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We welcome the Comment of Alves et al. ([3]) as an opportunity to further discuss the stratigraphic record of continental break-up, offshore NW Australia. However, it is important to note that the statement by Alves et al. ([3]) at least partly emanates from analyses of the Iberia margin, where the proximal domain was situated >100-350 km from the locus of breakup (e.g. Alves & Cunha, [2]; Soares et al., [24]). REFERENCES 1 Alves, T., Fetter, M., Busby, C., Gontijo, R., Cunha, T. A., & Mattos, N. H. (2020). 3 Alves, T. M., Fetter, M., Busby, C., Cunha, T. A., & Mattos, N. (2022). [Extracted from the article]

Continental breakup involves a transition from rapid, fault‐controlled syn‐rift subsidence to relatively slow, post‐breakup subsidence induced by lithospheric cooling. Yet the stratigraphic record of many rifted margins contain syn‐breakup unconformities, indicating that episodes of uplift and erosion interrupt this transition. This uplift has been linked to mantle upwelling, depth‐dependent extension and/or isostatic rebound. Deciphering the breakup processes recorded by these unconformities and their related rock record is challenging because uplift‐associated erosion commonly removes the strata that help constrain the onset and duration of uplift. We examine three major breakup‐related unconformities and the intervening rock record in the Lower Cretaceous succession of the Gascoyne and Cuvier margins, offshore NW Australia, using seismic reflection and borehole data. These data show the breakup unconformities are disconformable (non‐erosive) in places and angular (erosive) in others. Our recalibration of palynomorph ages from rocks underlying and overlying the unconformities shows: (i) the lowermost unconformity developed between 134.98–133.74 Ma (Intra‐Valanginian), probably during the localisation of magma intrusion within continental crust and consequent formation of continent–ocean transition zones (COTZ); (ii) the middle unconformity formed between ca. 134 and 133 Ma (Top Valanginian), possibly coincident with breakup of continental crust and generation of new magmatic (but not oceanic) crust within the COTZs; and (iii) the uppermost unconformity likely developed between ca. 132.5 and 131 Ma (i.e. Intra‐Hauterivian), coincident with full continental lithospheric breakup and the onset of seafloor spreading. During unconformity development, uplift was focussed along the continental rift flanks, likely reflecting flexural bending of the crust and landward flow of lower crust and/or lithospheric mantle from beneath areas of localised extension towards the continent (i.e. depth‐dependent extension). Our work supports the growing consensus that the 'breakup unconformity' is not always a single stratigraphic surface marking the onset of seafloor spreading; multiple unconformities may form and reflect a complex history of uplift and subsidence during continent–ocean transition. [ABSTRACT FROM AUTHOR]

The Svalbard Archipelago consists of three basement terranes that record a complex Neoproterozoic–Phanerozoic tectonic history, including four contractional events (Grenvillian, Caledonian, Ellesmerian, and Eurekan) and two episodes of collapse- to rift-related extension (Devonian–Carboniferous and late Cenozoic). Previous studies suggest that these three terranes likely accreted during the early to mid-Paleozoic Caledonian and Ellesmerian orogenies. Yet recent geochronological analyses show that the northwestern and southwestern terranes of Svalbard both record an episode of amphibolite (–eclogite) facies metamorphism in the latest Neoproterozoic, which may relate to the 650–550 Ma Timanian Orogeny identified in northwestern Russia, northern Norway, and the Russian Barents Sea. However, discrete Timanian structures have yet to be identified in Svalbard and the Norwegian Barents Sea. Through analysis of seismic reflection, as well as regional gravimetric and magnetic data, this study demonstrates the presence of continuous thrust systems that are several kilometers thick, NNE-dipping, deeply buried, and extend thousands of kilometers from northwestern Russia to northeastern Norway, the northern Norwegian Barents Sea, and the Svalbard Archipelago. The consistency in orientation and geometry, as well as apparent linkage between these thrust systems and those recognized as part of the Timanian Orogeny in northwestern Russia and Novaya Zemlya, suggests that the mapped structures are likely Timanian. If correct, these findings would imply that Svalbard's three basement terranes and the Barents Sea were accreted onto northern Norway during the Timanian Orogeny and should hence be attached to Baltica and northwestern Russia in future Neoproterozoic–early Paleozoic plate tectonics reconstructions. In the Phanerozoic, the study suggests that the interpreted Timanian thrust systems represent major preexisting zones of weakness that were reactivated, folded, and overprinted by (i.e., controlled the formation of new) brittle faults during later tectonic events. These faults are still active at present and can be linked to folding and offset of the seafloor. [ABSTRACT FROM AUTHOR]

The Svalbard Archipelago is composed of three basement terranes that record a complex Neoproterozoic-Phanerozoic tectonic history, including four contractional events (Grenvillian, Caledonian, Ellesmerian, and Eurekan) and two episodes of collapse- to rift-related extension (Devonian-Carboniferous and late Cenozoic). These three terranes are thought to have accreted during the early-mid Paleozoic Caledonian and Ellesmerian orogenies. Yet recent geochronological analyses show that the northwestern and southwestern terranes of Svalbard both record an episode of amphibolite (-eclogite) facies metamorphism in the latest Neoproterozoic, which may relate to the 650-550 Ma Timanian Orogeny identified in northwestern Russia, northern Norway and the Russian Barents Sea. However, discrete Timanian structures have yet to be identified in Svalbard and the Norwegian Barents Sea. Through analysis of seismic reflection, and regional gravimetric and magnetic data, this study demonstrates the presence of continuous, several kilometers thick, NNE-dipping, deeply buried thrust systems that extend thousands of kilometers from northwestern Russia to northeastern Norway, the northern Norwegian Barents Sea, and the Svalbard Archipelago. The consistency in orientation and geometry, and apparent linkage between these thrust systems and those recognized as part of the Timanian Orogeny in northwestern Russia and Novaya Zemlya suggests that the mapped structures are likely Timanian. If correct, these findings would indicate that Svalbard's three basement terranes and the Barents Sea were accreted onto northern Norway during the Timanian Orogeny and should, hence, be attached to Baltica and northwestern Russia in future Neoproterozoic-early Paleozoic plate tectonics reconstructions. In the Phanerozoic, the study suggests that the interpreted Timanian thrust systems represented major preexisting zones of weakness that were reactivated, folded, and overprinted by (i.e., controlled the formation of new) brittle faults during later tectonic events. These faults are still active at present and can be linked to folding and offset of the seafloor. [ABSTRACT FROM AUTHOR]

Seismic reflection data image now‐buried and inactive volcanoes, both onshore and along the submarine portions of continental margins. However, the impact that these volcanoes have on later, post‐eruption fluid flow events (e.g., hydrocarbon migration and accumulation) is poorly understood. Determining how buried volcanoes and their underlying plumbing systems influence subsurface fluid or gas flow, or form traps for hydrocarbon accumulations, is critical to de‐risk hydrocarbon exploration and production. Here, we focus on evaluating how buried volcanoes affect the bulk permeability of hydrocarbon seals, and channel and focus hydrocarbons. We use high‐resolution 3D seismic reflection and borehole data from the northern South China Sea to show how ca. <10 km wide, ca. <590 m high Miocene volcanoes, buried several kilometres (ca. 1.9 km) below the seabed and fed by a sub‐volcanic plumbing system that exploited rift‐related faults: (i) acted as long‐lived migration pathways, and perhaps reservoirs, for hydrocarbons generated from even more deeply buried (ca. 8–10 km) source rocks; and (ii) instigated differential compaction and doming of the overburden during subsequent burial, producing extensional faults that breached regional seal rocks. Considering that volcanism and related deformation are both common on many magma‐rich passive margins, the interplay between the magmatic products and hydrocarbon migration documented here may be more common than currently thought. Our results demonstrate that now‐buried and inactive volcanoes can locally degrade hydrocarbon reservoir seals and control the migration of hydrocarbon‐rich fluids and gas. These fluids and gases can migrate into and be stored in shallower reservoirs, where they may then represent geohazards to drilling and impact slope stability. [ABSTRACT FROM AUTHOR]

Reactivation of pre‐existing intra‐basement structures can influence the evolution of rift basins, yet the detailed kinematic relationship between these structures and overlying rift‐related faults remains poorly understood. Understanding the kinematic as well as geometric relationship between intra‐basement structures and rift‐related fault networks is important, with the extension direction in many rifted provinces typically thought to lie normal to fault strike. We here investigate this problem using a borehole‐constrained, 3D seismic reflection dataset from the Taranaki Basin, offshore New Zealand. Excellent imaging of intra‐basement structures and a relatively weakly deformed, stratigraphically simple sedimentary cover allow us to: (a) identify a range of interaction styles between intra‐basement structures and overlying, Plio‐Pleistocene rift‐related normal faults; and (b) examine the cover fault kinematics associated with each interaction style. Some of the normal faults parallel and are physically connected to intra‐basement reflections, which are interpreted as mylonitic reverse faults formed during Mesozoic subduction and basement terrane accretion. These geometric relationships indicate pre‐existing intra‐basement structures locally controlled the position and attitude of Plio‐Pleistocene rift‐related normal faults. However, through detailed 3D kinematic analysis of selected normal faults, we show that: (a) normal faults only nucleated above intra‐basement structures that experienced late Miocene compressional reactivation, (b) despite playing an important role during subsequent rifting, intra‐basement structures have not been significantly extensionally reactivated, and (c) preferential nucleation and propagation of normal faults within late Miocene reverse faults and folds appears to be the key genetic relationship between contractionally reactivated intra‐basement structures and rift‐related normal faults. Our analysis shows that km‐scale, intra‐basement structures can control the nucleation and development of newly formed, rift‐related normal faults, most likely due to a local perturbation of the regional stress field. Because of this, simply inverting fault strike for causal extension direction may be incorrect, especially in provinces where pre‐existing, intra‐basement structures occur. We also show that a detailed kinematic analysis is key to deciphering the temporal as well as simply the spatial or geometric relationship between structures developed at multiple structural levels. [ABSTRACT FROM AUTHOR]

Dike swarm emplacement accommodates extension during rifting and large igneous province (LIP) formation, with ancient dike swarms serving to localize strain during later tectonic events. Deciphering three-dimensional (3-D) dike swarm geometry is critical to accurately calculating magma volumes and magma-assisted crustal extension, allowing syn-emplacement mantle and tectonic processes to be interrogated. It is also important for quantifying the influence of ancient dike swarms on post-emplacement faulting. However, the essentially 2-D nature of Earth's surface, combined with the difficulties in imaging subvertical dikes in seismic reflection data and the relatively low resolution of geophysical data in areas of active diking, means our understanding of dike swarm geometry at depth is limited. We examine an ~25-km-wide, >100-km-long, west-southwest--trending dike swarm imaged, due to post-emplacement rotation to shallower dips, in high-quality 2-D and 3-D seismic reflection data offshore southern Norway. Tuned reflection packages correspond to thin (<75 m thick), closely spaced dikes. These data provide a unique opportunity to image and map an ancient dike swarm at variable structural levels. Crosscutting relationships indicate emplacement occurred in the Late Carboniferous--Early Permian, and was linked to the formation of the ca. 300 Ma Skagerrak-centered LIP. Dike swarm width increases with depth, suggesting that magma volume and crustal extension calculations based on surface exposures are dependent on the level of erosion. During the Mesozoic, rift-related faults localized above and exploited mechanical anisotropies within the dike swarm. We demonstrate that seismic reflection data are a powerful tool in understanding dike swarm geometry and the control of dikes on subsequent faulting. [ABSTRACT FROM AUTHOR]

Using bathymetric and multichannel seismic (MCS) data, we explored the volcanic influence on the bathymetric and stratigraphic features of the Mianhua Terrace. The Mianhua Terrace occupies the marine counterpart of the Northern Taiwan Volcanic Zone (NTVZ) along the collapsed Taiwan orogenic wedge and is dominated by post-collisional magmatism and extensional structures. The bathymetric data showed several semicircular-shaped features near the shelf break. The MCS profiles showed that the Pleistocene unconformity buried beneath the Mianhua Terrace is partly difficult to observe due to seafloor multiples, suggesting that the seafloor is dominated by physically hard lithology, probably volcanic lavas. We interpreted the high-amplitude reflectors and their projected seafloor relief as intrusive sills and associated extrusive edifice. Similarly, we interpreted high-amplitude reflectors in the vicinity of normal faults as intrusive sills emplaced and facilitated by fault structures. A volcanic or hydrothermal mound was also recognized. We propose that the Mianhua Terrace is a breached ramp in a transfer zone between the tips of two successive normal faults along the shelf break. Once the fault tips reactivate and extend toward each other, the Mianhua Terrace may continue to collapse, leading to catastrophic volcanic or associated hydrothermal events. [ABSTRACT FROM AUTHOR]