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.

A collection of basaltic rocks has been dredged from part of the Blackstones igneous centre, a major offshore intrusion situated about 50 km SW of Mull. The basalts are mainly olivine tholeiites and are closely similar to transitional basalts found on the Inner Hebrides. The mean of four concordant K—Ar dates obtained from the lavas indicates an age of 57.1 (± 0.9) Ma. The Blackstones complex thus appears to be coeval with other Tertiary centres of the area.

A quartzite-shale sequence forming the lowest part of the Ordovician reference section for NW Spain in the Cantabrian zone at Cabo Peñas, lacks body fossils and has hitherto been of uncertain age. This sequence has, however, yielded a variety of trilobite-produced trace fossils. The lowest exposed beds have Cruziana breadstoni and Rusophycus sp. while a few tens of metres higher C. furcifera, C. goldfussi, C. rugosa and Rusophycus asturiensis sp.nov., are also present. The highest beds have yielded only C. furcifera. The traces suggest that while the top of the sequence is at least as high as Arenig the lowest beds are of Tremadoc (post-Dictyonema flabelliforme Zone) age. This implies a thickness for the Arenig of no more than 400 m and probably considerably less. In contrast, thicknesses in excess of 1000 m occur to the W in the West Asturian–Leonese Zone. This, together with evidence of tidal to intertidal deposition at Cabo Peñas, tends to confirm that the area was the shelf to an Ordovician trough situated in the West Asturian–Leonese zone.

Ceratitic ammonoids from the Greville Formation in the Nelson Regional Syncline, South Island of New Zealand, were described as a new genus and species of the Ophiceratidae, Durvilleoceras woodmani, and dated as ‘late Middle Permian’ (Waterhouse, 1973). In fact, Durvilleoceras differs from all known Permian ammonoids in both conch form and sutural pattern, but closely resembles lower Triassic ceratites. Structural and sedimentologic complexities within the Nelson Syncline are such that stratigraphic interpretations are questionable, and the fauna of both the Greville and adjacent formations is sparse. Consequently, we consider that Durvilleoceras is best interpreted as a middle Scythian ceratite of the family Flemingitidae.

Garnets and biotites from pelitic, psammitic and quartzofeldspathic rock enclosing the Broken Hill orebodies are sensitive to syn and post high grade metamorphic metasomatism associated with orebody-wall rock reactions but the overall garnet—biotite partitioning relationships remain unchanged. KMg-FeDgarnet-biotite and metamorphic grade calculations increase from NW to SE over the 1000 m section examined which is in accord with the regional grade variation.

A mid-Cretaceous cobble conglomerate in the Beer district, south Devon, is interpreted as a Lower Cenomanian beach deposit.

Three-dimensional coastal exposures of the Middle Jurassic (Bathonian) Scalby Formation in Yorkshire, England, exhibit a complex, exhumed meander belt. The lateral accretion surfaces (epsilon-cross stratification) of individual meander loops are described. Field and aerial photograph measurements of accretion-surface dimensions have enabled direct determination of channel bankful depths and widths and meander wavelengths. Values for mean annual discharge of the channel system are derived using existing empirical equations. Palaeocurrents measured in the meander belt sandstones show a wide dispersal due to many periods of meander migration and cut off.

Material from the H. A. Nicholson collection, University of Aberdeen, provides information on three of Nicholson's species. Syntypes of Favistina calicina are described and the lectotype designated. Topotypes of Nyctopora billingsii are compared with an earlier description of the type thin sections. Columnopora cribriformis is considered synonymous with Calapoecia huronensis Billings, itself a poorly understood species; redescription of the type of the latter species shows it to be separate from C. canadensis Billings. Calapoecia ungava Cox is reinterpreted with a lectotype designated, and Nicholson material is placed with this species. All specimens are from eastern North America and of Upper Ordovician age excluding the Middle Ordovician N. billingsii and C. canadensis.

Activity on Etna is predominantly effusive with eruption of lavas of Hawaiitic composition. However, near Adrano some pyroclastic flow deposits outcrop among prehistoric lavas. The chemistry of the pumiceous fragments in these pyroclastic flows suggests they were erupted from magma of benmoreitic composition. This represents some of the most evolved and differentiated magma that has been produced by Etna. The presence of these deposits indicates that in the past Etna has displayed much more explosive activity than has been observed in historic times.

Within the basal Coal Measures between Ystradgynlais and Abercraf a number of liquefaction layers are seen displaying ball and pillow structures. These layers consist of balled-up, ovoid masses of sandstone some 0.25–0.3 m thick and 0.5–0.7 m across. It is considered that they were formed by loading, resulting from the lique-faction of underlying silts, produced by the passage of earthquake shock waves associated with the main fault zone of the Swansea Valley Disturbance. Elsewhere in South Wales, horizons displaying load and slump structures in rocks of Upper Palaeozoic age may have resulted from seismic shock waves caused by contemporary movements along major Variscan fractures.

The epizoan Vermiforichnus Cameron (1969b) from the Upper Ordovician (Caradoc) of the Berwyn Hills and the Welsh Borders is host-specific, occurring in association with the strophomenid Macrocoelia and the orthid Heterorthis. The spionid polychaete probably responsible for the production of the Vermiforichnus borings inhabited both live and dead individuals. In live individuals Vermiforichnus was located at the anterior margin and oriented perpendicular to the commissure, this position affording both a means of protection and a more efficient feeding position. In dead individuals population density was lower and the borings were randomly oriented. Vermiforichnus was restricted to inner—outer sublittoral environments and, as such, is a useful palaeoenvironmental guide.

The radioelement concentrations of K, U, and Th have been determined for 9 samples of granite from the Western Red Hills, Isle of Skye, Scotland, and for 10 granite specimens from the Mourne Mountains, Ireland, and are compared to 2 published results for Lundy Island granite. The concentrations are distinctly different for each of the 3 centres, and although the data do not provide conclusive proof, they favour generation of the granites by fractional crystallization of basic magmas.

The internal variations in the discordance of an inhomogenous zircon population from a bedded quartzite within a c. 2700 Ma old gneiss have been studied. Varying degrees of response to events in a common multi-episodic, post-depositional history are reflected in the uranium and lead isotopic systems of size and magnetic fractions.

A minimum 207Pb/206Pb age for non-magnetic zircons is 2840 Ma with 206Pb/238U and 207Pb/235U data for the three size fractions raising the possibility of an age of at least 3250 Ma. This is interpreted as a minimum age for crustal material that was in existence in the region before the formation of the Lewisian complex. Some of the slightly magnetic zircons also have a pre-2700 Ma radiogenic lead component.

The validity of using Devonian palaeomagnetic data to determine a post-Devonian displacement along the Great Glen Fault is assessed and it is concluded that there is no statistically significant difference between previous magnetic vectors E and W of the fault and thus no palaeomagnetic evidence for a large sinistral displacement in post-Devonian times. New palaeomagnetic results are presented which suggest that the Devonian red sandstones in the Orcadian Basin have such a complex diagenetic and palaeomagnetic history that they will then be unsuitable for such tectonic evaluations in the foreseeable future, although palaeomagnetic dating can be used to resolve some diagenetic-sedimentary features.

Pollen analyses have been made from sediments associated with vertebrate remains, including Arvicola cantiana, collected early in the 19th century from Ostend, Norfolk. They indicate that the fauna is of Cromerian zone IV date. Comparison with other pollen-dated Cromerian faunas implies that the early water vole Mimomys savini was replaced by the more advanced A. cantianaduring the second half of the Cromerian temperate stage. This is important in setting possible age limits to the faunas of such sites as Westbury, Mauer and Vérteszöllös.

An Archaean greenstone belt, occupied by rocks of the Nyanzian System, rests apparently unconformably on a basement composed of the metamorphites of the Dodoman System in the central part of the Tanganyika shield. The latter were originally metamorphosed in granulite facies. Two episodes of migmatization were imposed on this earlier crust producing two complexes of anatectic granitoids (Puma and Ikungi) which locally have a charnockitic character. Differences in structural setting suggest that they were developed in connection with two major tectonic events. A basin-like structure was built up during the second – Ikungi – in which the Nyanzian System occurs. The Nyanzian rocks are not migmatized and their juxtaposition with the migmatites suggests that they are of younger age. Another tectonism took place after deposition of the greenstones as a result of which they were intensely deformed. Two types of intrusive granites were emplaced in the greenschists upgrading them to hornfelses during this tectonism. An interesting feature is the coincidence of the general tectonic axes of these three events. For the successively established metamorphic processes in this Archaean nucleus a gradual downgrading of metamorphic facies is characteristic, showing its irreversible development.

The relationship between silicate rock density and composition has been investigated and empirical formulae have been obtained that give a factor equivalent to a ‘normative’ density. Comparison between this factor and measured density may provide useful diagrams assisting the interpretation of metamorphic petrogenesis. The factor itself is a viable differentiation index aiding comparison between the compositions and liquidus temperatures of volcanic suites.

The Carrai Granodiorite is an intrusive magmatic pluton with steeply dipping margins surrounded by a well-developed contact metamorphic aureole. Emplacement of the body was accompanied by little distortion of neighbouring rocks and involved vertical displacement of pre-existing material. Scarcity of country rock blocks, and the presence of numerous dioritic xenoliths indicate that stoping was unimportant, and the pluton was accommodated in the upper crust by vertical uplift of earlier rocks (‘block elevation’). A close relationship existed between faulting and granodiorite emplacement. Deep shears possibly account for the generation of the linear zone of plutons in which the Granodiorite is located.

A new record of an early retiolitid, Reteograptus sp., from the topmost Llanvirn strata of Abereiddi Bay, South Wales, is described and figured. An approximately contemporaneous upper Darriwillian form from Gisborne, Victoria, Orthoretiolites? speciosus (Harris) is redescribed and shown to differ radically from both Reteograptus sp. and R. geinitzianus Hall, the type species of the genus.