Fossil plants are described from the upper part of the Devonian Lolén Formation, Sierra de la Ventana, Buenos Aires Province, Argentina, in the area of Estancia Las Acacias. The sequence is composed mainly of dark grey shales, and fossils were found in a single horizon where thin interlayered beds of fine reddish-brown micaceous sandstones appear where the environment of marine deposition became more shallow. The age of the Lolén Formation is presently established on the basis of brachiopods, these being characteristic elements of the Malvinokaffric realm from the Gondwana Lower Devonian (Emsian). The fossil plants are remarkably preserved given that they are in rocks that have undergone intense deformation. The plants are identified as Haplostigma sp. and Haskinsia cf. H. colophylla, and suggest a Middle Devonian age (Givetian) for the fossil-bearing levels. Haskinsia, identified on the basis of leaf morphology, is the first well-delimited Middle Devonian lycopsid genus described from Argentina, and the record from the most southerly palaeolatitude. During the Middle Devonian, Haskinsia was distributed in tropical, warm temperate and high southern latitude, ?cool temperate zones.

Three small picritic dykes, intruded at a late stage in the evolution of the Rum basic–ultra-basic complex, Inner Hebrides, shed new light on the nature of the magmas responsible for the main complex. The magmas are of transitional (mildly alkalic) type, generated by relatively small-fraction (6–7%) melting of a depleted mantle source. Melting is tentatively deduced to have commenced at ±100 km, straddling the garnet–spinel transition. Of the three samples, one (M9) is remarkable for the preservation of very primitive characteristics, with olivines of Fo93 containing highly aluminous spinels; these appear unique within the British Tertiary Volcanic Province. Sr, Nd and Pb isotopes indicate only minor ([les ]4%) contamination with Precambrian crustal lithologies, reflecting the rapidity of ascent of the magma batches. The Rum picrites have 187Os/188Os ratios and trace element characteristics comparable to those of recent picrites from Iceland, suggesting minimal temporal change of the depleted parts of the Iceland plume over 60 Ma. Movements of the Long Loch Fault may have been instrumental in causing decompression melting of the spreading Iceland plume-head and facilitating ascent of the melts to near-surface levels.

The Maures Massif forms an important piece of the southernmost part of the Variscan belt of western Europe. This massif exhibits high-grade bimodal felsic–basic volcanic complexes, a distinctive lithological feature documented elsewhere in similar domains of the European Variscides and referred to the Cambro-Ordovician extensional episode. Two major alkalic and tholeiitic compositional groups and subordinate transitional metabasites have been identified, occurring at several distinct horizons or in bimodal complexes. This chemical diversity is interpreted in terms of variable degrees of partial melting of progressively depleted mantle source(s), which experienced melting at different depths, from garnet to spinel stability domains, during a progressive mantle upwelling associated with intracontinental rifting. This setting is reinforced by the presence of metabasites with compositions similar to continental flood basalts, showing slightly humped REE patterns, and interpreted as resulting from the melting of a partially depleted source at a relatively low degree of melting, in the garnet–spinel transition zone. The metafelsites from the tholeiitic bimodal complex exhibit the distinctive major and trace element characteristics of A-type rhyolites. Their elemental variations are consistent with fractional crystallization of major and accessory phases, but some discontinuous REE profiles result from a hydrothermal fractionation mechanism. The modelling of common anhydrous fractionating assemblages suggests that these A-type compositions may be derived from the associated tholeiites by extensive degrees of fractionation (90 %) with some continental crust involvement, or by anhydrous partial melting (∼30 %) of an underplated mafic parent of tholeiitic composition. The bimodal character of the Late Cambrian Maures magmatism, together with the chemistry of the various metabasites and metafelsites, suggests plume-induced intracontinental magmatic activity, resulting in lithospheric thinning prior to the onset of rifting and break-up of the Palaeozoic continental lithosphere, at this northern margin of Gondwana.

Thin, but laterally widespread, fallout ash tuff layers interbedded with complex fluviolacustrine successions of the Carboniferous–Permian late Variscan intermontane Saar–Nahe Basin in southwestern Germany provide important tephrostratigraphic markers in the purely continental depositional setting. The tuffs are rhyolitic to rhyodacitic and indicate geochemical affinities to Moldanubian Variscan S-type granitoids. The volcanic ashes are suggested to have been derived from the general region of the central and northern Black Forest (southwestern Germany) and the northern Vosges (eastern France) at 100–150 km distance south of the Saar–Nahe Basin. Six tuff beds from the Jeckenbach and Odernheim subformations (Meisenheim Formation, Glan Group) have been correlated within the basin over a distance of 50 km by mapping and whole-rock geochemical fingerprinting. In each subformation, three tuffs can be well distinguished using geochemical discriminant function analysis. Additional comparisons of trace and rare-earth element contents provide further criteria for the differentiation of individual tuff beds. These discriminations show that the tuffs have unique chemical fingerprints, probably reflecting differences in the original composition of the parent volcanic tephra. Thus, chemical differences between the tephrostratigraphic markers are geologically significant and provide a powerful tool for establishing tuff layer identification and correlation within the complex sedimentary sequence of the Saar–Nahe Basin. They also provide clues to the tectonomagmatic settings of the source volcanoes.

The Kraemer Island macrodyke that is exclusively exposed on Kraemer Island about 7 km west of the Skaergaard Intrusion belongs to a regional dyke swarm termed the ‘Skaergaard-like dykes’ (or FG-1 dykes). Weakly modally layered olivine gabbros dominate the exposed parts of the intrusion that has a width of 650 m to 1000 m. Plagioclase (core An68±2) and Ca-rich pyroxene (core Mg no. 79±1) grains are normally zoned, whereas olivine grains (Fo50–65) are homogeneous. Calculated mineral–magma equilibria, based on experimentally determined Mg–Fe magma–olivine and magma–clinopyroxene partition coefficients, suggest that the observed olivine and clinopyroxene compositions in the gabbros cannot have formed from a common parental magma. The unzoned nature of olivine grains and their iron-rich com-positions relative to clinopyroxene suggest post-cumulus Mg–Fe exchange between olivine and interstitial melt. A gabbroic pegmatite is developed in the centre of the intrusion along its entire exposed 5 km strike length. Here, mineral zonation is limited and compositions are similar to rims of cumulus minerals in the enveloping olivine gabbros. The pegmatite could therefore represent interstitial melt mobilized from gabbroic cumulates that later accumulated and crystallized at its present stratigraphic location. Cumulus olivines in the gabbros are close to equilibrium with Ca-rich pyroxene in the pegmatite. This is interpreted as reflecting interstitial melt mobility during the late stages of solidification of the macrodyke. Chilled margins are well preserved at the intrusion margins and are rich in Fe (14–15.3% FeOTOT), Ti (3–3.3% TiO2) and light rare-earth elements ([La/Sm]N = 1.2–1.3), similar to magmas well represented in the overlying sequence of contemporaneous High-Ti Series flood basalts. It is therefore likely that extensive wall-rock melting adjacent to the macrodyke reflects continuous feeding of the overlying flood basalts through the Kraemer Island macrodyke.

The Central Lapland Greenstone belt comprises rift-related metavolcanic and metasedimentary rocks representing one of the largest supracrustal belts in the Baltic Shield. The Sodankylä area in the central part of the belt represents a complex thrust duplex within a nappe overlying Belomorian Archaean basement and autocthonous Luirojoki calc-silicate rocks. Here, an early D1 schistosity is axial planar to at least three coaxial generations of southward-verging, subhorizontal, E–W-plunging D1 folds associated with major southwards thrusting. D2 is represented by broad, map-scale, upright, NE-trending folds in the south and crenulations in the north. Staurolite-grade metamorphism represented by post-tectonic andalusite + staurolite + kyanite assemblages occurred after D2 folding. Later D3 deformation was limited to local NW-trending folds and sinistral faults. The internal nappe-like structure of the Central Lapland Greenstone belt suggests that it represents the foreland of a large collisional complex cored by the Lapland Granulite belt.

The Cretaceous Fossil Bluff Group on Alexander Island, on the west side of the Antarctic Peninsula, contains a remarkably complete record of the evolution of a forearc basin. The latest (Aptian–Albian) stages in the basin history are recorded in a well-exposed succession at the southern end of the island, where a series of nunataks provide exposure of over a thousand metres of shallow marine and continental deposits. An abrupt facies shift from upper shoreface marine facies to braided fluvial deposits is interpreted as the record of regional uplift in the volcanic arc. This event coincides with the Palmer Land deformation event which may be related to a mid-Cretaceous mantle plume. A gradual reduction in depositional gradient and a return to shallow marine conditions towards the top of the exposed section is interpreted as a consequence of erosion of the arc and subsidence within the basin. Palaeocurrent data and facies distributions indicate that the continental deposits formed a fan-shaped wedge at least 30 km in diameter in the southern part of the forearc basin. Fossil plants indicate that the palaeoclimate was warm and humid throughout the period of deposition. Mapping and facies analysis of the upper part of the Fossil Bluff Group in southern Alexander Island has resulted in a revision of the stratigraphic terminology for the area. The Triton Point Member, formerly part of the Neptune Glacier Formation, has been raised to formation status and two members (the Citadel Bastion Member and the Coal Nunatak Member) and a Bed (the Upper Coal Nunatak Sandstone Bed) are defined here within the formation.

Fresh shale samples taken from a well-known outcrop section of the Silurian Vila Maria Formation, located on the northeastern margin of the Paraná Basin (Três Barras Farm, Goiás State, central-western Brazil), have been analysed for both palynological and radiometric age determinations. The rocks yielded a fairly diverse, age-definitive cryptospore assemblage, and the same samples proved suitable for Rb–Sr analysis, despite Silurian sedimentary rocks being rarely suited to radiometric dating techniques. This study thus introduces an alternative, independent method for estimating the minimum depositional age of the Vila Maria Formation. The Rb–Sr age value has been calculated via an isochron diagram that yields 435.9±7.8 Ma. Accordingly, the latter value is interpreted as the minimum depositional age of the analysed Vila Maria strata, implying their deposition during Llandovery times. This concurs with the palynological results, which indicate an age no older than Early Silurian and, more particularly, favour an Early to Middle Llandovery (Rhuddanian–Early Aeronian) attribution.

The timing of exhumation of metamorphic rocks and granitoids of the Niğde metamorphic dome, at the southern tip of the Central Anatolian Crystalline Complex, is a matter of debate. According to some authors, the metamorphic rocks are overlain nonconformably by a sedimentary sequence of late Maastrichtian to Late Palaeocene age. In contrast, other authors recently argued that the Niğde dome represents an extensional core complex of Oligocene–Early Miocene age, finally unroofed during late Miocene times. On the one hand, the results of our study contradict the latter interpretation. A sedimentary sequence of earliest Eocene to early Middle Eocene age nonconformably overlies the high-grade rocks of the Niğde dome on its southeastern flank. Pebbles from the metamorphic rocks are ubiquitous in the conglomerates of this sequence. As a result, the Niğde metamorphic rocks must have reached the surface before Eocene times, or at the very beginning of the Eocene at the latest. The Üçkapılı granite, whose crystallization age has been inferred to be Early Miocene, has intruded the metamorphic complex during exhumation. The granite is also found as pebbles within the conglomerates of the Eocene sedimentary sequence and, thus, is actually older than the Eocene. Apatite fission track dates of 12–11 Ma across the Niğde dome do not indicate that the metamorphic rocks were still on their way to the surface at that time; instead, they must reflect a later event, which is most probably heating during late Neogene magmatism. Lastly, there is no ductile-then-brittle extensional detachment in the two areas where it has been invoked, that is, on the western and southern flanks of the dome. An extensional detachment nevertheless exists at the top of the Niğde dome, best documented in its northern part, where the detachment fault superposes a superficial unit made up of massive ophiolitic rocks onto the high-grade metamorphic sequence. Field evidence indicates that this detachment developed before Eocene times. On the other hand, our observations do not confirm the nonconformity of the sedimentary sequence dated as late Maastrichtian–Late Palaeocene onto the Niğde high-grade rocks. Field relations show either a tectonic contact between the two, or the direct nonconformity of the Eocene sediments onto the metamorphic rocks. The lack of coarse clasts originating from the Niğde high-grade rocks within the Maastrichtian–Palaeocene sequence further suggests that the metamorphic dome did not reach the surface before Late Palaeocene times. These results compare well with available data from the north-western part of the Central Anatolian Crystalline Complex, suggesting that exhumation has been broadly synchronous on the scale of the massif, as a result of an episode of high magnitude extension that affected the region in Campanian to Palaeocene times.

Melting of Torridonian arkoses, due to intrusion of shallow bodies of mafic melts on the Isle of Rum, was locally extensive, reaching up to 95 vol.%. Crystallization (to form granophyre) of these highly melted rocks was generally static in the vicinity of minor intrusions, although disruption of bedding is apparent in the aureole of the main mafic pluton. A distinctive millimetre- to centimetre-scale spherulitic texture developed during solidification of the partially melted arkose, in both the aureole of the main intrusion, and also in those of associated minor gabbro plugs. The spherulites are formed of radiating, fan-shaped intergrowths of plagioclase and quartz set in a matrix of quartz, plagioclase and K-feldspar. The importance of nucleation rates in determining texture development is demonstrated by a dominance of Na-rich compositions in the first feldspar to form, even in non-spherulitic rocks. It is suggested that the spherulites formed by the early growth of metastable plagioclase due to difficulties in nucleating feldspar.

The blind reverse Bajo Segura Fault is located at the eastern extreme of the Trans-Alboran shear zone (Betic Cordillera, southeast Iberian Peninsula). The surface expression of recent activity of this blind ENE–WSW fault is represented by coseismic surface anticlines and growth synclines on both sides of the anticlines. In the synclines, the deformation of the most recent Quaternary materials is obscured by a sedimentary unit more than 30 m thick which was deposited during the later part of the Late Pleistocene and the Holocene. The present study reports three high-resolution seismic profiles made in the northern growth syncline, which was the one developed most by the Bajo Segura Fault. In these seismic profiles we recognize the boundary between pre-growth strata and growth strata. This marker, Early Pliocene in age, dates the start of the activity of this blind reverse fault. The geometry observed in the seismic profiles of the syntectonic strata, dating from the Late Pliocene and Quaternary, indicates a limb rotation folding mechanism. On seismic profile 2, the complex geometry of the Benejúzar anticline forelimb can be attributed to several splay faults close to the surface of Bajo Segura Fault.

Ar–Ar dating of high-strain ductile mylonites of the Eastern Palmer Land Shear Zone in the southern Antarctic Peninsula indicates that reverse movement on the shear zone occurred in late Early Cretaceous times (Albian), and not latest Jurassic times as previously supposed. The Eastern Palmer Land Shear Zone forms a major tectonic boundary, separating suspect arc terranes from rocks of Gondwana continental affinity. The dated mylonites are developed in Lower Jurassic plutonic rocks at Mount Sullivan, eastern Palmer Land, and form part of a zone of ductile reverse deformation up to 25 km wide. Biotite from a fine-grained mafic mylonite yields an Ar–Ar cooling age of 102.8±3.3 Ma. Movement of this age on the Eastern Palmer Land Shear Zone is coeval with circum-Pacific deformation, possibly related to a mantle superplume event, and provides support for allochthonous-terrane models for the Antarctic Peninsula with accretion in post-Early Cretaceous times.

A number of sedimentary basins formed within the Tauride–Anatolide Platform of Anatolia during the Late Cretaceous–Tertiary period. Previous studies have proposed different tectonic and evolutionary models for each basin. Geological characteristics of the basins, however, suggest that all these basins are of the same origin and that they followed a similar evolutionary model to one another. Basin development within the Tauride–Anatolide Platform took place in a post-collisional environment following the northward subduction of the northern Neotethys ocean beneath the Pontides. The closure of the northern Neotethys ocean ended with collision of the Tauride–Anatolide Platform with the Pontide volcanic arc and resulted in large bodies of oceanic remnants thrust over the Tauride–Anatolide Platform as ophiolite nappes. Formation of the sedimentary basins followed the emplacement of the ophiolite nappes as they formed as piggy-back basins on top of the underlying thrust ophiolite basement.

The chitinozoans recovered from six graptolitic horizons in the Buttington Brick Pit, Wales, are described. A correlation between the upper Llandovery and lower Wenlock chitinozoan and graptolite biostratigraphical schemes is presented. These data are compared with the recently refined chitinozoan biostratigraphical scheme in the nearby Banwy River section, Wales. Chitinozoans from definite turriculatus graptolite Biozone strata are described for the first time from the UK. Chitinozoans indicative of the Eisenackitina dolioliformis Biozone occur in the turriculatus Biozone, although the base of the former biozone probably occurs at a lower stratigraphical level. The Angochitina longicollis chitinozoan Biozone has been identified in middle or probably upper spiralis graptolite Biozone strata. Questionably identified A. longicollis occurs lower, in strata assigned to the middle spiralis Biozone, where it occurs with the short-ranging Conochitina mathrafalensis and Belonechitina cavei. This may indicate that: (1) the base of the longicollis Biozone occurs slightly lower in the Telychian in Buttington Brick Pit than in the more basinal Banwy River section; (2) the specimen assigned to A. longicollis? represents an undescribed species; or (3) C. mathrafalensis and B. cavei occur higher in Buttington Brick Pit than in the Banwy River section. The absence of A. longicollis in the turriculatus and crispus graptolite biozones in Buttington highlights the need to re-examine the specimens assigned to A. longicollis from these levels in Estonia, Sweden and Norway. Chitinozoans indicative of the Margachitina margaritana chitinozoan Biozone occur in murchisoni Biozone strata (the base of the former biozone has not been observed at Buttington), and the occurrence of Conochitina flamma indicates that the highest graptolite bed examined correlates with a level high in the murchisoni graptolite Biozone.

Arc-flank volcaniclastic sedimentation in the Murihiku Terrane of New Zealand lasted about 120 million years from Late Permian to Early Cretaceous time. Despite the effects of pervasive zeolite-facies alteration, whole-rock geochemical parameters for sandstones, siltstones and tuffs record changes in source-rock composition, both in time and along the length of the depositional basin. Sandstones are considered to give a more reliable indication of the state of evolution of the source volcanic arc than do the siltstones. The siltstones commonly contain detrital white mica flakes that are generally lacking in the sandstones, and are possibly of distal continental origin. Some also contain very fine felsic ash particles. Average abundances and normalized multi-element diagrams are used to estimate proportions of three model end-member source constituents, average upper-continental crust (UCC), high-K rhyolite (RHY) and basaltic andesite (AND). Sandstone provenance for the Southland Syncline sector changed from a predominantly basaltic-andesite source in Late Permian to early Middle Triassic time, for example, UCC:RHY:AND = 0:17:83 in the Early to early Middle Triassic, to highly felsic in the Middle to Late Triassic, reaching UCC:RHY:AND = 2:74:24 in the Late Triassic Oretian Stage. A UCC component became increasing significant from latest Triassic upward and the proportion of mafic to felsic volcanism increased again, with UCC:RHY:AND = 15:30:35 in the Middle Jurassic Temaikan Stage. Mix modelling suggests that along-arc source proportions varied, with greater mafic and upper continental crust contributions in the northern Kawhia segment than in the Southland segment. These patterns may be explained by deposition at an oceanic Aleutian-type arc margin, with transition to a continental oceanic arc character induced either by arc evolution and dissection, forearc sliver translation, or underplating of rafted microcontinental fragments.

Knowledge of the late Miocene–Pliocene climate of West Antarctica, recorded by sedimentary units within the James Ross Island Volcanic Group, is still fragmentary. Late Miocene glaciomarine deposits at the base of the group in eastern James Ross Island (Hobbs Glacier Formation) and Late Pliocene (3 Ma) interglacial strata at its local top on Cockburn Island (Cockburn Island Formation) have been studied extensively, but other Neogene sedimentary rocks on James Ross Island have thus far not been considered in great detail. Here, we document two further occurrences of glaciomarine strata, included in an expanded Hobbs Glacier Formation, which demonstrate the stratigraphic complexity of the James Ross Island Volcanic Group: reworked diamictites intercalated within the volcanic sequence at Fiordo Belén, northern James Ross Island, are dated by 40Ar/39Ar and 87Sr/86Sr at c. 7 Ma (Late Miocene), but massive diamictites which underlie volcanic rocks near Cape Gage, on eastern James Ross Island, yielded an Ar–Ar age of <3.1 Ma (Late Pliocene). These age assignments are confirmed by benthic foraminiferal index species of the genus Ammoelphidiella. The geological setting and Cassidulina-dominated foraminiferal biofacies of the rocks at Fiordo Belén suggest deposition in water depths of 150–200 m. The periglacial deposits and waterlain tills at Cape Gage were deposited at shallower depths (<100 m), as indicated by an abundance of the pectinid bivalve ‘Zygochlamys’ anderssoni and the epibiotic foram Cibicides lobatulus. Macrofaunal and foraminiferal biofacies of glaciomarine and interglacial deposits share many similarities, which suggests that temperature is not the dominant factor in the distribution of late Neogene Antarctic biota. Approximately 10 m.y. of Miocene–Pliocene climatic record is preserved within the rock sequence of the James Ross Island Volcanic Group. Prevailing glacial conditions were punctuated by interglacial conditions around 3 Ma.

Determination of the relationships between the southern, marine-dominated Miocene basins of south central Turkey and their continental hinterland in southern Turkey has traditionally been frustrated by the apparent absence of basin remnants within the Taurus Mountains. The Dikme basin, which seems to be an enclave of basin remnants within the Aladağ Mountains (Eastern Taurides), consists mainly of coarse-grained continental sediments of various facies. These mostly early–middle Miocene sediments were studied to determine the depositional environments and the factors controlling the basin formation and basin fill architecture, to attempt to close the information gap between the Adana Basin to the south and central Anatolian Miocene further to the north. A generally southwest-flowing axial fluvial system and interfingering coarse-grained marginal alluvial clastics derived from northwest and southeast were identified. The marginal facies to the northwest is bounded by a N 55° E-running structural lineament, that starts from the Ecemiş Fault Zone and in digital elevation models extends toward the north of the study area. Along this lineament, Miocene sediments onlap steep fault-line escarpments. Certain Miocene levels are tectonically disrupted, and an intraformational unconformity and boulder conglomerates are also well-developed in the Miocene sequence. The southeast boundary is similarly defined by a NE-trending fault that periodically elevated the adjacent Tufanbeyli autochthon, producing coarse clastics from this area. This boundary fault also induced fining-upwards vertical patterns and synsedimentary deformation in the marginal facies. Additionally, the central part of the basin exhibits a distinct fault-defined morphology characterized by small-scale (tens of metres to 150 m high) valley-and-sill topography. A thin marine interval was also encountered in the southernmost part of the basin, indicating that the clastic system originating around this area debouched into a Miocene sea situated further to the south. The proposed palaeogeography and basin fill model suggests that the Dikme basin and similar Miocene remnants, all controlled mainly by a northeast-running extensional or transtensional fault system, may have been parts of the terrestrial hinterland that supplied sediment to rapidly subsiding marine areas further south, such as the Adana Basin.

A new genus and species of primitive cryptodiran turtle, Siamochelys peninsularis n. g. n. sp., from the Middle Jurassic Mab Ching locality, in the southern peninsula of Thailand, is described on the basis of complete shells. They are characterized by a combination of primitive features (the presence of a pair of mesoplastra meeting on the midline) and a series of derived characters (loose plastron–carapace attachment, short diamond-shaped entoplastron, dorsal thickening of the lateral edge of the second to seventh peripheral plates, expanded seventh to eleventh peripheral plates, extension of the anal scute to the hyo-hypoplastral suture or onto the hypoplastron, midline sulcus sinusoidal), and thus closely resemble Chengyuchelys, from the Middle Jurassic of China, and more particularly Xinjiangchelys and its relatives from the Middle and Late Jurassic of China and Central Asia. This supports a Middle Jurassic age for the locality and suggests that the Sibumasu (Shan-Thai) block was in contact with the Asian mainland by that time.

The Blackstones Bank, located about 60 km WSW of the Isle of Mull in Western Scotland, is a submarine plutonic complex in the British Tertiary Igneous Province. Geochemical and isotopic analysis of gabbros, microgabbros and basic dykes shows that the magmas interacted strongly with crustal rocks during their emplacement. The isotopic signature of the contaminated Tertiary intrusions shows no evidence of any interaction with Archaean basement, despite the location of the Blackstones complex to the west of the Great Glen fault. Instead, the Blackstones rocks have crustal signatures resembling the Proterozoic basement and cover rocks of western Islay. It is therefore inferred that Early Proterozoic crust extends to the west of the Great Glen fault at this point on the Scottish continental shelf. In addition, the occurrence of similar isotopic signatures in Tertiary igneous rocks east of the Loch Gruinard fault confirms that Early Proterozoic basement extends under the Grampian block of mainland Scotland. When combined with published evidence from the Rockall bank, the new data constrain the location of an Archaean–Proterozoic crustal suture with a WNW trajectory which cuts across the continental shelf of northwest Britain.