Nature of the Cuvier Abyssal Plain crust, offshore NW Australia

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Authors

Matthew Reeve, Craig Magee , Ian Bastow, Carl McDermott, Christopher A-L Jackson , Rebecca E. Bell, Julie Prytulak

Abstract

Magnetic stripes have long been assumed to be indicative of oceanic crust. However, continental crust heavily intruded by magma can also record magnetic stripes. We re-evaluate the nature of the Cuvier Abyssal Plain (CAP), offshore NW Australia, which hosts magnetic stripes and has previously been defined as oceanic crust. We show chemical data from a basalt within the CAP, previously described as an enriched MORB, could equally be interpreted to contain evidence of contamination by continental material. We also recognise seaward-dipping reflector (SDR) sequences in seismic reflection data across the CAP. Borehole data from overlying sedimentary rocks suggests these SDRs were emplaced in a shallow-water (<200 m depths) or sub-aerial environment. Our results indicate the CAP may not be unambiguous oceanic crust, but may instead comprise a spectrum of heavily intruded continental crust through to fully oceanic crust. If the CAP represents such a continent-ocean transition zone, adjacent unambiguous oceanic crust would be located >500 km further offshore NW Australia than currently thought; this would impact plate tectonic reconstructions, as well as heat flow and basin modelling studies. Our work also supports the growing consensus that magnetic stripes cannot, by themselves, be used to determine crustal affinity.

DOI

https://doi.org/10.31223/X5202S

Subjects

Physical Sciences and Mathematics

Keywords

SDR, continental, oceanic, COTZ

Dates

Published: 2021-02-24 10:02

Last Updated: 2021-02-26 05:12

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License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
None

Data Availability (Reason not available):
The EW0113 seismic survey and EMAG2 magnetic anomaly grids used were, and can be acquired from, the UTIG Marine Geoscience Data System and the NOAA National Geophysical Data Centre, respectively. Other seismic reflection data used can be downloaded from Geoscience Australia.

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