Zoned dolomite rhombs which occur in the organic-rich Jet Rock Formation (Toarcian) of northeast England have been studied using backscattered scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray microanalysis. The rhombs, which are 5–20 μm in size, are variable in chemical composition, but many consist of a dolomite core surrounded by a zone of ferroan dolomite, ankerite or ferroan calcite. Zoned rhombs occur in early-diagenetic calcite-cemented concretions and layers as well as dispersed throughout the shales. Distributional and textural evidence suggests that they formed mainly by primary precipitation from pore fluids within the zone of bacterial sulphate reduction. The ferroan outer zones probably formed after burial below the sulphate reduction zone when insufficient H2S was available to react with all the Fe2+ in solution.

Interactive digital processing of satellite images reveals significantly more information than the standard product photographic versions of the same images. Interactively processed images preserve finer details and can show information in areas which appear too dark or too bright on standard product images. This is illustrated by comparisons between both types of image as used in a photogeological interpretation of the tectonics of the Tibetan plateau.

The stratigraphy and fauna of terrestrial deposits at Portland Bill is described. The fauna is restricted to the head and is indicative of a cool climate rather than the temperate conditions suggested by earlier authors. An age in the Devensian Glacial Stage is tentatively suggested.

Sectioning Cruziana shows that an intrastratal mode of formation is common, as postulated by Seilacher. Beds with Cruziana are typically composite. Burrows were sometimes washed out and then recast by sand with primary structures. Formation as open surface furrows on an eroded and firmed mud, as postulated by others, is sedimentologically plausible in some instances but is unproven and seems biologically unlikely.

Recent investigations indicate that three distinct lithostratigraphical units can be recognized in the Red and Norwich Crag deposits of the area around Aldeburgh and Orford, Suffolk. These effectively represent a refinement of a stratigraphy originally suggested by Prestwich in 1871. A lowermost coarse-grained shelly sand, the Red Crag Formation, rests on an eroded London Clay surface and is banked against the Pliocene Coralline Crag. The Red Crag Formation passes upwards into a fine-grained generally unfossiliferous well-sorted sand, the Chillesford Sand Member, which overlaps the Red Crag Formation to rest directly on the Coralline Crag. The Chillesford Clay Member is regarded as the lateral equivalent of the upper Chillesford Sand Member, the two members together comprising the Norwich Crag Formation in this area. Sections that have been zoned palaeontologically may be integrated into this lithostratigraphical framework. These indicate that the Red Crag Formation correlates with the Pre-Ludhamian Stage, and the Chillesford Sand Member and the Chillesford Clay Member correlate with the Bramertonian Stage. Type sections are established for the three units described.

Lithological, major element, trace element and Sr isotope data from cyclic unit 10 of the Rhum Eastern Layered Series are presented. The lower 65 metres of the unit are peridotite, subdivided on textural and geochemical grounds into a lower homogeneous portion approximately 50 metres thick and an upper heterogeneous portion approximately 15 metres thick. The uppermost 16.5 metres of the unit are allivalite. There are steep geochemical gradients across the peridotite-allivalite boundary in Ni content of olivine and whole-rock Sr isotope composition.

Calculations are presented on the geochemical evolution of a Rhum picritic liquid undergoing olivine precipitation, both when the olivines remain suspended in the residual liquid as they precipitate, and when they are continuously fractionated. Quenched groundmass and olivine compositions from the Rhum dykes and the unit 10 peridotite olivines show good agreement with the suspension model but are inconsistent with the fractionation model. The Rhum chamber is thought to have been replenished with a picritic liquid from which olivine crystallized while held in suspension; however, replenishment by a highly olivine-phyric basalt is also possible. The peridotite probably accumulated rapidly as olivines were dumped out of suspension onto the chamber floor.

The lower part of the peridotite is a poikilitic adcumulate; it is suggested that this formed by convective circulation of melt in the pores of the pile of cumulus olivines. In the latter stages of adcumulus growth, more Fe-rich and isotopically contaminated magma entered the top of the cumulus pile causing cumulus olivines to re-equilibrate and giving the intercumulus plagioclase a higher Sr isotope ratio than lower down. The olivines in the allivalite show steep stratigraphic gradients in major element composition but not in their Ni content. They also show substantial variation in major element composition laterally within the allivalite. It is suggested that these features are a consequence of postcumulus re-equilibration of olivine with migrating intercumulus magma.

The Whin Sill comprises a major quartz tholeiite sill of late Carboniferous age underlying an area of c. 5000 km2 and with a volume of c. 200 km3, associated with contemporaneous dykes emplaced within Carboniferous sedimentary rocks in northeast England. New trace element analyses of chilled margins, sill interiors and dykes indicate that the Whin Sill complex magmas show significant chemical variations in terms of the relatively stable trace elements Th, Ce, Y, Zr, Nb and Ni. These data indicate that the complex was fed by a large number of compositionally distinct magma pulses, and that certain of the dykes may have formed feeder channels for the sill. The chemical characteristics of the sill and dyke samples are consistent with derivation by extensive polybaric fractional crystallization of olivine tholeiite magma derived by partial melting of compositionally heterogeneous mantle peridotite and/or crustal contamination of mantle-derived magmas.

Rare pebbles of granite have been discovered in the raised Patella beach at Butterslade, Gower, South Wales. Their petrography, trace element geochemistry and the Rb/Sr whole rock age of 55 ± 5 Ma confirm that they are derived from the Lundy granite which is about 49 km to the southwest of Gower. Amino acid analyses of fossil gastropods in the Patella beach have provided an age of 210000 years. Various hypotheses of transportation of pebbles from Lundy and Pembrokeshire to Butterslade are considered. Erratics from Pembrokeshire were probably transported by Pleistocene ice into the area while clasts of Lundy granite were moved by progradation of beach deposits northeastwards towards Gower during glacio-eustatic marine transgressions in the Pleistocene.

A simple seismic refraction line some 115 km long has been made across Norfolk to provide constraints on the depth to the ‘igneous/metamorphic’ basement. Shots were fired in the Wash and off the coast near Lowestoft and attempts were made to record at approximately 2 km intervals along the line. Recording quality was only fair, resulting in incomplete coverage of the line, and this restricts the quality of interpretation. The results show a refractor of about 6.05 km s−1 revealed over the whole line with no first-arrival evidence of the 4.5–5.5 km s−1 velocity expected from Palaeozoic sediments. Using estimated velocities of 2.4 km s−1 for the post-Palaeozoic succession, 4.5–5.5 km s−1 for the Palaeozoic succession and an estimated sub-crop position of the basement on the sub-Mesozoic floor, models are produced which suggest that the Palaeozoic sediments are no more than 600–1500 m thick at the eastern end of the line, depending on the Palaeozoic velocity assumed.

Sr and Nd isotopic compositions together with whole rock Sr and Nd abundances and olivine compositions are presented for cumulates from unit 10 of the Eastern Layered Series of the Rhum intrusion, Northwest Scotland.

The results show an Nd–Sr isotopic correlation consistent with contamination by high 87Sr/86Sr, low 143Nd/144Nd crust. There is a strong correlation between the degree of contamination, Sr and Nd whole rock abundance and Fe enrichment in cumulus olivine. The allivalites are the most contaminated, while the basal peridotites are uncontaminated. This suggests that the cumulates crystallized from a primitive uncontaminated magma and the allivalites from an evolved contaminated magma. Subsequently, movement of contaminated feldspathic intercumulus liquid has perturbed the isotopic, trace element and olivine composition of the upper peridotites.

Finger-like protrusions of peridotite are developed on Rhum where peridotite is overlain by allivalite. These structures, which were described by Brown as ‘upward-growing pyroxene structures’, are found in the following environments: at the main intra-unit junctions; along the upper surface of subsidiary peridotites in certain allivalites; and along the lower surface of allivalite blocks in some peridotites.

The structures generally take the form of parallel-sided or tapering protrusions with circular cross-sections. The tops of fingers are conical or hemispherical in shape. Typical dimensions are: finger amplitude, 2–5 cm; finger diameter, up to 3 cm; and finger wavelength, 5–10 cm. Peridotite in the finger is modally and texturally similar to the underlying layer, varieties range from feldspathic peridotite to dunitic peridotite. In the field the fingers apparently cut through layering, laminae and lamination without any associated disruption of the planar structures.

Two contrasting mechanisms of formation are discussed: vertical deformation of crystal mushes, and metasomatic replacement. On balance, we prefer to interpret the fingers as evidence for the replacement of pre-existing allivalite by secondary peridotite. Replacement was achieved by pore magma from the underlying peridotite migrating upwards into the overlying allivalite, in response to compaction. This pore magma was able to resorb plagioclase but crystallize olivine and pyroxene in its place.