Abstract It is now more than 50 years since Tuzo Wilson published his paper asking ‘Did the Atlantic close and then re-open?’. This led to the ‘Wilson Cycle’ concept in which the repeated opening and closing of ocean basins along old orogenic belts is a key process in the assembly and breakup of supercontinents. This implied that the processes of rifting and mountain building somehow pre-conditioned and weakened the lithosphere in these regions, making them susceptible to strain localization during future deformation episodes. Here we provide a retrospective look at the development of the concept, how it has evolved over the past five decades, current thinking and future focus areas. The Wilson Cycle has proved enormously important to the theory and practice of geology and underlies much of what we know about the geological evolution of the Earth and its lithosphere. The concept will no doubt continue to be developed as we gain more understanding of the physical processes that control mantle convection and plate tectonics, and as more data become available from currently less accessible regions.

Abstract In the first application of the developing plate tectonic theory to the pre-Pangaea world 50 years ago, attempting to explain the origin of the Paleozoic Appalachian–Caledonian orogen, J. Tuzo Wilson asked the question: ‘Did the Atlantic close and then reopen?’. This question formed the basis of the concept of the Wilson cycle: ocean basins opening and closing to form a collisional mountain chain. The accordion-like motion of the continents bordering the Atlantic envisioned by Wilson in the 1960s, with proto-Appalachian Laurentia separating from Europe and Africa during the early Paleozoic in almost exactly the same position that it subsequently returned during the late Paleozoic amalgamation of Pangaea, now seems an unlikely scenario. We integrate the Paleozoic history of the continents bordering the present day basin of the North Atlantic Ocean with that of the southern continents to develop a radically revised picture of the classic Wilson cycle The concept of ocean basins opening and closing is retained, but the process we envisage also involves thousands of kilometres of mainly dextral motion parallel with the margins of the opposing Laurentia and Gondwanaland continents, as well as complex and prolonged tectonic interaction across an often narrow ocean basin, rather than the single collision suggested by Wilson.

Abstract There is an emerging consensus that Earth's landmasses amalgamate quasi-periodically into supercontinents, interpreted to be rigid super-plates essentially lacking tectonically active inner boundaries and showing little internal lithosphere–mantle interactions. The formation and disruption of supercontinents have been linked to changes in sea-level, biogeochemical cycles, global climate change, continental margin sedimentation, large igneous provinces, deep mantle circulation, outer core dynamics and Earth's magnetic field. If these hypotheses are correct, long-term mantle dynamics and much of the geological record, including the distribution of natural resources, may be largely controlled by these cycles. Despite their potential importance, however, many of these proposed links are, to date, permissive rather than proven. Sufficient data are not yet available to verify or fully understand the implications of the supercontinent cycle. Recent advances in many fields of geoscience provide clear directions for investigating the supercontinent cycle hypothesis and its corollaries but they need to be vigorously pursued if these far-reaching ideas are to be substantiated.

Abstract Disagreement about the existence of the late Neoproterozoic supercontinent Pannotia highlights the limitation of defining supercontinents simply on the basis of size, which, for pre-Pangaean supercontinents, is difficult to determine. In the context of the supercontinent cycle, however, supercontinent assembly and break-up, respectively, mark the end of one cycle and the beginning of the next and can be recognized by the tectonic, climatic and biogeochemical trends that accompany them. Hence supercontinents need only be large enough to influence mantle circulation in such a way as to enable the cycle to repeat. Their recognition need not rely solely on continental reconstructions, but can also exploit a variety of secular trends that accompany their amalgamation and break-up. Although the palaeogeographical and age constraints for the existence of Pannotia remain equivocal, the proxy signals of supercontinent assembly and break-up in the late Neoproterozoic are unmistakable. These signals cannot be readily attributed to either the break-up of Rodinia or the assembly of Gondwana without ignoring either the assembly phase of Pan-African orogenesis and the changes in mantle circulation that accompany this phase, or the reality that Gondwana cannot be a supercontinent in the context of the supercontinent cycle because its break-up coincides with that of Pangaea.

Abstract This review discusses the thermal evolution of the mantle following large-scale tectonic activities such as continental collision and continental rifting. About 300 myr ago, continental material amalgamated through the large-scale subduction of oceanic seafloor, marking the termination of one or more oceanic basins (e.g. Wilson cycles) and the formation of the supercontinent Pangaea. The present day location of the continents is due to the rifting apart of Pangaea, with the dispersal of the supercontinent being characterized by increased volcanic activity linked to the generation of deep mantle plumes. The discussion presented here investigates theories regarding the thermal evolution of the mantle (e.g. mantle temperatures and sub-continental plumes) following the formation of a supercontinent. Rifting, orogenesis and mass eruptions from large igneous provinces change the landscape of the lithosphere, whereas processes related to the initiation and termination of oceanic subduction have a profound impact on deep mantle reservoirs and thermal upwelling through the modification of mantle flow. Upwelling and downwelling in mantle convection are dynamically linked and can influence processes from the crust to the core, placing the Wilson cycle and the evolution of oceans at the forefront of our dynamic Earth.

Abstract Tectonic inheritance and structure reactivation have been of interest to geologists since it was noticed in the mid-nineteenth century that younger structures in an area tend to follow the direction of older structures. Three kinds of relationship may exist between these older and younger structures: younger structures may follow the older ones and repeat their function; younger structures may follow older ones, but function in the opposite sense to the older ones; and younger structures bear no relation to the older ones. These are named, respectively, resurrected, replacement and revolutionary structures. We present three examples, on three different scales, of tectonic inheritance and structure reactivation: Mesozoic and Cenozoic Europe on a continental scale; the US Rockies on a regional scale; and the Albula Pass in the Swiss Alps on an outcrop scale. We conclude that structure reactivation on a crustal scale occurs when the protective armour of the mantle lithosphere is removed and that, in such cases, resurrected and replacement structures form. In cratons with thick lithospheric roots, structure reactivation hardly ever occurs and when, in rare cases, it does occur, it commonly generates revolutionary structures. There can be no unique model for lithospheric strength.

Abstract This review of the role of the mantle lithosphere in plate tectonic processes collates a wide range of recent studies from seismology and numerical modelling. A continually growing catalogue of deep geophysical imaging has illuminated the mantle lithosphere and generated new interpretations of how the lithosphere evolves. We review current ideas about the role of continental mantle lithosphere in plate tectonic processes. Evidence seems to be growing that scarring in the continental mantle lithosphere is ubiquitous, which implies a reassessment of the widely held view that it is the inheritance of crustal structure only (rather than the lithosphere as a whole) that is most important in the conventional theory of plate tectonics (e.g. the Wilson cycle). Recent studies have interpreted mantle lithosphere heterogeneities to be pre-existing structures and, as such, linked to the Wilson cycle and inheritance. We consider the current fundamental questions in the role of the mantle lithosphere in causing tectonic deformation, reviewing recent results and highlighting the potential of the deep lithosphere in infiltrating every aspect of plate tectonics processes.

Abstract Although the Wilson cycle is usually considered in terms of wide oceans floored with normal oceanic crust, numerous orogens result from the closure of embryonic oceans. We discuss how orogenic and post-orogenic processes may be controlled by the size/maturity of the inverted basin. We focus on the role of lithospheric mantle in controlling deformation and the magmatic budget. We describe the physical properties (composition, density, rheology) of three types of mantle: inherited, fertilized and depleted oceanic mantle. By comparing these, we highlight that fertilized mantle underlying embryonic oceans is mechanically weaker, less dense and more fertile than other types of mantle. We suggest that orogens resulting from the closure of a narrow, immature extensional system are essentially controlled by mechanical processes without significant thermal and lithological modification. The underlying mantle is fertile and thus has a high potential for magma generation during subsequent tectonic events. Conversely, the thermal state and lithology of orogens resulting from the closure of a wide, mature ocean are largely modified by subduction-related arc magmatism. The underlying mantle wedge is depleted, which may inhibit magma generation during post-orogenic extension. These end-member considerations are supported by observations derived from the Western Europe–North Atlantic region.

Abstract Rheological inheritance occurs when older metamorphic and deformational fabrics impact the mechanics of younger tectonic provinces, such as occurs in extensional provinces developed on sites of previous orogenesis. The Funeral and Black Mountains from the Death Valley region of the US Basin and Range provide the opportunity to study such rheological inheritance. The Funeral Mountains expose shear zones containing high-grade metamorphic fabrics and evidence for synkinematic, decompression-driven melt of Late Cretaceous, orogenic origin. Quartz < c >- and [ a ]-axes patterns from the shear zones correlate with high-temperature slip systems. The quartz microstructures were formed via grain-boundary migration, and these are overprinted by high-strain layers of mixed-phase aggregates that underwent grain boundary sliding. Reaction textures from the Funeral Mountains illustrate that much of the fabric development post-dates melting, but locally involved melt–rock reactions. In contrast with the Funeral Mountains, the basement complex in the Black Mountains preserves few peak-metamorphic textures, largely owing to the overprinting by Cenozoic magmatism and deformation. However, local relicts of high-grade deformational fabrics yielding Late Cretaceous-through-Eocene magmatic zircon ages are overprinted by greenschist grade fabrics. Using outcrop and microstructural (including electron backscatter diffraction) observations, and thermodynamic modelling, we detail how segregation of melt products during orogenic partial melting resulted in chemically isolated compositional domains, favouring localization via the formation of fine-grained retrograde fabrics. We propose a conceptual model that builds on our results wherein the heterogeneous distribution of peak, orogenic metamorphic phases and melt products governs lower crustal strength and fabric evolution during extension. The Wilson Cycle may be sensitive to rheological inheritance as the width of continental margins formed during rifting will be sensitive to the fabrics and compositions formed during collision.

Abstract The Caledonian and Variscan orogens in northern Europe and the Alpine-age Apennine range in Italy are classic examples of thrust belts that were developed at the expense of formerly rifted, passive continental margins that subsequently experienced various degrees of post-orogenic collapse and extension. The outer zones of orogenic belts, and their adjoining foreland domains and regions, where the effects of superposed deformations are mild to very mild make it possible to recognize and separate structures produced at different times and to correctly establish their chronology and relationships. In this paper we integrate subsurface data (2D and 3D seismic reflection and well logs), mainly from the North Sea, and structural field evidence, mainly from the Apennines, with the aim of reconstructing and refining the structural evolution of these two provinces which, in spite of their different ages and present-day structural framework, share repeated pulses of alternating extension and compression. The main outcome of this investigation is that in both scenarios, during repeated episodes of inversion that are a characteristic feature of the Wilson cycle, inherited basement structures were effective in controlling stress localization along faults affecting younger sedimentary cover rocks.

Abstract To accurately reconstruct plate configurations, there is a need for a quantitative method to calculate the amount and timing of crustal extension independent of any one model for the formation of rifted margins. This paper evaluates the suitability of the various plate modelling methods for structural inheritance studies and proposes a classification scheme for the methods that are currently in use. A palinspastic deformable margin plate kinematic model is most suitable for tectonic inheritance studies, particularly at hyperextended margins. This type of plate model provides a valuable analytical tool that can be used to show the temporal and spatial relationship between pre-existing orogenic structures, evolving rift axes and global plate reorganization events. We use a palinspastic deformable margin plate model for the southern North Atlantic and Labrador Sea to quantitatively restore up to 350 km of Mesozoic–Cenozoic extension. This provides us with a pre-rift restoration of the Proterozoic and Paleozoic terranes and structural lineaments on the conjugate margins that helps us to analyse their relationship to evolving rift axes and global plate reorganization events through time. Interpretation of these modelling results has led to a clearer understanding of the relationship between inherited structural features and their control on rifting and the break-up history.

Abstract The geological evolution of Avalonia was fundamental to the first application of plate tectonic principles to the pre-Mesozoic world. Four tectonic phases have now been identified. The oldest phase (760–660 Ma) produced a series of oceanic arcs, some possibly underlain by thin slivers of Baltica crust, which accreted to the northern margin of Gondwana between 670 and 650 Ma. Their accretion to Gondwana may be geodynamically related to the break-up of Rodinia. After accretion, subduction zones stepped outboard, producing the main phase (640–570 Ma) of arc-related magmatism and basin formation that was coeval with the amalgamation of Gondwana. Arc magmatism terminated diachronously between 600 and 540 Ma by the propagation of a San Andreas style transform fault, followed by the Early Paleozoic platformal succession used by Wilson to define the eastern flank of the proto-Atlantic (Iapetus) Ocean. This implies the ocean outboard from the northern Gondwanan margin survived into the Cambrian. Avalonia is one of several terranes distributed obliquely with respect to the adjacent cratonic provinces of Gondwana and Baltica, implying that these terranes evolved on different cratonic basements. As a result, their ages and differing isotopic signatures can be used to reconstruct their respective locations along the ancient continental margin.

Abstract In the original Wilson cycle, the northern Appalachian–Caledonide orogen resulted from the collision of two continental masses separated by a single ocean. One of these corresponds to the modern concept of Laurentia, but the colliding continent to the east has been variously subdivided into many smaller terranes and domains, including Ganderia, Avalonia and Megumia. Using published stratigraphic evidence and detrital zircon provenance data from units of known depositional age, the timing of arrival of these units at the Laurentian margin between the Early Ordovician and Early Devonian can be constrained. Several of the accreted terranes do not extend over the entire length of the orogen, with the result that the lines separating them change character along strike from terrane-bounding sutures to simple accretionary faults. The Ganderia domain consists of at least four separate terranes that share a common origin on the continental margin of Gondwana, but were separated by back-arc oceanic crust as they crossed the Iapetus Ocean and collided diachronously with the Laurentian margin.

Abstract West Newfoundland was critical in developing the Wilson Cycle concept. Neoproterozoic rifting established a passive margin adjacent to the Iapetus Ocean. Ordovician (Taconian) arc–continent collision emplaced ophiolites and the thin-skinned Humber Arm Allochthon. Subsequent Devonian (Acadian) ocean closure produced basement-cutting thrust faults that control the present-day distribution of units. New mapping, and aeromagnetic and seismic interpretation, around Parsons Pond enabled the recognition of structures in poorly exposed areas. Following Cambrian to Middle Ordovician passive-margin deposition, Taconian deformation produced a flexural bulge unconformity. Subsequent extensional faults shed localized conglomerate into the foreland basin. The Humber Arm Allochthon contains a series of stacked and folded duplexes, typical of thrust belts. To the east, the Parsons Pond Thrust has transported shelf and foreland-basin units c. 8 km westwards above the allochthon. The Long Range Thrust shows major topographical expression but <1 km offset. Stratigraphic relationships indicate that most thrusts originated as normal faults, active during Neoproterozoic rifting, and subsequently during Taconian flexure. Devonian continental collision inverted the Parsons Pond and Long Range thrusts. Basement-cored fault-propagation folds in Newfoundland are structurally analogous to basement uplifts in other orogens, including the Laramide Orogen in western USA. Similar deep-seated inversion structures may extend through the northern Appalachians.

Abstract Eastern North America holds clear records of two Wilson cycles and hints of two earlier cycles, through which tectonic inheritance is evident at multiple scales. Large-scale transform offsets of rifted margins indicate inheritance through multiple cycles; transform-parallel intracratonic fault systems suggest a transform-parallel fabric in the lithosphere. Rift segments of the continental margins did not inherit the locations of earlier rifts; synrift intracratonic fault systems follow earlier contractional fabrics of supercontinent assembly. Large-scale curves of the Appalachian–Ouachita orogenic belt (closing of the Iapetus Ocean) mimic the shape of the Iapetan rifted margin of Laurentia. Basins along the Iapetan rifted margin reflect inheritance from transform faults in the greater magnitudes of early post-rift thermal subsidence and later synorogenic tectonic loading and flexural subsidence. Older synrift basement faults buttressed the frontal ramps of Appalachian–Ouachita thin-skinned thrust faults. Basement fault blocks and associated synrift stratigraphic variations in the weak layers that host the regional décollement localized transverse alignments of lateral ramps, as well as tectonic thickening of a mud-dominated graben-fill succession in a ductile duplex (mushwad). The many examples of tectonic inheritance attest to the linkages between processes of successive opening and closing of oceans, as well as the break-up and assembly of supercontinents, through successive Wilson cycles.

Abstract The Rheic Ocean is a persistent feature of Paleozoic palaeogeographies whose closure contributed to the development of the Variscan Orogen and the formation of Pangaea. Geological and geophysical data indicate repeated episodes of Paleozoic rifting and plate convergence around SW England and the adjacent offshore areas. SW England occupied a lower plate position during the Devonian–Carboniferous, on the northern passive margin of the short-lived Rhenohercynian Ocean that had formed near a recently closed segment of the Rheic Ocean. Variscan plate convergence resulted in the development of the composite southwards-dipping Rheic–Rhenohercynian suture zone by the latest Devonian and inversion of the lower plate basins during the Carboniferous. Early Permian NNW–SSE extensional reactivation of this suture zone controlled the development of the Western Approaches basins in its hanging wall and provides an excellent example of Wilson cycle structural inheritance. The onshore expression of this episode includes shear zones and detachment faults consistent with top-to-the-SSE extensional reactivation of Variscan thrust faults. There is a progression to higher-angle brittle extensional faults that cut out earlier structures. Exhumation of the lower plate was accompanied by Early Permian mantle and concomitant crustal partial melting, the construction of the Cornubian Batholith and W–Sn–Cu fracture-hosted mineralization.

Abstract The Atlantic Ocean margins formed the basis for the seminal Wilson cycle concept, which suggests that oceans close, form fold belts, and later reopen in a concertina-like fashion. However, we observe that continental break-up of the North Atlantic–Arctic region only weakly reflects Wilson's concept. Rather than utilizing fold belts, transforms have been the dominant weaknesses that guided break-up, primarily because less force is required to break a plate via strike-slip related shearing than via rifting. Some transforms were inherited features, whereas others formed as part of the continental break-up process. Regardless of cause, once a transform has formed, the plate is broken and further rifting is not required before seafloor spreading can start. This is particularly well expressed in the NE Atlantic, where the line of Early Eocene break-up is very sharp, with minor or no preceding Paleocene rifting. Other examples include the De Geer, Ungava and Lomonosov transforms. We propose that the transform break-up mechanism is an important adjunct to the Wilson cycle theory and that it provides an explanation for ‘non-Wilson’ oceans, where old collision zones are not reactivated.

Abstract The opening of the North Atlantic region was one of the most important geodynamic events that shaped the present day passive margins of Europe, Greenland and North America. Although well-studied, much remains to be understood about the evolution of the North Atlantic, including the role of the Jan Mayen microplate complex. Geophysical data provide an image of the crustal structure of this microplate and enable a detailed reconstruction of the rifting and spreading history. However, the mechanisms that cause the separation of microplates between conjugate margins are still poorly understood. We assemble recent models of rifting and passive margin formation in the North Atlantic and discuss possible scenarios that may have led to the formation of the Jan Mayen microplate complex. This event was probably triggered by regional plate tectonic reorganizations rejuvenating inherited structures. The axis of rifting and continental break-up and the width of the Jan Mayen microplate complex were controlled by old Caledonian fossil subduction/suture zones. Its length is related to east–west-oriented deformation and fracture zones, possibly linked to rheological heterogeneities inherited from the pre-existing Precambrian terrane boundaries.