A thin-section study of the orientation of long-axes of quartz grains was conducted for a similar type fold of overturned cross-bedding in Carboniferous sandstones. Preferred orientation of detrital grains of the fold shows that (a) apparent long-axes of grains are parallel to the axial plane in a plane normal to the fold axis, (b) long-axes of grains in the axial plane are oriented in a high angle to the fold axis, and (c) grains are aligned parallel to the fold axis in a plane perpendicular to the other two directions. From the dimensional orientation of quartz grains in this sample, it is concluded that the overturned fold was made by a shear mechanism immediately following sedimentation in which the original quartz grains were reorientated by small-scale slippage along the shear planes.

On Fuerteventura, inner Canary Islands, a phase of early Cretaceous deposition on a passive continental margin was terminated in Albian time by strong localized uplift associated with onset of calcareous pelagic sedimentation. Later, during early Tertiary times, spasmodic episodes of submarine alkali volcanism led to the construction of a thick lava pile. After folding of the lower submarine volcanic rocks, and the underlying pre-volcanic sedimentary rocks, parts of the Basal Complex were emergent by Oligocene to Miocene times, fringed by coral and algal reefs. With renewed early Miocene uplift, the reefs disintegrated, followed by block faulting, intrusion of plutons, and a final phase of submarine dyke intrusion. There was then strong uplift coupled with deep erosion, extrusion of sub-horizontal Neogene plateau lavas and further intrusion of plutons. Regional comparisons suggest that tectonic events on Fuerteventura may have a bearing on sedimentary hiatuses and gravity sliding events which affected the adjacent West African continental margin.

The palaeomagnetism of continental red beds is considered in the light of evidence concerning the diagenetic origin of various textural phases of hematite. The relative roles of pigmentary hematite and specularite as magnetization carriers is discussed and it is concluded that all magnetizations are post-depositional: the magnetization of continental red beds is therefore of diagenetic origin.

Three types of non-viscous magnetization, A, B and C, are recognized in continental red beds. Type-A magnetizations retain some features of the original magnetization and are most closely coincident with the depositional age of the rocks. Type-B are composite magnetizations acquired over a long period (more than 108 yr) of time and after substantial changes in the ambient geomagnetic field. Type-C magnetizations bear no relationship to the depositional age of the rocks and represent the ultimate end-product of the diagenetic processes which affect continental red beds. Thus, these magnetizations represent stages in the diagenetic evolution of red beds. The rate of diagenetic evolution, and hence of the modification of the magnetization, is variable and depends on a variety of local geological variables.

The study enables some assessment of the reliability of palaeomagnetic data from red beds. Type-A magnetizations, although of diagenetic origin, are considered to be palaeomagnetically reliable, but only within certain limits. Red beds with Type-B and Type-C magnetizations are not considered to be generally suitable for palaeomagnetic study. Palaeomagnetic studies are, however, considered to have great potential value for dating specific diagenetic processes in continental red beds.

Paleontological and petrological studies of clay beds in the Basilika Formation (Tertiary age) are presented. The petrology of the beds indicates that their main constituents were derived from volcanic activity and represent bentonites. Differing composition between beds suggests several spatially separated eruptions. The volcanic source area probably lay towards the N of the present Tertiary outcrops of Svalbard. Two foraminiferal assemblages are found in the bentonites: the lower is dominated by arenaceous forms while the upper consists of calcareous species.

Thirty-seven new K-Ar isotopic ages are reported from the Isle of Man. Thirty clay mineral concentrates from vein gouges and altered wallrocks when interpreted with the remaining seven whole rocks and mineral ages indicate that at least five periods of metasomatism have affected the rocks. It is argued that these can be identified with episodes of ore deposition. The earliest phase, N of the Foxdale area, occurred at 310–320 Ma and appears to be the most extensive of the episodes recorded. In the S of the island, mineralization occurred later at c. 285 Ma and again at c. 250 Ma. Minor Triassic activity is expressed by a cross-course on the Foxdale lode, and a single locality displaying Tertiary mineralization was recognized. The conformity of these ages to the general episodic pattern of ore deposition in the British Isles is demonstrated.

Chloritoid-biotite- and chloritoid-staurolite-bearing rocks occur around Blair Atholl, Perthshire. Textures suggest staurolite to be produced from chloritoid by a prograde ionic reaction involving muscovite. Chloritoid rocks are aluminous, lying above the muscovite-chlorite join, and staurolite formation involves the breakdown of chloritoid and muscovite. Their presence indicates that the chloritoid-biotite zone of Stonehaven continues as far SW as Central Perthshire, although its occurrence is severely limited by a lack of aluminium-rich rocks. The use of the chloritoid outcrop in the NE as an indication of pressure decrease to the SW is therefore queried.

In reviewing those fossil algae associated with biotic reefs since the beginning of the Mesozoic, examples are discussed of algae showing evolution attributed to reef or peri-reefal conditions, those showing diversification attributed to reef environments, and those with frequent occurrence in reef conditions but with evolution not directly attributable to reefs.

Distances measured between homologous reference points on fragmentary fossil material can be used to recover a three-dimensional framework by operations of standard matrix algebra. A procedure that combines both linear and non-linear algorithms is described and illustrated in a simple reconstruction of Waptia fieldensis. The approach attempts to provide a modelling process in which a palaeontologist can explore the geometrical consequences of fossil measurements through continuous interaction with programmed reconstructions.

This paper proposes an alternative to the complex stratigraphical nomenclature introduced in recent descriptions of the stratigraphy of Eastern Svalbard. We believe that the platform nature of the Mesozoic succession in Svalbard enables recognition of individual stratigraphical units over very wide areas. Our principal conclusions are that the Wilhelmøya Formation can be recognized as the upper formation of the Kapp Toscana Group and occurs throughout Eastern Svalbard. It overlies the De Geerdalen Formation on Hopen and Wilhelmøya. The Janusfjellet and Helvetiafjellet Formations can be recognized on Kong Karls Land.

It was recently proposed that the base of the Jurassic system be taken at the base of the Blue Lias in the Watchet area of Somerset thus including the underlying White Lias in the Triassic System. The mapped base of the Blue Lias however is a diachronous horizon ranging from pre-planorbis Beds age in Somerset to Schlotheimia angulata Zone age in Warwickshire. No certain chronological correlation is possible between the base of the Blue Lias in the Watchet area and any limestone or other horizon in the pre-planorbis Beds elsewhere nor is there even a palaeontological separation associated with this horizon. This paper reiterates established Geological Survey practice of taking the Triassic-Jurassic boundary in Great Britain at the top of the Cotham Beds and thus including the White Lias limestones in the Lower Lias. The White Lias limestones are regarded as a local shallow-water facies of the pre-planorbis Beds since they both contain similar non-ammonitiferous marine macrofossil assemblages;the Cotham Beds provide palaeontological separation since they divide theseassemblages from the different marine macrofossil assemblages found in the Lower Rhaetic Westbury Beds and also contain the boundary between the Rhaetipollis and Heliosporites miospore zones. The lacustrine or lagoonal Cotham Beds are similar in lithology to the Tea Green Marl and also include reddened beds of mudstone like those of the Keuper Marl; they are therefore better contained in the continental Triassic system rather than the marine Jurassic system.

Several conodont faunas from the Ilfracombe Slates are described and their age discussed. One is referred to the conodont zone of Polygnathus varcus (late Givetian-early Frasnian). The conodonts, the first from the Devonian of North Devon, indicate that, in terms of the German standard, the uppermost Ilfracombe Slates are no younger than basal Manticoceras Stufe in age. The position of the Middle/Upper Devonian boundary within the North Devon sequence is discussed with reference to the limestones of the Combe Martin Slates (the ‘Ilfracombe limestones’), which are regarded here as Middle Devonian in age.

An experimental investigation into the formation of crystallographically orientated etch pits on quartz sand grains was undertaken. The methods and materials used in the experiments differ considerably from those of other workers in this field. Using natural as opposed to artificial solutions, V-shaped or triangular etch pits as well as rectangular pits have been produced on the quartz grains after time periods of 4 hours and 20 hours. Features of intense surface disintegration have also been recorded. The etch pits are compared to those of natural occurrence on grains from the Millstone Grit (Namurian) sediments and the differences discussed.

Although the ammonoid Durvilleoceras is apparently very close in its morphology to early Triassic genera, it comes from a formation that underlies formations with early Triassic and late Permian faunas, and appears to be of late Middle Permian age. New occurrences of the ammonoid support this thesis. Conjecturally, the genus may have inhabited deep cold waters of the southern hemisphere during the Permian Period, before giving rise to genera found in shelf deposits of the early Triassic. Alternatively, if really Triassic in age, Durvilleoceras indicates a major low-angle thrust, previously unsuspected, that has repeated Triassic sequences for a length of over 450 km before disruption by the Alpine Fault. No evidence is yet known to support this alternative.

Iron-titanium oxides from Taberg in Sweden exhibit under the electron microscope several microstructural features not visible when studied by optical microscopy, including homogeneous nucleation of magnetitess from ulvöspinelss, and the spinodal decomposition of magnetitesss. Such microstructures have promise as indicators of cooling rates.

Carbonaceous dirt bands containing some 40% hydroxyapatite and 10% kaolinite are recorded from the Hornlo seam of the Brynammon district of the South Wales coalfield with an appreciable areal extension. X.R.D. and some chemical data are recorded. The origin of the deposits is ultimately biogenic, possibly located by the porous environment provided by fusinite; but the immediate cause remains uncertain.

Paired eruptive complexes consisting of a symmetrical and an asymmetrical cinder cone are described from Mount Etna. The contrasts in shape and fumarolic activity and the temporal relations of the cones are ascribed to the level of magma in the underlying conduit.