The submerged forearcs of Pacific subduction zones of North and South America are underlain by a coastally exposed basement of late Palaeozoic to early Tertiary age. Basement is either an igneous massif of an accreted intra-oceanic arc or oceanic plateau (e.g. Cascadia(?), Colombia), an in situ formed arc massif (e.g. Aleutian Arc) or an exhumed accretionary complex of low and high P/T metamorphic facies of late Palaeozoic (e.g. southern Chile, Patagonia) and Mesozoic age (e.g. Alaska). Seismic studies at Pacific forearcs image frontal prisms of trench sediment accreted to the seaward edge of forearc basement. Frontal prisms tend to be narrow (10–40 km), weakly consolidated and volumetrically small (∼35–40 km3/km of trench). In contrast, deep seismic imaging of submerged forearcs commonly reveals large volumes (∼2000 km3/km of trench) of underplated material accreted at subsurface depths of ∼10–30 km to the base of forearc basement. Underplates have been imaged below the southern Chile, Ecuador–Colombia, north Cascade, Alaska, and possibly the eastern Aleutian forearcs. Deep underplates have also been observed below the Japan and New Zealand forearcs. Seismic imaging of northern and eastern Pacific forearcs supports the conclusion drawn from field and laboratory studies that exposed low and high P/T accretionary complexes accumulated in the subsurface at depths of 10–30 km. It seems significant that imaged underplated bodies are characteristic of modern well-sedimented subduction zones. It also seems likely that large Pacific-rim underplates store a significant fraction of sediment subducted in Cenozoic time.

From the proposition of Professor Forbes, that a species once extinct never reappears, it follows that when a species recurs, it must have existed elsewhere during the whole of the time occupied by the deposition of the strata between the deposits containing it. In viewing the distribution of species through the cheif stages of the Lower Cretaceous system, it appears that the same species reappear when there is a recurrence of the same or similar physical conditions,—the Neocomian and Albian clays having more species in common than the intervening Aptian; and the Aptian and Cenomanian sands, being more closely allied than the intervening Albian clay. An examination of the latter, at Folkestone, appears to allow of its being divided into eleven lithological stages or beds which have been more or less recognized by all geologists and fossil collectors who have visited the district. To these beds provisional names have been assigned expressive either of their colour, position, or characteristic fossils. But in tracing all the recurring species from their genesis in one stratum to their extinction in another, these beds are found to have no great palæontological value, but to resolve themselves into two groups divided by a junction bed, in the same way as the “junction bed” separates the Albian from the Upper Aptian. Beds I. to III. forming an Upper, beds V. to X. a Lower Albian, beds IV. and XI. being the two phosphate junction beds,

The conditions under which ptygmatic veins develop occur when the country-rock—as in a granitized area—is locally less competent or more yielding than quartzo-felspathic magma which may intrude it. Veins therefore which are being driven forward by pressure from behind, will buckle plastically if they encounter a resistance during injection, and a succession of such buckles will produce a typical ptygmatic vein. The amplitudes of the flexures so formed depend on the relative physical states of the vein and host-rock; so for any particular vein there is usually a more or less constant size for the tortuosities developed. The mechanism explains several features observed in examples of ptygmatic veins, and has been reproduced experimentally in the laboratory. The contortions are therefore not necessarily due to the deformation of the veins by post-injection flowage or tectonic movements of the country-rock.

The first specimen of the ankylosaur genus Polacanthus from the mainland Barremian of southeast England is described as Polacanthus rudgwickensis sp.nov. Polacanthus rudgwickensis is larger than Polacanthus foxii, and there are significant differences in the dermal armour, the tibia and caudal vertebrae of the two species. Polacanthus foxii appears to be restricted at present to the Isle of Wight with one specimen from southwest England, whilst Polacanthus rudgwickensis is only known from Sussex. This geographical distribution, the palaeobiological implications and possible sexual dimorphism are discussed for this genus.

Acritarchs of Lower Cambrian age have been recovered from a clay horizon within conglomerates 6 m above the unconformity described by Cope & Gibbons (1987). The Wrekin Quartzite (34 m thick) represents beach deposits grading upwards into shelf sandstones. The stratigraphie evidence and recent age determinations suggest that although the granophyre was intruded at 560 ± 1 Ma the Cambrian Unconformity is younger than 533 ± 13 Ma.

Studies on the distribution of manganese-bearing rocks in the Birimian and their relationship with gold mineralization are still in progress. Both manganese and gold occur as stratabound lenses within volcano-sedimentary sequence. Evidence of pre- and post-tectonic mineralizations are present. Sedimentological evidence also suggests both may have been contemporaneous with their host rocks in an environment that was strongly Eh and pH controlled. Under present tropical conditions, other elements associated with Birimian gold mineralization, notably copper and arsenic, are highly mobile to remain in residual soils. However, manganese, like iron, remains in residual soils as oxides and could be a useful pathfinder element in the search for gold in tropical lateritic soils derived from Precambrian greenstones.

The Neoproterozoic Jiangnan orogenic belt records the accretion and collision between the Yangtze and Cathaysia blocks in South China. The orogen is divisible into three units: a northeastern domain (also referred to as the Huaiyu or Shuangxiwu domain), a central domain (Jiuling domain) and an undifferentiated southwestern domain. Detrital zircons from the oldest sequences (Shuangqiaoshan, Lengjiaxi, Fanjingshan and Sibao groups) in the central and southwest domains yield similar age spectra with major age populations at c. 875–820 Ma, along with minor Palaeo- to Mesoproterozoic and Archaean ages. The dominance of detrital ages close to the deposition ages of the units, along with juvenile zircon Hf isotopic compositions and arc-like whole-rock compositional data, indicate the sedimentary units accumulated adjacent to a convergent plate margin magmatic arc. The presence of Mesoproterozoic and older zircons, both as detritus in the units and as xenocrysts within igneous rocks displaying a subduction-related signature, along with the compositional data, place the magmatic arc along a continental margin. In the northeastern domain, the oldest coeval sequence (Shuangxiwu and Qigong groups) and arc igneous suites are dated at c. 970–850 Ma, and lack older detritus and xenocrysts, indicating they represent an accreted oceanic arc system.

The Caledonian deformation of the Brabant Massif and the Rügen Early Palaeozoic has been compared by structural analysis including strain determinations, X-ray texture analysis, illite crystallinity and vitrinite reflectivity. Both areas have experienced weak internal deformation under anchimetamorphic to very low-grade metamorphic conditions. The deformation of the Brabant Massif is characterized by (a) a pronounced diagenetic foliation which resulted from compaction and weak extensional tectonics; (b) tilting or weak folding of the Cambrian strata around the Cambrian/Ordovician boundary without internal deformation; (c) a main phase of Caledonian deformation in the Lower Devonian which was associated with open folding and an axial-plane pressure solution cleavage; (d) bending of Caledonian structures from northwest–southeast to northeast–southwest. The internal deformation appears homogeneous with decreasing strain values towards upper structural levels. The strain ellipsoid is predominantly prolate with the main axis of extension parallel to the bedding–cleavage intersection lineation. It is interpreted as the result of superposition of compaction, tectonic shortening and volume loss through pressure solution. The Rügen Early Palaeozoic is less deformed and less metamorphosed under anchizonal conditions. While the upper structural level is almost undeformed, towards the deeper structural levels a spaced and then a continuous slaty cleavage is developed which is successively crenulated by a fracture cleavage. The internal deformation appears inhomogeneous due to several thrust zones with somewhat higher strain values. Outside the thrust zones strain values increase towards lower structural levels, but not significantly. The strain ellipsoid is prolate with a strongly varying orientation of the X-axis. The structural inventory of both areas is comparable with other fold-and-thrust belts. While the Rügen Palaeozoic represents an imbricated thrust-fan of an upper structural level with discrete thrusts and inhomogeneous strain, the Brabant Massif represents a deeper structural level dominated by folding and more homogeneous internal deformation.

There is a lead-zinc (with subsidiary copper) metallogenic province on each side of the Vale of Eden. To the east the veins of the Alston Block are found in Carboniferous rocks and a Hercynian age is the generally accepted date of the mineralization. To the west the veins lie in the Lower Palaeozoic rocks of the Lake District. Within the latter area ore-veins associated with the Shap Granite are, by common consent, regarded as of Caledonian age. But these apart, there is a regional mineralization in the Lake District, best developed in the northern part of that topographical unit, which has also been regarded as of Hercynian age.

The helium method of determining the ages of fine-grained basic igneous rocks has now been so far developed as to be applicable to various geological and petrological problems, particularly where geological periods are involved, as in the problem here discussed. For details of the history of this development up to the beginning of 1937 reference may be made to Holmes, 1931; Urry, 1933; Lane and Urry, 1935; Urry, 1936 (b); Holmes and Paneth, 1936; and Holmes, 1937. During 1937 it was found that many of the helium-ratios on which the ‘helium’ time-scale had been based were too high, because of a previously unsuspected error in radium determination due to reliance having being placed on a radium standard which was seriously at fault. To clear up this embarrassing situation an immediate effort was made by several investigators in collaboration, and the first fruits of their work have recently become available (Evans, Goodman, Keevil, Lane, and Urry, 1939).

Stratigraphic fluctuations of carbon isotope values of terrestrial organic matter within the Upper Cretaceous (Cenomanian–Santonian) sequence in the Obira area of Hokkaido, Japan, record distinctive δ13C fluctuations for the Cenomanian–Turonian boundary, the Middle Turonian, the upper Turonian–lower Coniacian, and the Santonian. A biostratigraphic framework of the age-diagnostic taxa (ammonoids, bivalves and planktic foraminifers) indicates that these δ13C fluctuation events are comparable with those recorded in δ13C data of terrestrial organic matter in Japan and marine carbonates in Europe. These correlations reinforce the utility of these δ13C events in terms of global chemostratigraphy. In particular, the δ13C patterns within the overall positive interval of the Cenomanian–Turonian boundary event are highly conformable between marine and terrestrial records. The consistent nature of these different records of δ13C fluctuation patterns demonstrates that the terrestrial organic δ13C data mirror the global-scale δ13C patterns in the carbon reservoir of ocean–atmosphere–terrestrial biosphere during the Cenomanian–Turonian boundary event. In addition, global correlation of short-term marine and terrestrial organic δ13C fluctuations of the Upper Cretaceous sequence indicate that the magnitude of several terrestrial organic δ13C events appears more amplified than that of coeval marine carbonate δ13C events. This correlation is interpreted to mean that the effects of local CO2 emission into the atmosphere by release of terrestrial methane hydrate or biomass burning of terrestrial vegetation in the hinterland of the NE Asian region have been superimposed on the global δ13C trend and resulted in the terrestrial organic δ13C records of the Yezo Group.

Recent papers and discussions have called attention to the fauna of the Yoredale facies of the Lower Carboniferous. These beds are well exposed in the valleys of Wensleydale and Swaledale in North West Yorkshire and they are there, perhaps, the most fossiliferous. As this is the type district for the Yoredale series, a brief statement of the more important faunal horizons would not be out of place.

Reptilian bones, first observed by Mr. C. I. Gardiner in 1935, are found in two quarries in the Chipping Norton Limestone (top of Inferior Oolite, fusca and zigzag hemerae). These two quarries are the New Park Quarry, about 2½ miles N.W. of Stow-on-the-Wold, and the Oakham Quarry which lies about a mile W.N.W. of Little Compton. The bones occur in a hard cream-coloured limestone which is worked for road-metal. Fossils other than reptilian remains are not common, but among those found in the New Park Quarry is an ammonite determined by Mr. J. W. Tutcher as Parkinsonia neuffensis Oppel. The great majority of the bones come from the New Park Quarry, but the Oakham Quarry yielded certain of the crocodilian, theropod, and sauropod bones.

The increasing diversity of interpretation of the Jurassic Record is proving very troublesome to teachers and students alike. “To-day, hardly a subdivision of the Jurassic is free of controversy as to its exact scope and nomenclature,” wrote S. W. Muller in a recent laudable attempt to reconcile the differing opinions. More is involved, however, than a mere reconciliation of conflicting views. Our knowledge of the Jurassic Record is as yet far less complete than many geologists realize. For while some of the subdivisions of Jurassic time are in general use by all stratigraphers and have stood the test of time, others are in dispute because they are still based on too local and often defective material, or on too incomplete information; a number remain as much surmises as when they were originally introduced. Any scheme put forward at the present day cannot thus be regarded as the final word in the subdivision of the Jurassic, but merely as a contribution towards an ultimate, ideal, “Standard.”

An integrated bio-, magneto- and cyclostratigraphic study of the Ypresian/Lutetian (Early/Middle Eocene) transition along the Otsakar section resulted in the identification of the C22n/C21r chron boundary and of the calcareous nannofossil CP12a/b zonal boundary; the latter is the main correlation criterion of the Lutetian Global Stratotype Section and Point (GSSP) recently defined at Gorrondatxe (Basque Country). By counting precession-related mudstone–marl couplets of 21 ka, the time lapse between both events was calculated to be 819 ka. This suggests that the age of the CP12a/b boundary, and hence that of the Early/Middle Eocene boundary, is 47.76 Ma, 250 ka younger than previously thought. This age agrees with, and is supported by, estimates from Gorrondatxe based on the time lapse between the Lutetian GSSP and the C21r/C21n boundary. The duration of Chron C21r is estimated at 1.326 Ma. Given that the base of the Eocene is dated at 55.8 Ma, the duration of the Early Eocene is 8 Ma, 0.8 Ma longer than in current time scales. The Otsakar results further show that the bases of planktonic foraminiferal zones E8 and P10 are younger than the CP12a/b boundary. The first occurrence of Turborotalia frontosa, being approximately 550 ka older that the CP12a/b boundary, is the planktonic foraminiferal event that lies closest to the Early/Middle Eocene boundary. The larger foraminiferal SBZ12/13 boundary is located close to the CP12a/b boundary and correlates with Chron C21r, not with the C22n/C21r boundary.

A graptolite biostratigraphy is erected for the upper Telychian (upper crenulata Biozone) to lower Sheinwoodian (riccartonensis or dubius Biozone) strata of the Jabalón River section, Spain. Two unconformities are recognized in the section: one between the lapworthi and murchisoni biozones; the other between the murchisoni and riccartonensis biozones. These unconformities coincide with intervals of lowered eustatic sea-level. Graptolite assemblages include both cosmopolitan taxa and some which have been recorded previously from Morocco and/or other Spanish sections. At some stratigraphical levels Pristiograptus or Euroclimacis species are abundant; Monoclimacis, Streptograptus and Mediograptus species are generally uncommon. Conodonts were examined from the upper spiralis through to lower murchisoni Biozone; the occurrences of Pterospathodus amorphognathoides are consistent with the species' known range elsewhere. Four new graptolite species are described: Euroclimacis jabalonensis, E. hamata, Monoclimacis flexa and Stimulograptus pradoi.

The time range and proportional distributions of Permian brachiopod families are summarized for the Permian Period. The ‘imperfection’ of the record is calculated from the apparent absences of families known to have survived. It is shown that the phylum changed in composition during the late Middle and Late Permian, with increased importance of Orthida, Strophalosiacea, and Oldhaminida at the expense of the Productacea. Changes were over-printed by loss of families, markedly later than the extensive contraction of shelf-seas, concurrent probably with significant changes in geo chemistry and trophic resources. A number of highly significant families survived into the time of renewed transgression during the Otoceras and Ophiceras ammonoid zones, usually classed at the base of the Triassic Period. The demise of most Permian families proceeded in concert with climatic changes, but the initial deaths of families appear to have been caused by some other unknown factor, which may have severely disrupted Permian communities and biomes, and caused them to respond more than usual to climatic oscillations.

This is the first of a series of contributions dealing with various aspects of the petrology of Barnavave Mountain which have not been touched upon by earlier investigators. The general relationships existing between the various rock types on Barnavave were first described by Traill in 1878, though some of the rock types had been previously dealt with by Haughton. This was followed by the now classical work of Sollas on some of the hybrids occurring on the western side of the mountain. These are at present being redescribed by Dr. G. D. Osborne in a paper which will appear shortly. More recently, the Carlingford area as a whole has been dealt with by Richey and Osborne has described the metamorphosed limestones of the region. Many of the rock types, however, have never been described in detail, if at all, and it is with these that the present contributions are concerned. The author wishes to express his thanks to Prof. W. J. Pugh, Prof. C. E. Tilley and Dr. G. D. Osborne for facilitating the work in various ways, to acknowledge a grant from the Worts fund and a Royal Society grant which defrayed the cost of two of the analyses. The field work was carried out in 1932 but unforeseen circumstances prevented the earlier working up and publication of the results.

New work on the sedimentology and palaeontology of the classic area of the ‘basinal’ facies of the Carboniferous Limestone requires that a formal lithostratigraphic framework be established to rationalize the existing system of local rock units and regional lithofaunal ‘groups’ and ‘series’. Five formations, based on the existing ’groups‘ in the Clitheroe area, are defined for the whole Craven Basin outcrop. They are, from the base, the Chatburn Limestone Formation, the Clitheroe Limestone Formation (which includes the ’reef-knolls’ of the Clitheroe area), the Worston Shale Formation, the Pendleside Limestone Formation (to include the knolls of the Craven reef belt) and the Bowland Shale Formation. The chronostratigraphy, in terms of the six British Dinantian Stages, and a provisional micropalaeontological biostratigraphy are outlined.

The proposed correlation of Lower Old Red Sandstone dacitic ignimbrites between the Northern Midland Valley and Grampian terranes of central Scotland has been investigated in a combined palaeomagnetic and geochemical study. Statistically indistinguishable late Silurian palaeolatitudes (Grampian terrane 27.0° S±3.5°; Northern Midland Valley terrane 22.9° S± 1.8°), comparable remagnetization histories, a shared ‘normal’ polarity for the primary magnetization and equivalent gyroremanence acquisition, favour correlation across the Highland Boundary Fault. Similar chemistry for biotite phenocrysts further corroborates correlation which was initially made on the basis of a similar field appearance and petrography.

This correlation, together with evidence from provenance studies, suggests that the separation of the Northern Midland Valley and Grampian terranes inferred for the Ordovician period was largely removed by late Silurian times, with scope for relative displacements of the order of only tens of kilometres after Lower Old Red Sandstone deposition.