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Seismic imaging and crustal architecture across the Lachlan Transverse Zone, a possible early cross-cutting feature of Eastern Australia

Created 17/10/2025

Updated 17/10/2025

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A 2-D crustal velocity model has been derived from a 1997 364 km north-south wide-angle seismic profile that passed from Ordovician volcanic and volcaniclastic rocks (Molong Volcanic Belt of the Macquarie Arc) in the north, across the Lachlan Transverse Zone into Ordovician turbidites and Early Devonian intrusive granitoids in the south. The Lachlan Transverse Zone is a proposed west-northwest to east-southeast structural feature in the Eastern Lachlan Orogen and is considered to be a possible early lithospheric feature controlling structural evolution in eastern Australia; its true nature, however, is still contentious. The velocity model highlights significant north to south lateral variations in subsurface crustal architecture in the upper and middle crust. In particular, a higher P-wave velocity (6.24-6.32 km/s) layer identified as metamorphosed arc rocks (sensu lato) in the upper crust under the arc at 5-15 km depth is juxtaposed against Ordovician craton-derived turbidites by an inferred south-dipping fault that marks the southern boundary of the Lachlan Transverse Zone. Near-surface P-wave velocities in the Lachlan Transverse Zone are markedly less than those along other parts of the profile and some of these may be attributed to mid-Miocene volcanic centres. In the middle and lower crust there are poorly defined velocity features that we infer to be related to the Lachlan Transverse Zone. The Moho depth increases from 37 km in the north to 47 km in the south, above an underlying upper mantle with a P-wave velocity of 8.19 km/s. Comparison with velocity layers in the Proterozoic Broken Hill Block supports the inferred presence of Cambrian oceanic mafic volcanics (or an accreted mafic volcanic terrane) as substrate to this part of the Eastern Lachlan Orogen. Overall, the seismic data indicate significant differences in crustal architecture between the northern and southern parts of the profile. The crustal-scale P-wave velocity differences are attributed to the different early crustal evolution processes north and south of the Lachlan Transverse Zone.

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Field Value
Title Seismic imaging and crustal architecture across the Lachlan Transverse Zone, a possible early cross-cutting feature of Eastern Australia
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/3b1847d0-c7a9-44fc-b125-5c4393ed87bb
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 22/04/2018
Geospatial Coverage
Map data © OpenStreetMap contributors
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      [
        141.0,
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      ],
      [
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    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Seismic imaging and crustal architecture across the Lachlan Transverse Zone, a possible early cross-cutting feature of Eastern Australia". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/seismic-imaging-and-crustal-architecture-across-the-lachlan-transverse-zone-a-possible-early-cr