the prediction of possible future eruption centres within active volcanic fields.


This publication was led by Marine Mapping Group Member Yakup Niyazi, and Daniel Ierodiaconou from our group contributed to the publication. Yakup is supported by a Higher Degree Research Scholarship from the Deakin University and the Victorian Department of Environment, Land, Water and Planning as part of the Victorian Coastal Monitoring Program.


Congrats to Yakup and the DU Marine Mapping Group!

To read the full article, click here.

Last edited on the June 21th, 2021.

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