Basin Research - Volume 37, Issue 4, 2025

Seismic and well‐data show that the Porcupine Basin, offshore west of Ireland, is a rift propagator, with discontinuous rifting migration along the axis of the basin. Several deformation pulses are controlled by prerift basements that are laterally stacked and bounded by major transecting fault zones.

The influence of transversal crustal discontinuities on the development of continental rift systems remains poorly constrained, especially because their connection with shallow normal faults is often unclear. Nonetheless, these basement faults likely affect the dynamics and the kinematics of the rifting, especially during the early stages of extension. Our study focusses on the Porcupine Basin, offshore west of Ireland, an aborted rift propagator that experienced a 220 Myr‐long geological evolution with several rifting episodes. Detailed seismic analysis, integrated with exploration well data, illustrates the regional complexity of the structural patterns across the basin, with faults running subparallel or transverse to its axis. This tectonic framework controlled the northward migration of the crustal stretching during the Late Jurassic, followed by crustal thinning during the Early Cretaceous. Pre‐existing, orogenic‐derived structures bound crustal terranes that control deformation pulses when rifted apart. This suggests structural barriers that either slowed the northward rifting migration during the Oxfordian, Kimmeridgian and Tithonian when crosscutting through the Variscan and Caledonian fold‐and‐thrust belts, or stopped the rifting by the end of the Barremian when it encountered Caledonian and Grenvillian crystalline basements. We propose that this structural inheritance led to the formation of a typical rift propagator of continental nature, and that the Porcupine Basin constitutes a remarkable example of a termination of rifting processes in a well‐formed oceanic rift system.

We describe the results of 3D geological mapping of a large sill emplaced in a sedimentary basin, Svalbard. Our mapping work shows that (1) the sill is made of segments emplaced at different levels of stratigraphy, (2) the host rock lithology controls sill segment morphology and emplacement and (3) the sill segments connect through steeply dipping shear/dilatant steps.

Sills are fundamental elements of volcanic plumbing systems emplaced in sedimentary basins. Even though sills are commonly considered simple, planar concordant igneous sheets, they are actually complex 3‐dimensional objects. Detailed knowledge of the 3D structure of sills and their host rocks is of primary relevance to better constrain the emplacement mechanisms and the impacts of sills on sedimentary basins. This study describes the results of 3‐dimensional geological mapping of a large (~14 × 9 km), well‐exposed Early Cretaceous dolerite sill in Central Spitsbergen, Svalbard, Arctic Norway, using a combination of digital outcrop modelling and field mapping. The sill was emplaced within Upper Palaeozoic sedimentary formations of Svalbard. It is made of distinct segments emplaced at different stratigraphic levels of the host rock stratigraphy. The mapping shows a clear stratigraphic control on the intrusion morphology. Sill segments emplaced at the boundary between two formations, which mark a strong lithological and rheological boundary, are straight and concordant. Conversely, segments emplaced within a more homogeneous formation exhibit more irregular, locally discordant shapes. The sill segments emplaced at distinct stratigraphic levels are connected by steeply dipping steps, which formed through dilatant shearing between the tips of the sill segments. The preferred NW‐SE orientation of the steps and the thinning of the sill towards the SE suggests a propagation direction of the magma towards the SE. Our study shows how 3‐dimensional knowledge of igneous intrusions is key for revealing their emplacement mechanisms.

On magma poor rifted margins, the boundary between deformed and overlying post tectonic stratigraphy is a significant and long recognised feature: however its interpretation and origin remain debated. The boundary, the Top Taper Interface (TTI), forms the upper surface of tapered continental crust and pre/syn tectonic stratigraphy typical of rifted margins. Extending interpretations of the TTI across rifted margins into deep water where data are scarce is often challenging. The Iberian Atlantic Margin offers rare deep water (> 4 km) calibration but lacks borehole data across a key area, the ‘necking domain’, which lies between deep water and the proximal margin. By contrast the necking domain is well calibrated elsewhere around the European North Atlantic rim. Fault offsets often exceeding 1 km, with minimal syn‐tectonic hanging wall growth, are a recurring feature of the TTI. Re‐examining the Iberian margin and its North Atlantic counterparts indicates the TTI develops in < 10 Ma with fault generated subsidence and sediment starvation, immediately preceding a Jurassic—earliest Cretaceous termination, pause or migration of active extension in the continental crust. Significant basin reconfiguration is indicated by the often complex sub‐crop of the TTI. North Atlantic data indicate the TTI is often associated with stratigraphic condensation driven by deepening. Globally such interfaces occur regardless of sediment budget indicating an increase in basin width and volume that outpaces sediment delivery. The widening of the basin relative to earlier upper crustal graben results from faulting localised across a long‐wavelength crustal neck thinned during active extension, preceding a cessation or migration of active extension. However, observations from the European North Atlantic rim basins indicate that this process should also account for failed necking domains that did not reach such advanced stages of extension.

The interpretation of the upper surface of the crustal taper characteristic of magma‐poor rifted margins is often disputed. North Atlantic data indicate the surface forms via a rapid phase of faulting across the crustal taper, resulting in an increase in basin volume which outstrips sediment supply.

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.

This study examines the development of fault patterns in a multi‐phase rift system and demonstrates how pre‐existing faults influence the geometries and distribution of subsequent fault systems.

The present‐day west‐to‐east drainage network was established during the Late Miocene to Pliocene. Sedimentary dispersal exchange occurred no later than the Early Miocene, marking the initial convergence. Sedimentary dispersal signal is more sensitive in identifying the initiation of intracontinental convergence.

The collision and convergence between the Indian and Eurasian plates have induced significant intracontinental deformation, leading to convergence between the Pamir salient and the Southwestern Tian Shan during the Cenozoic. Key indicators for identifying the initiation of continent–continent collision include sedimentary dispersal exchange, superimposed thrust faults and lithospheric mantle contact. In this study, we conduct comprehensive stratigraphic and detrital zircon analyses of Late Cenozoic sediments in the eastern Pamir–Southwestern Tian Shan convergent zone to understand the tectono‐geomorphic evolution and identify the first instance of sedimentary dispersal exchange between the two tectonic domains. Our analyses reveal an upward‐coarsening sequence from the Keziluoyi Formation to the Anjuan Formation, followed by an upward‐fining sequence from the Anjuan Formation to the Pakabulake Formation in the Qiate section. Sedimentary facies interpretations indicate a shift from lacustrine delta deposits and alluvial plain deposits to shallow lacustrine deposits in the Qiate section. The presence of these distal deposits suggests that the study area exhibited a flat topography and relatively weak hydrodynamic conditions, supporting the idea that the Alai Valley–Western Tarim Basin closed progressively from west to east. Detrital zircon U‐Pb dating and reanalysis of the Late Cenozoic sediments in three sections suggest that the first instance of sedimentary dispersal exchange occurred no later than the deposition of the Anjuan Formation, marking an Eocene–Miocene initiation of the Pamir–Southwestern Tian Shan convergence. By integrating these findings with previous studies, we conclude that the present‐day west‐to‐east drainage system in the convergent zone was not established until the Late Miocene to Pliocene. We also find that the sedimentary dispersal exchange is a more sensitive indicator for identifying the initiation of the Pamir–Southwestern Tian Shan intracontinental convergence than the initial superimposed thrust faults and lithospheric mantle contact.

Beef calcite veins record paleo‐overpressure in sedimentary basins. In the Green River Formation, U–Pb ages, clumped isotope temperatures and stable isotope signatures suggest that overpressure developed from hydraulic head during the downward migration of mixed meteoric and evolved connate fluids along tectonically generated faults and fractures.

Beef calcite veins in the Green River Formation of the Uinta Basin, Utah, were geochemically characterised to test two hypotheses: (1) that beef calcite veins can form during extensional tectonism and (2) that fluid overpressure can develop in open or partially restricted hydrologic systems. Laser ablation U–Pb geochronology yielded three precipitation ages, with the most precise at 24.8 ± 4.8 Ma (2σ), consistent with maximum burial of the formation and coinciding with uplift of the Uinta Basin segment of the Colorado Plateau. Clumped isotope thermometry indicates precipitation temperatures between 55°C and 72°C—substantially lower than the estimated host rock temperatures of 110°C to 140°C based on a ~30°C/km geothermal gradient. δ¹³C and δ¹⁸O values of beef calcite range from 1.6‰ to −1.2‰ and −10.7‰ to −11.5‰ (VPDB), respectively, with calculated δ¹⁸O of the precipitating fluid (VSMOW) ranging from −3.3‰ to −5.2‰. These values are consistent with a mixed meteoric and shallow connate water source, suggesting the downward invasion of cold, evolved meteoric fluids along faults and fractures during post‐Laramide extensional tectonic deformation. The overpressure required for beef calcite formation may have been generated by hydraulic head associated with these downward‐migrating fluids and the subsequent lateral displacement of basin brines along stratigraphic interfaces beneath regionally continuous mudstone and evaporite seals.

Schematic depiction of the interactions of magmatism, deformation, and exhumation and their controls on the South Tianshan Kuqa basin coupling processes.

The intricate interplay of post‐collisional magmatism, deformation and related exhumation has reshaped the basin–range system at convergent plate boundaries, as exemplified by the South Tianshan (STS) and the northern part of the Tarim basin (i.e., the Kuqa basin). However, how magmatism, deformation and exhumation interact to control the evolution of the basin–range system remains unclear. This study applies multisystem thermochronometry to elucidate the links between exhumation and post‐collisional magmatism, sedimentary burial, thrusting, and deformation at the boundary of the STS–Kuqa basin. Our results reveal that the eastern Kuqa basin experienced rapid exhumation during Permian–early Triassic times, coinciding with volcanic eruptions (ca. 293–288 Ma and ca. 262–254 Ma) and accelerated tectonic subsidence in the western region. The early Permian exhumation was driven by post‐collisional continental extension, whereas the late Permian–early Triassic exhumation was associated with regional‐scale transpressive strike–slip faults. From the late Triassic to Early Cretaceous, the Kuqa basin experienced continuous burial reheating, corresponding to continuous denudation in the STS during that period. Subsequently, long‐term slow denudation in the STS region continued until the early Cenozoic. During the Oligocene–early Miocene, southward thrusting along the North Tarim Fault resulted in the growth and denudation of the STS, coupled with sedimentary burial reheating in the Kuqa basin. Then, deformation continued towards the Tarim basin and intensified since the late Miocene (ca. 5 Ma). The late Cenozoic deformation and exhumation were synchronous with the reactivation of preexisting faults in the STS, and exhibited a progressive westward increase, which can be linked to the clockwise rotation of the Tarim block during the India–Asia collision.

The North Sea rift basin is a prolific oil and gas province and is an active area of study for CO2 sequestration. Despite the economic importance of the North Sea basin, the timing and nature of rift initiation and subsequent development are poorly constrained. To address this issue, we focus on reconstructing the spatial and temporal distribution of fault activity from the late Permian to late Triassic across the Utsira High area, a key basement high in the centre of the North Sea basin, providing a framework for understanding Northern North Sea rift development and influence on subsequent Mesozoic rift phases. Results indicate rifting initiation in the latest Permian times with continuous but spatially variable extension through the Triassic and early Jurassic. Three main phases are recognised: (i) late Permian, with widespread extension across the region and development of the Utsira High; (ii) Early Triassic, characterised by localised extension across the Horda Platform, Stord Basin and Åsta Graben; (iii) Middle to Upper Triassic phase, where extension is still localised across the eastern rift shoulder, with minor faults forming across the South Viking Graben; and (iv) Jurassic continuation of rifting, with faulting localised across the Viking Graben and a decline in activity during the Cretaceous. Combined with a new model for the tectonic evolution and palinspastic reconstruction of the region, this research builds on previously published work across the area, advancing the understanding of the Triassic tectonic history of the Utsira High region.

Early Rift development started with the formation of Late Permian Rotliegend half‐grabens. Pre‐existing structures influenced rift location and evolution. Rift developed through Triassic times with the regional strain transferred progressively from east to west. From Late‐Permian to the Triassic, the Utsira remained a prominent high across the region. The lack of fully developed central segments indicates an early maturity of the rift system.