The energy-rich western Australian continental margin is considered to be an archetypal volcanic rifted margin, though a systematic spatiotemporal analysis of magmatic activity is lacking. We present a comprehensive margin-wide investigation of the dominantly mafic magmatic activity within the inboard sedimentary depocentres (from the Bonaparte Basin in the north to the Mentelle sub-basin in the south), where the preserved stratigraphic record and subsurface data coverage enable new insights into the distribution, timing and nature of the igneous record, and its impact on basin properties and prospectivity. In contrast to the Northeast Atlantic margin, where voluminous, margin-wide igneous activity occurred within a narrow time interval, magmatism along the western Australian margin is more protracted (spanning >100 Myr) and spatially variable. Initial magmatic activity, encompassing both intrusions and extensive subaerial and submarine volcanic deposits, was concentrated in the Canning and Roebuck Basins during late Permian to mid-Triassic rifting. Following a period of reduced igneous activity, the locus of magmatism (and active rifting) migrated to the Browse Basin during the early-mid Jurassic, characterised by widespread intrusive and extrusive activity, coeval with the deposition of prolific fluvio-deltaic reservoirs. During the late Jurassic, contemporaneous with the breakup of the Argo microcontinent, magmatic activity was concentrated in the Carnarvon Basin, characterised by complex networks of sill and dyke intrusions and rarely preserved volcanic activity. As the locus of rifting progressively migrated to the south, the final phase of extensive igneous activity along the margin was concentrated in the Mentelle sub-basin during the early Cretaceous.

The UK is currently importing hydrocarbons and petroleum products at levels not seen since the mid-1970s. While the country continues to advance its Energy Transition goals, hydrocarbons – particularly natural gas – are expected to remain a vital component of the UK's energy mix and as a chemical feedstock through 2050 and beyond. West of Shetland (WoS) holds the highest estimated undiscovered resource volume on the UK Continental Shelf, with an estimated 4.7 billion barrels of oil equivalent to be found. Despite this potential, the region presents significant technical challenges, particularly from a subsurface perspective, and lacks extensive pipeline infrastructure, which often results in challenging project economics. In 2022, the WoS region marked 50 years since the first exploration well was drilled. This contribution traces the basin's exploration history and provides a comprehensive overview of the current subsurface understanding. We argue that for WoS to play a meaningful role in supporting the UK's domestic oil and gas supply, rather than rely on imports to meet the country's needs, the region would benefit from being placed within a bespoke fiscal and economic regime – one that encourages exploration, accounts for the higher development costs and respects the increased geological risk.

In multi-phase rifts, pre-existing structural fabrics that are formed during earlier rifting stages can influence fault growth during later deformation. Successive extensional episodes cause pre-existing faults to reactivate, leading to the propagation of fault planes and/or generation of branching faults in surrounding strata. Pre-existing faults can also locally control geometries (e.g., fault bends) and distributions of subsequent faults by creating stress and strain perturbations without exhibiting observable fault displacements (i.e., structural inheritance). Constraining the evolution of faults in multi-phase rift basins is crucial for understanding how accommodation spaces form and pathways for subsurface fluids (e.g., water, hydrocarbons, magma) develop during active deformation. However, due to structural complexity and limitations in data availability and resolution, capturing detailed fault geometries in time and space remains challenging. This study focuses on the structural framework of the central Browse Basin, the Australian North West Shelf, which experienced repeated phases of rifting throughout the Mesozoic. Using multiple surveys of a high-quality 3D seismic reflection dataset, this study demonstrates how successive extensional episodes shaped fault geometries and hence the structural configuration of the central Browse Basin. Key findings include: (1) the development of distinct fault patterns such as zigzag, rhomboidal, arc-shaped and en echelon geometries through reactivations of pre-existing Permian-Triassic faults; (2) a rotation in extensional stress orientation after the Late Jurassic, resulting in the deepening of WNW-ESE striking grabens; and (3) quantification of fault growth histories revealing variations in displacement and periods of activity, including the cessation of some major faults by the Late Jurassic. These insights provide a detailed tectono-stratigraphic evolution model for the central Browse Basin and offer broader implications for understanding fault behaviour in multi-phase rift systems globally.

Ancient submarine volcanic systems preserved within sedimentary basins provide opportunities to investigate the time and spatial distributions of intrusive and extrusive rocks, though existing work has largely focused on the geometrical features of submarine volcanic products, with limited interrogation of their interactions with sedimentary processes. This study investigates a buried submarine volcanic system within the Browse Basin, Australian North West Shelf. Through the integration of three-dimensional seismic reflection survey with borehole data, our study reveals intricate geometric features of a submarine volcano and lava channels, and their relationship to an associated intrusive network of Early Cretaceous age that has been preserved beneath similar to 3.5 km of sedimentary overburden. In planform, the volcano has a diameter >4.5 km with a preserved height reaching 650 m. Meandering lava-flow channels extend similar to 20 km southward of the volcanic edifice, forming lava lobes with pressure ridges at the flow termini. Abundant sheet intrusions, identified within underlying Jurassic and older strata, indicate a magma transport from the north. The localized accumulation of sills led to variations in palaeo-seafloor topography, influencing the direction of lava flows and post-volcanic sedimentation patterns. Our findings have a broad range of implications encompassing submarine volcanism and their impacts on basin dynamics.

The Kerio Valley Basin is a classic half-graben within the Eastern Branch of the East African Rift System, although to date its tectonostratigraphic evolution has been interpreted only through an incomplete stratigraphic record exposed along structural highs. This study examines a 3 km thick volcano-sedimentary succession recorded within a hydrocarbon exploration well, Cheptuket-1, located within the hanging wall of the Kerio Valley Basin. A suite of silicic extrusive volcanic and volcaniclastic rocks are also recorded, calibrated by a dense collection of thin-sections from 84 side-wall cores. These volcanic rocks include phonolite lava flows. Through documentation of the well stratigraphy and integration of newly acquired Ar-40/Ar-39 age dates from outcrop, we detail a substantially revised, simpler tectonostratigraphic evolution of this basin. Cheptuket-1 penetrated a Middle Miocene to recent stratigraphic succession, bottoming in metamorphic basement, probably through a fault plane. Several phases of lake development are elucidated, including both pre- and syn-mechanical rifting, with the latter phase containing beds exhibiting high organic matter content. This study ultimately represents a rare insight into a near complete rift-basin hanging-wall succession, as well as detailing a workflow for characterizing mixed volcanic and sedimentary successions.

Sills play a leading role in the transport of magma in sedimentary basins. The contact between sills and host rocks reflects the acting emplacement processes during sill propagation and evolution. Recent studies have shown that the propagation of sills and dykes is strongly influenced by the lithology of the host rocks, but none have detailed documentation of marginal features in large-scale intrusive complexes. Three-dimensional seismic data is the primary method of mapping and investigating such complexes, but it is difficult to accurately image sills due to their low thickness compared to seismic resolution. By understanding the relationship between local lithology and marginal sill features, we can better understand the imaging of sills in seismic datasets and their resulting geometry. In this study, we present a seismic-scale sill analogue through multiple high-resolution three-dimensional models, with corresponding logs and field observations from Cedar Mountains, San Rafael Swell, US. This model was further used to develop a synthetic seismic dataset, providing us with a strong control on which marginal sill features fall beneath seismic resolution. We found that lithology plays a critical control in sill geometry and morphology. In Cedar Mountains, sills emplaced within massive sandstones frequently exhibit strata-discordant base contact with the host rock. Conversely, sills found within heterolithic intervals and mudstones typically display strata-concordant base contact with the host rocks. Sills within heterolithic intervals also tend to exhibit a more complex segmentation with multiple broken bridges. Furthermore, our findings show that sills are more than 3.7 times more likely to intrude in mudstone compared to sandstone and heterolithic intervals. These results suggest how sill geometries can be adapted to interpret lithology in seismic datasets from sedimentary basins with little to no well control. We anticipate that our findings may provide better knowledge for interpreting sills in sedimentary basins and contribute to developing more sophisticated geomechanical emplacement models for igneous intrusions. In our study, we investigate the limitations of seismic imaging of mafic sills by developing a synthetic seismic dataset rooted in field outcrops. Our observations highlights the limitations of seismic imaging of mafic sills, often due to subseismic structures and high density contrast between igneous intrusions and sedimentary host rocks.image

Developments in ultradeep azimuthal resistivity (UDAR) technology has recently progressed from their application in high-angle and horizontal wells to low-angle and vertical wells. This has presented the opportunity to assess their suitability as derisking tools because of their ability to look ahead of the bit, up to c. 100 ft (c. 30.5 m). Dominated by a complex interplay of structure, sedimentation, and volcanic activity, the NE Atlantic Margin presents a challenging environment to plan and drill wells safely and within planned budget, with many wells drilled within the Faroe-Shetland Basin (FSB) currently the most expensive to-date within the United Kingdom continental shelf (UKCS). The limited number of wells drilled in the FSB and their geographical sparsity relative to those of other areas of the UKCS, make offset analysis and derisking a challenge. The often-unpredictable distribution of igneous rocks throughout the basin presents significant challenges in the planning and drilling of oil and gas wells. Up to 88% of igneous intrusions within the FSB are estimated to be below seismic resolution, which alongside variation in composition, presents significant issues related to drilling safely, efficiently and successfully. Within this paper, we investigate the use of UDAR technology and how they could be deployed in areas of complex volcanic geology such as the West of Shetland (WoS). This paper reviews the nature of the drilling experiences within the FSB to date, the impact it has on exploration, and how improvements in drilling technology could help decrease nonproductive time (NPT).

Abstract The Northern Carnarvon Basin (NCB) located on Australia's North West Shelf hosts an extensive (∼40,000 km 2 ) intrusive igneous complex related to Mesozoic rifting and breakup. Using an extensive suite of modern 3D seismic reflection surveys, we have mapped this intrusive system across the NCB. We identify three predominant intrusion morphologies: Stacked sheets of large interconnected sill intrusions (up to ∼170 km long) and smaller (8 to 30 km long) isolated, strata concordant intrusions, which often interact with normal faults emplaced into deltaic sedimentary rocks; and variably sized (10 to 40 km long) saucer-shaped intrusions emplaced into marine shales, spread across seven zones (geographically constrained groups of intrusions of a specific morphology). We consider the zones' margin-parallel orientation, suggesting control by sub-crustal extensional processes during rifting; and, variation in intrusion morphology between these zones, suggesting a dominant control by host rock mechanical properties. We integrate previous work with our observations, constraining emplacement to between the Kimmeridgian and Valanginian, coinciding with key phases of margin evolution. Finally, we assess the impact of this intrusive complex on local petroleum systems. There is likely little to no adverse impact on source rock maturation or reservoir contamination by CO 2 . But, there is a spatial dissociation between the location of groups of intrusions and the gas fields, particularly in the Exmouth Plateau; this suggests that migrating hydrocarbons may be blocked, baffled and/or redirected by emplaced igneous rocks.

The application of high-resolution seismic reflection data has spurred major advances in knowledge of the emplacement of sub-volcanic mafic magma plumbing systems in sedimentary basins, highlighting the importance of interconnected sheet intrusions in facilitating lateral magma transport, the links between host rock mechanical properties and emplacement processes, and providing insights into how intrusive activity in basins impacts their resource potential. However, most studies have focused on Mesozoic-Cenozoic mafic magma plumbing systems situated along offshore rifted margins characterised by extensive subsurface datasets. The extensive Mesoproterozoic (c. 1300 Ma) Derim Derim Dolerite, which intrude the greater McArthur Basin in northern Australia, provide a unique opportunity to study the emplacement of a Proterozoic magma plumbing system due to its penetration by numerous hydrocarbon and mineral drillholes, in addition to seismic reflection coverage. Understanding the emplacement of this system is important because of its interactions with prospective unconventional shale reservoirs in the Velkerri and Kyalla Formations, which represent one of the world’s oldest known petroleum systems. This paper focuses on characterising the intrusion emplacement and magma plumbing system using an array of subsurface data, to constrain the distribution, morphology, and emplacement mechanisms of the Derim Derim Dolerite.The morphology of the large, strata-concordant intrusions encountered at shallow present-day depths (<2 km) in the greater McArthur Basin is indicative of greater original emplacement depths of >3–4 km, suggesting a significant extent of uplift and erosion. Density-derived porosity values for the Velkerri and Kyalla Formations are anomalously low for their present-day depths, corroborating a greater palaeo-depth at time of emplacement. The extent of alteration of the host rock surrounding the Derim Derim Dolerite is highly variable, with a small number of occurrences of graphitisation of the organic matter adjacent to intrusions. However, this appears to be highly localised and the detrimental impact of the Derim Derim Dolerite on potential reservoir and/or source rocks appears generally minimal.

Abstract The Faroe-Shetland basin (FSB) is considered challenging for oil and gas exploration due to its complex geological structure and limited exploration drilling activity. The costs of drilling in the basin are the most expensive within the United Kingdom Continental Shelf (UKCS) due to varying geological and engineering challenges. The prevalence of igneous sill complexes within the basin present drilling hazards that contribute to drilling nonproductive time (NPT) and are documented in multiple studies. Recent advancements in Ultradeep Azimuthal Resistivity (UDAR) technology which utilises the look-ahead portion of the electromagnetic (EM) signal presents an opportunity to assess its suitability as a derisking tool to ‘look-ahead’ and detect igneous intrusions in volcanic basins. This paper utilises resistivity log data from Well 214/28-1, which encountered multiple igneous intrusions and is used to validate the ability of these tools to detect the intrusions. The EM look-ahead technology detected with good confidence the top of an igneous intrusion 72ft (22m) true vertical depth (TVD) ahead of the transmitter and once drilled, detect the base of the intrusion 54ft (16m) TVD ahead of transmitter. The detection of the intrusions prior to drilling and information on intrusion thickness can enable proactive drilling decisions to reduce nonproductive time.

Pervasive igneous intrusive complexes have been identified in many sedimentary basins which are prospective for petroleum exploration and production. Seismic reflection and well data from these basins has characterized many of these igneous intrusions as forming networks of interconnected sills and dykes, and typically cross-cutting sedimentary host rocks. Intrusions have also been identified in close proximity to many oil & gas fields and exploration targets (e.g. Laggan-Tormore fields, Faroe Shetland Basin). It is therefore important to understand how igneous intrusions interact with sedimentary host rocks, specifically reservoir and source rock intervals, to determine the geological risk for petroleum exploration and production. The risks for petroleum exploration include low porosity and permeability within reservoirs, and overmaturity of source rocks, which are intruded. Additionally, reservoirs may be compartmentalized by low permeability igneous intrusions, inhibiting lateral and vertical migration of fluids. Based on a range of field studies and subsurface data, we demonstrate that sandstone porosity can be reduced by up to 20% (relative to background porosity) and the thermal maturity of organic rich claystones can be increased. The extent of host rock alteration away from igneous intrusions is highly variable and is commonly accompanied by mechanical compaction and fracturing of the host rock within the initial 10 to 20 cm of altered host rock. Reservoir quality and source rock maturity are key elements of the petroleum system and detrimental alteration of these intervals by igneous intrusions increases geological risk and should therefore be incorporated into any risk assessment of an exploration prospect or field development. Thematic collection: This article is part of the New learning from exploration and development in the UKCS Atlantic Margin collection available at: https://www.lyellcollection.org/topic/collections/new-learning-from-exploration-and-development-in-the-ukcs-atlantic-margin

Previous basin modelling of the Faroe–Shetland Basin (FSB, offshore UK) has suggested mid-Cretaceous petroleum generation, which predates the deposition of the working Paleogene reservoirs and traps. To justify the time discrepancy between generation, reservoir, and trap formation, factors such as intermediary accumulations and overpressure have been invoked. However, across much of the FSB, the Cretaceous sequences that overly the Kimmeridgian source rock are heavily intruded by Paleogene-aged intrusions. Recent modelling has shown that the emplacement of the intrusions, coupled with lower radiogenic heat production from underlying basement, leads to estimates of petroleum generation occurring up to 40 myr more recently than suggested by previous models. In this work, we seek to better understand the role that igneous intrusions have exerted on petroleum generation and migration in the FSB. Models with varying thicknesses of Paleogene intrusions are compared with those that consider the Cretaceous sequence as purely sedimentary (i.e. similar to assumptions in previous modelling). The estimated times of petroleum generation are compared with geochronological constraints on the ages of oils (i.e. c . 90–68 Ma) along with the deposition and formation of other petroleum system elements. By considering only the effect of igneous intrusions, the expulsion onset from the source rock is retarded by up to 12 myr. In addition, our models show the impact of the intrusions on petroleum saturation and migration, suggesting that intrusions have potentially compartmentalized the basin, trapping petroleum beneath or within the sill complex. Finally, our findings suggest that basin models in regions impacted by significant magmatism need to consider the impact of intrusions to more accurately constrain both petroleum generation and migration. Thematic collection: This article is part of the New learning from exploration and development in the UKCS Atlantic Margin collection available at: https://www.lyellcollection.org/topic/collections/new-learning-from-exploration-and-development-in-the-ukcs-atlantic-margin

Abstract Igneous intrusions in sedimentary petroleum basins are often perceived as having a negative impact on the elements of the petroleum system, though the impact of intrusion-related deformation features on petroleum systems and broader geoenergy applications is not well understood. In this study, we use 3D seismic reflection data to document a variety of deformation styles that are spatially and temporally associated late Cenozoic magmatic activity in the Bass Basin, offshore southeastern Australia; three types of normal fault systems (conjugate faults, concentric faults, radial faults) and fluid escape pipes. These deformation features occur in the overburden up to ∼600 m above underlying igneous intrusions, within the Eocene to Miocene Demons Bluff and Torquay formations. The conjugate faults bound graben and are interpreted to have formed in response to underlying dyke intrusions. The radial faults are interpreted to have formed in response to overburden uplift, though the link between these and associated igneous activity is less clear. We identify 101 fluid escape features that show variation in both the morphology of their surficial depressions and of the seismic reflection characteristics of their infilling deposits. These features are interpreted to be hydrothermal or volcanic vents with underlying pipe-like feeders, depending on their spatial association with adjacent or underlying igneous intrusions. The concentric fault systems are associated with surficial depressions, and quantitative analysis of reflection sags within these depressions suggest that they are a result of subsurface subsidence in response to formation of maar-craters. The intrusion-related deformation features documented in this study may have multiple effects on working petroleum systems, such as providing secondary fluid flow pathways that can either reduce seal integrity, or enabling migration of fluids into shallower reservoirs.

Abstract The Browse Basin is one of Australia's major hydrocarbon provinces, where significant discoveries have been made in recent decades including the Ichthys and Prelude fields, which accounted for ∼15% of the cumulative Australian liquified natural gas (LNG) production in 2019–20. This rift basin hosts extensive Mesozoic intrusive and extrusive igneous rocks, having been identified from both well and seismic data, and which are recognized as one of the key challenges for exploration and production activities in this region. Their impact on petroleum exploration is demonstrated by the number of wells which encountered unpredicted or thicker than expected igneous rock units both within and adjacent to target sections. This study therefore aims to document the reasons of such unexpectedness, and to develop capability to predict the occurrence of igneous rock units prior to drilling in the Browse Basin and other rift settings that contain igneous rocks. Multiple case studies of uncommercial exploration wells are developed by integrating petrophysical and seismic reflection data, focusing in particular along the outboard part of the basin where igneous rocks are most prevalent. Our study highlights the importance of understanding petrophysical, spatial and chemical heterogeneities of igneous rocks in basins to explain their emplacement and distribution, and thereby predict their occurrence prior to exploration and development activities.

The North West Australian Margin, which formed as Greater India rifted from Australia during the Jurassic to Early Cretaceous, is recognised as an archetypal magma-rich rifted margin, with records of extensive igneous activity in the Exmouth Plateau and Exmouth Sub-Basin (ESB) of the Northern Carnarvon Basin (NCB). Pre -breakup magmatism is manifested by a large-400 x 150 km intrusive sill complex, emplaced into Triassic and Jurassic strata in the Late Jurassic and Early Cretaceous. An apparent lack of extrusive igneous rocks has caused previous works to describe the region as a large intrusive igneous province. Here, we describe two recently identified Upper Jurassic volcanic centres: the Pyrenees Volcano in the eastern ESB (first reported here), and the Toro Volcanic Complex (TVC), in the western ESB. Although offset by Early Cretaceous normal faulting, the edifice of the Pyrenees Volcano and associated lava flows are well preserved beneath a protective carapace of Upper Jurassic strata below the angular Intra-Hauterivian Unconformity on the Novara Arch. In contrast, a significant proportion of the TVC was peneplaned beneath an intra-Valanginian (Early Cretaceous) unconformity following breakup-related uplift. As Upper Triassic to Lower Cretaceous strata appear to have been eroded over the Ningaloo Arch in the southern ESB, we postulate that Late Jurassic extrusive volcanism may have been more spatially extensive, prior to erosion associated with Early Cretaceous exhumation in the southern NCB. Hence our findings suggest that the NCB was potentially host to significantly more extrusive volcanism than has been preserved within basin fill. Our findings also have broader implications for the conditions required to preserve extrusive igneous material in sedimentary basins within large igneous provinces that have undergone complex histories of rift-related vertical motion.

Capturing the ubiquitous distribution and properties of igneous rocks is necessary to succeed in hydrocarbon exploration, field development and underground gas storage when dealing with magma-rich rift margins. In recent years, numerous researches have revealed detailed morphologies of intrusive and extrusive rock units embedded within sedimentary basins owing to advances in 3D seismic data. Outcrop studies have also provided deeper understandings of their occurrence and geometries. However, there has been comparatively little focus on the rock physics of igneous bodies and their relationships to seismic expression. To bridge this gap between the outcrop and the seismic information, we undertook a well-log-based petrophysical study of igneous rocks using subsurface dataset from the Browse Basin located in the Australian North West Shelf. In this contribution, we describe a classification of volcanic facies (e.g. lava flows, volcaniclastics, intrusive sills) based on well log motifs and textures apparent in borehole image data. Statistics of the petrophysical properties of each volcanic facies are also analysed in order to examine their correlation to seismic patterns. Our study implies the importance of detailed characterisation of igneous petrophysical properties of igneous rock units where concentrated within a sedimentary basin, which will help reconcile interpretations of seismic data.

Imaging both within and beneath subsurface igneous sill complexes is a seismic exploration challenge. A significant aspect of this challenge is due to a lack of understanding of the interaction between the heterogeneous geological structures and the seismic wavefield, which includes the seismic response to sub-resolution ‘thin’ sills. This study aims to provide some insight into the effect subsurface sills have on the observed seismic wavefield. This is achieved through high-resolution full-waveform elastic seismic modelling, using a realistic geological model developed from interpreted seismic data and statistics of sills from wireline logs and conceptual understanding from sill complexes in outcrop. We find that little energy penetrates through the sill complex to a target reflector below the sill complex, which is consistent with real-world observations. This is due to a number of factors, including energy lost to strong internal multiples (stratigraphic filtering), converted modes and leaky guided waves within the sills. These processes remove energy from the primary transmitted wavefront, contributing to degraded seismic imaging. Whilst these are all fundamental physical limitations that cannot be overcome, further work should focus on the processing of seismic data to ensure that these aspects of the seismic wave-field around sill complexes are optimally treated within processing workflows.

Quantifying the thermal histories of rift basins is important for evaluating their resource and CO2 storage potential because temperature controls hydrocarbon generation, and the diagenesis of reservoir rocks. However, in many rift basins, it is difficult to obtain evidence for elevated heat flow accompanying rifting, since paleotemperature data from drilled sections typically record heating related to post-rift burial. Here we integrate geochemical, geophysical and petrophysical data from the Duntroon Sub-basin, Great Australian Bight, that show how strain-migration during multiphase extension can preserve the signature of syn-rift elevated geothermal gradients. During the late Jurassic–early Cretaceous, rifting was focussed along ~ESE-striking normal fault systems in the northern part of the Duntroon Sub-basin. During the late Cretaceous, strain migrated to the southwest through the development of normal faults which accommodated the deposition of Upper Cretaceous strata. The Echidna-1 well was drilled into a basement high, in the footwall of a late Cretaceous fault system, penetrating ~2.5 km of Lower Cretaceous strata. Paleotemperature proxies define an early Cretaceous paleogeothermal gradient of ~60°C km−1, substantially higher than the present-day gradient. Our results indicate that preserved Lower Cretaceous strata were more deeply buried by ~1 km of additional section, which was likely eroded during an episode of mid-Cretaceous exhumation associated with the migrating locus of rifting; this enabled the preservation of thermal signature of elevated syn-rift heat flow. Similar evidence is also observed in the Otway Basin, demonstrating the regional extent of elevated syn-rift heat flow along the southern Australian margin.

The Northern Carnarvon Basin (NCB) contains extensive networks of igneous intrusions emplaced during Late Jurassic and Early Cretaceous rifting that led to the breakup of the Greater India from Australia. We present the first basin-wide study of the distribution and morphology of these igneous intrusions through the interpretation of regionally extensive 3D and closely spaced 2D seismic data across the Exmouth Plateau and Exmouth Sub-basin. We observe three dominant intrusion morphologies: (1) Saucer-shaped intrusions up to ~20 × 40 km, but commonly much smaller, present in Jurassic strata of the southern Exmouth Plateau and central Exmouth Sub-basin; (2) Large, stacked, strata parallel, sheet intrusions, often >100 km in length, dominant in Triassic strata in the Exmouth Plateau and southern Exmouth Sub-basin; and (3) Variably sized, predominantly strata parallel and occasionally fault hosted intrusions (ranging in dimension from ~5 × 8 to ~35 × 65 km) present in Jurassic rocks in the Exmouth Sub-basin, and uppermost Triassic rocks in the Exmouth Plateau. We suggest that the morphologies of intrusions in the NCB are predominantly controlled the mechanical properties of their host rocks.