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Reeve et al. (2022) address the stratigraphic record of continental breakup by focusing on a set of stratigraphic unconformities from a proximal sector of the NW Australian continental margin, inboard from the Exmouth Plateau. They suggest that such unconformities can potentially document a well‐defined three‐stage process: end of the syn‐rift phase, formation of a wide continent‐ocean transition zone (COTZ) and generation of 'true' Penrose‐type oceanic crust. We counterargue that continental breakup is a protracted event that can only be understood via seismic‐ and chronostratigraphic correlations of strata, and their composing sequences, across and along rifted margins. Tying proximal stratigraphic unconformities to magnetic anomalies outboard from the study area in Reeve et al. (2022) is open to question. In parallel, we suggest that age resolutions of ca. 1 Ma are not achievable using the micropaleontological data presented in Reeve et al. (2022), with an important reworking of microfossil assemblages potentially occurring during the erosional process forming local and regional unconformities. Our discussion addresses these points in more detail. [ABSTRACT FROM AUTHOR]

When extension events are greatly separated in time, older faults may be buried and stratigraphically separated from newly developing faults at shallower depths. During rifting, the buried structures may reactivate and propagate upwards to be expressed within the shallow system. The degree of linkage between structural levels determines the influence that the deeper structures can exert over the geometry and evolution of the incipient fault system. In this study we use 3D seismic reflection data to examine how a deep fault population across the Laminaria High, NW shelf of Australia influences the development of a younger fault system at shallow depths. These fault populations are non‐parallel and decoupled across a mechanically weak interval. The majority of shallow faults are not linked to those at depth. However, the reactivation and upward propagation of some of the deeper faults produce anomalously oriented structures at shallow depths, hard‐linked to the deeper structures. One fault in particular shows along‐strike variability, with the deep segment reactivated and present at shallow depths in the west. To the east, the shallow and deep fault segments become decoupled across the mechanically weak interval, although some soft‐linkage and strain transfer still occurs. We suggest that this switch in the degree of coupling along the fault is due to the geometry of the deeper structure, with the transition corresponding to a prominent relay ramp. We show how the geometry of a deeper fault may affect its propensity to reactivate during subsequent extensional events, ultimately affecting the degree of structural inheritance that is expressed within younger, shallower fault populations. [ABSTRACT FROM AUTHOR]

Continental rifting is accommodated by the development of normal fault networks. Fault growth patterns control their related seismic hazards, and the tectonostratigraphic evolution and resource and CO2 storage potential of rifts. Our understanding of fault evolution is largely derived by observing the final geometry and displacement (D)‐length (L) characteristics of active and inactive fault arrays, and by subsequently inferring their kinematics. We can rarely determine how these geometric properties change through time, and how the growth of individual fault arrays relate to the temporal evolution of their host networks. Here we use 3D seismic reflection and borehole data from the Exmouth Plateau, NW Shelf, Australia to determine the growth of rift‐related, crustal‐scale fault arrays and networks over geological timescales (>106 Ma). The excellent‐quality seismic data allows us to reconstruct the entire Jurassic‐to‐Early Cretaceous fault network over a relatively large area (ca. 1,200 km2). We find that fault trace lengths were established early, within the first ca. 7.2 Myr of rifting, and that along‐strike migration of throw maxima towards the centre of individual fault arrays occurred after ca. 28.5 Myr of rifting. Faults located in stress shadows become inactive and appear under‐displaced relative to adjacent larger faults, onto which strain localises as rifting proceeds. This implies that the scatter frequently observed in D‐L plots can simply reflect fault growth and network maturity. We show that by studying complete rift‐related normal networks, rather than just individual fault arrays, we can better understand how faults grow and more generally how continental lithosphere deforms as it stretches. [ABSTRACT FROM AUTHOR]

Within the Lorne Basin, Mesozoic granitoid plutons and dacitic to rhyolitic extrusions form extensive components in a faulted, eroded Triassic sedimentary basin. Late Cenozoic plugs and flows of evolved basalts represent easterly extensions of the eroded Comboyne Volcano. The basin marks a terminal outpost of the New England Orogen, much modified by later alkaline felsic intrusions and flow remnants. Many origins are invoked for its tectonic genesis and magmatic evolution including plate tectonic, caldera and even meteoritic impact events. This review uses extended field study, zircon fission track, K–Ar and Ar–Ar age-dating, petrography and geochemical analyses on igneous suites. These results are combined with previously published and unpublished studies to clarify relationships between volcanic and plutonic suites, structural features and paleotopographic developments, allowing for an enlarged synthesis of Lorne Basin magmatism and its tectonic contexts. Dating reveals rhyodacitic volcanism began at ca 221 Ma (Milligans Road) and culminated in emplacements of I- and A-type dioritic to granitic suites (North Brother, Middle Brother) at ca 217–212 Ma (MAGMATIC EPISODE 1, late Triassic). Voluminous alkaline rhyolitic feeders and flows (Bago Range, Batar Creek) erupted between ca 187 and 160 Ma (MAGMATIC EPISODE 2, early–mid-Jurassic). Lavas infilled extended drainages cut into a dissected, faulted terrain and disrupted former drainage patterns. An alkaline monzodioritic to granitic pluton and late-stage rhyolitic dyke swarm (South Brother) were emplaced at ca 126 and 119 Ma (MAGMATIC EPISODE 3, early Cretaceous). This chemically distinct magmatism coincided with thermal coastal faulting along eastern Australia. A large eroded plug and dyke complex (Mount Lorne) shows steep flow banding and lies within dissected radial flow infillings. This prominent eruptive conduit tapped a significant ring fault system. Although undated, its petrography resembles features related to MAGMATIC EPISODE 3. The study revealed a far greater profusion of rhyolitic feeders and flows than previously thought, making likely volcanic volumes within episodes difficult to estimate. The youngest volcanic remnants infill later drainages, are dated between ca 17 and 13 Ma (MAGMATIC EPISODE 4, mid-Neogene), and are evolved derivatives related to the adjacent Comboyne central volcano. Some evolved basalts contain feldspathic and mafic crystallisations indicating mid-crustal melt processes. These bimodal suites represent a traverse over an asthenospheric plume during northward lithospheric migration of eastern Australia. Minor vitrophyric bodies recorded across the Lorne Basin only intrude Carboniferous basement beds. Their origin and age are enigmatic and represent a final puzzle to solve in the evolution of Lorne Basin magmatism. [ABSTRACT FROM AUTHOR]

The Sisters shear zone is a newly discovered Late Cretaceous detachment fault system exposed for 40 km along the southeast coast of Stewart Island, southernmost New Zealand. Footwall rocks consist of variably deformed ca. 310 and 105 Ma granites that range from undeformed to protomylonite, mylonite, and ultramylonite. The hanging wall includes non- marine conglomerate and brittley deformed granite. K-feldspar thermochronometry of the footwall indicates moderately rapid cooling (20-30 C°/m.y.) due to tectonic denudation over the interval Ca. 89-82 Ma. Return to slow cooling at 82 Ma coincides with the age of the oldest seafloor adjacent to the Campbell Plateau and reflects the mechanical transition from continental extension to lithospheric rupture and formation of the Pacific-Antarctic Ridge. Our findings support a two-stage rift model for continental breakup of this part of the Gondwana margin. Stage one (ca. 101-88 Ma) is the northward propagation of continental extension and the Tasman Ridge as recorded in mylonite dredged from the Ross Sea and the Paparoa core complex. Stage two (ca. 89-82 Ma) is extension between the Campbell Plateau and West Antarctica leading to formation of the Pacific-Antarctic Ridge. [ABSTRACT FROM AUTHOR]

Antarctica's Lambert graben, Australia's North West Shelf, and the eastern Indian Peninsula all host thick, fault-bounded Permian-Triassic successions. These terranes were adjacent to each other in Gondwana. The Lambert graben intersects the modern coastline, strikes oblique to shelf architecture, and has a geophysical signature that can be traced >1000 km inland. Vitrinite reflectance data from the graben margins record Permian-Triassic infill. Australia's North West Shelf is the relict of an intracontinental Carboniferous-Permian rift that was infilled during the Permian-Triassic then driven to oceanic completion during Jurassic-Cretaceous Gondwana breakup. This rift was compartmentalized over length scales of ∼650 km, corresponding to accommodation zones, margin-normal geophysical lineaments, and long-lived crustal weaknesses. In eastern India, similar compartmentalization is marked by extensive coal-bearing graben systems. Gondwana reconstructions indicate that the Lambert graben corresponds to the orientation and length scale of Carboniferous-Permian rift compartmentalization. The Lambert graben represents an accommodation zone of a wide intracontinental rift that extended from Australia's North West Shelf, between India and Antarctica, to southern Africa. This rift collected Gondwana's thick Permian-Triassic sedimentary blanket and rich alluvial coal deposits. [ABSTRACT FROM AUTHOR]

Abstract: During the Late Palaeozoic and the Mesozoic, the development and evolution of the North West Shelf of Australia have been mostly driven by rifting phases associated with the break-up of Gondwana. These extensional episodes, which culminated in the opening of the Neotethys Ocean during the Permo-Carboniferous and a series of abyssal plains during the Jurassic-Cretaceous, are characterised by different stress regimes and modes of extension, and therefore had distinctive effects on the margin, and particularly on the Northern Carnarvon Basin. Interpretation of 3D and 2D seismic data enables a structural and stratigraphic analysis of the Late Palaeozoic sediments deposited in the proximal part of the Dampier Sub-basin (Mermaid Nose). Based on their seismic characters, stratigraphic relationship, internal patterns, lateral continuity, and architecture, these units are associated here with the Pennsylvanian?–Early Sakmarian glaciogenic Lyons Group and the Sakmarian–Artinskian Callytharra Formation. The former were deposited in a half-graben whose development is associated with the onset of the Neotethys rifting, and the latter is characterised by restricted deposition, inversion of prograding patterns, and uplift. The integration of seismo-stratigraphic characterisation of the Late Palaeozoic sequences and Mesozoic data from one exploration well (Roebuck-1) enables the construction of subsidence curves for the Mermaid Nose and the interpretation of its geohistory. The tectonic subsidence curves show a striking Permo-Carboniferous rifting phase related to the Neotethys rifting and a discrete Late Jurassic–Early Cretaceous event coeval with the opening and the spreading of the Argo Abyssal Plain. This result points out the predominance of the effects of the Permo-Carboniferous Neotethys episode, whereas the extension related to the Argo Abyssal Plain rifting that occurred later and closer to the studied area, had only limited effects on the subsidence of the proximal Dampier Sub-basin. Therefore, it supports a tectonic model with two distinct modes of extension for the Late Palaeozoic (widespread) and the Mesozoic (localised) rifting phases. [Copyright &y& Elsevier]

This study reviews the origin of two approximately east–west-trending synclines in the Lake Julius area at the eastern edge of the Leichhardt Rift. The genesis of one of these structures can be found in a north–south shortening event (D1) that occurred at the beginning of the compressional Isan Orogeny (at ca 1600 Ma). Metasediments in a cross-rift were rammed against a competent buttress defined by the pre-existing rift architecture, producing the approximately east–west-trending Somaia Syncline and its associated axial-plane slaty cleavage. In contrast, the Lake Julius Syncline was produced by reorientation of an originally approximately north–south-trending (D2) fold, in a transpressional zone adjacent to a strike-slip fault, at the end of the Isan orogeny. The effects of late fault movement can be partially reconstructed, based on correlations assuming that regionally developed trains of upright folds formed during the peak of the Isan Orogeny (D2). These folds have been offset, as well as having been tightened and disrupted at the same time as fault movements took place. The overall pattern of movement in the Lake Julius region can be explained as the result of an ‘indentor’ ramming into the ancient edge of the Leichhardt Rift, which acted as a buttress. [ABSTRACT FROM AUTHOR]

• The Kalakashi Group formed during 900–850 Ma and did not record any Grenvillian orogenic event. • The southwest Tarim Craton was probably in a long-term rifting environment in the Neoproterozoic. • The Tarim Craton was likely located at the peripheral, rather than the interior, of the Rodinia Supercontinent. The Rodinia Supercontinent assembled through global-scale Grenvillian (1300–900 Ma) orogeny, so identification and correlation of Grenvillian orogens is fundamental to the geological reconstruction of Rodinia. The Tarim Craton, NW China, has been considered as a building block of Rodinia, but its Neoproterozoic tectonic evolution and relationship with Rodinia remain enigmatic. It was proposed that a Grenvillian orogenic event occurred in the southwestern Tarim, possibly related to its amalgamation with northern Australia. Key evidence for this model came from the ~1.0 Ga 40Ar/39Ar ages of the Kalakashi Group in the Tiekelike belt, southwestern Tarim. In this contribution, we report zircon U-Pb ages and Lu-Hf isotopic data, as well as whole-rock geochemical data for the Kalakashi Group from the Buqiong section where a ~1.0 Ga 40Ar/39Ar age was reported. Our field and petrographic observations indicate that the primary rock assemblage of the Kalakashi Group is orthogneiss, garnet-bearing mica schist, marble and minor amphibolite. Zircon U-Pb dating of five orthogneisses and an amphibolite yielded crystallization ages of 900–850 Ma and a thermal/fluid overprinting event at ~420 Ma. Lu-Hf isotopic analyses of the dated zircon grains from two orthogneisses yielded ε Hf(t) values from −4 to +7, indicating a mixture of mantle- and crust-derived materials. Geochemical data show that the orthogneisses have relatively high FeOT/MgO and 10,000*Ga/Al ratios, elevated contents of high-field-strength elements (HFSE) and negative Ba, Sr and Eu anomalies, characteristic of A 1 -type granite, indicating that the parental magma erupted in an intra-plate rifting setting. Our results indicate that the Kalakashi Group is a volcanic-sedimentary succession that deposited in the Neoproterozoic, rather than the Paleoproterozoic or Mesoproterozoic as previously thought. We found no evidence for a Grenvillian orogenic event from the Kalakashi Group in the Buqiong section. Instead, the age and geochemistry of the studied orthogneisses are remarkably similar to those of the Sailajiazitage Group, although the latter was affected by weaker metamorphism and deformation. Reliable geochronological data from igneous and metamorphic rocks, as well as detrital zircons from Neoproterozoic strata, indicate that no typical record of Grenvillian orogeny occurred in either the north or the south of the Tarim Craton. Instead, we suggest that the northern Tarim was probably dominated by a long-term subduction-accretion, whereas the southern Tarim was likely in a long-term rifting environment in the early Neoproterozoic. [ABSTRACT FROM AUTHOR]