The Vagastie Bridge granite, central Sutherland, belongs to a regional suite of igneous intrusions within Moine psammites adjacent to the base of the east Sutherland migmatite complex. An isotopic date of 405 ± 11 Ma, obtained using U–Pb determinations on zircon and sphene taken from the granite, has previously been interpreted as an intrusion age. However, a reassessment of the field relationships demonstrates that intrusion was syn-tectonic with respect to the later stages of ductile Caledonian deformation affecting the Moine rocks. It is suggested that the granite suite magmas originated at depth and that they were channelled into the still active Caledonian ductile thrust zone (the Naver Thrust) which forms the tectonic base of the Naver Nappe. On regional grounds, the interpretation of the c. 405 Ma date as an intrusion age is untenable, which implies that the isotope systematics of the Vagastie Bridge granite require re-investigation.

Morphological changes in bedforms composing a tidal delta at the northern entrance to Moreton Bay, Queensland have been studied by examining aerial photographs spanning a 26-year time period. The aerial photographs show the movements of 51 different sand-bank crestlines, and the morphological characteristics of both sand banks and sandwaves. From the orientation of sandwave crests to the sand-bank crestlines, zones of ebb- and flood-dominance in sand-transport direction are distinguished. The migration directions of the sand banks are predicted by considering the cross-sectional asymmetry of the sand banks together with their adjacent ebb/flood zones of net sand transport. The reliability of the predictions is tested by comparisons with sequential air photo data. When applied to 53 bedforms, the predictions achieved a high success rate, with 45 predicted migration directions matching those observed on the sequential aerial photographs. Bedform movement can be predicted, therefore, for any water depths in which submarine bedforms can be clearly seen on aerial photographs (< 10 m).

Based upon their mobility, sand banks are classified into three categories: dynamic sand banks, which change quickly (within 2 years) and which have migration rates that are non-uniform along the bank crestline; progressive sand banks, which change slowly (from 2–10 years) and have migration rates that are uniform along their crestlines; and immobile sand banks, which change only over time intervals which exceed 10 years. Changes in sand-bank morphology occur by migration of the crestline together with growth and decay, and are considered to be linked with changes of larger ebb- and flood-dominant zones of net sand transport. The three different sand-bank types are characterized by distinctive heights, crestline lengths and wavelengths. They occur in different locations within Moreton Bay, possibly related to distance from external sand supplies and to relative tidal current and surface wave energy levels.

The dolerite and basalt intrusions within the Lower Palaeozoic sequence of northwest Wales are largely restricted to the outcrop of Ordovician strata. Their distribution and close association with known volcano-tectonic structures were controlled by a tectonic framework of deep-seated fractures. In central and northern Snowdonia, volcanism during Caradoc times was related to the evolution of a fracture-controlled trough. An increase in the extensional stress across the trough with time is reflected in the progressive increase in basaltic magma movement during the volcanic cycle. The trough represents an attempted rift in the lithospheric plate, which failed to create an ocean basin and was subsequently aborted.

Investigation of a section near Morston on the central north Norfolk coast has revealed evidence of a complex sequence of beach deposits laid down under interglacial conditions in association with relative sea levels similar to those of the present. This material rests upon a highly calcareous till and is itself overlain by a deposit comparable with the Hunstanton Till of northwest Norfolk. This site therefore represents the first location at which Hunstanton Till has been found overlying older till, and the only location so far discovered in East Anglia at which interglacial deposits separate glacigenic sediments. The site also contains the only indubitable Quaternary warm stage deposits to have been recognized in central north Norfolk.

The Old Red Sandstone (ORS) on the island of Hitra forms an approximately 1350 m thick succession of alternating continental mudstones, sandstones and conglomerates of possibly latest Silurian to Devonian age. Within the middle part of this succession, just above a major, scoured surface, a spectacular slump feature was observed. The phenomenon is interpreted as a unit of overbank/channel bank mudstones which, because of undercutting and liquidization, caved into a low sinuosity river channel. The Hitra sequence is the only one in the Norwegian ORS where such phenomena have as yet been identified.

The description of sandstone samples, defined by three components, is introduced through non-parametric sample density description. The composition of a particular sample defines a direction from the origin of the Cartesian reference frame. Radial difference between individual samples then provides the measure of their similarity. A sample set can be viewed as a bundle of compositional axes with a corresponding density distribution on both the ternary diagram (or unit constant sum plane) and the positive octant of the unit sphere. Because radial differences are disproportionately displayed on the ternary diagram, radial density calculations on the sphere are to be preferred. The mode of the sample set, the implied centre of greatest data concentration, is considered to be the most meaningful representative value, as the component joint mean can lie outside the data field with certain data configurations. In addition, the component joint mean cannot provide a useful representative composition for samples drawn from a bimodal distribution. Sample density distribution not only provides a data defined approach to describe sample dispersion, but also furnishes an indication of sample sufficiency in displaying the degree to which modes are supported by surrounding observations.

Sections exposing the Cambrian–Ordovician Boundary interval at Broom Point in western Newfoundland have been proposed earlier for a global systemic boundary stratotype. These lie within the Cow Head Group, a late Middle Cambrian to early Middle Ordovician allochthonous unit of limestone, shale, and conglomerate deposited at the toe of the ancient continental slope and on the adjacent continental rise. Several recent studies have further investigated the stratigraphy, sedimentology, and palaeontology of the Cow Head Group and others are under way on magnetostratigraphy and chemostratigraphy. These aspects are reviewed for six key boundary sections representing proximal to distal facies: Cow Head Ledge, Broom Point South, Broom Point North, St Pauls Inlet Quarry, Martin Point, and Green Point. In particular, new data are presented from 260 conodont samples that yielded 15500 conodonts. This intense sampling has allowed the discrimination of minor hiatuses in the proximal to intermediate facies where conglomerates have eroded and cannibalized underlying strata. New conodont data from Broom Point North have lowered the base of the C. lindstromi Zone into unit 74 conglomerates, thereby making this section unsuitable as a boundary stratotype. New collections from Green Point have yielded abundant conodonts and over 9400 conodonts have been recovered from 77 samples.

The conodont, graptolite, and trilobite biostratigraphy through the boundary interval is documented allowing accurate correlation between sections and more precisely revealing small hiatuses in the proximal and intermediate facies. The sequence of conodont zones is: Eoconodontus notchpeakensis, Cordylodus proavus, C. caboti, C. intermedius, C. lindstromi and C. angulatus. These can be correlated with trilobite zones established from both in situ and clast faunas from the proximal to intermediate facies and with graptolite assemblages (of Cooper 1979) especially in the intermediate to distal facies. Three new species of Cordylodus are described (C. andresi, C. hastatus and C. tortus) and the full apparatus of Iapetognathus preaengensis is illustrated.

The criteria for selecting a global boundary stratotype and point (GSSP) are reviewed in terms of the Cow Head sections. The Green Point section is shown to meet, and largely surpass, the prerequisites required of a stratotype. The Green Point section is proposed to be the global boundary stratotype with the base of the Ordovician System defined at the base of unit 23, which is the base of the Broom Point Member, Green Point Formation, at a level coincident with the base of the Cordylodus lindstromi Zone. In addition to an abundant and superbly preserved conodont fauna, this section preserves the best sequence of earliest planktic graptolites through a 40 m interval; the first nematophorous graptolites (of Assemblage 1) occur in unit 25, 6.9 m above the base of the C. lindstromi Zone. This level can be readily correlated into the proximal facies where both deep and shallow water trilobites (in situ and in clasts, respectively) show the base of the C. lindstromi Zone to lie within the Symphysurina brevispicata trilobite Subzone.

Aporate sphinctozoan sponges of the Family Cliefdenellidae Webby, 1969, are described for the Upper Ordovician (Ashgill) of northern and northwest China, including the new genus Khalfinaea and a new species K. shaanxiensis. They are characteristic cliefdenellids with conico-cylindrical and branching forms, a single central tube defined by a thickened, sieve-like endowall, and a filling of irregularly orientated astrorhizal canals, vesicles and thickened (?trabecular) tissue

Taxonomic relationships of the other cliefdenellids are also discussed. The conception of the genus Cliefdenella Webby, 1969, is restricted to those forms with massive, hemispherical to explanate form and multiple, bundled vertical excurrent canal-clusters, and the new genus Rigbyetia is introduced to include conico-cylindrical and branching forms with a central tube composed of a single, vertical, bundled, excurrent canal-cluster

In terms of their biogeographical record, the cliefdenellids have a restricted distribution in the Upper Ordovician (middle Caradoc-Ashgill) ‘fold-belt’ successions of the Palaeo-Pacific region (eastern Australia, Alaska and northern California) and in Asia (northern China, and in the Chinese and Soviet Altai)

Litophragmatoceras incomptum gen. et sp.nov. is a small dimorphic planulate ammonite from the Upper Cenomanian Metoicoceras mosbyense Zone of Arizona in which microconchs are adult at as little as 5 mm diameter and macroconchs at 23 mm diameter or less. The quinquelobate suture is very simple, with entire lobes and saddles. It is distinct from all contemporaneous ammonites and is referred, with no great certainty, to the otherwise exclusively Upper Albian and Lower Cenomanian Flickiinae Adkins, 1928.

The mesotidal coast of Georgia encompasses diverse sedimentary features and depositional environments, most of which typify major facies of the entire Georgia Bight – a broad embayment on the southeastern U.S. shelf. Barrier island strandline environments especially include tidal inlets and shoals, the beach shoreface, foreshore, and backshore, and dunes and washover fans. Low energy beach segments may grade directly into small seaside tidal flats. Relict salt marsh deposits crop out on erosional beaches. All deposits are in dynamic equilibrium with fluctuating coastal conditions and a gradual rise in sea level.

Most of these facies are important in interpreting ancient epeiric transgressive/regressive coastal sequences. Pronounced local variations in the overall sequence result from complex latero-vertical relationships between (1) the shoreface, foreshore, and shoals, and (2) the shoals, low energy beaches, and beach-related tidal flats. Washover fans and relict deposits on erosional beaches cause perturbations within present day lateral relationships but are normal in transgressive facies tracts along such coasts. Close stratigraphic control of outcrops or cores would be necessary for detailed reconstructions of, or correlations among, ancient analogs.

This paper provides a brief outline of the current, detailed inter-disciplinary work on the Xiaoyangquiao section, trying to expose all the aspects for reference tied to the Global Single Stratigraphic Point (GSSP) Concept for defining the Cambrian–Ordovician Boundary. The 45 m critical interval of this section outcrops very well along the steep bank of a stream and is free from folding, faulting, intrusions, and has not been affected by weathering. Colour alternation of conodonts and acritarchs, and crystallinity indices of illite all indicate a maximum thermal grade of 100 °C. The lithofacies, being of great lateral persistence for a hundred kilometres, consists mainly of a rhythmical sequence of lime mudstone and shales deposited in a moderately deep outer shelf environment of quiet water, well below the normal storm wave base. Chemical investigation of the rocks demonstrates strong positive correlation between A12O3 content and those of K2O, MgO, Fe2O3, TiO2, Be, Cr, Co, Ni, Zn and Ba, indicating these components are tied to the clay fractions. A stable depositional environment is demonstrated by the uniform chemistries through the boundary interval. Close to the boundary itself P2O5 contents are low, indicating continuous sedimentation at fairly substantial rates.

The major biological events, the biostratigraphic framework, and the stratigraphic range of conodont, graptolite, trilobite, and acritarch taxa are illustrated briefly with diagrams. Following the majority views of the Calgary Plenary Session, the boundary level is to be chosen at a point marked by the First Appearance Datum (FAD) of the selected conodont taxon or taxa in the vicinity of the level close to, but below, the first influx of nematophorous graptolites. The following four points marked by the incoming of conodont taxon or taxa are recommended for consideration of the ‘Golden Spike'‘: (1) FAD of Cordylodus intermedius at 5.28 m below the first influx of nematophorous graptolites; (2) FAD of Hirsutodontus simpler–Cordylodus drucei–Albiconus postcostatus at 5.23 m; (3) FAD of Semiacontiodus lavadamensis–Utahconus utahensis–Monocostodus sevierensis at 3.85 m; (4) FAD of Cordylodus lindstromi at 2.23 m. For the following reasons the FAD of H. simplex–C. drucei–A. postcostatus is favoured: (1) the taxa are all distinct and widely dispersed; (2) intensive evolutionary change took place in conodonts, graptolites, trilobites and acritarchs prior to or after this point; all the fossil groups occur together, providing correlation with many regions throughout the world; (3) the point is in a position between the previously widely accepted boundary levels based on graptolites and trilobites; (4) the proposed point lies within a thin, laterally persistent, rhythmical sequence. The FAD of Cordylodus lindstromi is also a favourable point, sharing many advantages mentioned above. But this point is less satisfactory in being defined by the FAD of a single taxon C. lindstromi which also has an extremely small population size.

An isochron age of 500.7 ± 7.4 Ma is determined from clay fractions of mudstones 8.5 m below the proposed point by means of the Rubidium–Strontium method.

The ɛND signature determined from conodonts, trilobites hyolithids and acrotretid brachiopods has a mean value of −6.7, comparable with that of the coeval oceanic water mass occupying southeastern North America and Europe, and indicating that northeastern China bordered the same ocean. The mean Tdm model age determined was 1.26 Ga at the time of sedimentation, compatible with the mean Tdm model age of approximately 1.1 Ga for the Pacific Ocean today. The relatively low value of the Tdm model age indicates a substantial input from young orogenic volcanic island arcs and terranes.

The previously termed Hanadir Shale of Saudi Arabia is described and re-defined as the Hanadir Formation. At the type locality of Al Hanadir the unit is probably entirely of Llanvirn age while further north shelly faunas of possible Llandeilo age occur in the upper part. Trace fossil assemblages with abundant cruzianids (C. furcifera, C. rugosa, C. goldfussi), Pelecypodichnus, Didymaulichnus and Diplichnites indicate an Arenig age for beds in the upper part of the underlying Saq Formation, while the top of this unit yielded hitherto unrecorded pendent and biserial scandent graptolites, a sparse shelly fauna of lingulacean brachiopods, Neseuretus sp. and the trace fossils Cruziana? imbricata and Phycodes.

Mount Dromedary pluton is one of several predominantly monzonite plutons and smaller intrusive bodies which constitute the Dromedary igneous complex in southeastern New South Wales. The pluton exhibits a striking arrangement of petrographically, but not always chemically, distinct zones ranging from mafic monzonite at the outside to quartz monzonite in the centre. The rocks display a mineralogical and geochemical integrity which indicates a consanguineous relationship. Minor compositional discontinuities between zones, together with observed and inferred minor intrusive zone boundaries, suggest that each zone has to some extent evolved independently. Negative Eu anomalies in REE abundance patterns show that some of the zones have been affected by fractionation of feldspar, but complementary accumulates are not found at the present levels of exposure. The pattern of zoning can be explained by a process of shallow fractional crystallization in which variations within zones are the result of lateral accretion of alkali feldspar as well as settling and/or lateral accretion of mafic phases at lower levels in the intrusion and upward displacement of fractionated magma. The parental magma of the pluton probaby originated by partial melting of an alkali basalt composition with an amphibolite mineralogy at the base of the crust.

Kink bands formed due to the rotation of cleavage are very common within the Irish Variscides. A detailed examination of those within the Dungarvan Syncline has enabled the recognition of three categories based on kink fold axis orientation; the subvertical, those parallel to first or second order fold axes and those with subhorizontal randomly trending axes. The subvertical variety were formed by strike-parallel compression within a hinge depression in the Dungarvan Syncline and modified by later north–south dextral shear stresses to produce cataclasis of the kink-band boundaries, tension-gashes within the kinked segment and over-rotation. Those, whose axes are parallel to major or minor fold axes, formed as accommodation structures during folding due to extension in the be plane. Those, with subhorizontal randomly trending axes formed due to a relaxation in the northward compression which allowed a reorientation of the principal stress directions, σ1 became vertical and kink bands were generated as a consequence of the increased overburden due to fold tightening and thrusting. It is considered that kink bands throughout the Irish Variscides may be divisible into similar categories.

The Woburn Sands (Lower Greensand Group, Aptian–Albian age), in Billington Crossing quarry, Leighton Buzzard, Bedfordshire, England, show, along bedding planes of tabular cross-stratification, foreset alternations of quartz grains and goethitic ooids. Field and petrographic evidence suggest that: (a) the goethite in the layers and cores is primary; (b) the ooids formed by mechanical accretion of original Fe-hydroxide gels around nuclei on the sea-floor in shallower nearshore adjacent environments; (c) goethite cores of some ooids represent an earlier stage of iron deposition within the sediment where silica adsorbed by the iron-gels segregated in inclusions; (d) short-term variations in current strength and iron supply are responsible for the different arrangements of goethite platelets (tangential to random to radial) in the ferruginous layers in connection with the degree of crystallization of the colloidal iron during the accretion stage; (e) the ooids were then swept away in deeper waters by tidal action where their segregation in the lower parts of each foreset lamina is believed to have been hydraulically controlled.

Recent field work on Gough Island combined with K–Ar dating of the lavas requires revision of the age and volcanic stratigraphy. Four main periods of volcanic activity on the island are recognized. These comprise the eruption of the Older Basalt Group which ranges in age from 2.5 to 0.52 Ma, the intrusion of aegerine-augite trachyte plugs (0.8−0.47 Ma), voluminous trachyte extrusion (0.30–0.12 Ma) and finally to eruption of the Edinburgh Basalt (0.20–0.13 Ma).

Within the Older Basalt Group three phases of activity can be recognized; the earliest involving the eruption of pillow basalts and hyaloclastites when the island emerged from below sea level. This was followed by subaerial as-type lava flows and also dyke intrusion (phase two) which probably contributed to forming a large shield-type volcanic island, which in turn supported the eruption and deposition of flat-lying flows on an angular unconformity (phase three). Intrusion of aegirine-augite trachyte plugs occurred concurrently with the latter stages of Older Basalt eruption. After a period of considerable erosion the voluminous trachyte lavas and pyroclastics were erupted. The Edinburgh Basalt, erupted in the vicinity of Edinburgh Peak, represents the youngest volcanic activity on the island.

Stratigraphically and geographically restricted ocellar komatiite flows at Kambalda, Western Australia, appear to represent the products of ground melting of sulphidic sediments by komatiites in lava channels that localized the Fe–Ni–Cu sulphide ores. An immiscible sulphide liquid formed and gravitationally separated from the melted sediment (xenomelt), the resultant buoyant silicate liquid being partly or wholly assimilated by the turbulently convecting komatiite magma. Rarely, the xenomelt gravitationally migrated to the top of flows, and overflowed into the less turbulent lava levees where it collected to form a separate layer overlying a komatiitic layer within a single flow. There was selective preservation of the hybrid felsic layer, as an upper ocellar unit within an ocellar komatiite flow, in lava levees flanking lava channels. The ocellar unit is enriched in elements previously concentrated in the sediments, and shows U–Th–Pb isotopic systematics akin to the underlying sediments. Moreover, the partitioning relationships of U and Pb between the immiscible xenomelt and sulphide liquid enhances the range of U/Pb ratios for components of the ocellar unit, thus allowing sufficient spread of modern uranogenic Pb isotopic ratios to form isochrons, albeit imprecise ones. The range and similarity of model Th/U data from these flows (2.8−3.9) and adjacent sulphidic sediments (2.3−4.4; mostly 2.8−3.9) contrasts with the generally invariable Th/U within Kambalda ultrabasic–basic flows (3.6−3.9), and further supports the ground-melting hypothesis.