The Canarian Archipelago is a group of volcanic islands on a slow-moving oceanic plate, close to a continental margin. The origins of the archipelago are controversial: a hotspot or mantle plume, a zone of lithospheric deformation, a region of compressional block-faulting or a rupture propagating westwards from the active Atlas Mountains fold belt have been proposed by different authors. However, comparison of the Canarian Archipelago with the prototypical hotspot-related island group, the Hawaiian Archipelago, reveals that the differences between the two are not as great as had previously been supposed on the basis of older data. Quaternary igneous activity in the Canaries is concentrated at the western end of the archipelago, close to the present-day location of the inferred hotspot. This is the same relationship as seen in the Hawaiian and Cape Verde islands. The latter archipelago, associated with a well-defined but slow-moving mantle plume, shows anomalies in a plot of island age against distance which are comparable to those seen in the Canary Islands: these anomalies cannot therefore be used to argue against a hotspot origin for the Canaries. Individual islands in both archipelagoes are characterized by initial rapid growth (the ‘shield-building’ stages of activity), followed by a period of quiescence and deep erosion (erosion gap) which in turn is followed by a ‘post-erosional’ stage of activity. The absence of post-shield stage subsidence in the Canaries is in marked contrast with the major subsidence experienced by the Hawaiian Islands, but is comparable with the lack of subsidence evident in other island groups at slow-moving hotspots, such as the Cape Verdes. Comparison of the structure and structural evolution of the Canary Islands with other oceanic islands such as Hawaii and Réunion reveals many similarities. These include the development of triple (‘Mercedes Star’) rift zones and the occurrence of giant lateral collapses on the flanks of these rift zones. The apparent absence of these features in the post-erosional islands may in part be a result of their greater age and deeper erosion, which has removed much of the evidence for their early volcanic architecture. We conclude that the many similarities between the Canary Islands and island groups whose hotspot origins are undisputed show that the Canaries have been produced in the same way.

Explosive volcanism has dominated the large phonolitic shield volcano of Tenerife, the Las Cañadas edifice, for the last 1.5 m.y. Pyroclastic deposits of the Bandas del Sur Formation are exposed along the southern flanks, and record the last two of at least three long-term cycles of caldera-forming explosive eruptions. Each cycle began with flank fissure eruptions of alkali basalt lava, followed by minor eruptions of basanite to phonotephrite lavas. Minor phonotephritic to phonolitic lava effusions also occurred on the flanks of the edifice during the latter stages of the second explosive cycle. Non-welded plinian fall deposits and ignimbrites are the dominant explosive products preserved on the southern flanks. Of these, a significant volume has been dispersed offshore. Many pyroclastic units of the second explosive cycle exhibit compositional zonation. Banded pumice occurs in most units of the third (youngest) explosive cycle, and ignimbrites typically contain mixed phenocryst assemblages, indicating the role of magma mixing/mingling prior to eruption. At least four major eruptions of the third cycle began with phreatomagmatic activity, producing lithic-poor, accretionary lapilli-bearing fallout and/or surge deposits. The repeated, brief phase of phreatomagmatism at the onset of these eruptions is interpreted as reflecting an exhaustive water supply, probably a small caldera lake that was periodically established during the third cycle. Accidental syenite becomes an increasingly important lithic clast type in ignimbrites up-sequence, and is interpreted as recording the progressive development of a plutonic complex beneath the summit caldera.

Successive eruptions during each explosive cycle increased in volume, with the largest eruption occurring at the end of the cycle. More than ten major explosive eruptions vented moderately large volumes (1−[ges ]10 km3) of phonolitic magma during the last two cycles. Culminating each explosive cycle was the emplacement of relatively large volume (>5−10 km3) ignimbrites with coarse, vent-derived lithic breccias, interpreted to record a major phase of caldera collapse. In the extracaldera record, explosive cycles are separated by ∼0.2 m.y. periods of non-explosive activity. Repose periods were characterized by erosion, remobilization of pyroclastic deposits by discharge events, and pedogenesis. The current period of non-explosive activity is characterized by the construction of the Teide-Pico Viejo stratovolcanic complex within the summit caldera. This suggests that eruptive hiatuses in the extracaldera record may reflect effusive activity and stratovolcano or shield-building phases within the summit caldera. Alternating effusive and explosive cycles have thus been important in the volcanic evolution of the Las Cañadas edifice.

This paper consists of three parts. The first part presents a critical review of previous mechanical models on the relationship between joint spacing (s) and bed thickness (t) in sedimentary rocks. The second part describes a new mechanical model dealing with the effects of interbed slip on joint spacing. The third part presents the comparison between theoretical results of the model and joint data measured from Cambrian flysch sediments at Plage Victor in the Saint-Jean-Port-Joli area of the Quebec Appalachians. This study demonstrates two formation mechanisms of tensile joints: near-end fracturing takes place in the layers with smaller tensile fracture strength (C0<30 MPa) and smaller interbed shear strength (τ0<20 MPa) while mid-point fracturing occurs in those layers with larger C0 (>50 MPa) and τ0(>30 MPa) values. For the rocks with moderate tensile fracture strength (30<C0<50 MPa) and interbed shear strength (20<τ0<30 MPa), the near-end fracturing and mid-point fracturing take place preferentially in the thicker and thinner brittle layers, respectively. In the regime of near-end fracturing, the correlation between s and t is linear and independent of the thickness of the bounding non-jointing layers (d). In the regime of mid-point fracturing, however, the s–t relationship can be either linear or non-linear, depending on the variation of d value. The present study also suggests that the near-end fracturing is probably the prevailing process for the formation of tensile joints in bedded sedimentary rocks and that the coefficient of joint spacing (K) defined by the ratio of s to t is considered as an indicator of C0/(2τ0) for the jointed layer.

Two successive assemblages of vertebrate microremains have been found at Grozon (Jura, northeastern France). Palynological analysis confirms a Norian age for the first one and a Rhaetian age for the second. A new species of neoselachian shark, Grozonodon candaui, is erected from isolated teeth of Norian age, based on their enameloid ultrastructure. Distinctive parallel-fibred enameloid is recognized among teeth previously assigned to Hybodus minor, which therefore represents another early neoselachian shark. These structural characteristics confirm the close relationship of hybodont and neoselachian sharks.

The c. 1.1 Ga Kgwebe metavolcanic rocks exposed in the northwest of Botswana are late Kibaran rocks. They represent a bimodal suite of Within-Plate low titanium-phosphorus (LTP) continental tholeiites and post-orogenic Within-Plate high-K rhyolites. The chemical compositions of the Kgwebe mafic rocks are characterized by low values of Ce/Pb (<10) and high La/Nb ratios (average c. 2, maximum 4). Mid-ocean ridge basalts (MORB)-normalized spidergrams show marked enrichment in mobile elements (Sr, K, Rb, Ba) and negative anomalies in Nb. These features suggest they may have originated in a mantle, enriched during a previous subduction event. The Kgwebe metarhyolites are marked by Y>60 ppm, Sr/Y<1, Rb/Th>20 and high K-contents. They cannot therefore be the product of melting of sediments or a subducting slab. It is inferred that they represent felsic magmas resulting from melting of Mesoproterozoic (Kibaran) calcalkaline rocks underplated in the middle and/or lower crust. The Kgwebe bimodal metavolcanic rocks pre-date the Neoproterozoic Ghanzi Group rocks which are correlated with the lower part of the Damara sequence. The chemical composition and field relations suggest that these metavolcanic rocks were emplaced during a late orogenic collision-associated extensional collapse. This collapse affected a crust thickened during the Kibaran orogeny in the Namaqua-Natal Belt of southwest Africa.

The subsidence and stratigraphic evolution in an eastern section of the Subbetic Zone (External Zones of the Betic Cordilleras, Spain) during Jurassic and early Cretaceous times have been examined. The sediments have been deposited on a passive margin undergoing rifting. The data indicate that the activity was complex and spasmodic, with two distinct rift and post-rift phases. The beginning of the first syn-rift and post-rift phases are recorded by two regional sedimentary breaks, in the Late Carixian and in the Bathonian, respectively. The second rift and post-rift phases began, with less clearly defined limits, during the Oxfordian and at the Jurassic–Cretaceous boundary, respectively.

Orogenesis is increasingly interpreted in terms of strain focusing, localization and partitioning processes. Such heterogeneous deformation is considered a consequence of the tectonic framework, with pre-existing structural and stratigraphic variability providing inherent zones of crustal weakness. Detailed structural investigation of Neoproterozoic Dalradian metasediments in the Glencolumbkille region, northwest Ireland, enables patterns of reworking and strain localization to be assessed in terms of four overprinting ductile deformation episodes. A well-defined and intricate Dalradian stratigraphy provides readily distinguishable markers which not only focus deformation along marked rheological boundaries, but also aid in the definition and identification of resultant geometries. Overall structural and stratigraphic relationships show that whilst D1 was not associated with major structures, D2 is related to north–northeast directed folding and ductile thrusting resulting in a major phase of crustal thickening and almandine-amphibolite facies metamorphism. Structures generated during D2 deformation subsequently became the locus of intense D3 strain and were reactivated in an oblique sense associated with south or southwest directed translations. Local overprinting relationships clearly demonstrate S2 fabrics being transposed by S3 resulting in a composite foliation over large areas. Similarly, the L2 mineral lineation is abruptly transposed by L3 over relatively small distances indicating high D3 strain gradients and the susceptibility of lineations to reworking. The final stage of ductile deformation (D4) which was increasingly localized and focused into earlier (D2−D3) high strain zones, is marked by a pronounced phase of sinistral transpression associated with clockwise cleavage and minor fold transection of northwest verging upright folds. Sinistral shear is strongly partitioned in to the steep limbs of mesoscopic F4 folds. The detailed investigation of structures generated within such multiply deformed and reworked zones provides evidence of both the kinematic and tectonic evolution of regional deformation systems.

A pterosaur specimen, consisting of the associated anterior portions of upper and lower jaws, is reported from the upper Kimmeridgian Argiles d'Octeville, in the cliffs of the Cap de la Hève, near Le Havre (France). It is described as a new taxon, Normannognathus wellnhoferi, and referred to the Germanodactylidae. Normannognathus wellnhoferi is distinguished by the association of jaws which bear teeth up to their anterior tip and a tall sagittal crest, formed by the premaxillae, which begins anterior to the nasopreorbital fenestra, has a concave anterior edge, and is much higher than the maxilla at that level. The Dsungaripterus-like crest and the slightly upturned upper jaw support the idea of a close relationship between the Germanodactylidae and Dsungaripteridae.