A crystal-rich volcaniclastic sandstone in the lower Peltura scarabaeoides Zone at Ogof-ddû near Criccieth, North Wales, yields a U–Pb zircon age of 491∓1 Ma. This late Late Cambrian date indicates a remarkably young age for the Cambrian–Ordovician boundary whose age must be less than 491 Ma. Hence the revised duration of the post-Placentian (trilobite-bearing) Cambrian indicates that local trilobite zonations allow a biostratigraphic resolution comparable to that provided by Ordovician graptolites and Mesozoic ammonites.

The western Koryak fold and thrust belt consists of a set of tectonostratigraphic terranes that contain units ranging from Lower Palaeozoic to Cenozoic. Three deformational events have been identified in the study area. The first event structures are folds, domes and shear zones with related high-pressure/low-temperature metamorphism. These structures are early Carboniferous and are only recognized in the metamorphic terranes. The second event structures are imbricate fans of thrusts and folds with southeast vergence, broken formation and serpentinite mélange. These are latest Jurassic to early Cretaceous (early Albian) and occur throughout the study area. During this event, thrusting was accompanied by dextral strike-slip faulting. The second event structures are overlapped by the Upper Albian sedimentary rocks with an angular unconformity at the base. During metamorphism associated with the first and second deformational events, some of the rocks were metamorphosed to blueschist grade and were affected by strain with axial ratios of up to 15[ratio ]1. The third deformational event is characterized by significant sinistral strike-slip displacement at higher crustal levels. This resulted in a new set of structures and rotation of pre-existing structures. The age of the sinistral strike-slip faults is interpreted to be late Cretaceous to Cenozoic. The kinematics of the second and third deformational events correspond to assumed proto-Pacific plate motions based on palaeomagnetic data.

The widespread Triassic volcanic rocks of Greece, dismembered during the Hellenide orogeny, are used to interpret the nature of Triassic rifting. Four assemblages of volcanic rocks are distinguished on geochemical criteria: (1) a predominant subalkaline basalt–andesite–dacite series with a high proportion of pyroclastic rocks; (2) minor shoshonites; (3) alkali basalt and (4) MORB. The stratigraphic and palaeogeographic distribution of these rock types is synthesized. New Pb and Nd isotopic data are used to discriminate between hypotheses suggesting that either subduction or extension was responsible for the Triassic volcanism. In the subalkaline basalt assemblage, εNd is negative with depleted mantle model ages >1.5 Ga. Pb isotopic compositions are mostly close to the very distinctive compositional field of Cenozoic extensional rocks of the Aegean area, with very high 207Pb/204Pb for relatively low 206Pb/204Pb ratios. These isotopic data confirm interpretations based on trace elements that subalkaline basalts were predominantly derived from melt-depleted peridotite in the sub-continental lithospheric mantle as a result of extension. Small areas of enriched hydrous mantle partially melted to yield shoshonitic magmas. Nd and Pb isotopic compositions of the alkali basalts are quite different from those in other rock types and suggest a HIMU mantle source component derived from a small plume, which also influenced MORB compositions. Distribution of these various rock types is used to constrain palaeogeographic reconstruction of Triassic micro-continental blocks.

Combined structural, geochemical and isotopic studies have allowed an understanding of the timing and nature of an orogen-scale fault array. The results indicate that the deformation loci within the internal western Alps, during the Alpine collision, occurred as a foreland propagating thrust sequence. The east to west deformation migration within the internal zones is apparently in-sequence in relation to the external zones. Rb–Sr white mica dating of syn-kinematic greenschist-facies mineral assemblages from the Basal Briançonnais Thrust indicate that thrusting ceased between 27 and 32 Ma, several million years after shearing in the hinterland and several million years prior to shearing in the foreland. The Briançonnais Domain, which constitutes the hanging wall to the Basal Briançonnais Thrust, preserves two major shearing episodes. The first, with a top-to-the-northwest overshear, has been tentatively dated at 45 Ma. The second, a very pervasive, east–west orientated, greenschist-facies event was previously dated at 34 Ma on the hinterland margin of the Briançonnais Domain and has now been dated at 27–32 Ma on the foreland margin of the Briançonnais Domain. The period between 34 and 27 Ma apparently dates the migration of deformation through the relict European passive margin, represented by the Briançonnais Domain. This is believed to be in response to overthrusting of Adria/Africa and its associated subduction complex. Structural mapping indicates that the present Basal Briançonnais Thrust in the Col du Petit St Bernard region, Franco-Italian Alps, is a break-back thrust which cuts through an already imbricated pile. Geochronological evidence suggests that the early imbrication of the Briançonnais stratigraphy occurred prior to full interaction of the European and Adria/African plates, that is, during subduction, docking and escape from the subduction complex under Adria. Therefore, although the present Basal Briançonnais Thrust is a break-back thrust in terms of local structural geometries, it is an in-sequence foreland-propagating structure. Geochronological, micro-structural and micro-chemical data indicate that the Briançonnais Domain in the Col du Petit St Bernard zone is formed from granitoid material which intruded and cooled at approximately 320 Ma. During the Alpine event, deformation and metamorphism were insufficient to affect the Sr isotopic system. This suggests that this portion of the Briançonnais Domain was probably subducted to much shallower depths and underwent much less pervasive deformation than the other internal European basement material.

This study presents new Rb–Sr age data concerning the metamorphic evolution of the Attic-Cycladic Crystalline Belt which represents a complex polymetamorphic terrane within the Alpidic orogenic belt of the Hellenides. Two major groups of tectonic units can be distinguished. Metamorphism in parts of the upper units is commonly considered as a Cretaceous event. In contrast, the group of lower units experienced Tertiary high-pressure metamorphism which was followed by a medium-pressure overprint. We focus on the island of Tinos where a representative spectrum of the rock units found in the Cyclades is exposed in three tectonic units: the Upper Unit, the Intermediate Unit and the Basal Unit. The complete range of tectono-metamorphic and magmatic events affecting the Attic-Cycladic Crystalline Belt is documented by numerous petrological and tectonic studies. Phyllites and phyllonites from the ophiolitic Upper Unit yielded Rb–Sr apparent ages (phengite–whole-rock) between c. 92 and 21 Ma. The older age differs from the Cretaceous dates reported for upper unit rocks elsewhere in the Cyclades. It is suggested that the sequence studied belongs to the Jurassic ophiolites of the Hellenides rather than to Cretaceous occurrences. The spread to younger ages is related to non-pervasive rejuvenation and resetting of the Rb–Sr system during tectonic juxtaposition of the Upper Unit over the Intermediate Unit. The youngest age obtained so far for a sample from the Upper Unit (21 Ma) is believed to approximate the timing of tectonic juxtaposition which probably occurred during a regional greenschist-facies episode producing a pervasive overprint in the structurally lower tectonic unit. The major phyllite/meta-gabbro/serpentinite sequence of the Upper Unit is interpreted as an emplacement-related ductile shear zone which experienced reworking under brittle conditions. In the Intermediate Unit, a gradient in Rb–Sr ages from top (c. 40 Ma) to the bottom (c. 22 Ma) was recognized, which is interpreted to represent greater effects of fluid infiltration and overprinting in the lower parts of this unit, possibly controlled by variable intensity of deformation which might be related to tectonic juxtaposition onto the Basal Unit. We suggest that synmetamorphic stacking of all three tectonic units took place during an Oligocene–Miocene greenschist event. Extensional deformation continued after tectonic stacking and after intrusion of the main granite, as is indicated by a Rb–Sr whole-rock isochron (15.1∓0.6 Ma) for a ductilely deformed garnet-bearing leucogranite from the marginal parts of the main undeformed pluton. Application of the Rb–Sr dating technique provided no unequivocal evidence that previously published Eocene K–Ar and 40Ar–39Ar dates for high-pressure phengites from the lower units are significantly contaminated with excess argon.

New geological field mapping along a 24-km-long portion of the Mere Fault, in the northern part of the Wessex Basin, together with seismic reflection and other subsurface data, allow an analysis of displacement, both along the length and down the dip of the reactivated fault. The principal segments of the Mere Fault dip south at about 70° and display components of both syndepositional normal displacement and later reversal of movement during basin contraction. Minimum estimates of the largest down-to-the-south displacements range from less than 100 m at the surface to 350 m at the top of the pre-Permian basement and these values decrease to zero toward the fault segment tips. Estimates that allow for reverse movement along the fault suggest that there must have been at least 500 m of normal displacement along the central portion of the segment. Stratigraphical separation at the surface indicates that the largest down-to-the-north displacements, associated with later fault reversal, are at least 200 m and occur in the east, where reversal of movement has taken place on an early, high-angle fault segment. In the west, the principal fault strands are eroded to deeper stratigraphical levels where largely normal slip is preserved and segments are linked by normal and oblique transfer faults. The Wardour Monocline was developed during basin contraction, in part by movement along a concealed fault segment, overstepping from the Mere Fault at the surface, and in part over a relay ramp between the two fault segments.

Upper Silurian–Lower Devonian ‘Lower Old Red Sandstone’ facies deposits cropping out in southwest Wales are poorly age-constrained and difficult to correlate. Spore assemblages have been recovered from sequences of these deposits belonging to the lower part of the Cosheston Group. The spore assemblages are equated with the breconensis–zavallatus and polygonalis–emsiensis Spore Assemblage Biozones and indicate an early Devonian age (late Gedinnian (late Lochkovian)–Siegenian (Pragian)). The new biostratigraphical data enable correlation of the lower part of the Cosheston Group with the Senni Beds from the main outcrop of the Lower Devonian in South Wales and the Welsh Borderland. In addition, the new age data and stratigraphical correlation place important plant megafossil assemblages from the Cosheston Group and Senni Beds in a more secure stratigraphical framework, thus facilitating comparisons with other Lower Devonian plant megafossil assemblages and enhancing palaeobotanical understanding. Evidence from palynofacies analysis supports sedimentological interpretations which suggest that the ‘Lower Old Red Sandstone’ facies deposits belonging to the Cosheston Group accumulated in a continental fluviatile environment.

Lowermost Ordovician (basal Tremadoc) cherts from the Little Port Complex, western Newfoundland, contain a distinctive, moderately well-preserved, radiolarian assemblage. The fauna differs from those reported from the Arenig, suggesting that some of the earliest radiolarian forms may have biostratigraphic potential. The abundance of radiolarians in chert and the ease with which they can be extracted suggest that they are a potentially valuable tool for use in investigations of the timing and development of early Palaeozoic orogenic systems. A previously undescribed radiolarian Beothuka terranova sp. nov., belonging to a new genus Beothuka gen. nov. and of uncertain higher-level affinity is formalized herein.

The terrigenous materials of the flysch deposits of the External Hellenides of mainland Greece have been characterized by their heavy mineral assemblages, based on 194 samples. Three major source types were distinguished. (1) A metamorphic source is shown by abundant garnet accompanied by traces of staurolite and chloritoid. In the source of the Pindos and Ionian zones, blueschist complexes were incorporated within the metamorphic terrains, demonstrated by the frequent occurrence of blue amphiboles. (2) The existence of ophiolitic sources is indicated by the occurrence chrome spinel. Pyroxenes, green amphiboles and partly epidote are related to volcanic/metavolcanic complexes. High ophiolitic detritus was especially found in Mid-Cretaceous turbiditic layers supplied from internal terrains. (3) Granitoid and gneiss source terrains are indicated, predominantly represented by zircon, tourmaline and apatite. This type of source is characteristic for Mid-Cretaceous turbidites sampled in western parts of the Pindos zone. In the terminal flysch deposits, granitoid detritus played only a subordinate role. An extensive recycling of Pindos Flysch material into the younger Western Hellenic Flysch can be excluded. Stratigraphic trends in the heavy mineral distribution of the terminal Pindos Flysch give insights into the changing tectonic situation of the source terrains. A regional east–west trend with changing ophiolitic detritus, observed in the Parnassos-Ghiona Flysch, points to a complex feeder system.