Flysch-type, syn-orogenic deposits of Carboniferous age occur in relation to the emplacement of a large allochthonous nappe stack in the Variscan belt of NW Iberia. New U–Pb age populations of detrital zircons obtained using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are considered together with others from previously dated samples to establish the relationships between sedimentation and thrusting. The age populations of four syn-orogenic formations are compared with those of the pre-orogenic sequence in the Autochthon and Parautochthon, representing the Gondwanan passive margin, and in the Allochthon, formed by peri-Gondwanan and oceanic terranes. In addition, a new structural study has been carried out to understand the relationships between the syn-orogenic deposits and the development of Variscan structures. The aims are to identify the sources of sediments and to establish the relationship between Variscan structural evolution and syn-orogenic sedimentation. Development of a forebulge outwards from the allochthonous front, deduced from the structural study, suggests the existence of depocentres that hosted the syn-orogenic sediments. Together with the trend shown by the more recent zircons in each formation, that are younger towards the external zones, the data suggest that sedimentation occurred in progressively migrating depocentres formed in front of the allochthonous wedge during its emplacement. The zircon age populations point to the Allochthon as the main source of detritus for the syn-orogenic basins, with perhaps a limited participation of the Parautochthon and Autochthon in the younger formations.

Twenty-three samples of Quaternary sands from Deep Sea Drilling Project (DSDP) Leg 87 Sites 582 (trench axis) and 583 (lowermost terrace of uplifted trench sediments in the accretionary prism) off Shikoku show a 70–80% volcanic component in the terrigenous grain population. This component comprises 30–40% neovolcanic grains, among which basic and intermediate types are present in roughly equal proportions, and 60–70% palaeovolcanic grains, which are predominantly of acidic composition. No volcanic terrane occurs, in the hinterland of the Shikoku portion of the Nankai Trough, and the first such rocks to the east (up the very slight depositional slope of the Nankai Trough axis) are not encountered for more than 500 km. These, occupying the Izu Peninsula and the majority of the Tokai drainage basin to the north, are Neogene and Recent volcanics which are of comparable variability to the volcanic grains in the sands off Shikoku.

The minor component of sedimentary, metamorphic and plutonic grains in the Leg 87 sand samples can be matched with the basinal clastic ophiolitic Shimanto and Chichibu terranes and the high-pressure metamorphic Sambagawa terrane which border the Nankai Trough fore-arc along southwest Japan. This detritus also most likely derives from the Tokai drainage basin, where the easternmost outcrops of the above-mentioned terranes occur, because most sediments deriving from Shikoku and the Kii regions are ponded in terraced fore-arc basins or in basins on the lower slope. Only three major submarine canyons debouch into the floor of the Nankai Trough. The easternmost of these, the Suruga Trough, taps the volcanic Izu/Tokai hinterland, and is therefore the conduit for most sand fed to the trench off Shikoku.

The Nellore–Khammam schist belt, SE India, is sandwiched in between the Proterozoic Eastern Ghats terrane and the Archaean Dharwar–Bastar craton. We report Sm–Nd and Rb–Sr mineral isochron ages of amphibolite from the schist belt. The Sm–Nd and Rb–Sr ages are 824±43 Ma and 481±16 Ma, respectively. The Sm–Nd age indicates the timing of peak metamorphism, whereas the Rb–Sr age indicates the Pan-African thermal overprint. The peak metamorphism was related to collision of the Eastern Ghats terrane with the Dharwar-Bastar craton, which occurred during early Neoproterozoic time.

WHILST working through a batch of slides of heavy minerals of the Millstone Grit of the Pennine region some interesting outgrowths on zircon have been noticed which are worthy of record. The writer is not aware that they have been recorded before, but they must have a wider distribution than the Millstone Grit of this area, and therefore this mention of them may lead to further records being made known.

Seven genera of stegosaurian dinosaur have been named on the basis of material from the Upper Jurassic of China, and this represents a diversity of stegosaurs unparalleled around the world at this time. However, many of the original specimens used to diagnose and describe these species are currently unavailable, and the original descriptions and figures are often inadequate. The Chinese stegosaurs have proven ‘unstable’ in the few cladistic analyses of Stegosauria that have been carried out, causing a loss of resolution in cladograms. Supplementary data on previously described specimens are presented here along with a taxonomic revision. Only Tuojiangosaurus multispinus, Chungkingosaurus jiangbeiensis and Gigantspinosaurus sichuanensis are considered to be valid taxa, with autapomorphies pertaining to features of the ilio-sacral blocks and dermal armour in all cases. The holotype specimen of ‘Chialingosaurus kuani’ is a juvenile, bearing no diagnostic characters, and ‘Monkonosaurus lawulacus’ is based on fragmentary and undiagnostic material. ‘Changtusaurus’ and ‘Yingshanosaurus’ have never been described or figured and their whereabouts are unknown, so they are regarded as nomina nuda. This taxonomic revision significantly reduces known stegosaurian diversity worldwide, and shows that the Chinese diversity was similar to that of Europe and North America in the Upper Jurassic. Previously, it had been suggested that the diversity of Chinese stegosaurs indicated an Asian origin for the clade, a claim that cannot now be upheld.

IN the early days of the Geological Survey of Scotland, the rocks of the Ballantrae Igneous Complex were thought to be of metamorphic origin. Thus in the memoir explanatory of sheet 7, scale 1 inch = 1 mile, published in 1869, it is stated that the chief interest attaching to the altered strata of this district consists in the fact that they exhibit certain arrested stages of metamorphic action. But less than ten years after that date the erroneous character of this opinion was made abundantly clear by Professor Bonney.Equipped with experience gleaned in the Lizard, Bonney quickly recognized in Ayrshire a correspondence in the nature of the phenomena. Excellent descriptions were furnished by him of some of the lavas, serpentines, and gabbros, and their true igneous character emphasized.

The noble element (Os, Ir, Ru, Rh, Pt, Pd, Au) patterns from sulphides associated with the komatiites at the Alexo mine show variable degrees of fractionation. Massive sulphides at the contact between underlying intermediate volcanics and overlying komatiites have the least fractionated patterns (Pd/Ir = 44). Net-textured sulphides which immediately overlie the massive sulphides have extremely fractionated noble element patterns (Pd/Ir = 171). The disseminated sulphides in the overlying komatiite exhibit an intermediate degree of fractionation (Pd/Ir = 110). The variations in noble element patterns are complemented by variations in the Ni, Cu and Co concentrations. The massive sulphides are depleted in all three of these elements relative to the net-textured sulphide ore. The disseminated sulphides have intermediate values of Ni and Co, but are enriched in Cu relative to the other two sulphides.

Processes that could have affected the composition of the sulphides include: (a) fractionation of monosulphide solid solution (Mss) from a sulphide liquid during initial cooling of the komatiite, and (b) mobilization of Pt, Pd, Au, Cu, Ni and Co from the massive sulphide into footwall veins. A mass balance calculation indicates that the sum of the massive and net-textured sulphide agrees with the disseminated sulphide for all elements except Au. Thus the massive sulphide cannot have lost significant amounts of Pt, Pd, Ni and Co to footwall veins and significant mobilization of these elements does not appear to have occurred. The crystallization of Mss from a sulphide liquid will account for the enrichment of Ir, Os, Ru and Rh in the massive sulphide relative to the net-textured sulphide, and enrichment of Pd, Pt, Au, Co and Ni in the net-textured sulphide relative to the disseminated sulphide.

In the pre-Anglian Pleistocene of East Anglia and Essex are unfossiliferous gravels with pebbles of flint, quartz, quartzite, chert and volcanic rocks. All appear to belong to the Kesgrave Sands and Gravels of Rose & Allen (1976), which are largely or wholly fluviatile and probably of Beestonian age. Forty-six of the volcanic pebbles, from three different localities, have been examined microscopically. Almost all are fine-grained acid igneous rocks or vitric tuffs, evidently derived from a single suite. Various possible source-areas are considered, of which North Wales, with its Ordovician volcanics, is thought to be the most likely.

Fluid inclusions trapped in coesite-bearing rocks provide important information on the fluid phases present during ultrahigh-pressure metamorphism. The subduction-related coesite-bearing eclogites of the Tso Morari Complex, Himalaya, contain five major types of fluids identified by microthermometry and Raman spectroscopy. These are: (1) high-salinity brine, (2) N2, (3) CH4, (4) CO2 and (5) low-salinity aqueous fluids. These fluids were trapped during both deep subduction and exhumation processes. The coesite-bearing rocks are inferred to have been buried to a depth of >120 km, where they experienced ultrahigh-pressure metamorphism. The fluid–rock interaction provides direct evidence for fluid derivation during a deep subduction process as demonstrated by silica–carbonate assemblages in eclogite. High salinity brine, N2 and CH4 inclusions are remnants of prograde and peak metamorphic fluids, whereas CO2 and low-salinity aqueous fluids appear to have been trapped late, during uplift. The high-salinity brine was possibly derived from subducted ancient metasedimentary rocks, whereas the N2 and CH4 fluids were likely generated through chemical breakdown of NH3-bearing K minerals and graphite. Alternatively, CH4 might have been formed by a mixed fluid that was released from calcareous sediments during subduction or supplied through subducted oceanic metabasic rocks. High density CO2 is associated with matrix minerals formed during granulite-facies overprinting of the ultrahigh-pressure eclogite. During retrogression to amphibolite-facies conditions, low-salinity fluids were introduced from external sources, probably the enclosing gneisses. This source enhances salinity differences as compared to primary saline inclusions. The subducting Indian lithosphere produced brines prior to achieving maximal depths of >120 km, where fluids were instead dominated by gaseous phases. Subsequently, the Indian lithosphere released CO2-rich fluids during fast exhumation and was then infiltrated by the low-salinity aqueous fluids near the surface through external sources. Elemental modelling may improve quantitative understanding of the complexity of fluids and their reactions.

The Lower Yangtze foreland basin is situated to the northwest of the early Palaeozoic Wuyi–Yunkai orogen in South China. To demonstrate its provenance history and the denudation of the orogen, seven sandstone samples were collected from the upper Ordovician to Silurian strata for U–Pb dating. The zircons show a broad range of ages that can be linked with the ages of specific units in the Wuyi–Yunkai orogen. The zircon spectra in the late Ordovician samples are similar to those in the pre-orogenic strata, suggesting a recycled source. The dominant age population of 880–740 Ma in the early Llandovery samples indicates that the middle Neoproterozoic volcanic rocks were the primary source. A significant age population of 460–425 Ma in the late Llandovery to Wenlock samples reflects the fact that the synorogenic magmatic and metamorphic rocks were exposed to provide detritus. The youngest zircons from the uppermost Silurian strata yield an age of 425 Ma, which approximates the inferred depositional age. This age, together with available biostratigraphic data, indicates that the foreland basin was formed 448–425 Ma ago. We surmise a possible link between the Wuyi–Yunkai orogen and the Appalachian–Caledonian orogen based on the geological constraints and palaeomagnetic data.

Subduction initiation is a cornerstone in the edifice of plate tectonics. It marks the turning point of the Earth's Wilson cycles and ultimately the supercycles as well. In this paper, we explore the consequences of subduction zone invasion in the Atlantic Ocean, following recent discoveries at the SW Iberia margin. We discuss a buoyancy argument based on the premise that old oceanic lithosphere is unstable for supporting large basins, implying that it must be removed in subduction zones. As a consequence, we propose a new conceptual model in which both the Pacific and the Atlantic oceans close simultaneously, leading to the termination of the present Earth's supercycle and to the formation of a new supercontinent, which we name Aurica. Our new conceptual model also provides insights into supercontinent formation and destruction (supercycles) proposed for past geological times (e.g. Pangaea, Rodinia, Columbia, Kenorland).

Chlorite–mica stacks in the Wenlock turbidites have been studied using backscattered electron microscopy and electron microprobe analysis, combined with thin-section work and bulk rock chemical analysis. The stacks occur in fine sandstones and silt–mud turbidites and range in length from < 30 μm to 1.5 mm. They consist of interlayered packets of Fe-rich chlorite and mica.

Combined textural and chemical data suggest that many of the stacks represent altered detrital biotite micas. A four-stage alteration sequence is proposed:

(1) Subaerial alteration of biotite, in the source area, to interlayered biotite–hydrobiotite/vermiculite.

(2) Post-depositional collapse of vermiculite to form a mica phase under conditions of high K+/H+ in the sediment pore waters.

(3) Decrease in K+/H+ ratio, possibly due to H+ build up in the fermentation zone, causing alteration of biotite layers to chlorite.

(4) Kinking of the stacks and pressure solution of chlorite early in the development of cleavage.

In his paper on “The Yellow Limestone of Jamaica and its Mollusca” (Geological Magazine, Vol. LX, 1923, p. 345) Dr. C. T. Trechmann referred to an Upper Senonian fauna from shales at Providence, near Port Antonio, underlying a limestone with Rudistae. He recorded Baculites from the upper portion of these shales, and “rather low in the sequence” he collected some ammonites, one of which had been identified by the writer as belonging to the genus Parapachydiscus. The Shales at Providence had already been mentioned by the late Mr. Lucas Barrett1 as containing Baculites and Hamites, and in his collection, now in the British Museum (Natural History), there are preserved a number of fossils including the Pholadomya and Trigonia he recorded and two fragments of Hamites. The matrix of these is the same as that of Dr. Trechmann's examples, namely a brown calcareous sandstone, and the ‘Hamites’ in both collections belong to the same species, but Mr. Lucas Barrett's Baculites I have not been able to trace.

Ion microprobe (SIMS) dating shows that three plutonic rock bodies representative of the major, ∼15 000 km2, late tectonic (late-D3), plutonic rock series in the Central Iberian Zone of the Hercynian belt in west-central Iberia have indistinguishable zircon crystallization ages. Ledrada biotite granite and Colmenar cordierite-bearing biotite granite show gradual transitions in field appearance, petrography and chemistry and have statistically indistinguishable weighted average ages of 306.8 ± 1.9(2σ) Ma and 306.5 ± 1.5(2σ) Ma, respectively, which indicates that they originated during a single event involving a heterogeneous magma which notably varied in Al-content. The third rock body, Navahermosa meta-gabbronorite, has a weighted average zircon crystallization age of 305.6 ± 1.4(2σ) Ma, statistically indistinguishable (variance analysis, F-test, α = 0.05) from the granites. Zircon crystals in the gabbronoritic rock are anhedral, skeletal, millimetre-sized and partake in main magmatic textures, whereas the zircon grains in the granites are of more common appearance, much smaller, usually euhedral and enclosed in main magmatic crystals. As gestation times of granitic zircon, the time between zircon crystallization and magmatic intrusion, may be up to 5 Myr, the crystallization age of the gabbronoritic zircon may be the best estimate of the time of emplacement of the magmatic complex. Our study indicates co-existence of basic and silicic magmas in the Hercynian crustal section at c. 306 Ma, suggesting common genetic control. The two granitic rocks carry inherited zircon ranging from c. 1300 to 330 Ma, indicating that pre-Hercynian basement rocks of Proterozoic to Palaeozoic age contributed to the granitic magma.

Four species of Ophisaurus, O. fejfari, O. spinari, O. robustus and O. holeci, are recognized on the basis of parietals from the Early Miocene of the Czech Republic and Germany. The fifth species, O. acuminatus, is described from the Late Miocene of Germany, but its parietal is not preserved. This paper describes new O. fejfari, O. spinari, O. robustus and O. holeci specimens from the Early and Middle Miocene of the Czech Republic and Germany. The O. fejfari and O. holeci parietals from Germany are the first records of these species outside the Czech Republic. This paper provides a significant contribution to the understanding of both interspecific and intraspecific Ophisaurus variability in the Cenozoic of Europe. A well-preserved parietal of Anguis rarus sp. nov. is described from the Early Miocene of Germany. This is the first record of the parietal of Anguis in the Cenozoic. A new parietal from the Middle Miocene of Germany is described as Pseudopus sp. It differs from the contemporaneous P. laurillardi only in the absence of the large and distinctly laterally projecting anterolateral processes of the parietal. In the Miocene, Ophisaurus and Pseudopus exhibit a higher diversity than that of the preceding geological periods of the Cenozoic. Besides, Ophisaurus emigrates from Europe to (1) Asia and via the Bering Strait to North America, and (2) North Africa during the Oligocene and Miocene. By contrast, Anguis and Pseudopus are limited to Eurasia. The palaeobiogeography of members of Anguinae is discussed.

Fossils of Mesozoic terrestrial vertebrates from Lithuania and the wider East Baltic region of Europe have previously been unknown. We here report the first Mesozoic terrestrial vertebrate fossils from Lithuania: two premaxillary specimens and three teeth that belong to Phytosauria, a common clade of semiaquatic Triassic archosauriforms. These specimens represent an uncrested phytosaur, similar to several species within the genera Paleorhinus, Parasuchus, Rutiodon and Nicrosaurus. Because phytosaurs are currently only known from the Upper Triassic, their discovery in northwestern Lithuania (the Šaltiškiai clay-pit) suggests that at least part of the Triassic succession in this region is Late Triassic in age, and is not solely Early Triassic as has been previously considered. The new specimens are among the most northerly occurrences of phytosaurs in the Late Triassic, as Lithuania was approximately 7–10° further north than classic phytosaur-bearing localities in nearby Germany and Poland, and as much as 40° further north than the best-sampled phytosaur localities in North America. The far northerly occurrence of the Lithuanian fossils prompts a review of phytosaur biogeography and distribution, which suggests that these predators were widely distributed in the Triassic monsoonal belt but rarer in more arid regions.

The updated geological and potential fields data on the East European Platform margin in SE Poland confirm the existence of several regional units differing in Ediacaran to Silurian development: the Upper Silesian Block, Małopolska Block and Łysogóry Block. All the blocks are characterized by a distinct crustal structure seen in Vp velocity models obtained from the seismic refraction data of the CELEBRATION 2000 Programme. The first two units are interpreted as exotic terranes initially derived from Avalonia-type crust and ultimately accreted before the late Early Devonian. The Łysogóry Block is probably a proximal terrane displaced dextrally along the Baltica margin. The sutures between the terranes do not precisely match lateral gradients in Vp models. This is partly explained by a limited resolution of refraction seismic data (20 km wide interpretative window). Most of the difference is related, however, to a post-accretionary tectonism, mainly Variscan transtension–transpression. The latter processes took advantage of lithospheric memory recorded earlier as zones of rheological weakness along the former suture zones. The course of the East European Platform margin (= Teisseyre–Tornquist Zone) corresponds most likely to the Nowe Miasto–Zawichost Fault marking the NE boundary of the proximal Łysogóry Terrane.

The middle Cambrian Lejopyge laevigata Zone is poorly exposed in Scandinavia. Both this zone, however, and the succeeding Agnostus pisiformis Zone are well exposed at a classic locality at Gudhem, Västergötland, south-central Sweden. The sequences consist of finely laminated alum shale with scattered stinkstone (orsten) lenses. Three measured and sampled sections yielded a diverse fossil fauna, dominated by trilobites, in particular agnostoids, and the bradoriid Anabarochilina primordialis. Fossils are excellently preserved but restricted to the stinkstones. The L. laevigata Zone at Gudhem includes several geographically widespread key agnostoid species, notably Tomagnostella sulcifera, Clavagnostus spinosus, Glaberagnostus altaicus, Lejopyge laevigata and L. armata. The L. laevigata Zone in Scandinavia is here extended to include the traditional Solenopleura? brachymetopa Zone, and its lower boundary is defined by the FAD of L. laevigata. Trilobite evidence shows that the upper part of the Scandinavian L. laevigata Zone approximately correlates with the Proagnostus bulbus Zone of China and elsewhere.

The Comores Archipelago comprises four principal islands, lying in a WNW–ESE line at the northern end of the Mozambique Channel. The Islands are almost entirely volcanic and show a simple age progression from Grande Comore, with its active shield volcano Kharthala (2650m), east-south-eastwards through Mohéli and Anjouan, which are quite deeply dissected, to Mayotte, which is in an advanced stage of erosion and subsidence, and is encircled by a barrier reef. There is also evidence of minor volcanic rejuvenation in relatively recent times in Mayotte, and perhaps Anjouan and Mohéli. The lavas of Kharthala, and the neighbouring extinct shield volcano (Massif de la Grille) on Grande Comore are all basaltic, ranging from oceanitic and ankaramitic to aphyric types. Numerous tuff cones occur, especially on the flanks of Massif de la Grille. Basaltic lavas, similar to those of Grande Comore, form the bulk of the dissected volcanic shields of Mohéli and Anjouan, but there is also evidence of differentiation towards alkalic under-saturated end products, both as lavas and as intrusive bodies. Lherzolitic and gabbroic nodules are locally abundant on each of the islands, while xenoliths of sandstone and quartzite have been found on the three westernmost islands. Petrochemical data are presented for a considerable variety of Comores rocks, and the volcanic activity is discussed in terms of the major structural features of the Madagascar-Mozambique region.

A number of acid plutonic xenoliths from the volcano Surtsey are described, along with fine-grained rock fragments, consisting chiefly of anorthitic plagioclase and tridymite. The chemistry of the xenoliths indicates a compositional pattern from tonalitic to pyrometamorphic types. A hypothesis is put forward that the tonalitic xenoliths have undergone partial fusion during transport to the surface in the basaltic magma, and the removal of a salic liquid from granitic xenolith into the magma has resulted in the formation of a residue of anorthitic plagioclase and tridymite. Granitic xenoliths from other parts of Iceland, and their fusion products, are also described.