Results of in situ U–Pb dating of calcite spherulites, cone-in-cone (CIC) calcite and calcite fibres from a calcareous concretion of the upper Ediacaran of Finnmark, Arctic Norway, are reported. Calcite spherulites from the innermost layers of the concretion yielded a lower intercept age of 563 ± 70 Ma, which, although imprecise, is within uncertainty of the age of sedimentation based on fossil assemblages. Non-deformed CIC calcite from the bottom part of the concretion yielded an age of 475 ± 25 Ma, which is interpreted as the age of CIC calcite formation during a period of fluid overpressure induced during burial of the sediments. Deformed CIC calcite from the top part of the concretion yielded an age of 418 ± 23 Ma, which overlaps with a known Caledonian tectono-metamorphic event, and indicates a potential post-depositional overprint at this time. Calcite fibres that grew in small fissures along spherulite rims, which are interpreted as a recrystallization feature during deformation and formation of a cleavage, gave an imprecise age of 486 ± 161 Ma. Our results show that U–Pb dating of calcite can provide age constraints for ancient carbonates and syn- to post-depositional processes that operated during burial and metamorphic overprinting.

The pre-Caledonian NYF Skoddefjellet pegmatite in Wedel Jarlsberg Land, Svalbard, contains xenotime-(Y) that is partly replaced by fluorapatite-hingganite-(Y) reaction coronas. Hingganite-(Y) contains up to 2.0 wt.% of Gd2O3, 4.7 wt.% of Dy2O3, 3.3 wt.% of Er2O3 and 5.5 wt.% of Yb2O3. Such unusual, previously undescribed, xenotime-(Y) breakdown was caused by Ca- and F-bearing fluids interacting with the pegmatite. The occurrence of hinnganite-(Y) as a breakdown product of xenotime-(Y) implies that a Be-bearing phase (beryl in this case) was also involved in the reaction. There are few Ca-bearing primary phases in the pegmatite, indicating that the source of fluid was probably located in the generally Ca-richer host rocks (metasediments), though the fluid composition was modified during metasomatism of the pegmatite (i.e. beryl dissolution).

The Neoproterozoic Hedmark Basin in the Caledonides of South Norway was formed at the western margin of the continent Baltica by rifting 750–600 Ma ago. The margin was destroyed in the Caledonian Orogeny and sedimentary basins translated eastwards. This study uses provenance analysis to map the crustal architecture of the pre-Caledonian SW Baltican margin. Conglomerate clasts and sandstones were sampled from submarine fan, alluvial fan and terrestrial glacigenic sedimentary rocks. Samples were analysed for U–Pb isotopes and clast samples additionally for Lu–Hf isotopes. The clasts are mainly granites c. 960 Ma and 1680 Ma old, coeval with the Sveconorwegian Orogeny and formation of the Palaeoproterozoic Transscandinavian Igneous Belt (TIB). Mesoproterozoic (Sveconorwegian) ages are abundant in the western part of the basin, whereas Palaeoproterozoic ages are common in the east. Lu–Hf isotopes support crustally contaminated source for all clasts linking them to Fennoscandia. Detrital zircon ages of the sandstones can be matched with those from the granitic clasts except for ages within the range 1200–1500 Ma. These ages are typically found in the present-day Telemark, SW Norway. The sandstones and conglomerate clasts in the western part of the Hedmark Basin were sourced from the Sveconorwegian domain in the present SW Norway or its continuation to the present-day NW. The conglomerate clasts in the eastern part of the Hedmark Basin were sourced mainly from the TIB domain or its northwesterly continuation. The Hedmark Basin was initiated within the boundary of two domains in the basement: the TIB and the Sveconorwegian domains.

The Rogart igneous complex is unique within the northern Scottish Caledonides because it comprises an apparent continuum of magma types that records a progressive change in emplacement mechanisms related to large-scale tectonic controls. Syn-D2 leucogranites and late-D2 quartz monzodiorites were emplaced during crustal thickening and focused within the broad zone of ductile deformation associated with the Naver Thrust. In contrast, emplacement of the post-D2 composite central pluton was controlled by development of a steeply dipping dextral shear zone along the Loch Shin Line, interpreted as an anti-Riedel shear within the Great Glen Fault system. The mantle-derived nature of the late-to-post-D2 melts implies that the Naver Thrust and the Loch Shin Line were both crustal-scale structures along which magmas were channelled during deformation. A U–Pb zircon age of 425±1.5 Ma for the outer component of the central pluton provides an upper limit on regional deformation and metamorphism within host Moine rocks. These findings are consistent with the view that a fundamental change in tectonic regime occurred in the Scottish Caledonides at c. 425 Ma, corresponding to the switch from regional thrusting that resulted from the collision of Baltica and Laurentia, to the development of the orogen-parallel Great Glen Fault system.

The tectonic origin of pre-Devonian rocks of Svalbard has long been a matter of debate. In particular, the origin and assemblage of pre-Devonian rocks of western Spitsbergen, including a blueschist-eclogite complex in Oscar II Land, are enigmatic. We present detrital zircon U–Pb LA-ICP-MS data from six Mesoproterozoic to Carboniferous samples and one U–Pb TIMS zircon age from an orthogneiss from Oscar II Land in order to discuss tectonic models for this region. Variable proportions of Palaeo- to Neoproterozoic detritus dominate the metasedimentary samples. The orthogneiss has an intrusion age of 927 ± 3 Ma. Comparison with detrital zircon age spectra from other units of similar depositional age within the North Atlantic region indicates that Oscar II Land experienced the following tectonic history: (1) the latest Mesoproterozoic sequence was part of a successor basin which originated close to the Grenvillian–Sveconorwegian orogen, and which was intruded by c. 980–920 Ma plutons; (2) the Neoproterozoic sediments were deposited in a large-scale basin which stretched along the Baltoscandian margin; (3) the eclogite-blueschist complex and the overlying Ordovician–Silurian sediments probably formed to the north of the Grampian/Taconian arc; (4) strike-slip movements assembled the western coast of Spitsbergen outside of, and prior to, the main Scandian collision; and (5) the remaining parts of Svalbard were assembled by strike-slip movements during the Devonian. Our study confirms previous models of complex Caledonian terrane amalgamation with contrasting tectonic histories for the different pre-Devonian terranes of Svalbard and particularly highlights the non-Laurentian origin of Oscar II Land.

New U–Pb ID-TIMS geochronological and whole-rock geochemical data from the Hurry Inlet Plutonic Terrane in Liverpool Land provide evidence of a Late Ordovician to Silurian magmatic arc in the East Greenland Caledonides. These voluminous granitoid rocks range from meladiorite to monzonite and granite, they are alkali-calcic to calc-alkaline and magnesian, and have characteristic arc granitoid trace element signatures. Zircon data give ages of 446 ± 2 and 438 ± 4 Ma for two phases of the Hurry Inlet Composite Pluton, 426 ± 1 Ma for a meladioritic xenolith in the anatectic Triaselv granite, and 424 ± 1 Ma for the Hodal-Storefjord Pluton. The Late Ordovician plutons can be correlated with similar plutons in the uppermost nappes of the Scandinavian Caledonides, likely representing the northern branch of magmatic arcs formed on the Laurentian margin. Magmatism appears to have continued sporadically until about 425 Ma when a major, short-lived, magmatic event formed the bulk of the batholith on Liverpool Land. This activity was likely mantle-driven and can be correlated with the Newer Granites in Scotland, for which a slab break-off mechanism has been proposed. The increased heat flow from this process can also explain the generation of the crustally derived, syntectonic, two-mica granites, which are the areally most important Caledonian suite in East Greenland.

New Re–Os age determinations from the Galway Granite (samples: KMG = 402.2 ± 1.1 Ma, LLG = 399.5 ± 1.7 Ma and GBM = 383.3 ± 1.1 Ma) show that in south Connemara, late Caledonian granite-related molybdenite mineralization extended from c. 423 Ma to c. 380 Ma. These events overlap and are in excellent agreement with the published granite emplacement history determined by U–Pb zircon geochronology. The spatial distribution of the late-Caledonian Connemara granites indicates that initial emplacement and molybdenite mineralization occurred at c. 420 Ma (that is, the Omey Granite and probably the Inish, Leterfrack and Roundstone granites) to the N and NW of the Skird Rocks Fault, an extension of the orogen-parallel Southern Uplands Fault in western Ireland. A generally southern and eastward progression of granite emplacement (and molybdenite mineralization) sited along the Skird Rocks Fault then followed, at c. 410 Ma (Roundstone Murvey and Carna granites), at c. 400 Ma (Errisbeg Townland Granite, Megacrystic Granite, Mingling Mixing Zone Granodiorite, Lough Lurgan Granite and Kilkieran Murvey Granite) and at c. 380 Ma (Costelloe Murvey Granite, Shannapheasteen and Knock granites). The duration of granite magmatism and mineralization in Connemara is similar to other sectors of the Appalachian–Caledonian orogeny and several tectonic processes (e.g. slab-breakoff, asthenospheric flow, transtension and decompression) may account for the duration and variety of granite magmatism of the western Irish Caledonides.

Analysis of pelites with detrital white-micas in the Clew Bay–Galway Bay segment of the Irish Caledonides indicates that b0 data from whole-rock and < 2 μm fractions generally show differences smaller than the errors of the method, irrespective of (001) illite crystallinity values, probably due to metamorphic recrystallization. Intermediate pressure metamorphism of the Ordovician–Silurian Clew Bay Group indicates slow subduction, allowing partial thermal re-equilibration before exhumation. In contrast, the Croagh Patrick Group Laurentian shelf-sediments underwent high-pressure alteration, suggesting rapid subduction/exhumation, synchronous with strike-slip faulting. The Murrisk Group, which underwent high-intermediate pressure metamorphism in an Ordovician back-arc, forms a separate terrane to the Croagh Patrick Group to the north and also to the Ordovician Lough Nafooey and Tourmakeady groups and Rosroe Formation in the south, in which low-intermediate pressure alteration occurred. These, together with the Silurian North Galway Group, may have undergone heating due to movement over or deposition on the hot Gowlaun Detachment as the Connemara Dalradian was exhumed. The South Connemara Group also underwent a high-pressure alteration, consistent with its inferred subduction environment. Evidence of contact alteration, due to known or inferred buried late- to post-Caledonian granitoid plutons, has been found in the Clew Bay, Louisburg–Clare Island, Croagh Patrick, Murrisk and South Connemara groups. These show evidence of lower-pressure alteration than the surrounding country-rocks.

The presence of major crystalline basement provinces at depth in NW Ireland is inferred from in situ Hf isotope analysis of zircons from granitoid rocks that cut structurally overlying metasedimentary rocks. Granitoids in two of these units, the Slishwood Division and the Tyrone Central Inlier, contain complex zircons with core and rim structures. In both cases, cores have average ϵHf values that differ from the average ϵHf values of the rims at 470 Ma (the time of granitoid intrusion). The Hf data and similarity in U–Pb age between the inherited cores and detrital zircons from the host metasedimentary rocks suggests local contamination during intrusion rather than transport of the grains from the source region at depth. Rims from the Slishwood Division intrusions have average ϵHf470 values of −7.7, consistent with a derivation from juvenile Palaeoproterozoic crust, such as the Annagh Gneiss Complex or Rhinns Complex of NW Ireland, implying that the deep crust underlying the Slishwood Division is made of similar material. Rims from the Tyrone Central Inlier have extremely negative ϵHf470 values of approximately −39. This isotopic signature requires an Archaean source, suggesting rocks similar to the Lewisian Complex of Scotland, or sediment derived wholly from it, occurs at depth in NW Ireland.

Southwest Spitsbergen, Wedel Jarlsberg Land, consists of two Proterozoic crustal blocks with differing metamorphic histories. Both blocks experienced Caledonian greenschist-facies metamorphism, but only the southern block records an earlier pervasive M1 amphibolite-facies metamorphism and strong deformational fabric. In situ EMPA total-Pb monazite geochronology from both matrix and porphyroblast inclusion results indicate that the older M1 metamorphism occurred at 643 ± 9 Ma, consistent with published cooling ages of c. 620 Ma (hornblende) and 580 Ma (mica) obtained from these same rocks. This region thus contains a lithostratigraphic profile and metamorphic history which are unique within the Svalbard Archipelago. Documentation of a pervasive late Neoproterozoic Barrovian metamorphism is difficult to reconcile with a quiescent non-tectonic regime typically inferred for this region, based on the occurrence of rift-drift sequences on the Baltic and Laurentian passive margins. Instead, our new metamorphic age implies an exotic origin of the pre-Devonian basement exposed in SW Spitsbergen and supports models of terrane assembly postulated for the Svalbard Archipelago.

Within the Scottish Caledonides, the Glen Scaddle Metagabbro was intruded into the Moine Supergroup of the Northern Highland Terrane after Grampian D2 folding and prior to regional D3 and D4 upright folding and amphibolite-facies metamorphism. A U–Pb zircon age of 426 ± 3 Ma obtained from the metagabbro is interpreted to date emplacement. D3–D4 folding is constrained to have occurred during the Scandian orogenic event. In contrast, polyphase folding and regional metamorphism of the Dalradian Supergroup southeast of the Great Glen Fault is entirely Grampian. These differences are consistent with published tectonic models that invoke a minimum of 700 km of post-Scandian sinistral displacements across the Great Glen Fault to juxtapose the Grampian and Northern Highland terranes.

An approximately 250 m thick polydeformed and polymetamorphosed, isotopically unusual, variegated marble (locally termed the ‘Leivset marble’) shows a great lateral extent in the Scandinavian Caledonides. Its extremely 13C-depleted primary nature (−7.9±1.2‰ on average, n=93) makes the Leivset marble unique. This, together with a high Sr content (up to 8740 ppm) that buffered 87Sr/86Sr ratios between 0.70802 and 0.70872, suggests correlation with the worldwide Shuram–Wonoka isotopic event occurring within the 600–550 Ma time interval during the Ediacaran (Vendian) period. Despite a high-grade deformation and metamorphism, the Leivset marble has retained its original carbon and strontium isotope ratios. A combination of the variegated colour with unusually low δ13Ccarb can potentially be used for stratigraphic correlations in high-grade, non-fossiliferous, marble-dominated terranes across the Caledonian orogenic belt in Baltica and Laurentia. Isotope chemostratigraphy has identified a prominent cryptic stratigraphic discontinuity and suggests that the Ediacaran Leivset marble was tectonically juxtaposed above low-grade, Llandovery-age, fossiliferous marbles during the Scandian orogeny.

In one of the higher nappes of the Caledonides of Troms, northern Norway, rare thin dykes of calcite marble lie subparallel to the axial surfaces of folds in multilayered marble beds. The dykes emanate from pure calcite marble layers mostly in or close to the hinge zones of these flat-lying, tight to sub-isoclinal, F3 folds. In many cases, they appear to penetrate along the axial surfaces of these same folds, and there is an up to 10° angular disparity between dyke orientation and axial surfaces. The dykes are considered to have originated, and been expelled, from parent calcite marble layers either at or shortly after the peak of amphibolite-facies metamorphism between the D2 and D3 deformation phases of the Scandian orogeny. The dykes display a dyke-parallel, dark grey to white, colour banding, the origin of which is uncertain at present. In thin-section, an equigranular texture is dominated by 2–3 mm, equant, unstrained, calcite grains with straight boundaries and low-T twin lamellae, denoting a late-stage recrystallization. A weak, oblique, calcite grain-shape orientation fabric curves into a dyke-parallel alignment along the finer-grained margins, reflecting the simple-shear deformation imposed on the host rock. Regarding the initiation of these marble dykes, it seems likely that a combination of P–T conditions and possibly partial melting processes was conducive to generating extreme ductility/superplasticity, at least locally, and that this led to the sudden expulsion of a partially molten carbonate aggregate which had momentarily attained a critical pressure and intruded preferentially along available, transient fractures prior to the imposition of the D3 simple-shear regime.

As an example of microstructural and magnetic fabric evolution, and geochemistry of mafic dykes during a subsequent orogenic overprint, a major Mesoproterozoic dyke complex in Scandinavia, the Västerbotten complex of the Central Scandinavian Dolerite Group, is traced westwards into the crystalline nappes of the early Phanerozoic Caledonian orogen. Using geophysical, field, microscopic, magnetic and geochemical information, dykes and sills are characterized, and their overprint during Caledonian orogeny documented. The Västerbotten complex is composed of sets of dykes, trending NE–SW, NW–SE and WNW–ESE, respectively. Similar dykes are exposed in allochthonous positions (Lower and Middle allochthons) in the Caledonian fold-and-thrust belt. The autochthonous dykes are generally undeformed and retain both their primary texture and mineralogy. Chilled margins are well preserved. In the Caledonian Lower and Middle allochthons, similar dykes in crystalline basement rocks are progressively faulted and sheared when proceeding from the marginal to the interior parts of the orogen. Dyke margins are more likely to be sheared than the interior parts of dykes. In the Lower Allochthon, under very low- and low-grade metamorphic conditions, dykes are distinctly less competent than granitic host rocks. Thick dykes are more competent than gneisses; thin dykes do not show such competence contrasts. In the Middle Allochthon, metre-scale dykes with patches of altered plagioclase phenocrysts can still be discerned in low-strain domains. Highly sheared dykes are drawn out to thin layers of centimetre thickness. Dykes are deformed together with the crystalline country rocks under greenschist-grade metamorphic conditions without major competence contrasts. Magnetic fabrics show an evolution similar to the silicate mineral fabrics. The magnetic fabrics in the dykes are transformed successively from ferromagnetic–magmatic in the Autochthon to ferromagnetic deformational in the Lower Allochthon and, finally, paramagnetic deformational in the Middle Allochthon. As a consequence, the magnetic susceptibility decreases for several orders of magnitude. Geochemically, the dykes are dominantly sub-alkaline basalts typical for continental tholeiites and can be distinguished from the Neoproterozoic dykes in the Särv-Nappe equivalents (highest part of the Middle Allochthon), which show a more MORB-like (E-MORB) magmatic signature. Preliminary age information from a dyke in the Lower Allochthon of the Børgefjell area and the Middle Allochthon is consistent with the assumption that these dykes are time equivalent with the Central Scandinavian Dolerite Group. Therefore, the studied dykes may represent an extension of the Västerbotten complex or a new complex of the Central Scandinavian Dolerite Group. According to section restorations, the Caledonian allochthons were situated further WNW relative to their present position, and, originally, the mafic dykes cut across all of the Fennoscandian lithosphere, at least to the present Atlantic margin and the earlier passive margin of the Baltica terrane. As a consequence, these dykes may provide a link for pre-Caledonian and pre-Grenvillian plate reconstructions.

The Seiland Igneous Province (SIP) of northern Norway comprises a suite of mainly gabbroic plutons, with subordinate ultramafic, syenitic and felsic intrusions. Several intrusions from the Seiland Igneous Province have been dated by ID-TIMS U–Pb zircon and monazite analyses. The Hasvik Gabbro on the island of Sørøy, previously assigned an age of 700±33 Ma by Sm–Nd, yields a U–Pb zircon age of 562±6 Ma, within error of the Storelv Gabbro (569±5 Ma) and a diorite associated with the Breivikbotn Gabbro (571±4 Ma). Various intrusions on the Øksfjord peninsula give nearly identical ages of 565±9 Ma (gabbro), 566±4 Ma (monzonite), 565±5 Ma (monzodiorite), 570±9 Ma (norite), and 566±1 Ma (orthopyroxenite). These ages overlap with those from Sørøy, and define a single and short-lived period of gabbroic (to felsic) magmatism for the region between 570 and 560 Ma, pre-dating a subordinate episode of alkalic magmatism at 530–520 Ma. The U–Pb ages contradict the previous geochronological interpretation for the Finnmark area, which implied a period of 250 m.y. for the emplacement of the SIP intrusions. The new age data also clearly distinguish the Seiland intrusions, emplaced into the Sørøy Group metasediments of the Kalak Nappe Complex, from several older granitic intrusions (c. 850 to 600 Ma) that cut the Sørøy Group farther east and south. The coincident ages of the different Seiland intrusive bodies also contradict the previous structural model for the area, which posits that the different gabbro bodies were emplaced at intervals, with compressional deformation affecting the gabbros between periods of intrusion. The short time span between the main plutonic phases strongly suggests that the mechanism for the emplacement of mafic magma operated in a single, probably extensional, tectonic regime. The mafic intrusions were later deformed and metamorphosed to at least amphibolite facies, most likely by the Scandian (420 Ma) phase of the Caledonian Orogeny.

A detailed field and microstructural investigation of mineral fabrics in the late-Caledonian Galway Granite Batholith (∼400 Ma) provides insights into the relationship between emplacement-related deformation and crystallization state. These relationships are used to infer the regional instantaneous strain pattern at the time of intrusion. A Marginal Deformation Zone occurs in the granite along part of its northern sector, where planar fabrics are contact-parallel and dip steeply to the north. Within the Marginal Deformation Zone, the granite has similar patterns of pre- and post-RCMP (Rheologically Critical Melt Percentage) fabrics on either side of the NNE-trending Shannawona Fault Zone, which separates the Western and Central blocks of the batholith. Oblate pre-RCMP fabrics, which intensify towards the contact, are overprinted in a down-temperature continuum of deformation by co-axial post-RCMP fabrics that also become more intense towards the contact. At the southern edge of the Marginal Deformation Zone, deformation ceased before the granite reached its RCMP whereas, close to the contact, deformation ceased at ∼500°C. Within the Central Block, oblate fabrics also developed parallel with internal granite facies boundaries. Throughout the batholith, the fabrics formed by co-axial deformation as a result of lateral expansion operating in successive magma batches at the emplacement level. These intrusion-related fabrics are consistent with other evidence that indicates the Galway Granite was emplaced into a transtensional setting at the end of the Caledonian Orogeny.

Dolerite dykes in the East Finnmark Scandinavian Caledonides form three geochemical suites: Digermulhalvøya–Magerøya – WNW–ESE-trending, c. 337–332 Ma, possibly also c. 293 Ma, continental within-plate; East Varangerhalvøya – NE–SW and N–S, c. 376 Ma, continental plate-margin; Styret – NE–SW, also c. 376 Ma, chemically intermediate to the other two groups. New K–Ar data from metadolerites on Varangerhalvøya give a 7-point ‘lower envelope’ isochron of 577 ± 14 Ma (MSWD 1.04). This is concordant with a published upper intercept U–Pb zircon age (567+30−23 Ma) from an East Varangerhalvøya dolerite, here re-interpreted to reflect Neoproterozoic basement fracturing contemporaneous with the emplacement of the metadolerites. Intrusion of the younger dolerites at c. 376 Ma reactivated this trend, and may be responsible for the published zircon lower intercept age of 392+25−36 Ma. Clarification of the intrusion and structural chronology, integrated with extensive new geochemical data, enables a better understanding of the evolution of this part of the Scandinavian Caledonides.

New U–Pb zircon dating yields a crystallization age of 458±3 Ma for the largely gabbroic Grøndalsfjell Intrusive Complex in the Gjersvik Nappe of the Caledonian Upper Allochthon in Scandinavia. This is identical, within error, to the age of the adjacent Møklevatnet Complex that is dominated by quartz monzodiorite (456±2 Ma), and the two intrusive suites may be regarded as members of a composite intrusion here referred to as the Nesåa Batholith. Mafic members of this calc-alkaline batholith are characterized by slightly positive εNd–εSr values, marked enrichment of the light rare earth elements and high Th/Yb ratios suggestive of a subduction-modified mantle source. The I-type granitoids have similar isotope values and highly fractionated rare earth element patterns, and are interpreted as products from partial melting of garnet-bearing mafic rocks. The Nesåa Batholith intruded a previously deformed, 483 Ma or older, metavolcanic sequence of oceanic arc affinity. The margins of the pluton show evidence for synkinematic emplacement, which is tentatively interpreted in terms of magma ascent controlled by deep-seated shear zones. Further uplift and exhumation of the crystallized plutons was followed by rapid deposition of batholith-derived conglomerates and arkoses in a marginal basin represented by the Limingen Group. The age of the Nesåa Batholith fills the gap in reported ages for Caledonian magmatism, between the Early to Middle Ordovician, oceanic to continental margin type, arc sequences of Laurentian palaeotectonic affinity, and the Late Ordovician–Early Silurian batholith complexes of interpreted Laurentian margin affinity. It is interpreted as an early phase of the more extensive plutonism recorded in the Bindal Batholith of the Uppermost Allochthon to the west. Our model implies that the Early Ordovician oceanic arc sequences of the Gjersvik Nappe were deformed and accreted on to Laurentian margin lithologies prior to Late Ordovician times. This composite crustal assemblage was the source for the voluminous quartz monzodioritic intrusions of the Nesåa Batholith, which formed by partial melting due to ponding of subduction-related mantle derived mafic magmas either within or at the base of the active continental margin.

Structures deforming Llandovery turbidites of the Gala Group in the Southern Uplands terrane are spectacularly exposed in the Berwickshire coastal section, southeastern Scotland. The upward-facing, upright to NW-vergent folds and associated structures appear to record a single regional phase of subhorizontal NW–SE contractional deformation, with a steeply dipping direction of bulk finite extension. These structures are markedly different from those developed in rocks correlated with the Upper Llandovery Hawick Group exposed some 5 km to the south in the Eyemouth–Burnmouth coastal section. Here a highly domainal system of sinistral transpressional strain occurs, with zones of steeply plunging curvilinear folds, clockwise cleavage transection and bedding-parallel sinistral detachment faults. The markedly different bulk strain patterns in the Berwickshire coastal sections are thought to reflect the regionally diachronous nature of transpressional deformation in the Southern Uplands terrane. There are striking similarities in the structures recognized in the Berwickshire coastal sections and those developed in stratigraphically equivalent units along strike in southwestern Scotland and Northern Ireland. This confirms the lateral structural continuity and correlation of tracts and tract boundaries along the entire length of the Southern Uplands terrane. The regional structure suggests that a phase of top-to-the-NW backthrusting and backfolding associated with the southern margin of the Gala Group outcrop marks the transition from orthogonal contraction to sinistral transpression in the Southern Upland thrust wedge during late Llandovery times.