Late Precambrian (∼ 750±200 Ma) glaciogenic sequences exhibit substantial evidence for marked climatic inequability of seasonal and longer periodicity (10° to ∼ 106 yrs): (1) tillites are closely associated with dolomites, limestones and evaporites apparently of warm-water origin; (2) tillites occur with red beds and iron-formations whose iron probably was derived ultimately from lateritic weathering; (3) glacial dropstones occur locally within carbonates and iron-formations; (4) laminae, interpreted as varves by many workers, are common in argillites, carbonates and iron-formations; and (5) permafrost structures attributable to repeated seasonal changes of temperature are locally abundant. Such climatic, particularly seasonal inequability apparently conflicts however with the probable low (≲30°) palaeolatitudes of deposition of numerous late Precambrian glaciogenic sequences.

The contradictions presented by such sequences may be resolved by postulating a considerably increased obliquity of the ecliptic (ε) in late Precambrian time. Substantial increase in e would: (1) greatly amplify global seasonality; (2) weaken climatic zonation, thus allowing warm-water sedimentation and lateritic weathering over wide latitudes; and (3) increase the ratio of radiation received annually at either pole to that received at the equator, so when 54° < ε < 126° low and middle latitudes (≤ 43°) would be glaciated in preference to the poles. Ice sheets and permafrost thus can be envisaged principally in low and middle latitudes with contiguous warm-water and iron-rich facies under a markedly seasonal climate. The concept of secular change of e is supported by other geological evidence.

Textural patterns characteristic of supposed pre-, post- and to a lesser extent syn-tectonic porphyroblasts are reviewed. Difficulties of interpretation arise where an Si (internal schistosity) is absent, and Se (external schistosity) behaviour adjacent to porphyroblast margins is the only available criterion; examples may be found showing truncation of Se by pre-Se porphyroblasts. Truncation and/or deflection textures are not by themselves sufficient criteria for determining the time relations of particular phases of deformation and crystallization.

Stratigraphic sections measured at Wilhelmøya and Hellwaldfjellet in eastern Svalbard are described in their entirety in terms of formal lithostratigraphic units for the first time. They include rocks of mid-Triassic to late Jurassic age. The Uleneset Member is newly described and palynological evidence is used to show that it is largely Norian (late Triassic) in age.

Pollen analyses from sediment adhering to fossil mammalian bones from Barrington, Cambridgeshire, have demonstrated that the deposit is of Ipswichian zone IIb age. This is also indicated by the mammal fauna. Herb-dominated communities, which appear to have been largely maintained by the activities of herbivorous mammals, grew locally on the river floodplain, whilst temperate mixed-oak forest was present further away.

Phlogopitization of pyroxenite is common in contact zones between clinopyroxenites and carbonatite dikes of the Cargill ultramafic rock—carbonatite complex near Kapuskasing, Ontario. The most typical development is a mica zone 1–10 cm wide but phlogopite is also developed in a more pervasive manner throughout the groundmass of several types of ultramafic rock. Fenitization is most commonly thought of as a process whereby aegirine and riebeckitic amphiboles are formed in the host rock while feldspar is recrystallized and silica progressively removed. Phlogopitization of pyroxenite can properly be referred to, however, as a type of fenitization. It is clearly related to the intrusion of carbonatite into pyroxenite and is further testimony to the fact that many carbonatite magmas are initially alkalic but lose alkalies to the surrounding rocks and crystallize as calcitic and dolomitic carbonatite with alkali contents restricted to the amounts that could be fixed as micas, pyroxenes or amphiboles. This in turn is controlled by the silica and alumina activity of the carbonatite magma. Abundant evidence for considerable amounts of fluorine in carbonatite magmas suggests that alkalies may be transported into the country rocks as fluorides. It is further suggested that late-stage feldspathization in carbonatite complexes is explained by the abstraction of potassic halide solutions from the crystallizing carbonatite magma. The conclusion seems inescapable that alkali carbonatite magmas, far from being the curiosity thought by many petrologists, are in fact very common during the evolutionary history of carbonatites. The common calcitic and dolomitic carbonatites have not generally crystallized from a magma of the same composition but are the residue remaining after the abstraction of an alkali-rich aqueous fluid. Consequently, there is a need to redesign the experimental phase equilibrium approach to problems of carbonatite genesis in order to take account of the presence of alkalies in most carbonatite magmas.

Three samples of low-grade metamorphic rocks from the Hazara Group, northern Pakistan, analysed as total-rock samples by the Rb—Sr method, give model ages of 765±20 and 950±20 Ma. The results are discussed in terms of the stratigraphy of Hazara, northwestern Iran, and certain other areas.

An examination of narrow zones of bare sand, usually averaging 10 m in width, situated between the patch reef and the sea grass beds (Thalassia and Cymodocea), shows that they appear to be primarily the result of wave action. Experiments were conducted in the U.S. Virgin Islands over a period of 5 years, which show the effect of subsurface interference of wave patterns in the forming of these bare sand zones. It is thought by the present author that these sand zones are a major factor in the equilibrium balance of sand quantity necessary for on and offshore transportation, and also in the balance of sand retained behind the patch reefs of the West Indies.

Two new total degassing argon-40/argon-39 age determinations are quoted for crystals of adularia from hydrothermal veins within gabbro of the Lizard, Cornwall. The apparent ages of 147±3 Ma and 201±4 Ma obtained suggests the presence of at least two phases of hydrothermal mineralization long after the close of metamorphism.

The supposed cyclostome bryozoan Bolopora undosa Lewis 1926 is reinterpreted as a chemogenic and/or bacteriogenic dubiofossil.