Search

The salt-bearing conjugate rifted margins of Morocco and Nova Scotia contain one of the oldest stratigraphic records documenting the opening history of the Central Atlantic Ocean, starting in Late Triassic times. Although there is certain consensus on the Middle Jurassic to Present evolution of this ocean basin, the Early Jurassic rift to drift transition stage is still under discussion. Through the interpretation of unpublished, recently acquired deep seismic reflection data, integrated with legacy 2D surveys from offshore Morocco, this study presents new evidence supporting a revised 3D passive-margin evolutionary model with a focus on the rift-to-drift transition phase. Eight regional seismic transects illustrate the along-strike variability of crustal structural styles, magmatic budget, and the interaction between rifting and evaporite deposition. Assuming evaporite deposition was near-isochronous along the margin, the interpretation of the autochthonous salt distribution elucidates the northward propagation of rifting and breakup. We interpret that salt was deposited during the exhumation stage in the Tarfaya and southern Agadir basins (southern segment) and during late syn -stretching to early syn-thinning in the Safi Basin and the Mazagan Plateau (northern segment). Furthermore, structural inheritance from Paleozoic tectonic boundaries, such as the South Atlas Fault Zone, were reactivated as transfer zones during rifting, separating segments with different crustal deformation styles and extension rates. Moreover, one of these inherited structures, the Sidi Ifni Transfer Zone, is located at the boundary between rheologically distinct pre-rift units and marks the transition between a magma-rich (south) and a magma-poor (north) segment of the margin, suggesting a direct link between compositional/structural inheritance and magmatic supply during rifting and breakup. [ABSTRACT FROM AUTHOR]

The offshore rifted margins of the North Atlantic have a spatially complex crustal structure comprised of variable crustal morphologies, continental blocks, and inherited structures. Recently, deformable plate tectonic models have permitted the interplay of plate kinematics and deformation to be assessed throughout the North Atlantic, and elsewhere. In particular, the ability to calculate temporal variations in crustal thickness has provided insight into the kinematic role of continental blocks and their interplay with large and micro‐tectonic plates during the formation of the North Atlantic offshore rifted margins. In this study, the deformable plate modeling workflow introduced in the companion contribution of this study (Part 1) is used to investigate previously published and newly presented deformable plate models of the Newfoundland, Irish, and West Iberian margins. This approach permits the deformation and subsequent crustal thickness evolution within previously recognized continental blocks and sedimentary basins throughout the southern North Atlantic Ocean to be visualized and assessed from 200 Ma to present day. The segmentation of early rift crustal thicknesses calculated by deformable plate models demonstrate strong correlations with the offshore extension of Appalachian and Caledonian terrane boundaries. Thus, our observations suggest that inherited orogenic boundaries potentially play a key role in the early rift crustal structure of sedimentary basins and the partitioning of deformation around and within continental blocks. Plain Language Summary: The Earth is made up of large and small tectonic plates that are actively moving and can have variable thicknesses and morphologies. Over the last 200 million years, the gradual separation between the North American and Eurasian plates has led to the formation of the southern North Atlantic Ocean. Consequently, its present day form represents a natural playground for geoscientists to study the formation of oceans and plate tectonic processes through the interplay of data acquisition, interpretation, and modelling studies. In this work, we use an innovative and open‐source modelling workflow to study the evolution of large and small tectonic plates by reconstructing their present day template and thicknesses back through time. The results of our study reveal the influential role of smaller tectonic plates and their necessity for accurately restoring the southern North Atlantic Ocean back through time. In addition, this study highlights the potential impact of approximately 300–500 million year old geological structures that are inherited from the closure of earlier oceans that were re‐activated during the creation of the southern North Atlantic Ocean. Key Points: Continental blocks had a large impact on pre‐rift crustal thicknesses calculated within sedimentary basins throughout the North AtlanticThe Flemish Cap, Porcupine Bank, and Rockall‐Hatton Bank played a key role during rift related deformation throughout the North AtlanticAppalachian and Caledonian terrane boundaries were very influential on pre‐rift templates calculated throughout the North Atlantic [ABSTRACT FROM AUTHOR]

Deformable plate tectonic models have been demonstrated to be a useful technique for quantifying temporal variations in strain rate and crustal thickness within recent plate kinematic studies. Using the GPlates software, deformable plate models offer an approach to visualize and assess the interplay of plate kinematics and deformation. However, several assumptions are imposed in previous studies that limit their ability to explain the crustal evolution of various tectonic regimes. Examples of these assumptions include, but are not limited to, the rigid nature of continental blocks and boundaries used to define deformable regions, and uniform crustal thickness assumptions at model start times. In this study, we address these assumptions with newly presented applications using the interplay of GPlates and its python programming library, pyGPlates. In particular, we demonstrate the ability to create deformable continental blocks, reconstruct present day crustal thickness estimates back through time, and how the landward extent of present day crustal thickness estimates can be used to define the limits of deformable plate models and rift domain boundaries a priori. To demonstrate their application and validity, these concepts are evaluated using a previously published deformable plate model of the southern North Atlantic that is tested using 4 modeling scenarios herein to assess the impact of variable model inputs. These models provide insight regarding the pre‐Jurassic (200 Ma) crustal thickness template of the southern North Atlantic, the evolution of continental blocks during rift‐related deformation, and the potential impact of ancient orogenic terranes during subsequent rifting within the North Atlantic. Plain Language Summary: The opening and closing of oceans and the development of Earth's landscapes such as mountain ranges and volcanoes can all be attributed to plate tectonic theory. The theory of plate tectonics depicts the Earth's surface and shallow interior as a collection of large and small tectonic plates that independently move over time. Consequently, an active area of research in geosciences consists of reconstructing tectonic plates back through geological time using observations and data acquired within present day tectonic regimes to resolve their temporal evolution and kinematic history. In this study, we present a novel workflow that is used to reconstruct tectonic plates and deformation experienced within their interiors back through time using open source software and codes. To demonstrate its validity, this workflow is applied to study the plate tectonic evolution of the southern North Atlantic Ocean. Furthermore, this application provides insight into the plate kinematics and deformation experienced within the southern North Atlantic Ocean over the past 200 million years. Key Points: A new deformable plate modeling approach is presented using GPlates and pyGPlatesThe pre‐rift templates of offshore rifted margins throughout the North Atlantic are assessedTemporal variations in deformation within continental blocks throughout the North Atlantic are investigated [ABSTRACT FROM AUTHOR]

Ice shelves regulate the stability of marine ice sheets. We track fractures on Pine Island Glacier, a quickly accelerating glacier in West Antarctica that contributes more to sea level rise than any other glacier. Using an on‐ice seismic network deployed from 2012 to 2014, we catalog icequakes that dominantly consist of flexural gravity waves. Icequakes occur near the rift tip and in two distinct areas of the shear margin, and TerraSAR‐X imagery shows significant fracture in each source region. Rift‐tip icequakes increase with ice speed, linking rift fracture to glaciological stresses and/or localized thinning. Using a simple flexural gravity wave model, we deconvolve wave propagation effects to estimate icequake source durations of 19.5–50.0 s and transient loads of 3.8–14.0 kPa corresponding to 4.3–15.9 m of crevasse growth per icequake. These long‐source durations suggest that water flow may limit the rate of crevasse opening. Plain Language Summary: Large shelves of floating ice strengthen glaciers in Antarctica, helping to protect against rapid sea level rise that can occur when glaciers flow into the ocean. Ice shelves can collapse through rapid cracking (synonym of fracturing), but it is difficult to directly observe cracking on ice shelves. In this paper, we track cracks on Pine Island Glacier, an ice shelf in Antarctica that is particularly vulnerable to collapse. We see cracks in pictures taken by satellites. Cracking causes the ice shelf to shake up and down, which we record using the same equipment that records earthquakes. We record shaking located at a set of cracks at the side of the ice shelf and at the tip of a single massive crack called a rift. Rift cracking seems related to the speed that the ice shelf is flowing. We also use a computer simulation of shaking to learn about the details of the crack process. Our simulation suggests that the crack process might be more complicated than a single crack opening evenly at a constant rate. Key Points: Fracture at Pine Island Glacier generates flexural gravity waves, a wave type related to interaction between a floating plate and supporting fluidRift‐tip seismicity rate increases with ice speed either due to changes in the underlying ice shelf stress state or localized thinningRecorded flexural gravity waves are consistent with a point load of ∼10 kPa applied over ∼30s, corresponding to ∼10m of vertical cracking [ABSTRACT FROM AUTHOR]

One fundamental lesson from the last decade's research into rifted margins is that stratigraphic horizons cannot be simply correlated from the proximal into distal domain, which makes the interpretation of poorly calibrated and largely inaccessible distal margins difficult. In this contribution, we propose a new tectono‐stratigraphic model to help break through the proximal/distal interpretation frontier. After reviewing the scientific advances on rifted margins achieved during the last century, we describe the primary spatio‐temporal evolution of active deformation during rifting. We show that different rift domains are associated with specific (1) periods of active deformation; (2) tectonic structures and related stratigraphic architecture; (3) amounts of accommodation creation owing to specific ranges of horizontal widening and vertical deepening and (4) depositional environments. We demonstrate that the sequential localization of extension during rifting results in a younging of the base of passive infill (i.e. sediment deposited in a non‐tectonic setting) oceanward. We propose a panel of few to few tens of My time intervals related to specific tectonic events—our Tectonic Sequences—that may be correlated more or less easily and continuously across rifted margins. This study underlines the value of an iterative approach between fieldwork on fossil rifted margins and offshore geophysical studies, where field studies offer easy‐to‐access and high‐resolution calibration of dismembered rifted margin remnants, while geophysical studies provide comparatively low‐resolution imaging of entire, intact but largely inaccessible, rifted margins. It also highlights the necessity of jettisoning outdated dogma on rifted margins and changing our routines when interpreting seismic sections and outcrops. [ABSTRACT FROM AUTHOR]

This study processes borehole data from the coal-bearing Kleidi basin (Ptolemais sedimentary basin, Western Macedonia, Greece) to unravel the timeline of the neotectonic configuration of the basin and correlate it with the neotectonics of the broader region. Coal (lignite) deposits preserve faulted sequences, and for this reason they are ideal locations for studying deformation patterns. Lithostratigraphic data acquired by previous investigations revealed a continuous stratigraphic sequence which spans from the Upper Miocene to the Middle Quaternary. These Neogene deposits demonstrate their maximum thickness towards the SE of the basin. Boreholes also revealed that in the subsurface, the basin is actually divided into two separate grabens on either side of a ridge of the alpine basement. Stratigraphic interpolations using the inverse distance algorithm-generated thickness rasters which, through successive derivation, allowed the discovery of normal faults. Repetition of the algorithm using the new structural constraints returned patterns of deformation in the southern part of the Kleidi basin different from those revealed in the northern part. The configuration of the southern part of the Kleidi basin seems to reflect the Late Miocene–Pliocene extensional event. In contrast, configuration of the northern part of the basin is compatible with a later extensional phase in Pliocene‒Quaternary. Both events are manifested in the tectonostratigraphy of the Ptolemais sedimentary basin and the broader area. [ABSTRACT FROM AUTHOR]

Distributions of the density contrast and velocity of seismic waves into the crust and upper mantle in the Yellow Sea region are considered. The rheological section of the tectonosphere of the Yellow Sea consists of two rigid (crystal crust and lower layer of the lithosphere) and two viscous (subcrustal and asthenospheric) layers. The crust of the Yellow Sea is shattered and decreased in density. Processes of stretching and shifting are depicted as crustal shift duplexes as a result of which the Liaodong and Korean peninsulas were torn off from the continent and moved, respectively, in the northeast and east directions. In the central region of the Yellow Sea, manifestations of a central type mantle structure, screened by the lower layer of a lithosphere, have been revealed. This structure was disturbed by the neotectonic rifting processes. [ABSTRACT FROM AUTHOR]

The article examines the regional patterns of rifting in the Arctic and assesses the impact of large (supra-regional) rift systems on the geological evolution of the region. Against the background of the description of main Arctic structures, the Atlantic–Arctic rift system (AARS) is described as a tectonotype of a large planetary geophorm that has evolved from continental rifting to spreading proper with the development of a full-fledged ocean. The main properties of this system are its development towards the North Pole, the longitudinal orientation of the rifts, their separation by latitudinal faults, and predominantly sinistral shear displacement of individual segments. We believe that such a structure reflects the influence of the rotational factor on distribution of lithospheric masses of the Earth. Their tendency to the equilibrium position relative to the rotation axis is implemented by movements towards the equator and along it. The outflow of masses to low latitudes makes possible the growth of the rift system, but does not contribute to its further development after reaching the Pole. This phenomenon is of general nature and determines the development of all longitudinal rift systems, which leads to their spatial convergence and attenuation of dynamics in the circumpolar space. Within the Arctic region, in addition to the Atlantic–Arctic system, areas of possible termination of the West Siberian, Okhotsk–Verkhoyansk, and East Pacific rift systems are considered. It is assumed that their evolution initiated the destruction of the continental lithosphere of the Arctic region and determined the subsequent transformations of its structure. Special attention is paid to the problems of the possible influence of rifting on the hydrocarbon generation due to serpentinization of hyperbasites, when the lithosphere is penetrated by faults to the upper mantle depths, as well as on the remobilization of gases as a result of the disturbance of both gas hydrate reservoirs and permafrost. It is shown that the greatest generation of methane is generally associated with the development of faults in the cold lithosphere and serpentinization of mantle rocks. [ABSTRACT FROM AUTHOR]

A Robust tectonic reconstruction of the Philippine Sea Plate around ∼52 Ma is a prerequisite in understanding the process of subduction initiation and establishment of the Izu‐Bonin‐Mariana arc. This study investigates origins and timing of basin formation in the still poorly understood oldest part of the northern Philippine Sea plate. We have established that andesitic magmatism in the form of the Northern Philippine Sea volcanics is widely distributed across this area. It is founded on both a Mesozoic arc terrane (Daito Ridge Group) and an intervening basin (Kita‐Daito Basin). Their narrow Eocene age range (45‐41 Ma) and lack of systematic spatial variation in geochemistry implies that this magmatism was not associated with on‐going subduction, but related to the rifting/spreading event forming the Kita‐Daito Basin. The arc‐like geochemistry of the volcanics seems to indicate melting of lithospheric mantle which had been previously metasomatized by Mesozoic subduction of a plate with Pacific‐MORB isotopic characteristics. Late Eocene basaltic magmatism also found in the Kita‐Daito Basin does not have arc‐like characteristics, and could have formed from low‐degree melts of asthenospheric mantle associated with the final stage of Kita‐Daito Basin spreading. As onset of activity of the Northern Philippine Sea volcanics is essentially synchronous with the magmatism associated with the Oki‐Daito mantle plume, it is possible that both magmatism and rifting of the Kita‐Daito Basin were triggered by the arrival of the Oki‐Daito mantle plume in this region. These results demonstrate that the Kita‐Daito Basin postdates subduction initiation of the Pacific Plate along the Izu‐Bonin‐Mariana arc. Plain Language Summary: This study investigates origin and age of ocean basins in the still poorly understood northern Philippine Sea plate. This area will help us appreciate what happens during the initiation of a new destructive plate margin. We recovered rock samples from the Northern Philippine Sea Seamounts and Kita‐Daito Basin, and determined their age and composition. These volcanoes were active between 45 and 41 Ma and are found widely distributed across the older crust of the northernmost Philippine Sea Plate. Despite the geographical spread of these volcanoes, they have a similar composition across the region. This indicates they were produced during stretching of the older crust, which reactivated the older underlying upper mantle. A possible reason for this stretching may have been the impact of a mantle plume beneath this region. Key Points: Widely spread Eocene andesitic magmatism in northern Philippine Sea marks the onset of rifting in the Mesozoic arc terraneLate Eocene basalts in the Kita‐Daito Basin could represent the last stage of spreading of the Kita‐Daito BasinRifting and spreading of the Mesozoic arc terrane in northern Philippine Sea postdate subduction initiation along the Izu‐Bonin arc [ABSTRACT FROM AUTHOR]

Sedimentological analysis has shown that during the syn-rift phase (Upper Triassic) the Mohammedia–Benslimane–ElGara–Berrechid basin (MBEB) is characterized by detrital and evaporite sediment filling. A gradual decrease of palaeoslope over time led to the evolution of paleoenvironments of proximal alluvial fans system to braided rivers and then to an anastomosing system. These environments evolve finally to an alluvial plain associated with a coastal plain where playa lakes, mudflats and lagoons had developed.We have identified fourteen genetic sequences which are included in four progradational-retrogradational minor cycles that are themselves grouped in one major cycle. These cycles are related to the variations of the base level. The dominance of the retrogradation phases giving an asymmetrical appearance to the cycles is related to the predominance of the base level rise. These variations are probably of allocyclic origin: tectonic and probably climatic, in relation with the Tethys and the Atlantic Ocean being opened.

Abstract Deformable plate tectonic models have been demonstrated to be a useful technique for quantifying temporal variations in strain rate and crustal thickness within recent plate kinematic studies. Using the GPlates software, deformable plate models offer an approach to visualize and assess the interplay of plate kinematics and deformation. However, several assumptions are imposed in previous studies that limit their ability to explain the crustal evolution of various tectonic regimes. Examples of these assumptions include, but are not limited to, the rigid nature of continental blocks and boundaries used to define deformable regions, and uniform crustal thickness assumptions at model start times. In this study, we address these assumptions with newly presented applications using the interplay of GPlates and its python programming library, pyGPlates. In particular, we demonstrate the ability to create deformable continental blocks, reconstruct present day crustal thickness estimates back through time, and how the landward extent of present day crustal thickness estimates can be used to define the limits of deformable plate models and rift domain boundaries a priori. To demonstrate their application and validity, these concepts are evaluated using a previously published deformable plate model of the southern North Atlantic that is tested using 4 modeling scenarios herein to assess the impact of variable model inputs. These models provide insight regarding the pre‐Jurassic (200 Ma) crustal thickness template of the southern North Atlantic, the evolution of continental blocks during rift‐related deformation, and the potential impact of ancient orogenic terranes during subsequent rifting within the North Atlantic.

Abstract The offshore rifted margins of the North Atlantic have a spatially complex crustal structure comprised of variable crustal morphologies, continental blocks, and inherited structures. Recently, deformable plate tectonic models have permitted the interplay of plate kinematics and deformation to be assessed throughout the North Atlantic, and elsewhere. In particular, the ability to calculate temporal variations in crustal thickness has provided insight into the kinematic role of continental blocks and their interplay with large and micro‐tectonic plates during the formation of the North Atlantic offshore rifted margins. In this study, the deformable plate modeling workflow introduced in the companion contribution of this study (Part 1) is used to investigate previously published and newly presented deformable plate models of the Newfoundland, Irish, and West Iberian margins. This approach permits the deformation and subsequent crustal thickness evolution within previously recognized continental blocks and sedimentary basins throughout the southern North Atlantic Ocean to be visualized and assessed from 200 Ma to present day. The segmentation of early rift crustal thicknesses calculated by deformable plate models demonstrate strong correlations with the offshore extension of Appalachian and Caledonian terrane boundaries. Thus, our observations suggest that inherited orogenic boundaries potentially play a key role in the early rift crustal structure of sedimentary basins and the partitioning of deformation around and within continental blocks.

The Cambrian source rock is a key indicator that will guide future hydrocarbon explorations in ultra-deep strata. Despite its importance, the characteristics of paleotopography on the Precambrian basement and the distribution of source rocks above it remain unclear. The seismic and borehole data, isopach data, and the unconformity analysis are used to study the relations of the Cambrian source rock distribution to the paleotopography. The consistency of the strata thickness distribution maps of the Nanhua–Cambrian sequences show that the extensive thermal subsidence lasted the whole Sinian period, and makes the paleotopography of the Precambrian basement inherited from the landform after the Nanhua continental rifting. A major transgression caused by rapid subsidence of the Tarim Basin took place during the Cambrian. Shales were deposited offshore along the slopes of a paleo-uplift on the inherited paleotopography and formed the onlap in seismic profiles. The onlap on the inherited paleotopography reflects the distribution range of Yuertusi source rocks in the Cambrian.

Abstract A Robust tectonic reconstruction of the Philippine Sea Plate around ∼52 Ma is a prerequisite in understanding the process of subduction initiation and establishment of the Izu‐Bonin‐Mariana arc. This study investigates origins and timing of basin formation in the still poorly understood oldest part of the northern Philippine Sea plate. We have established that andesitic magmatism in the form of the Northern Philippine Sea volcanics is widely distributed across this area. It is founded on both a Mesozoic arc terrane (Daito Ridge Group) and an intervening basin (Kita‐Daito Basin). Their narrow Eocene age range (45‐41 Ma) and lack of systematic spatial variation in geochemistry implies that this magmatism was not associated with on‐going subduction, but related to the rifting/spreading event forming the Kita‐Daito Basin. The arc‐like geochemistry of the volcanics seems to indicate melting of lithospheric mantle which had been previously metasomatized by Mesozoic subduction of a plate with Pacific‐MORB isotopic characteristics. Late Eocene basaltic magmatism also found in the Kita‐Daito Basin does not have arc‐like characteristics, and could have formed from low‐degree melts of asthenospheric mantle associated with the final stage of Kita‐Daito Basin spreading. As onset of activity of the Northern Philippine Sea volcanics is essentially synchronous with the magmatism associated with the Oki‐Daito mantle plume, it is possible that both magmatism and rifting of the Kita‐Daito Basin were triggered by the arrival of the Oki‐Daito mantle plume in this region. These results demonstrate that the Kita‐Daito Basin postdates subduction initiation of the Pacific Plate along the Izu‐Bonin‐Mariana arc.

We present a petrologic study of the ca. 110 ka Halarauður eruption (7 ± 6 km3 magma), associated with collapse of Krafla caldera in northeast Iceland. Whole-rock compositions of juvenile Halarauður products span a continuous range between quartz tholeiite basalt (50.0 wt% SiO2, 5.0 wt% MgO; Mg# 42) and rhyolite (74.6 wt% SiO2). Linear correlations between all major elements are consistent with two-component mixing of sub-equal volumes of these end-member magmas, whereas correlations between trace elements are influenced by diffusive fractionation during chaotic mixing. Evolved compositions (andesite to rhyolite) and compositional heterogeneity are typical of early-erupted units, reflecting tapping of the upper, more silicic regions of a compositionally heterogeneous reservoir undergoing chaotic mixing. Later-erupted deposits are more compositionally homogeneous and grade smoothly upward from andesite to basalt, reflecting tapping of denser hybrid magma and uncontaminated basalt from lower in the chamber. All erupted products host < 1–2 modal% macro-crysts, implying storage at near-liquidus temperatures. Geobarometry and MELTS modeling suggest shallow storage pressures of ~ 200 MPa (~ 8 km depth) for the quartz tholeiite. Plagioclase (An60-76) and augite (Mg# 68–75) macro-crysts crystallized from this basalt during shallow storage, while sparse glomerocrysts (plagioclase ± augite ± olivine ± orthopyroxene) in late-erupted basaltic material are derived from disaggregated cumulate mush and include more primitive compositions. Occasional narrow sodic rims on plagioclase crystals from the quartz tholeiite record short periods of re-equilibration with hybrid magmas during mixing, constrained by experimental growth rates as at most two months and possibly as short as tens of hours. A second population of calcic plagioclase (cores An83-91) with adhering primitive basaltic glass selvages (Mg# 53–59) occurs sparsely in deposits of the first eruptive phase and is scarce or absent in later-erupted units, providing evidence for eruption of a second, more primitive basalt that was of insufficient volume to skew whole-rock mixing trends. Nucleation delay models suggest that the absence of overgrowth rims or quench crystals in these glassy basaltic selvages reflect residence times of a few hours at rhyolitic temperatures before eruption. Short basalt–rhyolite mixing timescales reflect rapid destabilization of the magmatic system and triggering of the eruption by mafic recharge. The ascent of both primitive and evolved basaltic magmas from depth mirrors events in recent volcano-tectonic episodes in the north of Iceland, suggesting that mafic recharge was driven by a plate boundary rifting event. [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]

A fully integrated 3D basin model was built to study the lithospheric structural evolution and the thermal history of the offshore part of the Gippsland Basin to investigate the type, timing and magnitude of its initial opening mechanism and their effects on source rocks. The applied workflow included seismic interpretation of major faults and magmatic features, seismic reinterpretation of existing main stratigraphic boundaries and adjustment of the basement topography. Different scenarios for a McKenzie-type basal heat flow evolution were tested based on a two-step inversion approach, which translates the thickness changes of lithospheric layers into basal heat flow. Finally, a crustal layer model was assigned to the existing 3D numerical basin model and the effects on thermal maturation of petroleum source rocks were investigated. The results of the calibrated inversion model suggest intense lithospheric stretching and mantle upwelling during the Early Cretaceous caused initial breakup and subsidence of the Gippsland Basin. This syn-rift phase was accompanied by increasing basal heat flow from initially ∼50 mW/m2 to a maximum of 80–90 mW/m2. The resulting upwelled Moho with an associated crustal thickness of locally only 8 km agrees with geophysical observations. Elevated paleogeothermal gradients between 50 and 60 °C/km prevailed from ca 120 to 80 Ma. Episodes of compression, uplift, erosion, and thermal subsidence resulted in fast and continuous cooling during the early post-rift and a constant basal heat flow of 45–50 mW/m2 since the Eocene. Two main pulses of petroleum generation were identified in the Paleocene and in the Miocene–Pliocene. This novel two-step crustal layer inversion method allows a detailed reconstruction of the thermal history of rift basins and can provide useful information about the maturation of petroleum source rocks. A temperature history reconstruction of the Gippsland Basin is given based on a large-scale numerical 3D model. Tectonically induced strong variability in paleoheat flows is recognised. Strong maturation and petroleum generation developed during the Paleogene and Neogene. [ABSTRACT FROM AUTHOR]

A mixed siliciclastic‐carbonate system that responds to changes in Permian climate and subsequent carbonate platform evolution is investigated using microscopic details of the Middle Permian Amb Formation (Fm.), in Saiyiduwali section, Khisor Range, northern Pakistan. Thin sections were made from rocks throughout the stratigraphic section of the Amb Fm. and analyzed with an emphasis on carbonate and clastic microfacies, and the latter interpreted within the existing chronostratigraphic framework. Outcrop observations reveal that the units comprise coarse‐grained, channelized, ripple‐marked, and burrowed sandstone and sandy, fossiliferous limestone with minor marls and shale intercalations, suggesting deposition in a subaqueous tide‐dominated delta to beach barrier. Based on the determined seven microfacies coupled with outcrop observation, the Amb Fm. was deposited in a tide‐influenced subaqueous delta to middle shelf environment under fluctuating sea level. The deposition of compositionally mature sandstone in the lower part of the formation suggests reworking of detritus from the rift shoulders and an adjacent source area with an ambient warm and humid climate. The stratal mixing of carbonates and compositionally mature siliciclastic units in the middle part suggest deposition under tectonic and climate‐induced terrigenous and carbonate fluxes to the basin. Thus the deposition shows a perfect transition from clastic‐dominated deltaic to pure carbonate platform settings as a result of warm climate and tectonics. This Middle Permian warming is confirmed by sea‐level rise and the presence of a temperature‐sensitive fusulinid fauna in association with photozoan‐based ooids. Deposition of the Amb Fm. and establishment of a carbonate platform are envisaged to be associated with major rifting of northern Gondwana, which subsequently resulted in the development of a rift basin at the passive margin of the NW Indian Plate then in northern Pakistan. [ABSTRACT FROM AUTHOR]

Zircons from the Early Carboniferous granitoids of the Neplyuevka pluton of the Southern Urals have been dated (SIMS). Two age groups are distinguished among the studied zircons: group 1 from 334 to 342 Ma and group 2 from 354 to 356 Ma. The older ages probably correspond to the time of zircon crystallization from the melt, while the younger ones resulted from a partial loss of radiogenic lead by zircons during the cooling of the pluton or from the thermal impact of the Early Carboniferous or even the Early Permian intrusions. The formation of the Neplyuevka complex at the very beginning of the Carboniferous marks the most important stage in the geodynamic evolution of the Southern Urals, a rapid transition from island arc margmatism, which continued during the Devonian, to rift-related magmatism, which ended only in the Middle Visean. [ABSTRACT FROM AUTHOR]

The study was focused on the tectonic structure features of the Gulf of Aden, which includes three provinces. The western, central and eastern provinces differ in morphostructural segmentation of the spreading ridge of the Gulf of Aden, which took place in different geodynamic regimes of their formation and development. In our study, physical modeling was performed to investigate the segmentation mechanisms of the three parts and the formation of the marginal plateau and the island of Socotral. In experiments, an elastic-plastic plate lying on a liquid base (simulating melt) was subjected to normal or oblique stretchig. Plate sections imitating the continental or oceanic lithosphere in the model had different thicknesses. Various heterogeneities, such as cuts, linear weakened zones (rift heating zones) etc., were set in the plate sections in accordance with natural analogues. The modeling results show that morphostructural segmentation of the spreading axis in the Gulf of Aden depends on the degree of heating and the thickness of the lithosphere, associated with different distances from the Afar plume and local thermal anomalies, spreading obliquity and the existence of structural inhomogeneities with increased lithosphere strength, which are associated in this case with the presence of Mesozoic grabens on the pre-breakup basement. The smaller is the lithosphere thickness, the smaller is the size of the segments. The sharper is the angle, the more pronounced is segmentation.The study of the connection of the Gulf of Aden continental rift with the rift zone of the Carlsberg ridge suggests that during their development, these rift fractures propagated towards each other. The experiment results show that in case of a «sharp» boundary between blocks that differ in thickness, a shear zone is likely to occur. Such a case is applicable, for example, to the Alula-Fartak fracture zone, or to Owen’s fracture zone. With a less ‘sharp’ boundary, overlapping structures are often formed, such as microplates or microblocks enclosed between two rift fissures. In such case, one microblock then dies, while the other develops into a spreading ridge. Apparently, such a microblock is represented by the marginal plateau and the island of Sokotra. As shown by the modeling, propagation of the two rifts towards each other was important for the formation of the plateau and the island of Socotra. Moreover, a significant role was played by the initial geometry of the rift zones and their initial positioning separate from each other.

The authors studied the formation conditions and the character of deformations of the margin plateau and Socotra Island using the physical modeling. In experiments, a plate with elastic-plastic properties lying on a liquid base was subjected stretching. Plate’s zones imitating the continental or oceanic lithosphere in the model had different thicknesses. In accordance with natural analogues, various heterogeneities were set in the zones: sections, linear reduced zones (rift heating zones) etc. The authors considered the tectonic structure of Socotra Island. The submerged plateau and Socotra Island were investigated using physical modeling, the conditions of formation and the nature of deformations. It is shown that the formation of the submerged Socotra plateau was caused by the interaction of two rift cracks, advancing towards each other. One crack transformed into a spreading ridge (the Sheba Ridge), and the other disappeared, forming an aulacogen-type structure (graben Guardafui). During the process of transition from rifting to spreading, Socotra Island rotated, both in horizontal and vertical planes, which led to jumps of the rift axis and the formation of an asymmetric structure of conjugated continental margins.

The evolution of the Alpine Tethys margins during the beginning of the African-Eurasian convergence was little studied compared to their evolution during the post-Pangea rifting and oceanic expansion, i.e., from the Early Jurassic to the early Late Cretaceous. The present work firstly aims to make up for this shortcoming in the case of the distal European margin of the Alpine Tethys, namely the Briançonnais domain of the Western Alps. We show that this margin was affected by strong post-rifting extension mainly in Late Cretaceous-Paleocene times and propose to make it the type of the (rare) “Late Extension Passive Margins”. Remarkably, this extension shortly preceded Lutetian times, when Briançonnais margin encroached the SE-dipping subduction zone under the Adria microplate. Secondly, we assess the post-rifting evolution of the north-Tethyan paleomargin in the Maghrebides transects, i.e., south-west of the Briançonnais transect along the same European-Iberian paleomargin. For this purpose, we consider the Triassic-Eocene series of the “Dorsale Calcaire” in the Alkapeca Blocks located along southeastern Iberia until the Eocene then transported onto the North African margin. Examination of the literature shows that the Tethyan margin of the Alboran block was strongly affected by normal faulting as early as Late Jurassic-Early Cretaceous times whereas post-rifting extension of the Kabylian blocks mainly occurred in the Late Cretaceous-Paleocene like in the Briançonnais. We propose that post-rifting extension of the Alboran block southern margin resulted from the sinistral movement of Africa relative to Iberia while the later extension of the Kabylian blocks can be related to the further convergence kinematics. Subduction of the Ligurian-Maghrebian slab under the North African margin would have occurred at that time in the southward continuation of the Alpine subduction. The overriding Adria and North African margins did not experience significant compression at that time. During the Eocene, a subduction polarity reversal occurred, which was associated with the relocation of the subduction zone along the Alkapeca block. This was the beginning of the Apenninic subduction, which triggered the back-arc opening of the Mediterranean basins.

In the Corbières area, a large-scale nappe has been identified at the beginning of the 20th century: the “Nappe des Corbières Orientales” (NCO) resting over a thick Triassic sole. This geological object is located at the NE of the Pyrenees, close to the Gulf of Lions. At this place, the chain changes in orientation from E-W to NE-SW and presents in detail, a great complexity. The existence of the nappe itself has never been contested. However, due to its overall complexity, several controversies exist regarding the style and chronology of deformation of its substratum in the so-called the “Pinède de Durban” in particular. We show that the new concepts of salt tectonics can clarify these old debates. Indeed, the rise of the Triassic salt during Mesozoic rifting episodes results in the development of characteristic sedimentary sequences (halokinetic sequences) on top of salt walls. It is along one of these, coinciding with the prolongation of the Cévenole Fault System, that the NCO has been individualized. During its Cenozoic emplacement, a gravity-gliding component, explaining the importance of the observed translation, could result from an uplift preceding the rifting at the origin of the Gulf of Lions.

Radiogenic isotopes of igneous and detrital minerals from various clastic rocks of mountain belts are used to reveal tectonic and sedimentary processes, which are otherwise difficult to detect. Here, we discuss the results of U-Pb and Lu-Hf zircon systems, and 40 Ar/ 39 Ar on detrital white mica in Eastern Alps. Zircon and white mica are chemically and mechanically stable and occur in magmatic, metamorphic and sedimentary rocks. During subsequent metamorphism, zircon is resistant against high temperature, >650 °C (U-Pb) and 900 °C (Lu-Hf). The Lu-Hf zircon system is used as a tracer of initial magma separation from the mantle, and the U-Pb zircon system records magmatic crystallization. The 40 Ar/ 39 Ar white mica system is stable up to 400-450 °C dating either formation or cooling after high-grade metamorphism. Detrital U-Pb zircon ages on two major rivers draining the Eastern Alps do not record any sign of Alpine orogeny or metamorphism. Consequently, U-Pb zircon studies can entirely miss the record of collisional orogeny in cool, magma-poor collision orogens. In contrast, 40 Ar/ 39 Ar white mica ages record Early and Late Alpine metamorphism but are limited to revealing the pre-orogenic history. U-Pb zircon and 40 Ar/ 39 Ar white mica yield different information in provenance studies. In the Eastern Alps, U-Pb zircon dating of magmatic and clastic rocks indicates intense formation of magmatic rocks between 630 and 230 Ma. Felsic rocks dominate the older age groups, and increasingly young mafic rocks were dated, specifically between 265 and 230 Ma. Hf isotopes record increasing juvenile input since ∼630 Ma. Two different groups with respect to Mesoproterozoic depleted mantle ages are shown: (1) one group with a Mesoproterozoic age gap typical for Gondwana-derived units, and (2) a rare group with Mesoproterozoic ages recording a new tectonic element in the Austroalpine basement in Alps.

This article, titled "Editorial: Episodic plate destruction and construction in Southeast Asia: observations, modeling, and case studies," explores the phenomenon of episodic plate deformation in Southeast Asia. The authors discuss various aspects of this topic, including crustal thickening and thinning, lithospheric deformation along orogenic margins and passive margins, and episodic arc volcanism. They present case studies and use geophysical techniques to understand the underlying mechanisms of these processes. The article provides valuable insights into the tectonic dynamics of Southeast Asia and contributes to the field of Earth science research. [Extracted from the article]

The relative timing between crustal extension and salt deposition can vary spatially along passive margin salt basins as continents unzip, or as the locus of extension shifts toward the embryonic ocean spreading center. Determining the relative timing of salt deposition, rifting, and seafloor spreading is often problematic due to the diachronous nature of rifting, the ability of salt to fill pre‐existing topography, and the subsequent flow and deformation of that salt. We here use 2D PSDM seismic data and structural restorations to investigate the Merluza Graben, a large rift‐related depocentre located in the southern, most proximal part of the Santos Basin, Brazil, along‐strike of a failed spreading center, the Abimael Ridge. The graben is defined by up to 3.5 km of base‐salt relief along its basinward‐bounding fault and internal base‐salt horsts that are up to 1 km high. This compartmentalizes deformation, producing intra‐graben extensional and contraction salt structures, ramp‐syncline basins, and expulsion rollovers, resulting in a remarkably different salt‐tectonic structural style to that seen in the adjacent areas. We also conduct structural restorations to analyze the spatial and temporal evolution of salt‐tectonic structural styles and the relationship this has to potential prolonged crustal extension in the Merluza Graben. This approach further constrains local variations in the relative timing of rifting and salt deposition, and the impact this has on salt tectonics along the margin. The results of our study can be applied to better understand the tectono‐stratigraphic development of other salt‐bearing rifted margins. Key Points: The Merluza Graben is a large rift depocentre located in the proximal part of the Santos Basin, connected to a failed spreading centerThe graben compartmentalizes salt deformation producing extensional and contraction structures, ramp‐syncline basins and rolloversRestorations and discrepancies in salt area indicate that the Merluza Graben and related sub‐salt faults were active after salt deposition [ABSTRACT FROM AUTHOR]

The Oligocene-Recent Red Sea rift is one of the preeminent examples of lithospheric rupture in the recent geological past, forming the basis for many models of how continental breakup occurs and progresses to the formation of new oceanic crust. Utilisation of low-temperature thermochronology in the Red Sea Rift since the 1980s has been key to constraining its spatio-temporal evolution, providing constraints for the propagation of strain and geomorphological development of its margins where datable syn-tectonic strata and/or markers are absent. We review the wealth of published apatite fission track and (U-Th-Sm)/He data from along the Red Sea, affording insights into the Oligocene-Recent thermo-tectonic evolution of the Nubian and Arabian margins. A regional interpolation protocol was employed to synthesise time-temperature reconstructions generated from the mined thermochronology data and burial histories produced from vitrinite reflectance and well data. These cooling-heating maps record a series of pronounced episodes of upper crustal thermal flux related to the development of the Oligocene-Recent Red Sea Rift. Assimilation of these regional thermal history maps with paleogeographic reconstructions and regional magmatic and strain histories provide regional perspectives on the roles of tectonism and geodynamic activity in Red Sea formation and their effects on rift margin development.

Spatial distributions of the gravity inhomogeneities and their comparative rheological parameters estimated from the density contrast of the crust and upper mantle of northeastern China are analyzed. The features of rheological layering of the tectonosphere and deep spatial relationships between tectonic structures (cratonic blocks, marginal terranes, and sedimentary basins) are revealed. The formal signs of Paleozoic subduction of the North China Craton and Mesozoic subduction of the Pacific plate beneath the Amurian Plate are distinguished in the density contrast distributions. The crustal deformations contrast sharply with the upper mantle deformations, which can be explained by the different directions of tectonic stresses in the Paleozoic and Mesozoic. The indications of upthrusting of the Jiamusi and Khanka continental marginal terranes on the lower lithosphere of the Amurian plate are inferred. The rheology and deep structure of northeastern China have much in common with other regions of the Pacific western margin in Asia and Australia. [ABSTRACT FROM AUTHOR]

Nummulite facies are known to be a good indicator of Eocene shallow-water paleoenvironments. Nummulitic limestones are widespread in the Lower Eocene of Armenia—the Tethys/northern Peri-Tethys transition zone, but they are studied insufficiently so far. The objective of this work was an integrated study of Lower Eocene deposits in the typical Urtsadzor section (Ararat region, Armenia): detailization of the stratigraphic subdivision based on larger benthic foraminifers (LBF); restoration of sedimentation settings based on the facies analysis and tectonic conditions of the basin origin, and evolution in the Early–Middle Eocene by studying the rock fracture system and formational analysis. For the first time, the Ypresian shallow benthic zones SBZ 9-10 and SBZ 10-11 of the Tethyan Chronostratigraphic Scale were identified in Kotutz and Sevan formations—an important contribution to the development of a modern stratigraphic chart of Armenia. Restoration of depositional settings based on the microfacies analysis was accomplished for Lower Eocene carbonate rocks of Armenia for the first time. Nine microfacies were determined and interpreted in the Ypresian part of the Urtsadzor section. Evolution of paleobiocoenoses represented mainly by nummulites, orthophragmines, and red algae was traced through the section. A transgressive succession of microfacies types was revealed from the littoral to lower–middle parts of the middle ramp. Comparison of the section with the adjacent Shagap and Landzhar sections allowed us to estimate the facies variability of rocks and the main direction of transgressional expansion. Ypresian LBF in paleobiocoenoses of southern Armenia are similar to the Peri-Tethyan varieties at the generic and specific level, and distinguished from the Tethyan biocoenoses by the absence of porcelaneous foraminifers (alveolinids and soritids). The South Armenian Ypresian paleobiota is distinguished from the assemblages in northern Armenia and northern Peri-Tethys by the abundance of red algae remnants. Wide Late Ypresian transgression resulted in the proliferation of LBF in the shallow oligotrophic basins, and their hydrological differences provoked the diversification of biocoenoses. The study of jointing systems in nummulitic limestones healed with aluminous products of karstification demonstrated that the jointing was formed at the Early/Middle Eocene transition due to the northeastern to sublatitudinal tension during uplift of the southern rift shoulder of the emerging Middle Eocene Shirak–Sevan–Megri rift. Rifting was preceded by the Early Eocene attenuation of tectonic activity and expansion of a wide carbonate sedimentation basin with development features typical of pre-rift basins. [ABSTRACT FROM AUTHOR]

The Tyrrhenian back‐arc basin developed at the rear of the E‐ward migrating Apennine fold‐and‐thrust belt, with northward decreasing rollback of the subducting Adria slab leading to northward fading of back‐arc extension. The northern portion of the Tyrrhenian basin is made of thinned continental crust, whereas in the central/southern portion extension eventually evolved to oceanic crust production. In this framework, a long‐lasting debate concerns the existence of a >200 km long transform zone along the 41st parallel, which should separate the two portions of the Tyrrhenian basin. At its eastern termination, a branch of the presumed transform zone enters the Tyrrhenian margin of the Apennine belt and occurs as an accommodation zone made of a ribbon of extensional faults and related basins. This accommodation zone, which separates areas of mutually perpendicular extension directions, is here introduced, described, and named the Ponza‐Alife accommodation zone. Interpretation of seismic lines and new structural and stratigraphic data from this accommodation zone have been used to constrain the pre‐orogenic and syn‐orogenic architecture of the subducting plate and the Plio‐Quaternary back‐arc extensional stage. Our data indicate that the studied zone retraces a deep‐seated transform fault system located in the subducting plate and inherited from an Early Jurassic rifting episode, which caused the lateral juxtaposition of different rift domains in the subducting plate. We propose that during collision and trench retreat, this lateral juxtaposition has controlled differential retreat of the subducting plate across the studied zone, forcing the development of the Ponza‐Alife accommodation zone in the overlying back‐arc basin's margin. Key Points: The Ponza‐Alife accommodation zone segmenting the Apenninic margin of the Tyrrhenian back‐arc basin is introducedStructural and stratigraphic data, and seismic interpretation allowed us to unravel the evolution of this accommodation zoneThe accommodation zone originated from tearing in the downgoing plate reworking Jurassic faults that segmented the associated rift system [ABSTRACT FROM AUTHOR]

The Dom João de Castro seamount in the Hirondelle Basin (Azores) is a central volcano on the ultraslow diverging Terceira Rift axis. The combination of structural and geochemical data provides insights into the evolution of central volcanoes in oceanic rift systems above the Azores melting anomaly. The orientation of fault scarps and volcanic structures at D. João de Castro and the adjacent Castro fissure zone indicate that the regional SW‐NE extending stress field dominates the morphology of the NW Hirondelle Basin. The regional tectonic stress field controls the crustal melt pathways and leads to dike emplacement along fissure zones and the prevalent eruption of mafic lavas. The occurrence of mafic to felsic lavas at D. João de Castro gives evidence for both a deep and a shallow crustal melt reservoir generating a subordinate local stress field at the seamount. New Sr‐Nd‐Pb isotope data along with incompatible trace element ratios indicate that D. João de Castro and the Castro Ridges originated from similarly heterogeneous mantle source but did not form simultaneously. Our new model implies that central volcanoes along the Terceira Rift form by the growth of volcanic ridges and transitioned into circular edifices after magmatic systems generate local changes in the regional lithospheric stress field. The geometry of D. João de Castro and other magmatic systems along the Terceira Rift combined with the alkaline nature of the erupted lavas, and the large lithosphere thickness indicates that young oceanic rifts are more similar to continental rifts rather than mid‐ocean ridges. Plain Language Summary: Dom João de Castro seamount is a large submarine volcano located in the submarine Hirondelle Basin in the Azores archipelago. The Hirondelle Basin is formed as a result of extensional forces in the oceanic crust along the Azorean Terceira Rift that causes rifting of the Eurasian and Nubian plates. The presence of the D. João de Castro volcano and several elongated volcanic ridges inside the basin shows that the extensive magmatic activity in the Azores contributes to the opening of the basin. By quantifying the orientations of the tectonic and volcanic structures in the basin, it can be shown that the formation is controlled by a dominant SW‐NE directed extensional stress combined with extensive magmatic activity. Based on combined structural and geochemical observations, we conclude that the D. João de Castro seamount formed from the growth of elongated volcanic ridges and transitioned into a circular edifice after a magma system generates a local change in the crustal stress field. The geometry and geochemical composition of volcanic rocks from the D. João de Castro magmatic system, as well as other magmatic systems along the Terceira Rift are more similar to continental rift systems rather than oceanic spreading centers. Key Points: D. João de Castro seamount in the Terceira Rift, Azores is influenced by a SW‐NE regional transtensional and a local radiating stress fieldStructural, seismic, and geochemical data imply formation by the growth of volcanic ridges along with local stress field changesThe geometry, chemistry, and rifting rates of the Terceira Rift are more comparable to continental rifts rather than mid‐ocean ridges [ABSTRACT FROM AUTHOR]

The plate kinematics of the Iberian plate and their implications on the plate tectonic evolution of the Bay of Biscay during rifting and subsequent opening of the southern North Atlantic continue to be topics of scientific discussion and debate. Constrained by previous plate reconstruction, geophysical, and geological studies, deformable plate tectonic reconstructions of the Bay of Biscay‐Parentis rift system are created in this study using the GPlates software. These deformable plate models are used to investigate the kinematics of the Landes High, Le Danois High, and Ebro Block previously recognized as independent continental blocks within deformable regions. A comparison between results calculated via deformable plate models with previously published and newly presented gravity inversion crustal thickness estimates provided a good metric for delineating the most probable plate kinematic scenario for the Bay of Biscay‐Parentis system and investigating the effect of the plate kinematic scenarios on the present‐day structure. The preferred plate kinematic model implies a transtensional Bay of Biscay‐Parentis rift system from the Jurassic to Early Cretaceous, with the onset of significant crustal thinning initiating during the Late Jurassic (∼150 Ma) induced by the motion of the Landes High and its interplay with the Ebro Block. Aside from demonstrating the role of the Landes High and its suggested interplay with structural inheritance on the deformation experienced within the Bay of Biscay, the timing and orientation of regional stress directions, and the velocities induced by the preferred deformable model provide good comparisons with previously calculated subsidence rates. Key Points: The independent plate kinematics of the Landes High played an important role during the formation of the Bay of BiscayResults of deformable plate models suggest the Ebro Block had minimal impact on the deformation experienced within the Bay of BiscayMajor lithospheric boundaries played a significant role in shaping the present‐day crustal structure of the Bay of Biscay [ABSTRACT FROM AUTHOR]

• Elongated calderas were often considered proxy for the regional extension. • We run circular caldera collapse analogue models afterward elongated by extension. • We prove that extension justifies only 13% of elongation for calderas in the MER. • Only specific sectors of caldera faults are capable of reactivation under extension. • Caldera structures influence the architecture of newly forming regional faults. Caldera collapses are paramount volcano-tectonic features because they form during hazardous explosive volcanic eruptions, they are ideal sites for geothermal development and mineral resources exploitation, and also because they preserve the evidence of the interaction between caldera magmatism and the regional tectonic processes. Despite this, many aspects of the caldera collapse process remain unclear, particularly concerning the interaction between caldera and tectonic related fault systems. We therefore used analogue models 1) to quantify the effect of regional strain on caldera elongation in extensional settings, such as the Main Ethiopian and the Kenya rifts, 2) to describe the effect of regional strain on caldera structures and, vice-versa 3) to document, for the first time, "the other side of the coin", that is how caldera structures affect the formation of newly forming regional extensional faults. Our models showed that tectonic extension only explains a small proportion (e.g. 13% for the Main Ethiopian Rift) of the elongation of most rift calderas. Furthermore, we showed how specific segments of caldera faults may accommodate regional extension by reactivating, therefore precluding caldera elongation. Finally, we showed how the presence of caldera structures may influence the geometry of newly forming regional normal faults, that display a marked curvature, "faking" caldera ring faults. We have suggested that these "fake" curved caldera ring faults may lead to incorrect estimations of caldera elongation in nature. In addition, such faults may also mislead geothermal fluid exploration, as they are likely disconnected from the caldera structures or the caldera plumbing system, and less likely the locus of hydrothermal fluid flow. [Display omitted] [ABSTRACT FROM AUTHOR]

The structure of the eastern part of the Gulf of Aden is peculiar for the presence of a submerged plateau and the island of Socotra, which were formed at the initial stage of its formation. With the beginning of continental rifting in the Oligocene-Miocene, more ancient riftogenic structures of the Mesozoic age were reactivated. This was most revealed in the relief in the Guardafuy graben, which cuts off the base of the Socotra plateau from the shelf of the modern eastern tip of the Horn of Africa. During tension, there were significant rotational deformations of the entire plateau. Socotra Island is divided into two parts by the large Hadibo transfer zone. The morphostructure of the elevated eastern part is determined by the asymmetric arch-like Hajhir Mountains. The western part is deformed much more strongly than the eastern part and is strongly broken by steeply falling faults. The continental margins of Socotra Island in the eastern province of the Gulf of Aden are amagmatic, asymmetrical and fractured by a series of faults and detachments. The difference in their structure is explained by the peculiarity of the transition from continental rifting to spreading, associated with the hyper-extension of the continental crust. In order to understand the conditions of riftogenesis, under which the formation of the continental block of the submerged marginal plateau and the island of Socotra is possible, the authors carried out a physical simulation, the results of which are presented in Article 2.

The Eocene-Miocene successions recovered at DSDP sites on the Jan Mayen Ridge (NE Atlantic) and on the adjacent East Greenland margin provide a sedimentary record of the rifting and separation of the Jan Mayen Microcontinent from East Greenland. A combination of palynology, conventional heavy mineral analysis, single-grain major and trace element geochemistry and radiometric dating of amphibole and zircon has revealed a major change in sediment provenance took place at the Early/Late Oligocene boundary corresponding to a prominent seismic reflector termed JA. During the Eocene and Early Oligocene, lateral variations in provenance character indicate multiple, small-scale transport systems. Site 349 and Kap Brewster were predominantly supplied from magmatic sources (Kap Brewster having a stronger subalkaline signature compared with Site 349), whereas Site 346 received almost exclusively metasedimentary detritus. By contrast, Late Oligocene provenance characteristics are closely comparable at the two Jan Mayen sites, the most distinctive feature being the abundance of reworked Carboniferous, Jurassic, Cretaceous and Eocene palynomorphs. The Site 349 succession documents an evolution in the nature of the magmatic provenance component. Supply from evolved alkaline magmatic rocks, such as syenites, was important in the Middle Eocene and lower part of the Early Oligocene, but was superseded in the later Early Oligocene by mafic magmatic sources. In the latest Early Oligocene, the presence of evolved clinopyroxenes provides evidence for prolonged magmatic fractionation. Initial low degrees of partial melting led to generation of alkaline (syenitic) magmas. The extent of partial melting increased during the Early Oligocene, generating basaltic rocks with both subalkaline and alkaline compositions. Towards the end of the Early Oligocene, the amount of partial melting and magma supply rates decreased. In the Late Oligocene, there is no evidence for contemporaneous igneous activity, with scarce magmatic indicator minerals. The provenance change suggests that the hiatus at the Early/Late Oligocene boundary represents the initiation of the proto-Kolbeinsey Ridge and separation of the Jan Mayen Microcontinent from East Greenland.

We present a series of 2D thermo-mechanical numerical experiments of thick-skinned crustal extension including a pre-rift salt horizon and subsequent thin-, thick-skinned, or mixed styles of convergence accompanied by surface processes. Extension localization along steep basement faults produces half-graben structures and leads to variations in the original distribution of pre-rift salt. Thick-skinned extension rate and salt rheology control hanging wall accommodation space as well as the locus and timing of minibasin grounding. Upon shortening, extension-related basement steps hinder forward propagation of evolving shallow thrust systems; conversely, if full basin inversion takes place along every individual fault, the regional salt layer is placed back to its pre-extensional configuration, constituting a regionally continuous décollement. Continued shortening and basement involvement deform the shallow fold-thrust structures and locally breaches the shallow décollement. We aim at obtaining a series of structural, stratigraphic and kinematic templates of fold-and-thrust belts involving rift basins with an intervening pre-rift salt horizon. Numerical results are compared to natural cases of salt-related inversion tectonics to better understand their structural evolution.

The Itina Trough is a late Miocene rift graben formed at the beginning of Woodlark Basin opening where the northern Louisiade Plateau micro‐continent had collided with the eastern Pocklington Rise remnant arc. We infer that it was the collisional suture of this Plateau subducted at the Pocklington Trough that either thickened the crust and weakened the lithosphere and/or adjoined the apparently thicker Louisiade micro‐continent to the thinner crust of the eastern Pocklington Rise, and thereby localized the rifting. Other examples of rifting across a remnant arc‐trench system in the SW Pacific include the South Rennell Trough and the Norfolk Basin. Plain Language Summary: Long thought to be an eastern continuation of the Pocklington (subduction) Trough, the deeper and steeper Itina Tough is actually a late Miocene rift graben that truncates it. As part of the earliest opening of the Woodlark Basin, the Itina Trough ruptured the northern edge of the Louisiade micro‐continent where it had collided with the Pocklington remnant arc. This was the third and most recent rift across the former arc‐trench system inferred to have extended once from Papua New Guinea via New Caledonia to New Zealand. Key Points: The Itina Trough is a late Miocene graben formed during rifting prior to seafloor spreading in the easternmost Woodlark BasinThe Itina Trough is deeper and steeper‐sided than the Pocklington Trough, and truncates itIt is the third rift to have crossed and separated the Paleogene subduction system that formerly linked New Guinea and New Zealand [ABSTRACT FROM AUTHOR]

The Jameson Land Basin lies within the Greenland–Norway rift, to the south of Triassic basins on the Halten Bank and East Greenland shelf, and can therefore offer insights into the development of these less-well-documented offshore basins and the wider North Atlantic. This study focuses on the stratigraphic development of the Jameson Land Basin. Broad-scale stratigraphic logging is augmented with heavy mineral analysis that constrains the dominant source catchments during this period. A thickness of over 1.5 km of Middle–Late Triassic strata fill the Jameson Land Basin, predominantly comprising continental deposits laid down during arid to semi-arid climatic conditions. The basal Pingo Dal Group thickens westwards into the Stauning Alper Fault, forming a typical syn-rift succession. Thickness variations have also highlighted the presence of an intrabasinal high and an associated unconformity between the Pingo Dal Group and the overlying Gipsdalen Group, which provides the first direct evidence for Middle–Late Triassic rifting in East Greenland. Thickness variations in the overlying Gipsdalen Group are more subdued, and the Fleming Fjord Group, and its formations, display remarkably tabular geometries, with little evidence for significant lateral facies variance; this is suggestive of reduced topography and a more regional thermal subsidence signature. Provenance data indicate sediment sourcing from both the western and eastern basin margins during the deposition of the Pingo Dal Group, above which the western source area becomes dominant, alongside some axial input from the south. [ABSTRACT FROM AUTHOR]

During rifting, pre‐existing penetrative basement fabrics can affect new faults in cover rocks by a mechanism that does not appear to involve reactivation. This subtle form of inheritance can significantly impact fault network architecture in rift basins above laterally variable basement domains with geomechanical anisotropies. Here we use multi‐layer, brittle‐ductile, crustal‐scale analogue experiments to study the influence of penetrative basement anisotropies on fault patterns in the overlying cover during a single phase of orthogonal rifting. The experiments were designed to test whether basement anisotropies, oriented 45° to the extension direction, can lead to the formation of rift faults that are oblique to both the imposed extension direction and basement anisotropies. Our experiments show that a penetrative, vertically layered, mm‐wide basement anisotropy creates extension‐oblique faults in the overlying cover. We interpret this to arise when local strike‐slip kinematics along the interfaces of mechanically contrasting materials in the basement combine with the regional imposed orthogonal extension, creating a transtensional regime. The width and spacing of alternating "strong" and "weak" basement zones interact with rift kinematics, impacting the orientation, kinematics and spacing of new faults in the cover. New insights on the influence of penetrative, pre‐existing basement fabrics on localized re‐orientation of 3D strain in the cover have implications for understanding complex fault systems in rift basins and transfer zones. Key Points: Analogue models of rifting demonstrate how extension‐oblique faults in cover rocks are inherited from penetrative basement anisotropiesThe width and spacing of basement anisotropies impact the distribution, orientation, and kinematics of faults in the coverWe invoke strain re‐orientation as the mechanism for inheritance as opposed to direct reactivation of basement weaknesses [ABSTRACT FROM AUTHOR]

Hyperextended basins are increasingly recognized along the outboard parts of continental margins as aborted basins created during continental break-up. Many of the concepts for understanding and modelling basin evolution and fill were developed for regions that have undergone modest crustal stretching (ß < 2) and may not be valid in basins where the crust and upper mantle are heavily modified by extreme stretching. The present study uses extensive 2D and 3D seismic and well data to analyse the Late Jurassic-Cretaceous tectono-stratigraphic evolution of the Porcupine Basin, bracketing the timing of hyperextension. It is an instructive basin, offshore west of Ireland, preserving low-magnitude strain in the north, with increasing degrees of hyperextension in the south. Detailed mapping of strain domains (proximal, necking and hyperextended) across the Porcupine Basin reveals five main rift segments, each with a distinctive geometry and strain history. During early low-strain rifting, inherited crustal structures strongly influenced the rift architecture by controlling the location and geometry of fault-controlled marine depocentres. The transition from hyperextension to post-rift subsidence was marked by locally developed, unconformity-bounded, marine sequences that draped the underlying rift topography. Whilst these 'transition sequences' are dated as Tithonian above the necking domain, similar but younger Early Cretaceous transition packages developed in the hyperextended domain, suggesting extension migrated towards the rift axis during hyperextension. Early post-rift sequences were broadly distributed across the rift centre and basin flanks before strong, thermally-controlled subsidence of the hyperextended crust, along with hinging of the necking domain, locally to the point of slope failure, gave rise to axially-focused marine deposition. Hyperextension may have left the basin susceptible to intra-plate stress changes accounting for several unconformities within the post-rift fill. This study provides an improved basin-wide understanding of the tectono-stratigraphic evolution of hyperextended basins. [ABSTRACT FROM AUTHOR]

The latest multichannel seismic data from the Yap subduction zone is presented to investigate the Caroline Ridge fault system, developed by faulting and bending processes within the incoming oceanic plateau. We reveal that horst and graben structures exist along the entire incoming Caroline Ridge adjacent to the trench and that pervasive bending-related faults trending ~N30°E have developed subparallel to the trench. However, the widths of the horst and graben structures decrease gradually from north to south. The two-stage ancient abyssal hill fabrics overlap the incoming Caroline Ridge. Abyssal hill faults trending ~N65°W present large trench-ridge angles (85–90°); in the southern segment, abyssal hill faults trending ~N70°E have relatively low trench-ridge angles (~35–40°). From the Caroline Ridge to the horst and graben structures, the topography decreases, and slump bodies with deformed internal reflections have developed above an irregular reflector. Little stable pelagic sediment with horizontal reflectors accumulates on the horst and graben structures, suggesting that the faulting and bending processes involve long and intense tectonic processes that affect the sedimentary environment. The sedimentary strata and fault distributions differ between the North and South Caroline Ridge, which is primarily attributable to the different rifting processes. Furthermore, we propose that N65°W-trending ancient faults sufficiently decrease the yield strength of the incoming Caroline Ridge to facilitate the bending-related faulting. During subduction, the incoming North Caroline Ridge that has a large degree of rifting and the Sorol Trough, which has a thin crust, may resist less flexural bending and generate the wide horst and graben structures. The ancient faults and rifting model of incoming oceanic plateaus play a significant role in bending-related faulting Unlabelled Image • The two-stage ancient faults trending ~N65°W and N70°E overlap the incoming Caroline Ridge. • Slump bodies and little stable pelagic sediment on horst and graben structures involve long and intense tectonic processes. • The ancient faults and rifting model of incoming oceanic plateaus play a significant role in bending-related faulting. [ABSTRACT FROM AUTHOR]