The Upper Jurassic–Lower Cretaceous strato-tectonic belts of the southern Andes and South Georgia, 2000 km apart, can be correlated and explained as the products of an island-arc–back-arc system. From the Pacific Ocean to the Atlantic, these belts, which exhibit structural and metamorphic differences, are: (1) a pyroclastic belt developed on an ensialic volcanic arc; (2) a back-arc flysch sequence underlain in the southern Andes by a basic complex with oceanic affinities; this was intruded into continental crust as a result of sea-floor spreading which created a marginal basin; (3) a slate sequence deposited on a continental shelf. The pyroclastic and marginal basin belts and the adjacent part of the continental shelf were folded and uplifted during the early Upper Cretaceous, whereas the foreland part of the continental shelf assemblage underwent deformation during the early Tertiary.

40Ar/39Ar age studies of some glauconites from well-known stratigraphical horizons reveal unexpectedly high ages compared with the conventional K–Ar age determinations. These have been interpreted in terms of nuclear and physico-chemical reactions sustained by the glauconites in the reactor. These impose severe limitations on the use of glauconite in the 40Ar/39Ar irradiation technique.

Near San Sebastian, northern Spain, are outcrops of a system of deep-water fans deposited beyond the mouth of a submarine canyon from southward flowing currents. The sandstones consist of mixed siliciclastic detritals and carbonate fragments. The latter includes a derived heterogeneous marine fauna. Carbonate content varies and has played a major part in diagenesis. Early cementation by limited quartz and to a greater extent calcite involved local expansion. Later compaction has led to prominent pressure-solution phenomena of calcite and quartz with formation of microstylolites. Leaching owing to weathering has led to removal of some carbonate and formation of kaolinite from micas.

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.

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.

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.

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.

Cleavage structures from two localities in the Northern Lake District, England, are described, and they are discussed critically in relation to the tectonic de-watering hypothesis. It is concluded that, whilst tectonic de-watering may aid in the formation of a slaty cleavage, strain is the primary mechanism for producing such structures.

Previous mechanisms of syntectonic growth of porphyroblasts, leading to sigmoidal inclusion patterns, are thought to be based on invalid assumptions. A new mechanism, which involves the formation of extension fractures, is outlined.