The Ballantrae complex, variously interpreted in the light of plate tectonics, is reappraised on the basis of comparisons with ophiolites of the Newfoundland Appalachians and the southwestern Pacific. All the main components of a typical ophiolite sequence can be recognized although the sequence has been greatly disturbed by post-emplacement Caledonian deformation. The presence of a garnet granulite-amphibolite ‘aureole’ beneath the peridotite member of the complex is confirmed, thus establishing the affinity of the complex to other ophiolite-amphibolite associations of the Appalachian and Alpine systems. Rock units previously described as agglomerates are re-interpreted as olistostromes, and the important Pinbain Beach ‘shaly group’ containing fragments of ophiolitic debris, garnet-ariegite, and glaucophane schist, is considered to be a Wildflysch unit of Middle Arenig age. The olistostromes were deposited following obduction of oceanic lithosphere represented by the ultramafic and mafic rocks of the Ballantrae complex. Recognition of the complex as overthrust ophiolite removes certain constraints on the position of a Lower Paleozoic subduction zone within the Southern Uplands.

The Eller Beck Formation is a thin marine intercalation in a predominantly non-marine Middle Jurassic sequence of coal measures facies. The formation consists of thin transgressive ironstones and siltstones at the base which are overlain by a thicker regressive sequence of shale passing upwards into sandstone. The close association between changes in the local subsidence pattern and the transgression suggest that the incursion resulted from epeirogenic movement rather than from eustatic rise in sea level or a purely sedimentation-controlled change in delta distributary pattern. Facies distribution was greatly affected by local synsedimentary tectonic movement. Water depths were probably very small throughout, and tidal effects on sedimentation minimal.

Horizons characterized by the trilobites Staurocephalus clavifrons and/or Phillipsinella parabola have long been regarded as significant in Upper Ordovician correlation. From time to time this idea has been formalized by the erection of Phillipsinella parabola or Staurocephalus clavifrons Zones or by equating the range of a ‘Phillipsinella parabola fauna’ with Series sub-divisions within the Standard Ordovician succession. At the present time the Phillipsinella parabola-Staurocephalus clavifrons fauna is widely regarded as indicating a Rawtheyan age (Ashgill Zones 5–7).

Recent work by the author, however, together with a review of available evidence from the literature casts grave doubts on the validity of such concepts. It is suggested that in some areas the Phillipsinella parabola-Staurocephalus clavifrons fauna may range at least as low as basal Cautleyan (Ashgill Zone 1).

The Miocene phonolite succession of the Uasin Gishu Plateau comprises seven flows totalling about 600 km3 in volume and covering an area of some 6500 km2. Each flow has a number of recognizable and laterally persistent features which permit it to be recognized over a wide area (thousands of square kilometres). These flows originated within the Rift Valley and flowed westwards for distances of up to 60 km across the marginal plateau area.

Potassium-argon age determinations on rocks from the Sierra de San Carlos, State of Tamaulipas, México, which are petrographically very similar to other bodies in north-eastern México and the south-central U.S.A., indicate that a NW-trending zone of alkaline complexes, at least 1,400 km in length, stretches from the Gulf coast to southern New Mexico. This zone may be structurally related to the parallel, but somewhat younger, Rio Grande rift.

Characteristics of mineralogy and texture, together with systematic changes in the enstatite content of orthopyroxene and in the anorthite content of plagioclase, indicate that intrusions of pyroxenite, norite and gabbro, and diorite and leucocratic diorite in the Dahomeyan gneiss of Ghana are genetically related, and that they belong to a subalkaline comagmatic series derived from a parental mafic magma. Partial recrystallization (deuteric) of the igneous rocks during and after intrusion and protoclasis produced minerals characteristic of temperatures higher than those that existed during the medium-grade regional metamorphism of the Dahomeyan gneiss, thus indicating that emplacement of the igneous rocks occurred late during, or perhaps after, the metamorphism. Contact metamorphism appears to have resulted in higher than normal anorthite contents of the plagioclase in the surrounding Dahomeyan gneiss.