Boreholes penetrating the inverted limb of a major fold in an allochthonous thrust sheet at Chillaton, West Devon, revealed highly fossiliferous strata spanning the Devonian–Carboniferous boundary in continuous succession. Details of the fauna, which includes conodonts, trilobites and ostracods, are given. Abundant siphonodellid conodonts allow the boundary to be determined according to the recommendations of the working group on the Devonian–Carboniferous boundary of the IUGS Commission on Stratigraphy. The nature of the imbricate zone beneath the Main Thrust, in which the succession is situated, is described. In addition, the fabrics associated with thrusts which cut the olistostromic succession lower in the tectonic unit are discussed.

A revised stratigraphy is presented for the rocks which lie between the Upper Cretaceous Semail ophiolite and its post-emplacement sediment cover of uppermost Cretaceous to Tertiary age. Above the pelagic sediments of the ophiolite (Suhaylah Formation, Cenomanian–Turonian) occur ophiolite-derived clastic sediments (Zabyat Formation, ?Turonian–?Campanian) related to early stages of ophiolite emplacement. These formations are structurally overlain by the Batinah Complex, comprising Triassic to Cretaceous lithologies, all previously equated with the Hawasina rocks that now lie tectonically beneath the ophiolite. We recognize a lower melange unit to the complex, which demonstrably includes Hawasina lithologies. The melange formed by superficial rather than deep processes, but the mechanism by which Hawasina material was supplied to the ophiolite surface is unproven. The upper unit of the Batinah Complex shows a coherent stratigraphy which contrasts with that of the Hawasina. It comprises three main allochthonous tectonic sheets, within which we recognize three formations and one other informal unit. The upper Batinah Complex may have been tectonically derived not from the now subjacent Arabian margin but from another margin with a passive Mesozoic history.

Abundance data, determined by epithermal neutron activation analysis, are reported for radioelements in the northern units of the Leinster granite. Compared to similar data for silicic igneous rocks and British Caledonian granites, the Leinster granite shows normal U and K contents but is low in Th. Inter-element correlations and fission-track results suggest that most Th and up to 40% of the U is bound in resistate accessory phases (zircon, sphene, apatite), but that the bulk of U is associated with late-stage alteration products and is located at interstitial labile sites within the host-rock matrix. Mobilization of U located at such sites in the Leinster granite by hydrothermal leaching could lead to redeposition and enrichment in marginal sediments of Old Red Sandstone or younger age.

The Precambrian Murchisonfjorden Supergroup of Nordaustlandet, Svalbard, contains approximately 6000 m of folded, but essentially unmetamorphosed, shallow marine sedimentary rocks. The abundant microfossils found through much of the section allow confident biostratigraphic subdivision of the succession and correlation with contemporaneous sequences in East Greenland and Scandinavia.

Diamictite-bearing rocks of the Gotia Group (uppermost in the sequence) contain a depauperate assemblage of acritarchs dominated by Bavlinella Javeolata. A Vendian age of deposition is indicated. Carbonates of the immediately underlying Ryssö Formation contain a wide variety of microfossils including stromatolitic associations of several types, planktonic acritarchs, and, near the top of the formation, vase-shaped heterotrophic protists. The acritarchs, including Chuaria circularis, Kildinella hyperboreica, K. sinica, Trachysphaeridium spp., and others, and the protistan remains indicate a latest Riphean age. The underlying Hunnberg Formation is similarly fossiliferous. A typically Late Riphean acritarch suite is present, and in addition double-walled forms and large (500 μm), thick-walled spheroids bearing club-shaped 10 μm diameter spines are found. Thus, it appears that the entire carbonate sequence of the Roaldtoppen Group was deposited late in Late Riphean time.

The thick detrital succession comprising the lowermost part of the unmetamorphosed Nordaustlandet sequence, the Celsiusberget and Franklinsundet groups, contains fossils at various levels. Although microfossils are often somewhat coalified, identifiable Late Riphean taxa such as Chuaria circularis and Kildinella spp. are present in rocks as low as the middle Westmanbukta Formation. The presence of the distinctive carbonaceous macrofossil Tawuia dalensis in the Kapp Lord Formation permits an age estimate of 850–900 Ma for this formation.

All told, the entire Murchisonfjorden Supergroup of Nordaustlandet appears to have been deposited during the Late Riphean and Vendian intervals. The long-recognized lithostratigraphic parallels between this sequence and the Eleonore Bay and Tillite Groups of East Greenland are complemented by strong biostratigraphic similarities.

A freshwater and land molluscan assemblage from an Ipswichian stream channel at Maxey, Cambridgeshire, is discussed. The presence of Belgrandia marginata and Vallonia enniensis suggests that summer temperatures may have been somewhat warmer in the Ipswichian period. The assemblage represents the silting processes under relatively quiet water conditions, possibly in a side channel or backwater of a meandering river system.

Authigenic albite occurring as euhedral overgrowths up to 400 μm in size is a characteristic feature of the Pendleside Limestone in the Craven Basin of northern England. The albite is very pure, low-albite in keeping with other authigenic albites in carbonate rocks. The detrital cores of the albites are angular plagioclase grains of approximately An20 composition which are sometimes altered to kaolinite. The albite crystals with their detrital cores are frequently concentrated in discrete laminae, suggesting that the plagioclase cores may have been supplied by a basic volcanogenic source. This view is supported by geochemical studies of limestones which reveal significant correlation between K–Na, Na–Al and K–Al.

Interstitial alteration of detrital components, in particular the reaction intermediate plagioclase → kaolinite + albite, was primarily responsible for albite authigenesis. The initial products of this reaction probably included smectite which fixed Mg2+ in the decomposing volcanic grains. Subsequent alteration of the smectite resulted in the formation of small microdolomite inclusions which are commonly seen in the authigenic albites. An equilibrium model in terms of Na+/H4 ratios and H4SiO4 activity is proposed for the silicate assemblages in the Pendleside Formation.

K–Ar ages of biotites from a variety of alkaline volcanics and minor intrusive rocks in the nothern Oman mountains allochthon give a range of ages from Triassic (230 Ma) to mid Cretaceous (92 Ma) and represent igneous activity on the Oman continental margin throughout the Mesozoic. This was a passive margin destroyed by the emplacement across it of a pile of nappes in the late Cretaceous, including a largely intact thrust sheet of Upper Cretaceous oceanic lithosphere (the Semail ophiolite). Biotite ankaramite dykes, cutting compositionally similar volcanics, in the thrust complex immediately beneath the ophiolite, give Triassic ages and are related to the rifting and break-up of the northeast Arabian margin at the beginning of formation of the Oman Tethys. Mid Cretaceous (Cenomanian–Turonian) ages are mostly recorded from the northern part of the mountains where there are alkaline tuffs in a sedimentary melange. They are approximately the same age as the ophiolite and may be related to tectonic instability of the Oman margin immediately prior to ophiolite emplacement. Alkaline sills, intrusive into a variety of rocks, including Triassic volcanics, give Jurassic and Cretaceous ages and are interpreted as periodic alkaline activity on the Oman margin throughout passive margin development.

Thick subaerial volcanic sequences of probable mid Triassic age rest unconformably on Permo-Carboniferous limestones in the ‘Phyllite Series’ within the Gavrovo-Tripolitsa zone of the external Hellenide nappes. The volcanic rocks are varied in character. Pyroclastic rocks (often reddened) predominate, but minor basalt or andesite and rhyolitic hypabyssal intrusions and flows are also found. The rocks have experienced low-grade metamorphism and the only relict primary minerals are pyroxene and rare plagioclase in basic rocks and potash feldspar in acid rocks. The most important metamorphic phases are albite, chlorite, potassium mica, epidote, hematite, quartz and pumpellyite. Twenty-seven whole-rock major-element analyses suggest that there has been some exchange of Na2O and K2O for CaO during metamorphism, but that other elements have been relatively stable. A genetic interpretation of the rocks is attempted using published geochemical discriminator diagrams. The basic rocks are tholeiitic in major element chemistry and pyroxene composition. Trace element (Hf, Ta, Th, Ce, Yb) distribution suggests magma generation at a destructive plate margin.

Two examples of point bars in single-channel gravel-bed rivers in Wales illustrate some of the morphological and surface sedimentary features observed during a wider examination of 40 sites of recent (less than 100 years) channel sedimentation. The point bars consist of predominantly sandy gravel bar platforms overlain by discontinuous sand bodies. Cut bank exposures show generally massive sandy gravels abruptly underlying a silt/sand unit. Morphologically the bars are platformlike, with primary inner-attached, or secondary medial, chutes. This relief, together with the effects of seasonal vegetation, determines the locations of finer-grained (non-gravel) material. The frequency with which deposits produced by this type of channel sedimentation may be encountered in Quaternary and pre-Quaternary successions is briefly discussed.

Pre-Anglian terrace stages of the proto-Thames system are traced from the present middle Thames area into Essex and south East Anglia. Gravel composition indicates that each of the main terrace stages is associated with an influx of far-travelled material, probably signifying at least three phases of pre-Anglian glaciation in the south Midlands. Gravel composition also indicates the occurrence of major changes during Early and Middle Pleistocene times in the extent of the Thames catchment, and in the disposition of the main drainage lines. The important role of the Goring Gap in the development of the drainage system is noted, and the nature and distribution of Anglian fluvioglacial gravels are described.

The Dalma volcanic belt in the Precambrian Eastern Indian shield is composed of a thick sequence of volcani-sedimentary assemblage with a group of predominantly ultramafic volcaniclastics having komatiitic chemistry. A volcanic origin is suggested by textural relationships and mineralogical composition, together with the presence of devitrified glass shards; these rocks are now mostly chlorite-tremolite schist.

Leaf compression fossils are abundant within the lower Cretaceous part of the Fossil Bluff Formation in southern Alexander Island, Antarctica. They occur in lacustrine laminated siltstones with a high volcaniclastic component. During zeolite facies metamorphism of the rocks, breakdown of clay minerals, volcanic glass and calcic plagioclase generated new mineral phases. The growth of these minerals was concentrated within and around leaves: finely disseminated oxide of titanium crystallized within the organic material, a thin film of chlorite was precipitated around leaves and silica, calcite and laumontite grew disruptively between leaf cuticles. Despite relatively low levels of organic maturation the structure of the leaf cuticles was destroyed and the only details which survived were those preserved as impressions in the chorite film.

Potassium-argon ages measured on 11 volcanic rocks, mainly lavas, from Tristan da Cunha range from 0.21 ± 0.01 to 0.01 ± 0.02 Ma, and confirm the youthfulness of this volcano, which lies on the Walvis Ridge just to the east of the crest of the Mid Atlantic Ridge.

Rb-Sr analyses of syntectonic single-crystal garnets from the Svartsobacken and Dikanas schist units of the Seve Nappe, Scandinavian Caledonides, show systematic differences. One group yields a Precambrian age spectrum consistent with that given by whole-rock analyses; the other group gives Caledonian ages similar to those given by mica analyses. It follows that the tectonic events reflected in the garnet inclusion patterns are also of different ages and, subject to certain limitations, the method can be used to provide a clearer interpretation of the deformational and metamorphic history of the rock.

A submarine fissure eruption of Upper Miocene age produced a modest volume of alkaline basalt at Low Layton, on the north coast of Jamaica. The eruption occurred in no more than a few hundred metres of water and produced a series of hyaloclastites, pillow breccias and pillow lavas, massive lavas, and dikes with an ENE en échelon structure. The volcano lies on the trend of one of the island's major E–W strike-slip fault zones: the Dunavale Fault Zone. The K–Ar age of the eruption of 9.5 ± 0.5 Ma. B.P. corresponds to an extension of the Mid-Cayman Rise spreading centre inferred from magnetic anomalies and bathymetry of the Cayman Trough to the north and west of Jamaica. The Low Layton eruption was part of the response of the strike-slip fault systems adjacent to this spreading centre during this brief episode of tectonic readjustment.

Extremely fine-grained granular rocks are found interleaved with cumulates in some layered differentiated intrusions. The question arises as to whether these can be interpreted as chilled magmas. If this were so it would allow the liquid line of descent to be determined directly. A study of extremely fine-grained granular rocks in the differentiated, layered basic Fongen–Hyllingen complex, Norway, however, showed rocks of this type to be cumulates. Fluctuations in volatile pressure due to crystallization of a hydrous phase may give rise to modal and grain-size variation in layered intrusions.

Granophyre patches on the sites of former sedimentary feldspars in the feldspathic Appin Quartzite show that partial melting took place in the inner parts of the aureoles of late Caledonian minor intrusions. Mobilization of the melt and refractory quartz residue as a thixotropic suspension is shown to result in the formation of veins and breccias. Textures are related to the wetting of quartz/quartz grain bounderies by the eutectic melt and the later growth of crystals during cooling. From the presence of high (β) quartz coexisting with melt, minimum contact temperatures are estimated as 780°C, showing that some convective circulation of magma took place.

The interrelationships of dolomite, anhydrite, gypsum and cargneule (a yellow-brown dedolomitised breccia), are discussed with specific reference to the Gran Paradiso region, Western Alps. The dolomite is a highly deformed rock which occurs along the soles of both early and late-Alpine thrusts. Evidence suggests that cargneule formed late in the geological history of the region. It is suggested that dolomite + anhydrite + water acted as an important decollement horizon. Recent exposure to the surface, hydration of anhydrite to gypsum and dedolomitisation resulted in cargneule formation.

Costacadoceras bluethgeni gen. et sp.nov. and Articoceras harlandi sp.nov. are described from the base of the Kongsøya Formation of Kong Karls Land, Svalbard, and dated as mid boreal Bathonian (early ishmae Zone).

Planktonic foraminifera are recorded for the first time from the St Erth Beds but they are small and very rare. A late Pliocene G. inflaia Zone age is postulated on the presence of Globorotalia inflata and dextrally coiled Neogloboquadrina pachyderma. It is suggested that the depth of water at the time of deposition was much less than 100 m, possibly in the photic zone, and the palaeotemperature was in the range of 10–18 °C.