Tectonic joints localized within deformation band shear zones on the Kaibab uplift in Utah, USA, show the same spacing and distribution characteristics as joints controlled by primary lithological mechanical stratigraphy, despite the fact that deformation band shear zones are secondary structural features oblique to primary sedimentary layers. The spacing and distribution of joints that traverse deformation band shear zones are important factors in the permeability and connectivity of sandstone reservoirs compartmentalized by deformation band shear zones.

New geochemical, isotopic and age data from igneous rocks complement earlier models of a long-lived and complex accretionary history for East African Orogen lithologies north of the Blue Nile in western Ethiopia, but throw doubt on the paradigm that ultramafic complexes of the region represent ophiolites and suture zones. Early magmatism is represented by a metavolcanic sequence dominated by pyroclastic deposits of predominantly basaltic andesite composition, which give a Rb–Sr whole-rock errorchron of 873±82 Ma. Steep REE patterns and strong enrichments of highly incompatible trace elements are similar to Andean-type, high-K to medium-K calc-alkaline rocks; εNd values between 4.0 and 6.8 reflect a young, thin continental edge. Interlayered basaltic flows are transitional to MORB and compare with mafic rocks formed in extensional, back-arc or inter-arc regimes. The data point to the significance of continental margin magmatism already at the earliest stages of plate convergence, in contrast with previous models for the East African Orogen. The metavolcanites overlap compositionally with the Kilaj intrusive complex dated at 866±20 Ma (U–Pb zircon) and a related suite of dykes that intrude thick carbonate-psammite sequences of supposedly pre-arc, continental shelf origin. Ultramafic complexes are akin to the Kilaj intrusion and the sediment-hosted dykes, and probably represent solitary intrusions formed in response to arc extension. Synkinematic composite plutons give crystallization ages of 699±2 Ma (Duksi, U–Pb zircon) and 651±5 Ma (Dogi, U–Pb titanite) and testify to a prolonged period of major (D1) contractional deformation during continental collision and closure of the ‘Mozambique Ocean’. The plutons are characterized by moderately peraluminous granodiorites and granites with εNd values of 1.0–2.0. They were coeval with shoshonitic, latitic, trachytic and rare trachybasaltic intrusions with very strong enrichments of highly incompatible trace elements and εNd of 0.4–8.0. The mafic end-member is ascribed to partial melting of enriched sub-continental mantle that carried a subduction component inherited from pre-collision subduction. Contemporaneous granodiorite and granite formation was related to crustal underplating of the mafic magmas and consequent melting of lower crustal material derived from the previously accreted, juvenile arc terranes of the East African Orogen.

Two generations of sulphide-hosted platinum-group element mineralization occur in the West Sgaorishal ultramafic plug, Rum. Disseminated Cu and Ni sulphides around the margin of the plug host a restricted platinum-group mineral assemblage that is dominated by Pd bismutho-tellurides and sperrylite (PtAs2) with subordinate electrum (AuAg), froodite (PdBi2) and unidentified Pt–Bi–Te phases. Later sulphide-rich dykes cross-cut the plug and host an assemblage dominated by Pd bismutho-tellurides, sperrylite and locally very abundant paolovite (Pd2Sn). Whole rock combined platinum-group element+Au concentrations are proportional to the sulphide abundance with slightly elevated values in disseminated sulphide lithologies (>400 ppb) and very high values (>2000 ppb) in the sulphide-rich dykes. Both generations have relatively flat chondrite-normalized plots indicating a primitive magmatic source. Negative δ34S values (−9.2 to −18.3 ‰) indicate that the disseminated mineralization is due to contamination probably derived from Jurassic sedimentary rocks leading to sulphur saturation and collection of platinum-group elements. The sulphide-rich dykes must have entrained a platinum-group element-rich sulphide liquid collected from a much larger volume of magma. The presence of platinum-group elements and sulphide-rich dykes with δ34S values between −10.8 and −15.0 ‰ indicates that parts of the Rum Layered Suite became sulphur saturated through magmatic contamination. It appears likely that platinum-group element mineralization styles within the southern North Atlantic Igneous Province are diverse and may be present in a wider variety of mineralogical associations than previously recognized.

Markedly different cooling histories for the hanging- and footwall of the Vari detachment on Syros and Tinos islands, Greece, are revealed by zircon and apatite fission-track data. The Vari/Akrotiri unit in the hangingwall cooled slowly at rates of 5–15 °C Myr−1 since Late Cretaceous times. Samples from the Cycladic blueschist unit in the footwall of the detachment on Tinos Island have a mean zircon fission-track age of 10.0±1.0 Ma, which together with a published mean apatite fission-track age of 9.4±0.5 Ma indicates rapid cooling at rates of at least ∼60 °C Myr−1. We derive a minimum slip rate of ∼6.5 km Myr−1 and a displacement of <∼20 km and propose that the development of the detachment in the thermally softened magmatic arc aided fast displacement. Intra-arc extension accomplished the final ∼6–9 km of exhumation of the Cycladic blueschists from ∼60 km depth. The fast-slipping intra-arc detachments did not cause much exhumation, but were important for regional-scale extension and the formation of the Aegean Sea.

Illite crystallinity data from the Silurian slate belts of England and Wales indicate anchizone to low epizone metamorphism during the Acadian deformation in late Early Devonian time. This metamorphic grade implies a substantial overburden, now eroded, of Lower Devonian non-marine sediments of the Old Red Sandstone (ORS) magnafacies. A minimum 3.5 km pre-tectonic thickness of ‘lost’ ORS is estimated in the southern Lake District and comparable thicknesses in North Wales and East Anglia. Tectonically driven subsidence of the underlying Avalonian crust is required to accommodate such thicknesses of non-marine sediment. One proposed mechanism is flexure of the Avalonian footwall during convergence that continued from Iapetus closure in the Silurian until Acadian cleavage formation in the Emsian. The evidence for this model in the critical area of northwest England is reviewed and found to be unconvincing. An alternative model is developed following a recent suggestion that the Early Devonian was a period not of continued convergence but of orogen-wide sinistral transtension. Transtensional accommodation of the lost ORS is evidenced by Early Devonian extensional faults, by synchronous lamprophyric magmatism, and by compatibility with previously diagnosed sediment provenance patterns. A summary of Siluro-Devonian tectonostratigraphy for Britain south of the Highland Border emphasizes that, unlike the Scottish Highlands, this area was not affected by the Scandian Orogeny, but was by the Acadian. An important period of sinistral transtension in the Early Devonian (c.420–400 Ma) was common to both regions. This was a time of high heat flow, lamprophyric and more evolved magmatism, and major southward sediment transport, involving mainly recycled metamorphic detritus from the Highlands and from contemporaneous volcanicity. Old Red Sandstone, deposited in coalescing transtensional basins over much of Britain from the Midland Valley to the Welsh Borders, was largely removed and recycled southward during Acadian inversion.

The role played by Cenozoic deformation in denudation and landscape development in Ireland has historically been difficult to assess because of the lack of widespread pre-glacial Cenozoic deposits onshore. Here we combine analysis of apatite fission-track data and geomorphic observations to place constraints on the timing, kinematics and magnitude of onshore deformation in southeastern Ireland. Relationships between apatite fission-track central age and elevation for samples from the Wicklow and Blackstairs Mountains and Tullow Lowland suggest that these rocks record an exhumed apatite partial annealing zone, which after cooling was dismembered by differential vertical displacements of up to several hundred metres. We use inverted models of sample thermal history to show that samples across the region experienced very similar thermal histories up to and including a cooling event in late Paleocene or early Eocene time. This effectively rules out strongly spatially heterogeneous denudation, and implies that differential rock uplift occurred in post-early Eocene time. The central age–elevation relationships define at least three spatial domains with internally consistent apatite fission-track data, separated by known faults or topographic escarpments. Geomorphic analysis of these structures shows that patterns of catchment incision and sinuosity, as well as the presence of antecedent drainage, are best explained by differential vertical displacements at or near the domain boundaries. The kinematics and magnitudes of these displacements are consistent with those implied by the apatite fission-track results, and are compatible with other examples of known Cenozoic deformation from Ireland and the adjacent continental margin.

In the Putorana region of the Siberian continental flood basalt province, tuffs form thin layers or small bodies between single basaltic lava flows. Based on our fieldwork, these ash fall deposits have relatively small volumes (≤100 000 m3) compared with the associated basaltic flows and the tuffs of the adjacent Noril'sk region in the north. Six tuff units with different degrees and modes of alteration were analysed by XRD, SEM and XRF in order to determine mineralogical and chemical changes which occurred during progressive alteration. Pyroxene compositions and immobile element ratios suggest that the tuffs were derived from a basaltic lava like the flood basalts. Post-eruptive, low-temperature alteration processes have significantly changed the primary composition of the tuffs. Therefore the different tuffs have variable petrography, mineralogy and geochemistry (MgO 5.2–9.2 wt %, SiO2 33.6–69.1 wt % and TiO2 0.6–1.6 wt %) compared to the tholeiitic basalts in which they are interbedded. Crystallization of secondary minerals, such as carbonate, clay minerals, zeolites and analcime, occurred from circulating fluids. The results show that the fluid compositions varied significantly between the different tuffs. This implies that the elements behaved differently depending on the circulating agent, which led to the formation of different minerals. In addition, two samples show an input of quartz, derived either by wind from terrigenous sediments or generated by magma–sediment interaction, and one sample was deposited in a subaqueous, possibly lacustrine environment. These results indicate that the conditions during alteration varied despite the close spatial relationship of the tuffs and that a generalization about the alteration processes cannot be made in the Putorana region. The analyses of the clay minerals show alteration of chlorite to vermiculite. Interestingly, corrensite (a regularly stacked, 50/50 mixed layered clay mineral composed of chlorite and vermiculite) is still preserved in two samples. This indicates different alteration stages in the different tuff outcrops. The state of alteration deduced from immobile element ratios, plagioclase compositions and mineral assemblages shows contradictory results. This suggests that the state of alteration is best deduced from clay minerals, as one can follow this process step by step.

Major and trace element data on Tertiary continental basalt flows from the Shalatein area, Red Sea coastal plain of Egypt, have been presented and used to obtain more information about their source region and the processes involved in their generation. The rocks are mainly alkali olivine basalt with MgO and Mg no. in the range of 9.8–5 wt % and 65–46, respectively. They display wide variations in incompatible element concentrations, particularly LREE, Zr, Nb, K, Y, Ba and Sr. There is no evidence of significant crustal contamination or a lithospheric mantle signature in these rocks. Normalized trace element patterns and diagnostic elemental ratios are very similar to those of modern ocean-island basalts (OIB) a feature which suggests that the mantle source region was the asthenosphere. Comparison with the different types of OIB indicates that the basalts may be derived from a high U/Pb (HIMU) source with slightly elevated K and Ba contents. The basalts show general trends of increasing incompatible elements (K2O, Nb, Y, Sr and Yb), and decreasing contents of compatible elements (Cr, Ni, Sc and Ca) with decreasing Mg no. Furthermore, TiO2, P2O5, LREE and Th define maxima at about Mg no.=56, suggesting late fractionation of Fe–Ti oxides and apatite. Although these variations are consistent with fractional crystallization processes, the wide variations in LREE contents and the incompatible trace element ratios Ce/Y (1.2–3.8), Zr/Nb (2.3–7.1) and Nb/Y (0.6–4) in the least fractionated samples (Mg no. > 56) suggest that fractional crystallization involving the observed phenocryst assemblage (olivine and clinopyroxene) cannot fully explain such compositional variations. Modelling of the mafic rocks (Mg no. > 56) using REE suggests varying degrees of partial melting of an enriched mantle source region in the garnet stability field. Partial melting is attributed to plume-related mantle upwelling beneath the Red Sea rift system.

Mesoproterozoic marine successions worldwide record a shift in average δ13C values from 0 to +3.5‰, with the latter value evident in successions younger than 1250 Ma. New carbon isotope data from the ∼1300 to 1270 Ma Dismal Lakes Group, Arctic Canada, provide further insight into this fundamental transition. Data reveal that the shift to higher δ13C values was gradual and marked by occasional excursions to values less than 0‰. When compared to records from older and younger marine successions, it is evident that the difference between isotopic minima and maxima increased with time, indicating that the marine system evolved to become isotopically more variable. We interpret these patterns to record an increase in the crustal inventory of organic carbon, reflecting eukaryotic diversification and a change in the locus of organic carbon burial to include anoxic deep marine sites where preservation potential was high. We speculate that the release of O2 to Earth's surface environments associated with increased organic carbon storage induced irreversible changes in the Mesoproterozoic biosphere, presaging the more extreme environmental and evolutionary developments of the Neoproterozoic.

Abundant and well-preserved material of the ligulate lycopsid genus Leclercqia is reported from a new Middle Devonian locality in northeastern Queensland (Australia). The plants occur in a chert horizon in the Storm Hill Sandstone of the Dosey-Craigie Platform. Lithological data and conodont analyses combined with information from in situ spores provide an age for the plant levels ranging from Eifelian, possibly Middle Eifelian, to Early Givetian. Plant taxonomic identification is based on vegetative and fertile stems that display both external morphology and anatomy. This material represents the best documented occurrence of Leclercqia outside Laurussia and possibly the earliest in Gondwana; it provides evidence that colonization of Gondwana by the species L. complexa was contemporaneous to that of Siberia and Kazakhstan. Analysis of the distribution patterns of L. complexa suggests that it was adapted to a wide range of environments, but within certain limits which we hypothesize to be those of a climatic belt. Such considerations support previous studies using other biological data, such as faunas and palynomorphs, for reconstructing Devonian palaeogeography. They favour a close proximity of Laurussia and Gondwana rather than the occurrence of a wide ocean separating the two palaeocontinents in Middle Devonian times.

Carbon and oxygen isotope data from a succession of Cretaceous (Barremian–Cenomanian) age recovered from the Pacific Ocean (DSDP site 463) are presented. The carbon isotope curve reveals a large isotope excursion within the early Aptian where δ13C values reach ~4.8‰ in the L. cabri–G. ferreolensis foraminifera zone. A decrease in δ13C values is observed at the base G. algerianus zone, before a return to more positive values at the top of the G. algerianus–T. bejaouaensis zone. The pronounced early Aptian positive event is preceded by a large negative isotope excursion, confined to the G. blowi zone. Synchronous with this excursion are increased total organic carbon values and increases in Mn and Fe concentrations. Integrated biostratigraphic and magnetostratigraphic data, together with the carbon isotope profile, suggest that the organic-rich units of site 463 are correlatable with Oceanic Anoxic Event 1a. The input of isotopically light volcanic CO2 in concert with the intensification and upwelling of intermediate water enriched in 12C could account for the observed trends. A potential trigger may have been the destabilization of the water column and the prodigious CO2 emissions associated with hydrothermal activity and the emplacement of the Ontong Java Plateau. Coupled with faunal evidence, the subsequent positive carbon isotope excursion is interpreted to be resulting from high, but decreasing, productivity and possibly increasing ocean stratification resulting in strong carbon isotopic gradients and 13C-enriched surface waters. The decrease in δ13C within the G. algerianus zone is coincident with more positive δ18O values. If these are interpreted in terms of temperature this interval may be characterized by a period of cooling and possibly a waning of Corg cycling. A return to lower δ13C values during the middle Albian is considered to be related to the increased influence of upwelling, as opposed to a waning of Corg cycling. Upwelling introduced isotopically light carbon to the surface, arresting the stratified oceanic conditions.

The occurrence of along-strike thickness variations in pretectonic sedimentary packages is expected to influence the structural architecture of doubly verging thrust wedges. To test this hypothesis, we used laboratory sandbox experiments. Model results show that longitudinal tapering of pretectonic sediments causes a great complexity in the internal tectonic fabric of the wedge, particularly in the pro-wedge, dominated by highly segmented, curvilinear thrusts. The along-strike variation of the mode by which the same amount of bulk contraction is accommodated in different regions of the orogen produces the obliquity of the deformation fronts in both the pro-wedge and the retro-wedge. Comparison with the overall architecture of the Lesser Antilles and Manila accretionary systems validates our experimental results.

A much-revised Quaternary stratigraphy is presented for ignimbrites and pumice fall deposits of the Bandas del Sur, in southern Tenerife. New 40Ar/39Ar data obtained for the Arico, Granadilla, Fasnia, Poris, La Caleta and Abrigo formations are presented, allowing correlation with previously dated offshore marine ashfall layers and volcaniclastic sediments. We also provide a minimum age of 287±7 ka for a major sector collapse event at the Güimar valley. The Bandas del Sur succession includes more than seven widespread ignimbrite sheets that have similar characteristics, including widespread basal Plinian layers, predominantly phonolite composition, ignimbrites with similar extensive geographic distributions, thin condensed veneers with abundant diffuse bedding and complex lateral and vertical grading patterns, lateral gradations into localized massive facies within palaeo-wadis, and widespread lithic breccia layers that probably record caldera-forming eruptions. Each ignimbrite sheet records substantial bypassing of pyroclastic material into the ocean. The succession indicates that Las Cañadas volcano underwent a series of major explosive eruptions, each starting with a Plinian phase followed by emplacement of ignimbrites and thin ash layers, some of co-ignimbrite origin. Several of the ignimbrite sheets are compositionally zoned and contain subordinate mafic pumices and banded pumices indicative of magma mingling immediately prior to eruption. Because passage of each pyroclastic density current was characterized by phases of non-deposition and erosion, the entire course of each eruption is incompletely recorded at any one location, accounting for some previously perceived differences between the units. Because each current passed into the ocean, estimating eruption volumes is virtually impossible. Nevertheless, the consistent widespread distributions and the presence of lithic breccias within most of the ignimbrite sheets suggest that at least seven caldera collapse eruptions are recorded in the Bandas del Sur succession and probably formed a complex, nested collapse structure. Detailed field relationships show that extensive ignimbrite sheets (e.g. the Arico, Poris and La Caleta formations) relate to previously unrecognized caldera collapse events. We envisage that the evolution of the nested Las Cañadas caldera is more complex than previously thought and involved a protracted history of successive ignimbrite-related caldera collapse events, and large sector collapse events, interspersed with edifice-building phases.

Twenty-two graptolite species are described from the Tremadoc portion of the Road River Group. In a 220 m thick, graptolite-rich section on Peel River, six graptolite biozones are recognized which in ascending order are: Staurograptus dichotomus, Anisograptus matanensis, Adelograptus cf. A. tenellus, Adelograptus antiquus, Kiaerograptus pritchardi and Paradelograptus kinnegraptoides. The Psigraptus fauna appears to be confined to a single bedding-plane within a thick interval dominated by Adelograptus cf. A. tenellus, and for this reason we propose a new zone characterized by the latter species rather than identify a Psigraptus Biozone as in China. The Adelograptus cf. A. tenellus Biozone has yielded Adelograptus? bulmani Spjeldnaes 1963, which we propose as the type species for the new genus Ancoragraptus. Graptolites recorded from the Tremadoc of the Yukon for the first time are: Ancoragraptus bulmani, Clonograptus magnificus, C. cf. C. multiplex, C. cf. C. rigidus, Hunnegraptus copiosus, Kiaerograptus? bulmani and K? kutchini sp. nov.

Thermochronological data reveal that the Late Cretaceous–Tertiary nappe pile of the Anatolide belt of western Turkey displays a two-stage cooling history. Three crustal segments differing in structure and cooling history have been identified. The Central Menderes metamorphic core complex represents an ‘inner’ axial segment of the Anatolide belt and exposes the lowest structural levels of the nappe pile, whereas the two ‘outer’ submassifs, the Gördes submassif to the north and the Çine submassif to the south, represent higher levels of the nappe pile. A regionally significant phase of cooling in the Late Oligocene and Early Miocene affected the outer two submassifs and the upper structural levels of the Central Menderes metamorphic core complex. In the northern part of the Gördes submassif, cooling was related to top-to-the-NNE movement on the Simav detachment, as the apatite fission-track ages show a northward-younging trend in the direction of movement on this detachment. In the Çine submassif, relatively rapid cooling in Late Oligocene and Early Miocene times may have been related to top-to-the-S extensional reactivation of the basal thrust of the overlying Lycian nappes. The second phase of cooling in the Anatolide belt is related to Pliocene to Recent extension resulting in the formation of the Central Menderes metamorphic core complex in the inner part of the Anatolide belt. Core-complex development caused the formation of supra-detachment graben, which document the ongoing separation of the Central Menderes metamorphic core complex from the outer submassifs.

Heavy minerals in Ordovician successions in western Ireland record, in the Upper Arenig Sheeffry Formation, the erosion of an ophiolite/island arc complex. The appearance of staurolite and garnet at a basin-wide horizon in the Lower Llanvirn Upper Derrylea Formation signals the unroofing of the Dalradian metamorphic complex. Parts of the Ordovician sequence on Inishturk and in two small inliers are correlated with the standard sequence with unexpected results. The garnet-, sillimanite-, and staurolite-bearing Letter Formation correlates with the Upper Derrylea Formation and, on Inishturk, heavy minerals in south-younging turbidites reveal a sinistral ramp zone, that places the Sheeffry Formation structurally above and to the south of the younger Derrylea Formation.

A new Middle Permian locality in northern Johore, Peninsular Malaysia, yields a small-sized, but compositionally unique, brachiopod fauna consisting of eight species: Pseudoleptodus sp., Caricula cf. salebrosa Grant, Neochonetes (Nongtaia) aff. arabicus (Hudson & Sudbury), Karavankina sp., Transennatia cf. insculpta (Grant), Hustedia sp., Orthothetina sp., and martiniid indet. The first four genera are new records for Malaysia; in particular, the rare taxa Pseudoleptodus and Caricula characterize the fauna. The brachiopods occur together with the ammonoid Agathiceras sp., the nautiloid Foordiceras? sp., bivalves, and crinoid stems. The locality belongs to the East Malaya terrane of the Cathaysian biotic region, but some affinities to species of the Sibumasu province are recognized. The Malaysian forms of Pseudoleptodus, Caricula and Transennatia are similar to those of the Ratburi Limestone (southern Thailand). A Roadian–early Wordian age is interpreted for the Johore fauna. The similarity of brachiopods reported here with those from the Ratburi Limestone suggests that there was species interchange or one-way migration between shallow waters of East Malaya and Sibumasu across the main Palaeo-Tethys. The Tethyan seaway between the two terranes must have been narrower than previously interpreted by some authors to allow such faunal traffic during the Roadian–Wordian time period.

The model of a foreland propagating sequence already presented for the External Hellenides is significantly modified in this paper. New data are used, including structural maps, cross-sections, stratigraphic determinations and seismic profiles. In general, thrusts formed a foreland propagating sequence but they acted simultaneously for a long period of time. Thus, during the Middle Eocene the Pindos thrust resulted in the formation of the Ionian–Gavrovo foreland and acted in tandem with the newly formed Gavrovo thrust within the basin until the Late Oligocene. The Gavrovo thrust consists of segments, showing that out-of-sequence thrusting was important. Thrust nucleation and propagation history is strongly influenced by normal faults formed in the forebulge region of the Ionian–Gavrovo foreland basin. Shortening rates within the Gavrovo–Ionian foreland are low, about 1 mm/year. Although thrust load played an important role in the formation of this basin, the additional load of 3500 m thick clastics in the basin enhanced subsidence and underthrusting.

Palaeomagnetic data from the 337 Ma Magerøy dykes (northern Norway) are of exceptionally high quality, and a positive contact test along with an existing regional result from the Silurian Honningsvåg Igneous Suite attests to a primary Early Carboniferous magnetic signature. The palaeomagnetic pole (S14.8°, E320.1°, dp/dm=4.4/8.6°) is the first Early Carboniferous pole from Baltica, and implies that northernmost Norway–Greenland, the Barents Sea and Svalbard were located at tropical to low northerly latitudes at this time. Northward drift during Carboniferous times (5–6 cm/yr) as demonstrated from palaeomagnetic data is also reflected in the sedimentary facies in the Barents Sea realm, that is, a change from tropical (Early Carboniferous) to subtropical (20–30° N) carbonates and evaporites in the Late Carboniferous. The Magerøy dykes are continental tholeiites which intruded into a set of NW–SE-trending normal faults parallel to the Trollfjorden–Komagelva Fault Zone and the Magerøysundet Fault immediately to the north and south of Magerøya, respectively. These, and many other NW–SE-trending faults (onshore and offshore), were active during Late Palaeozoic extension, and the dykes were probably contemporaneous with the earliest syn-rift sedimentation in the Barents Sea (for example, the Nordkapp Basin).

The Montréal area belongs to the St Lawrence Lowlands, a Cambrian Early Ordovician passive margin of the Iapetus Ocean, later covered by Appalachian Middle to Upper Ordovician foreland deposits. A structural and palaeostress analysis has been carried out in order to reconstruct its tectonic evolution. The structural map has been revised with new data. Palaeostresses are reconstructed based on inversion of fault slip data, and these results are independently corroborated by the microstructural study of calcite mechanical twinning. Field relationships are used to establish the relative chronology of fractures and to deduce the motion on regional faults. The reconstructed structural and tectonic evolution brings to light some relationships between structural inheritance and tectonic events that have affected the area since Early Palaeozoic times. An early NW–SE extension is responsible for N040-trending faults along the northern border of the St Lawrence Lowlands, and for N090- and N120-trending faults cross-cutting the Montréal area. This extension is followed by WNW–ESE and NNW compressions, which have induced reverse motion on pre-existing faults and generated strike-slip conjugate faults. Subsequent NE–SW and NNW–SSE-directed extensions have reactivated previous faults with normal to strike-slip motions. A late NE–SW compression is recorded in the Monteregian plutons. Compressions in WNW–ESE and NNW directions are consistent with Appalachian collisional tectonism, but N040- and N090-trending faults cross-cut Appalachian folds and foreland deposits. Although the early NW–SE extension is consistent with the collapse of the Iapetan margin in Early Palaeozoic times, most of the present geometry of the St Lawrence Lowlands could be attributed to Mesozoic tectonism, recorded as nearly N–S-directed extensional events.