The only substantial descriptions of the small, generally ice-bound archipelago in eastern Svalbard were from an expedition led by Nathorst in 1898 which landed in Kong Karls Land for fourteen days. Our paper amplifies those findings, from work with a helicopter-borne expedition in 1969. The easternmost of the three main islands, and all the small islands, are formed of basic igneous rocks of Cretaceous age. Two of the main islands, Svenskøya and Kongsøya, are formed of latest Triassic to early Cretaceous strata, protected by caps of Cretaceous lava that determine their shape and the general topography. The third, Abeløya, is basaltic throughout.

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.

In three assemblages of widely differing paragenesis, sillirnanite and mullite have been found in apparently stable coexistence. This is interpreted as evidence for the presence of a miscibility gap between the two phases. A fourth occurrence, remini-scent of the early hydrothermal syntheses, is metastable.

Conventional K—Ar age determinations are frequently discrepant. A major factor is the failure of rocks to conform to the basic simplifying assumptions made in the total fusion method. Many rocks incorporate initial argon with an isotopic composition different from the present atmosphere and others have not remained closed systems.By careful sampling and the application of isochron geochronometry more reliable and geologically acceptable K-Ar ages can be obtained. K-Ar step heating isochrons from Kenyan Miocene volcanic sanidines are used to illustrate the accumulating evidence for the presence in ancient rocks of initial argon with an isotope ratio unlike that of the modern atmosphere. Single whole rock total fusion K-Ar isochrons from the Olduvai basalt, Tanzania and the Upper basalts of Antrim are presented to illustrate a new version of the K-Ar isochron technique. Special circumstance multiple rock K-Ar isochrons from the Belfast section of the Antrim basalts and from an ignimbrite-ash flow unit in Bed I, Olduvai Gorge, are used in a further discussion of the general applicability and usefulness of K-Ar isochrons.

The extreme rarity of alkaline rock suites bearing both calcic plagioclase and magmatic carbonatites is believed to reflect a fundamental bifold division between Gabbroic and Carbonatitic types, plagioclase being present only in the former and carbonatite only in the latter. Alkali basalt magma may be parental to both lineages, the gabbroic lineage deriving from normal differentiation under low CO2 pressure, and the carbonatitic by suppression of plagioclase crystallization under high pressures of CO2, leading through pyroxene fractionation to a ‘secondary parental’ olivine-poor nephelinite magma. Support for this hypothesis is found in evidence for the suppression of plagioclase in CO2-rich alkali basaltic magmas and for the secondary origin of olivine-poor nephelinites, in the nature of xenoliths and cumulates at carbonatite complexes, in Sr isotopic data, and in major and trace element compositions of the magmas. The possible origin of melilitic rocks at carbonatite complexes is also briefly discussed.

The Upper Jurassic–Lower Cretaceous strato-tectonic belts of the southern Andes and South Georgia, 2000 km apart, can be correlated and explained as the products of an island-arc–back-arc system. From the Pacific Ocean to the Atlantic, these belts, which exhibit structural and metamorphic differences, are: (1) a pyroclastic belt developed on an ensialic volcanic arc; (2) a back-arc flysch sequence underlain in the southern Andes by a basic complex with oceanic affinities; this was intruded into continental crust as a result of sea-floor spreading which created a marginal basin; (3) a slate sequence deposited on a continental shelf. The pyroclastic and marginal basin belts and the adjacent part of the continental shelf were folded and uplifted during the early Upper Cretaceous, whereas the foreland part of the continental shelf assemblage underwent deformation during the early Tertiary.

40Ar/39Ar age studies of some glauconites from well-known stratigraphical horizons reveal unexpectedly high ages compared with the conventional K–Ar age determinations. These have been interpreted in terms of nuclear and physico-chemical reactions sustained by the glauconites in the reactor. These impose severe limitations on the use of glauconite in the 40Ar/39Ar irradiation technique.

The unfossiliferous Maestrichtian Summerfield Formation of Central Jamaica is composed entirely of hornblende andesite. A measured section shows a 90 m-thick lower unit of greenish-grey, crystal-rich, pumice-poor sandstones and rare mudstones, which interdigitate with shallow-marine rudist limestone. The upper 370 m comprise pink-coloured, pumice-rich fluviatile sandstones and conglomerates with devitrified ignimbrites at two horizons. Although no lavas are exposed it is likely that the erupted magma is represented by the hornblende andesite boulders of the conglomerates. Whole rock chemical analyses show the lava boulders to have around 65% SiO2 the ignimbrites 62%, the shallow-marine crystal-rich sandstones 58% and the interstratified mudstones 69%. The marine sandstones are concentrations of phenocrysts and the mudstones represent the finest glassy ash — originally the liquid which coexisted with the phenocrysts before eruption. These variations illustrate that after leaving the vent the pyroclastic material lost much fine glassy ash during the pyroclastic flow stage to produce crystal-enriched ignimbrites. Where the pyroclastic material was deposited in a shallow- marine environment it underwent further mechanical separation with loss of pumice by flotation, lithics and separation into crystals (sandstones) and glassy ash (mudstones). Subtraction of glass (rnudstone) from the magma (conglomerate boulders) shows that the ignimbrite composition can be obtained by loss of around 40 wt. % of glassy ash. The crystal-rich marine sandstones – although no longer containing the phenocryst minerals in their original magmatic proportions – represent a loss of about 60 wt. % glassy ash.

Changes in the Upper Cretaceous faunas of northeastern Ireland point to rising Cenomanian temperatures, and to progressive falls in temperatures from early Santonian to Maastrichtian times. At first sight, these changes fit the Cretaceous climatic trends claimed from isotopic data; but comparison with faunas seen in England suggests that this fit is illusory. It is suggested that faunas were more directly controlled by the influence of contrasting Atlanto-West Tethyan and Russo-Germanic water masses, and by changes in their relative distribution. Changes seen through the Irish Senonian may reflect the progressive submergence of a Scotland—Pennines barrier, permitting an increasing westward spread of the Russo—Germanic (‘boreal’) water and fauna.

A summary is given of the preservation and general abundance information on palynomorphs of post-Silurian age in Svalbard. An explanation of the distribution of successful and unsuccessful palynomorph extraction is attempted, with a conclusion that varying burial history under other sediment was the principal controlling factor.

New stratigraphic data for the Ordovician ectoproct Diplotrypa cf. D. westoni in the Shan Plateau region of Central Burma indicates correlation with the Trentonian of New York State.

The three species of Placoparia; P. (Placoparia) cambriensis Hicks, P. (Coplacoparia) tournemini (Rouault) and P. (Coplacoparia) borni Hammann have been recognized from the Ordovician of North Portugal. New subspecies of P. (Placoparia) cambriensis have been established on the basis of differences in the pygidium and suggests the presence of two, broadly coeval, populations in western Europe during the Llanvirn. Quantitative analyses have provided information on growth patterns.

The lithostratigraphical division of the Wolstonian Stage of the British Pleistocene is reviewed in the light of borehole records along the line of the M 69 motorway. The Wolston Clay is divided into 5 members. The evidence from the M 69 shows that 2 periods of glacier advance were separated by a major period of recession of the order of 104 years, in which most of the sediments of Glacial Lake Harrison were deposited. It is argued that this recession was interstadial rather than interglacial.

Near San Sebastian, northern Spain, are outcrops of a system of deep-water fans deposited beyond the mouth of a submarine canyon from southward flowing currents. The sandstones consist of mixed siliciclastic detritals and carbonate fragments. The latter includes a derived heterogeneous marine fauna. Carbonate content varies and has played a major part in diagenesis. Early cementation by limited quartz and to a greater extent calcite involved local expansion. Later compaction has led to prominent pressure-solution phenomena of calcite and quartz with formation of microstylolites. Leaching owing to weathering has led to removal of some carbonate and formation of kaolinite from micas.

The structure of the partly exposed lower section of the Jimberlana Intrusion has been determined by combining the geophysical evidence with the available geological and diamond drill hole data. The results have been added to the wellknown upper section to show that Jimberlana is not a dyke-like body as had previously been thought, but is a horizontal pipe-like intrusion 180 km long, 2.5km wide and 5.5 km deep, with a V-shaped cross-section. A marginal series with ‘reversed’ fractionation and high primary dips, similar to the marginal series of the Muskox Intrusion, occupies the lower part of the intrusion. The rocks of this series display rhythmic layering and a variety of cumulate textural types indicating that cumulate processes can take place during deposition on near-vertical dipping surfaces.

Large sediment-filled solution pipes in Middle Devonian Limestone near Newton Abbot are described. A succession of gravels, sands and clays is identified in the pipes, and the presence of umber, ochre and residual clays is noted. The unusually large size of the pipes is discussed and the infilling sediments are related to the Cretaceous and Tertiary formations of the nearby Bovey Basin and Haldon Hills.

Silurian fossils have been identified from Oscar II Land, western Spitsbergen. They are the first Silurian fossils recorded from Spitsbergen, and throw new light on regional correlations and the dating of Palaeozoic orogenic events in the region.

Ordovician echinoderms from Greenland include: Glyptocystites groenlandicus sp.nov. which is distinguished from other Glyptocystites by a very coarse slit spacing in its pectinirhombs (1 slit per 0.365 mm) and by its ambulacral structure; ?Macrocystella sp.; Cheirocystella sp and ?Carabocrinus sp. A variety of unidentified stem and cup plates of crinoids is described and illustrated.

A pebble lineation has been produced as a result of the first phase deformation that formed the Chamba syncline and the associated slaty cleavage. The lineation indicates the principal direction of maximum elongation of the finite tectonic strain ellipsoid of the first phase deformation and lies nearly normal to the axial direction of the Chamba syncline. The mineral lineation and the long axes of deformed crinoid ossicles show paralelism to subparallelism with the pebble lineation. The second and third phases of deformation, which are characterized by open style folds and associated crenulation cleavage, appear to be of weak magnitude and have not modified the orientations of pebble lineation.

The history of investigation of the rocks at present classed as Precambrian in the type region of the Cambrian system in the north-west corner of wales (Cambria), where that system was first named and its lower limit locally defined, is reviewed. The Arvonian volcanic series was originally included in the Cambrian System, the Monian metamorphic group remaining as Precambrian.