Processed Stacked and Migrated SEG-Y seismic data and uninterpreted and interpreted section images for the Capricorn Deep Crustal Seismic Survey. This survey was a collaborative ANSIR project between AuScope, the Geological Survey of Western Australia and Geoscience Australia. Funding was through AuScope and the Western Australian Government royalites for Regions Exploration Incentive Scheme. The objectives of the survey were use deep seismic profiling to improve the understanding of the Western Australian continent by imaging the subsurface extent of Archean crust beneath the Capricorn Orogen and determining whether the Pilbara and Yilgarn Cratons are in direct contact or separated by one of more elements of Proterozoic crust. Raw data for this survey are available on request from clientservices@ga.gov.au

Crustal magnetism is predominantly caused by the abundantly distributed ferrimagnetic mineral magnetite which posses the property of spontaneous magnetisation. Such magnetisation is dependent on temperature, which if high enough, will cause magnetite minerals to lose their magnetic property of spontaneous magnetisation and become paramagnetic. This temperature, known as the Curie point isotherm, occurs at ~580oC for magnetite. As temperature increases with depth in the crust, the Curie point can be taken as the depth at which the crustal magnetism ceases to be recorded. Using power spectral analysis of aeromagnetic data, we have generated a Curie point depth map for the Olympic Dam region in South Australia, host to the world's largest iron oxide-copper-gold-uranium deposit. The map shows an approximately 55 km long by 35 km wide and 40 km deep hemispherical depression in the Curie point depth beneath Olympic Dam, from a background average of around 20 km. Olympic Dam is notable for its large iron and uranium content, and it is located in a region of unusually high heat flow (av. 73 mWm-2). With such high heat flow one would expect the Curie point depth to be shallow. The paradox at Olympic Dam is that the Curie point depth is deep, raising questions about the geothermal gradient, depth-integrated abundance of heat-producing elements, and the source of the iron. A possible solution to the paradox is to interpret the deep Curie point depth as a giant hydrothermal alteration zone, where the heat-producing elements have been scavenged and concentrated into the upper crust, along with the gold and copper. The iron must have a significant mantle source as it is measured throughout the full crustal column. As iron is electrically conductive, such an interpretation is supported by the high conductivity measured deep beneath Olympic Dam.

The Antarctic Ice Sheet plays a fundamental role in influencing global climate, ocean circulation patterns and sea levels. Currently, significant research effort is being directed at understanding ice sheet dynamics, ice mass balance, ice sheet changes and the potential impact on, and magnitude of, global climate change. An important boundary condition parameter, critical for accurate modelling of ice sheet dynamics, is geothermal heat flux, the product of natural radiogenic heat generated within the earth and conducted to the earths surface. The total geothermal heat flux consists of a mantle heat component and a crustal component. Ice sheet modelling generally assume an 'average' crustal heat production value with the main variable in geothermal heat flux due to variation of the mantle contribution as a function of crustal thickness. The mantle contribution is typically estimated by global scale seismic tomography studies or other remote methods. While the mantle contribution to the geothermal heat flux is a necessary component, studies of ice sheet dynamics do not generally consider local heterogeneity of heat production within the crust, which can vary significantly from global averages. Heterogeneity of crustal heat production can contribute to significant local variation of geothermal heat flux and may provide crucial information necessary for understanding local ice sheet behaviour and modelling.

Australia's North West Margin (NWAM) is segmented into four discrete basins which have distinct rift and reactivation histories: Carnarvon, offshore Canning (Roebuck), Browse and Bonaparte. Bonaparte Basin incorporates Vulcan and Petrel sub-basins. The Bonaparte Basin stands out as an extensive sedimentary basin which has a geological history spanning almost the entire Phanerozoic, with up to 20 km of sediment accumulation in the centre. Browse Basin has considerably less thick sediment accumulation ? 12 km at maximum, which is still high for general hydrocarbon potential estimation. The structural architecture of the region is the product of a number of major tectonic events, including: ? Late Devonian northeast-southwest extension in the Petrel Sub-basin; ? Late Carboniferous northwest-southeast extension in the proto-Malita Graben, Browse Basin and proto-Vulcan Sub-basin; ? Late Triassic north-south compression; ? Early-Mid Jurassic development of major depocentres in the Exmouth, Barrow and Dampier sub-basins, and extension in the Browse Basin; ? Mid-Late Jurassic breakup in the Argo Abyssal Plain, onset of thermal sag in the Browse basin and extension in the Bonaparte Basin; ? Valanginian breakup in the Gascoyne and Cuvier abyssal plains, and onset of thermal sag in the Bonaparte Basin; and ? Late Miocene reactivation and flexural downwarp of the Timor Trough and Cartier Sub-basin Many of these events have involved processes of lower crustal extension and are strongly controlled by the pre-existing regional structural fabrics and basement character. Most reliable information on basement and deep crustal structure in the region comes from combined ocean-bottom seismograph (OBS) and deep reflection profiling along several regional transects (including Vulcan and Petrel transects in the Bonaparte Basin, and one transect in the Browse Basin). Average spacing between the OBSs of 30 km and shot spacing of 100 m with data recording to maximum offsets of 300 km enabled development of accurate crustal-scale seismic velocity models. Deep reflection data along the coincident profiles were recorded as part of Geoscience Australia?s regional grid of seismic lines. Consistent interpretation of several key horizons tied to petroleum exploration wells through the entire grid created the basis for co-interpretation of the OBS and deep reflection data supplemented by gravity field modelling.

This repository contains a static version of the data and software that accompanies the article by Stephenson et al. (2024) published in the Journal of Geophysical Research: Solid Earth. Note that the data and software repositories are up to date as of 07/03/2024. For more recent updates users are referred to the primary repositories on Github. Contents of zipped repository files includes four directories: 1. The manuscript directory `STEPHENSON_ET_AL_2024_JGR/` containing - The manuscript file (pre-print before final peer review and acceptance by the journal). - Supplementary text accompanying the manuscript. 2. The `SMV2rho` software package version `v1.0.1` for converting seismic velocity into density. 3. The `SeisCruST` database of global crustal thickness and velocity profiles. 4. The `global-residual-topography` database containing estimates of continental residual topography after correcting for isostatic effects of crustal thickness and density variations. Abstract for the article: Continental topography is dominantly controlled by a combination of crustal thickness and density variations. Nevertheless, it is clear that some additional topographic component is supported by the buoyancy structure of the underlying lithospheric and convecting mantle. Isolating these secondary sources is not straightforward, but provides valuable information about mantle dynamics. Here, we estimate and correct for the component of topographic elevation that is crustally supported to obtain residual topographic anomalies for the major continents, excluding Antarctica. Crustal thickness variations are identified by assembling a global inventory of 26 725 continental crustal thickness estimates from local seismological datasets (e.g. wide-angle/refraction surveys, calibrated reflection profiles, receiver functions). In order to convert crustal seismic velocity into density, we develop a parametrization that is based upon a database of 1 136 laboratory measurements of seismic velocity as a function of density and pressure. In this way, 4 120 new measurements of continental residual topography are obtained. Observed residual topography mostly varies between±1–2 km on wavelengths of 1 000–5 000 km. Our results are generally consistent with the pattern of residual depth anomalies observed throughout the oceanic realm, with long-wavelength free-air gravity anomalies, and with the distribution of upper mantle seismic velocity anomalies. They are also corroborated by spot measurements of emergent marine strata and by the global distribution of intraplate magmatism that is younger than 10 Ma. We infer that a significant component of residual topography is generated and maintained by a combination of lithospheric thickness variation and sub-plate mantle convection. Lithospheric composition could play an important secondary role, especially within cratonic regions.

Crustal structure associated with the northern Perth Basin is largely unknown. To help address this uncertainty, we constructed 3D gravity models. We adopt an approach whereby 'flawed' models are used to provide insight into basin thickness and crustal structure by highlighting areas where computed gravity does not fit measured gravity anomalies. The initial flawed models incorporate no arbitrary adjustments to geometry or density. In these models, two different Moho geometries are used, one based on Airy isostasy, the other incorporating an independently-computed Moho model for the Australian region. The resulting flawed models show that the crust of the northern Perth Basin is not in Airy isostatic equilibrium. A reasonable fit to long-wavelength observed gravity data is achieved for a model incorporating the Australia-wide Moho model. The deep Moho beneath the onshore Dandaragan Trough is interpreted to be the result of crustal-scale block rotation on the Darling Fault about a pivot point close to the Beagle Ridge. Flawed model results in the outboard Zeewyck Sub-basin suggest that the thickness of low-density sediment interpreted from seismic reflection data is underestimated. However, by making minimal adjustments to the model geometry, the gravity field over the Zeewyck Sub-basin can be explained by a deep and steep-sided depocentre associated with large variations in Moho depth over short distances. This geometry is suggestive of a transtensional formation mechanism. The flawed models do not explain the gravity field over the Turtle Dove Ridge, where computed gravity is less than observed. The results of our modelling highlight the benefits of considering 'flawed' gravity models that do not necessarily generate a good fit between observed and calculated gravity anomalies. These models help to more clearly identify areas with insufficient constraints and also provide impetus for re-assessing the interpretation of seismic reflection data.

Paleoproterozoic-earliest Mesoproterozoic sequences in the Mount Isa region of northern Australia preserve a 200 Myr record (1800-1600 Ma) of intracontinental rifting, culminating in crustal thinning, elevated heat flow and establishment of a North American Basin and Range-style crustal architecture in which basin evolution was linked at depth to bimodal magmatism, high temperature-low pressure metamorphism and the formation of extensional shear zones. This geological evolution and record is amenable to investigation through a combination of mine visits and outcrop geology, and is the principal purpose of this field guide. Rifting initiated in crystalline basement -1840 Ma old and produced three stacked sedimentary basins (1800-1750 Ma Leichhardt, 1730-1670 Ma Calvert and 1670-1575 Ma Isa superbasins) separated by major unconformities and in which depositional conditions progressively changed from fluviatile-lacustrine to fully marine. By 1685 Ma, a deep marine, turbidite-dominated basin existed in the east and basaltic magmas had evolved in composition from continental to oceanic tholeiites as the crust became increasingly thinned and attenuated. Except for an episode of minor deformation and basin inversion at c. 1640 Ma, sedimentation continued across the region until onset of the Isan Orogeny at 1600 Ma.

Interpretation of 2014–2015 deep crustal seismic reflection and magnetotelluric data has revised the architecture and geodynamic framework of western Queensland, with implications for the assembly and dispersal of the supercontinents Nuna, Rodinia and Gondwana. In the Mount Isa Province, crustal-scale boundaries of the Leichhardt River Domain, Kalkadoon-Leichhardt Domain and Eastern Subprovince are mapped in the third dimension. The Leichhardt River and Kalkadoon-Leichhardt domains have similar Nd isotopic T 2DM model ages to provinces to the west, indicating they were part of ancestral North Australian Craton (NAC); the Eastern Subprovince is a separate terrane, with the Pilgrim Fault a collisional suture. The Gidyea Suture Zone separates the Mount Isa Province from the subsurface Numil Seismic Province. To the east, the west-dipping Yappar Fault separates east-dipping structures in the west from west-dipping structures in the east, forming a classic doubly vergent orogen within the upper plate of a convergent margin. The northwestern boundary of the Bernfels Seismic Province, the Kynuna Fault, truncates the Gidyea Suture Zone, implying this seismic province was welded to the NAC prior to initial deposition of the Etheridge Province. The Cork Fault truncates the north-south grain of the Mount Isa Province; the easternmost part of the NAC has been excised, presumably during breakup of Nuna. The subsurface Brighton Downs Seismic Province, formerly part of the northern Thomson Orogen, is a discrete seismic province, located between the NAC and the Thomson Orogen, and welded to the NAC during the accretion of Rodinia. Basement to the Thomson Orogen is a collage of microplates, accreted to the Brighton Downs Seismic Province during the assembly of Gondwana. By 530 Ma, eastern Australia faced an open Pacific Ocean, with the Thomson Orogen in a backarc setting. Thus, northeastern Australia contains a record of repeated continental accretion and breakup over at least three supercontinent cycles. <b>Citation: </b>Russell J. Korsch, Michael P. Doublier, Dominic D. Brown, Janelle M. Simpson, Andrew J. Cross, Ross D. Costelloe, Wenping Jiang, Crustal architecture and tectonic development of western Queensland, Australia, based on deep seismic reflection profiling: Implications for Proterozoic continental assembly and dispersal, <i>Tectonophysics</i>, Volume 878, 2024, 230302, ISSN 0040-1951, https://doi.org/10.1016/j.tecto.2024.230302.

The Major Crustal Boundaries web service displays the synthesized output of more than 30 years of acquisition of deep seismic reflection data across Australia, where major crustal-scale breaks have been interpreted in the seismic reflection profiles, often inferred to be relict sutures between different crustal blocks. The widespread coverage of the seismic profiles now provides the opportunity to construct a map of major crustal boundaries across Australia.

The Major Crustal Boundaries web service displays the synthesized output of more than 30 years of acquisition of deep seismic reflection data across Australia, where major crustal-scale breaks have been interpreted in the seismic reflection profiles, often inferred to be relict sutures between different crustal blocks. The widespread coverage of the seismic profiles now provides the opportunity to construct a map of major crustal boundaries across Australia.