It is suggested that Alpine serpentinites are not a characteristic of eugeo-synclinal mountain development, but represent a special case in which the leading edge of a drifting continental mass overrode an oceanic ridge. Serpentinites younger than Caledonian are overwhelmingly of Mesozoic age, and essentially contemporaneous with the latest principal episode of continental drift. Furthermore, they occupy the leading edges of continental blocks which must have been moving during that episode.

Older serpentinite belts of comparable proportions may reflect geosynclinal seaways originally wide enough to accommodate oceanic ridges. The Baltic-Breton and Siberian continents must in that case have drifted westward (with respect to their present alignments) in early Caledonian time, and Australia eastward in early Hercynian. The principal episode of Mesozoic drift is thought to have occurred during Triassic and Jurassic times, and not during Jurassic and Cretaceous.

A marginal variant of the Mullach nan Coirean granite contains orthoclase microperthite, quartz and plagioclase, with some andalusite, muscovite and iron ore. The stability of andalusite as an igneous mineral is discussed.

Zonal arrangements in ancient ignimbrites have usually been interpreted as a reflection of variations in welding. Detailed study of two Lower Palaeozoic ignimbrites from Newfoundland demonstrates that crystallization zones can also be recognized and that in some cases it is these zones which are responsible for the gross features of the cooling unit.

The supposed Aravalli basal conglomerate near Morchana, considered to mark an erosional unconformity above the older Precambrian Banded Gneissic Complex in central Rajasthan, is a tectonic mélange in a terrain involved in superposed deformations. The supposed pebbles represent tectonic inclusions of various shapes, formed by isoclinal folding, stretching and disruption of concordant, pre- or early-kinematic vein quartz and rare pegmatite sheets in the Aravalli mica schist during the first folding.

Dykes of limestone breccia, brecciated masses of limestone within vents, and intrusive relations between basalt and limestone are described as features of interest within a short distance of Beirut.

A detailed gravity survey, carried out to determine the thickness of the Bovey Tracey beds, is described. After removal of the regional gradient a residual gravity anomaly of – 15 mgal can be attributed to the Bovey beds. This has been interpreted assuming that the clay density increases with depth and a maximum Bovey bed thickness of 1245 m is predicted. The western contact of the basin is shown to be faulted with dips of up to 63° and is possibly an extension of the Lustleigh–Sticklepath fault system.

Chemical and modal analyses of five Kunavaram amphibolites, together with mineralogical data on the pyroxenes and amphiboles, are given. Using petrochemical plots based on Niggli numbers, the trends of variation suggest an igneous origin.

The rarity or absence of clastic grains in oolitic ironstones is often explained by the hypothesis of a ‘clastic trap’ in which the clastic grains are deposited before reaching the zone of iron oolith formation. If the hydrodynamic behaviour of the iron ooliths and clastic grains is considered, this is unnecessary. The two components are spatially separated due to their different densities and different behaviour, depending on whether they are in suspension or saltating, or rolling. Iron ooliths can be rolled more easily than the equivalent clastic grain size, whereas clastic grains are more easily saltated or moved in suspension than the equivalent size of iron oolith. These differences cause spatial separation of the two facies.

The occurrence of stout and stumpy crystals of biotite elongated parallel to the schistosity and showing askew cleavage is found to be due to rotation. The relation between rotation of biotite and deformation is described. Rotated biotite contains a higher amount of FeO, TiO2 and Al2O3 in comparison to the unrotated fresh and recrystallized biotite.

Cross-stratified units, of the order of 1 to 12 m thick, are described from the Devonian Slieve Mish Group in the Dingle Peninsula of south-west Ireland. They are composed entirely of purplish-red or yellowish-grey and violet, medium- to fine-grained sandstone. An aeolian origin for this cross-stratification is indicated by the large size and morphology of the fore-sets, the excellent sorting of the sandstones and the associated evidence of aridity in a continental environment within a restricted basin.

Large ignimbrite dykes continuous with an overlying sheet of rhyolitic ignimbrite have been found at two localities in the centrally-subsided block of the Sabaloka cauldron. There is good evidence that these dykes fed ash-flow eruptions. Other possible feeder vents occur along the marginal fracture zone of the cauldron but evidence for the origin of some of these structures is ambiguous. Ignimbrites within the dyke-shaped feeders contain a very strong eutaxitic foliation oriented parallel to the contacts and this feature is thought to result from inwardly-directed pressures exerted by the dyke walls during a collapse which followed eruption of the ash-flows. Vents of this type are believed to originate by permissive intrusion through the roof of a shallow-seated magma chamber, in contrast to forcefully injected diatreme vents. A broad genetic classification of these bodies is suggested, based on their mode of emplacement.