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.

Core material from proven or probable Silurian sedimentary rocks beneath East Anglia has been re-examined. Four recognizable facies probably represent an environmental transition from anoxic basin slope or outer shelf through oxygenated outer shelf to storm-dominated inner shelf. This transition could have occurred laterally, from east to west across the Anglian Basin, or in time, from Llandovery (early Silurian) up to Př (late Silurian). Partial biostratigraphical constraints allow either interpretation, but the regional setting favours a marked facies transition through time as the Anglian Basin shallowed prior to the Acadian Orogeny. Reddening of the Silurian is mostly secondary beneath the sub-Triassic unconformity.

An intrusion-breccia filling a pipe is made of two parts, one of facetted quartzite fragments in a granophyric matrix, the other of calc-silicate-rock fragments in an appinitic matrix. The quartzite fragments are derived from a horizon at least 1,000 ft. below the breccia level, the calc-silicate-rock fragments are local. The mechanism of emplacement of the breccia is considered to be similar to that proposed by H. Cloos for the Swabian tuff-pipes. Neither the granophyre nor the appinite of the Kilkenny pipe is regarded as of magmatic origin.

The Boom Clay Formation of northeast Belgium consists of a sequence of alternating, laterally persistent beds of silt and clay. Power-spectral analysis of grain-size variations indicates regular sedimentary cycles with wavelengths of about 100 and 46cm that had periods of 124 and 57 thousand years (ka) or less. The lateral continuity ofthe beds, combined with the regularity and estimated periods of the cycles, suggests an indirect link to the 100 and 41 ka orbital (Milankovitch) cycles. The variations in meangrain size were caused by changing bottom-water turbulence as controlled by storms and/or glacio-eustatic water depth fluctuations. This study confirms that certain marinesiliciclastic sequences can provide proxy-records of palaeoclimatic variance.

A series of metamorphosed (amphibolite facies) basic and intermediate igneous rocks from upper Swat, Pakistan, is described, with seven chemical analyses. The rocks intrude ?Palaeozoic metasediments and are partially bordered by other, later, intrusive and volcanic rocks. The group, now represented by, from S–N, epidote amphibolites, amphibolites, noritic and hypersthene gabbros, and quartz diorites, is considered to be derived from a series of plagioclase hypersthenites, norites, hypersthene gabbros, and hypersthene diorites. Variation diagrams are used to show that the series forms a differentiated sequence; FMA and lime-alkali diagrams suggest that it is similar to the rocks of the Garabal Hill–Loch Fyne area of Scotland. Some of the mineralogy of the group is briefly discussed, with five chemical analyses. A K/Ar age determination gives 67 Ma; thus the rocks probably derive from an early Himalayan (Alpine) tholeiitic basalt magma.

A nesw Ophiceratid genus and species Durvilleoceras woodmani is described from the late Middle Permian Greville Formation of New Zealand, with Episageceras aff noetlingi Haniel. The horizon is close in age to the Kathwai dolomite of the Salt Range, which also has a mid-Permian Ophiceratid species, Ophiceras connectens Schindewolf. The occurrence of these two species shows that the Ophiceratidae cannot serve as an index of early Triassic rocks. The so-called basal Triassic Griesbachian Stage may prove to be closely linked to the Permian period. The key Griesbachian ammonoid genus Otoceras is related to Permian genera, with no later survivors. Moreover the widespread occurrence of Permian-type Productacea and other brachiopods in beds of the Griesbachian Stage in North America and Himalayas also suggests that the Griesbachian is Permian rather than Triassic. To judge from faunas, the start of the Triassic could be based on the incoming of numerous ammonoid families and Triassic brachiopods in the Smithian Stage. The intervening Dienerian Stage between the Griesbachian and Smithian stages is relatively barren of faunas, reflecting some sort of catastrophe at the end of the Paleozoic Era, but has mainly Permian survivors. Such a picture of the Paleozoic–Mesozoic boundary conforms with the intention if not the practice of early paleontologists.

Sediments deposited from the Permian–Triassic boundary (~252 Ma) until the end-Smithian (Early Triassic; c. 250.7 Ma) in the Sonoma Foreland Basin show marked thickness variations between its southern (up to c. 250 m thick) and northern (up to c. 550 m thick) parts. This basin formed as a flexural response to the emplacement of the Golconda Allochthon during the Sonoma orogeny. Using a high-resolution backstripping approach, a numerical model and sediment thickness to obtain a quantitative subsidence analysis, we discuss the controlling factor(s) responsible for spatial variations in thickness. We show that sedimentary overload is not sufficient to explain the significant discrepancy observed in the sedimentary record of the basin. We argue that the inherited rheological properties of the basement terranes and spatial heterogeneity of the allochthon are of paramount importance in controlling the subsidence and thickness spatial distribution across the Sonoma Foreland Basin.

Conodonts are rare in the Permian carbonates of Indochina but abundant conodonts and ostracodes have been obtained from turbiditic limestones of the Permian E-Lert Formation along with radiolarians from overlying cherts, all deposited on the margins of the interplatform Nam Duk Basin. Conodonts are typically Tethyan and are very similar to faunas from Sicily and south China. They include Hindeodus gulloides, Pseudohindeodus oertlii, Mesogondolella siciliensis and Sweetognathus subsymmetricus which indicate a probable late Kungurian – Roadian age range although a Wordian age cannot be excluded. M. siciliensis, which has a high blade and small cusp supposedly typical of warm-water conodonts, is found in deep (<500 m) carbonate turbidites in Thailand and in very deep deposits in Oman and Sicily, but generally not in shallow-water tropical limestones in Thailand, Oman and Sicily. The chert sequence yields a radiolarian fauna consisting of 11 confidently assigned species of which Albaillella asymmetrica, A. sinuata, Tormentum delicatum and Latentifistula patagilaterata suggest a latest Kungurian – earliest Roadian age, deposited at a palaeodepth of c. 500 m. Ostracodes consist of 16 genera and 23 species which belong to Shivaella, Paraberounella, Carinaknightina, Paraparchites, Shemonaella, Bairdia, Cryptobairdia, Bairdiacypris?, Spinocypris, Pseudobythocypris, Baschkirina, Microcheilinella, Basslerella, Polycope and Cyathus, of which Shivaella elertensis sp. nov. Chitnarin is newly described. The ostracodes are a palaeoecologically mixed assemblage comprising external platform and deeper-water forms, suggesting that the limestone turbidites were deposited on the proximal part of the slope. Cyathus caperata and C. elliptica show a palaeobiogeographic link to south China.

Re-assessment of the idea that the Monian and Longmyndian accumulated along the margin of a palaeo-ocean suggests that Monian sedimentation occurred near the eastern shoreline of a micro-continent. If Monian igneous activity, metamorphism and deformation are attributed to an underlying subduction zone, this must have dipped northwestwards away from a small ocean basin to the southeast. Consumption of this ocean floor brought about collision with the continental shield and simple deformation of the Longmyndian.

Ultrapotassic plutons from several domains of the Variscan orogenic belt have been in turn interpreted as syn- to post-orogenic due to their age spread, but assessment of their geodynamic setting and source regions is still open to interpretation. In the Svoge region (Bulgaria), at the southern margin of the Balkan orogen, peralkalic plutons are hosted within Ordovician pelites. The main intrusion, with lamproitic affinity, which hosts monzodiorite xenoliths and a polyphase syenite suite, was emplaced at a shallow level. 40Ar–39Ar dating by step-heating of amphibole and biotite yielded a Early Carboniferous intrusion age for the main body (337 ± 4 and 339.1 ± 1.6 Ma). The lamproite intrusion is silica-rich compared with bona fide lamproites and characterized by moderate LILE and LaN/YbN enrichments. Sr and Nd isotopic data (initial ϵNd in the range −4.87 to −5.88) suggest an origin in a depleted lithospheric mantle, possibly refertilized by eo-Variscan subduction. The high-K syn-tectonic plutonism in several zones of the Variscan orogen (Bohemian, Austro-Alpine, Vosges, French and Corsica domains) is consistent with a derivation of high-K magmatism from partial melting of metasomatized mantle following the subduction along the collision front between Gondwana and Laurasia.

The pelitic hornfelses surrounding the Carn Chuinneag–Inchbae complex have, with the other rocks in the area, been subjected to the regional metamorphism which affected the Moine Series as a whole. The minerals of the original hornfelses have reacted to form assemblages which are typical of regional rather than purely thermal metamorphism although the massive structure of the hornfelses is well preserved.

By studying the changes which took place in the hornfelses during the regional metamorphism it has been possible to deduce the most likely mineral assemblages indigenous to the original hornfelses.

The results of the chemical analyses of some of the pelitic hornfelses are presented and chemical data on some of the garnets are given. It is considered unlikely that all the garnets in the hornfelses, which are essentially almandines, formed as a result of the earlier contact metamorphism: some at least probably occur as a result of the later regional metamorphism.

The Builth district was visited by one of us (O. T. J.) in the spring of 1939 with a view to arranging an excursion for the International Geological Congress which was to have been held in London in 1940. Amongst other places the magnificent range of quarries in the Ordovician volcanic rocks of Llanelwedd, near Builth, was examined. Beyond the western end of the quarries a striking boulder bed was observed which promised to give an insight into a remarkable episode in the history of the district. This bed is shown on the I in. Geological Survey Map, Old Series, Sheet 56, S.W.

A new species of Lepidostrobus, L. zea, is described. Two cones, from Yorkshire and from Ayrshire, and some isolated megasporangia are known. The megaspores have long been known, occurring isolated in coal, and have been described as Triletes auritus Zerndt. The microspores, also known previously from coal macerations, are of the type described as Endosporites globiformis (Ibrahim) (E. zonalis (Loose) and the C1 type of Raistrick). Endosporites has hitherto been regarded as cordaitalean (gymnosperm) pollen, and this is the first record of Endosporites from a lycopod.

Jurassic sandstones in the Xiongcun porphyry copper–gold district, southern Lhasa subterrane, Tibet, China were analysed for petrography, major oxides and trace elements, as well as detrital zircon U–Pb and Hf isotopes, to infer their depositional age, provenance, intensity of source-rock palaeo-weathering and depositional tectonic setting. This new information provides important evidence to constrain the tectonic evolution of the southern Lhasa subterrane during the Late Triassic – Jurassic period. The sandstones are exposed in the lower and upper sections of the Xiongcun Formation. Their average modal abundance (Q21F11L68) classifies them as lithic arenite, which is also supported by geochemical studies. The high chemical index of alteration values (77.19–85.36, mean 79.96) and chemical index of weathering values (86.19–95.59, mean 89.98) of the sandstones imply moderate to intensive weathering of the source rock. Discrimination diagrams based on modal abundance, geochemistry and certain elemental ratios indicate that felsic and intermediate igneous rocks constitute the source rocks, probably with a magmatic arc provenance. The detrital zircon ages (161–243 Ma) and εHf(t) values (+10.5 to +16.2) further constrain the sandstone provenance as subduction-related Triassic–Jurassic felsic and intermediate igneous rocks from the southern Lhasa subterrane. A tectonic discrimination method based on geochemical data of the sandstones, as well as detrital zircon ages from sandstones, reveals that the sandstones were most likely deposited in an oceanic island-arc setting. These results support the hypothesis that the tectonic background of the southern Lhasa subterrane was an oceanic island-arc setting, rather than a continental island-arc setting, during the Late Triassic – Jurassic period.

Altered volcanic ash interbeds (bentonites) in the upper Katian of Baltoscandia indicate significant volcanic activity in neighbouring tectonically active areas. Katian bentonites in the East Baltic can be reliably correlated using sanidine phenocryst composition. Ratios of immobile trace elements TiO2, Nb, Zr and Th to Al2O3 enable extension of the correlations to Scandinavia, where late diagenetic alterations could have caused recrystallization of sanidine phenocrysts. At least seven volcanic eruptions were recognized in Baltoscandian sections. Several bentonites found in deep-sea sediments are absent in shallow-sea sediments, indicating extensive breaks in sedimentation and erosion during late Katian and Hirnantian times. The areal distribution pattern of Katian bentonites in Baltoscandia indicates a volcanic source from the north or northwest (present-day orientation) from the margins of the Iapetus Palaeo-Ocean. Signatures of ultra-high-pressure metamorphism in the Seve Nappe (Central Sweden) and intrusions in the Helgeland Nappe Complex in Central Norway have been proposed as potential sources of the magmas that generated the volcanic ashes deposited in the East Baltic in Katian times. Geochemical similarities between Baltoscandian and Dob's Linn bentonites from southern Scotland suggest a common volcanic source in Katian times.

Recent studies in N.W. England have indicated the need for a review of Wenlock and Ludlow (Silurian) stratigraphy. Detailed re-mapping, mainly for the first time since 1872, has modified and more clearly defined the established terminology. Determinations of new graptolite and shelly faunas have resulted in a revision of some earlier work and the establishment of a modern zonal classification for parts of the Wenlock and Ludlow. Lithofacies are broadly summarized and described with comments on some palaeocurrent data.

The Shyok Suture in western Himalaya preserves a record of the opening and closure of the Mesotethys Ocean between the Shyok ophiolite and Karakoram terrane prior to the India–Eurasia collision. The formation age of the Shyok ophiolite was unknown, which impeded correlation with similar rocks along the Shyok Suture in Pakistan and corresponding sutures in Tibet. We report the first zircon U–Pb ages of a newly documented suite, here named the Changmar Complex. The Changmar Complex gabbronorite and plagiogranite yielded SHRIMP U–Pb zircon Late Jurassic ages of 159.4 ± 0.9 Ma and 151.9 ± 1.5 Ma. Their highly positive initial εHf values (+14.9 to +16.9) indicate a juvenile mantle origin, without continental crust influence on the magma source. The Shyok ophiolite represents either: (1) a separate island arc that preceded formation of the Cretaceous–Eocene Ladakh Arc; or (2) the oldest magmatism and early stage of the Ladakh Arc. Intrusive and extrusive mafic rocks from the Shyok Suture analysed in this study have typical supra-subduction zone enrichment characteristics in their geochemistry and are classified as part of the volcanic-arc ophiolite. The U–Pb age and Hf isotopic signatures for the Shyok ophiolite are similar to the Late Jurassic Matum Das tonalite within the Kohistan Arc; we therefore suggest that they are part of the same intra-oceanic island-arc system that formed in the Mesotethys Ocean prior to Late Jurassic time.

The succession in the Upper Dalradian is described. The author follows Anderson in correlating the Leny and Ben Ledi Grits. Way-up evidence indicates that the Leny Limestone does not occupy a syncline as previously supposed, but is a stratigraphical intercalation in the Leny Grits. It is shown from way-up evidence and structural analysis that the Aberfoyle Anticline closes downwards and is a synform.

Trilobites are an iconic group of extinct arthropods that lived in Palaeozoic oceans for c. 270 Ma, before their demise at the end of the Permian Period. Despite their considerable diversity (> 22 000 species) and abundance, particularly in Cambrian and Ordovician rocks, as well as intensive study for well over 200 years, trilobite systematics remains in a state of flux. In this contribution, the complex history of trilobite classification over the last century is briefly reviewed, including the seminal scheme published by Henry Swinnerton in 1915. The cryptogenesis problem, which relates to the supposedly obscure phylogenetic links between major post-Cambrian trilobite clades and their Cambrian sister taxa, is also discussed. Previous studies have suggested that the cryptogenesis problem is largely a taxonomic artefact, but the Cambrian origins of some post-Cambrian groups, such as the orders Proetida and Odontopleurida, are still unclear. Future directions for research on trilobite systematics are outlined, from taxonomic studies involving comprehensive documentation and extensive illustration of morphology at the species level, through to broad-scale phylogenetic analyses that initiate or test hypotheses about relationships across the major groups. Other ongoing issues to be addressed include identifying the sister group of Trilobita, and determining whether certain taxa, such as the suborder Agnostina and Cambrian family Burlingiidae, represent trilobites.

Sillimanite produced by the contact action of the Donegal Granite shows varied textural and time relationships with the other minerals of the schists in which it occurs. Early Sillimanite was formed in the main stage of metamorphism by destruction of biotite, K, Fe, and Mg being expelled in the process. A later influx of new K from the granite led to the growth of muscovite metacrysts. This was associated with destruction of part of the early Sillimanite, recrystallization of part, growth of a new crop of Sillimanite needles, and formation of muscovite-sillimanite intergrowths.