Structures affecting certain bedding planes, and simulating sedimentary ripples, have been found at a number of horizons in the Wenlock and Ludlow rocks of Denbighshire, North Wales. The megascopic appearance of the ripples, including their association with linear structures and their miscroscopical fabric are described in detail; and it is concluded that they are of tectonic origin, being manifestations of bedding-plane slip. The orientations of the ripples and other minor structures suggest that the stress responsible was the regional stress that produced folding, faulting and cleavage.

Clearly boudined and folded igneous sheets occur in Durness Limestone on the south side of the Tertiary Ben an Dubhaich granite. Obvious Tertiary dykes in nearby Mesozoic rocks are not deformed at all, nor has such deformation been described previously from the Caledonian activity in the Cambro-Ordovician of the north-west Highlands. Its appearance here does fit Clough's description (in Peach et al. 1907) of an unusually strong Caledonian penetrative deformation in the Strath Limestone, while the fact that all but one of the sheets are dolerites, a rock not elsewhere known from the Cambro-Ordovician but typical rather of the Tertiary activity for which Skye is famous, and that the other is a two feldspar porphyry very like the Ben an Dubhaich granite, point to the possibility of Tertiary deformation.

A new method of contouring polar diagrams using 1% area curvilinear counting cells is described. The method is fast and accurate over the whole area of the stereogram including the periphery and is, therefore, especially suitable for counting weak or diffuse concentrations.

Evidence of substantial dextral strike-slip displacements along the Caledonoid fault-set of northern Lleyn is revealed by the distribution of Pre-Cambrian igneous and metamorphic rocks, Ordovician volcanic rocks and Caledonian ‘early granodioritic’ intrusions. These apparently occurred prior to some smaller sinistral strike-slip movements which left total net dextral displacements of 91/2 km. Both types of movement were completed before the Caledonoid faults were disrupted by NNW sinistral faulting and more intrusions of Lower Old Red Sandstone age were emplaced.

The Comores Archipelago comprises four principal islands, lying in a WNW–ESE line at the northern end of the Mozambique Channel. The Islands are almost entirely volcanic and show a simple age progression from Grande Comore, with its active shield volcano Kharthala (2650m), east-south-eastwards through Mohéli and Anjouan, which are quite deeply dissected, to Mayotte, which is in an advanced stage of erosion and subsidence, and is encircled by a barrier reef. There is also evidence of minor volcanic rejuvenation in relatively recent times in Mayotte, and perhaps Anjouan and Mohéli. The lavas of Kharthala, and the neighbouring extinct shield volcano (Massif de la Grille) on Grande Comore are all basaltic, ranging from oceanitic and ankaramitic to aphyric types. Numerous tuff cones occur, especially on the flanks of Massif de la Grille. Basaltic lavas, similar to those of Grande Comore, form the bulk of the dissected volcanic shields of Mohéli and Anjouan, but there is also evidence of differentiation towards alkalic under-saturated end products, both as lavas and as intrusive bodies. Lherzolitic and gabbroic nodules are locally abundant on each of the islands, while xenoliths of sandstone and quartzite have been found on the three westernmost islands. Petrochemical data are presented for a considerable variety of Comores rocks, and the volcanic activity is discussed in terms of the major structural features of the Madagascar-Mozambique region.

Non-stratified, poorly-sorted rhyolitic ash deposits previously described as morainic and mudflow deposits are reinterpreted as ignimbrites emplaced in the topographically lower parts of the Santiago basin by pyroclastic flows. These flows probably originated from sources high in the Andes, and swept down the deep Maipo valley to spread out over the sediments filling the basin. An ignimbrite with a zone of dense welding but otherwise of similar character to the non-welded ashes of the basin occurs in one of the Andean valleys; and peculiar ‘pipe’ structures in the ashes of the basin support a pyroclastic flow origin.

Further study of the nature and origin of these rocks may lead to a better understanding of the structural evolution of the area.

A second specimen of Osculocystis confirms that the genus occurs in the Upper Llandovery (Purple Shales) near Buildwas, Shropshire and adds information on morphology. The subvective system consists of a single long brachiole; the stem lacks a root structure. The mouth, gonopore and hydropore are described and the three pectinirhombs B2:IL2, L2:R1 and L4:R3 are confirmed.

The incommodus, atavus and cyphus monograptid groups appear more or less simultaneously in the atavus Zone. The atavus and cyphus groups are related, one of these probably giving rise to the later tenuis group of monograptids, Possible roots of these groups and relationships with later monograptids are discussed. Monograptus strachani sp. nov. is proposed to replace the name M. incommodus sensu Elles & Wood.

Palaeocurrent directions from cross-beds in the Proterozoic Kimberley Basin sediments, north-western Australia indicate sediment transport predominantly from the north-east in the lower part of the succession, and from the north-west in the middle and upper parts. Most of the sediment was probably derived from the north and only a little from the adjacent exposed areas of older Pre-Cambrian rocks to the south. The suggested northerly source of the sediment is consistent with a probable former position of Western Australia close to Peninsular India and to Burma.

Phonolite lava from the Viejo and Teide volcanoes show a wide variation in flow morphology, from viscous, spoon-shaped lavas to thin flows more than 8km long that often show well developed lava channels. The apparent fluidity of these lavas is considered to be largely due to their strongly alkaline character.

The historical background of correlations between various Dalradian successions is examined, and on the basis of recent mapping and observations it is suggested that the Ballachulish succession is the downward extension of the standard Perthshire sequence.

Four stage names are erected within the southern part of the type area of the Llandovery Series, south-east of Llandovery, Carmarthenshire, Wales. They are Rhuddanian, to incorporate the existing Lower Llandovery; Idwian for the Middle Llandovery, and Fronian and Telychian for the Lower and Upper parts of the Upper Llandovery. Correlation with the sequence of graptolite zones is suggested.

The base of the Llandovery at Llandovery is poorly exposed and unfossiliferous, and detailed correlation with other areas may always remain uncertain. Thus the base of the Llandovery Series, and hence the base of the Silurian System, is defined in Lapworth's classic locality at Dobb's Linn, Moffat, Scotland, at the base of the zone of Glyptograptus persculptus.

Transverse sand bodies of a new type from the continental shelf are commonly 2m high, 500m long and crescentic in plan view. They are believed to be transported at the present day by weak tidal currents (approximately 1 knot peak velocity near the surface) associated with wave induced oscillatory water movements of similar strength, rather than being formed near the shores at times of lower sea level.