Laser ablation techniques permit the determination of the stable isotopic ratios of finely crystalline calcite cements in chalks for the first time. Modelling of fluid–rock interaction using whole rock and laser ablation stable isotopic data indicates that carbonate mineral diagenesis in the Eldfisk Field consisted largely of the dissolution and reprecipitation of calcite with little associated loss of porosity. Cementation by calcite derived from stylolites apparently occurred throughout the Eldfisk Field chalk, but had only a subsidiary effect on whole rock isotopic ratios. Oxygen isotopic data indicates a pore water temperature of 50–80 °C during the bulk of chalk recrystallization. Increases in whole rock δ13C values with depth are likely the result of bacterial methanogenesis during chalk recrystallization.

The sediments and organic calcite geochemistry (Fe2+, Mn2+, Sr, Mg, δ18O, δ13C) of the Plenus Marls at Dover (southeast England) reflect the changing oceanographic conditions associated with the development of the late Cenomanian-early Turonian S1SC excursion.

The Plenus Marls of Dover consist of five marl-chalk couplets with a total thickness of up to 3 m. The sediments were deposited in an increasingly shallowing sea during a major regressional phase of the Chalk Sea over Europe. Each marl horizon was deposited in slightly cooler water of lower productivity and higher energy level than the overlying chalk, and represents a phase of enhanced regression. Inoceramus prisms and shell fragments from the marls have enhanced Mg values, whereas all the biogenic calcite from the chalks is enriched in Fe2+. The high clay content of the Plenus Marls probably originated from the post-depositional argillization of unstable silicate detritus (possibly of volcanoclastic origin) introduced into the regressing sea by rejuvenated river systems. The δ18O values of individual planktic and benthic foraminifera species have been lightened by diagenetic reaction; however they demonstrate (1) the presence of a constant temperature gradient in the water column with warmer surface waters relative to the bottom waters, and (2) the association of a marked temperature drop with the appearance of Jefferies' cold water occidental fauna and the development of a Mn2+ anomaly (Bed 5) in the average calcite skeletons of all particle size fractions. The δ13C values of individual planktic and benthic foraminifera species show that a normal oceanic gradient existed except at two levels (Beds 3, 5), where this is reversed with heavier values shown by the benthic forms. The normal δ13C gradient steepened rapidly as the water shallowed and the δ13C excursion reached maximum values. Dysaerobic and anaerobic water conditions were completely absent and the level of oxygenation (macrofaunal diversity) increased in parallel with the shallowing and the enhanced δ13C excursion.

Comparison with the Plenus Marls section at Flixton (east Yorkshire), which shows evidence of restricted faunas and deposition under anoxic conditions (black bands rich in terrestrial organic matter), demonstrates that between these two localities there is unequivocal correlation of the δ13C excursion and the temperature drop associated with Jefferies' cold water occidental fauna. Anomalous geochemical features of the Dover Plenus Marls are explained by the redeposition of Flixton-type coccolith-rich chalk (very low Fe2+ content) and by the occasional introduction of cold northern bottom waters enriched in 13C.

The status of the Cenomanian-Turonian oceanic anoxic event and its supporting evidence is discussed and is considered to be untenable on present evidence. An alternative hypothesis based upon a glacial mechanism is put forward; this is supported by evidence of widespread regression, restricted ocean circulation, lower ocean temperatures, enhanced input of terrestrial organic matter, and the presence of dropstones.

Rb–Sr isotope whole-rock data from the end-Caledonian Leinster Batholith define an errorchron age of 464±26 Ma, appreciably older than the accepted emplacement age of c. 405 Ma. This anomalously old age is the consequence of a highly variable initial Sr isotopic composition. Initial Nd ratios and TDM model ages also show a wide range of values. However, these isotopic variations are neither randomly distributed nor related to petrographic changes but instead reflect, in a simple way, geographic position about the axis of the batholith. The isotopic pattern revealed in the Leinster Batholith means that isochron ages obtained from S-type granites may be largely dependent on the sampling scheme adopted. The variable isotopic composition of the granite most likely resulted from either a heterogeneous metasedimentary source or hybridization of coeval, dominantly crustal melts.

The Sulitjelma Gabbro in the central Norwegian Caledonides has been dated with the U/Pb zircon/sphene method to 437±2 Ma. Geological relationships as well as trace-element geochemistry and Nd and Sr isotopic compositions suggest that the gabbro and associated dyke swarms and pillow lava formed during the initial stages of back-arc spreading. The age constrains the timing of juxtaposition of an older island-arc terrane and continental-margin lithologies exposed within the Caledonian nappes. The age of the gabbro is similar to that of the Solund–Stavfjord Ophiolite in west Norway, and confirms that spreading-related magmatism and marginal-basin development took place along the margin of Iapetus in late Ordovician–early Silurian times.

A number of garnetiferous minor intrusions have been mapped within the Borrowdale Volcanic Group. They underlie garnetiferous extrusive volcanic rocks which occur toward the top of a sequence of ignimbrite and lava – the Airy's Bridge Formation – which is the product of a major caldera-forming eruptive episode. Garnet and whole-rock geochemistry indicate that most of the intrusions are indistinguishable from garnetiferous dacite forming the final eruptive unit of the Airy's Bridge Formation: a co-magmatic link is therefore postulated. One of the intrusions, which intrudes the Airy's Bridge Formation, is distinct and may be related to the later Eskdale pluton.

It is suggested that following the emplacement of ignimbrites forming the basal half of the Airy's Bridge Formation, caldera collapse partially sealed a fissure-conduit system and degassed, garnet-bearing magma was intruded as dykes and sills and locally extruded as a post-explosive lava dome. It is also postulated that garnet crystallized in a high-level magma chamber (P < 3 kb) and that reverse chemical zoning was due to growth while sinking through compositionally stratified magma.

Depressions and embayments of the southern Fenland margin and islands are ascribed to periglacial processes in the Devensian Stage (last cold stage) of the Pleistocene. The processes, which may be included in the general term thermokarst, include thermal erosion as an important element. The age of the active landscape evolution appears to be Late Devensian. The Crowland Bed of the Fenland Pleistocene succession is a product of these processes.

Low and very low grade metamorphism in a mudrock-dominated succession, ranging from Upper Cambrian to Wenlock, is characterized by the white mica (illite) crystallinity technique. Kubler indices indicate that grade ranges from late diagenetic to low epizonal. The prograde reaction most easily observed by XRD study is the progressive ordering of K/Na micas; diagnostic 2M1 polytypic reflections become recognizable at 0.4 Δ 2θ and strengthen as grade advances. Grade generally correlates with thickness of overburden in the > 9 km thick succession. However, strain exercises additionally a profound influence on grade, and the distribution of strain was related to décollement resulting from inhomogeneities and ductility contrasts within the succession. Strain energy is seen as an additional and important variable in the development of white mica crystallinity in slates. The distribution of metamorphic grade implies that the Lower Palaeozoic succession was augmented by several kilometres of Lower Devonian (Old Red Sandstone) strata at the metamorphic culmination. The culmination was syntectonic and represents an Acadian rather than an early diastathermal event. Subsequent dextral movement on the Bala Fault displaced the regional isocryst pattern by c. 4 km. Retrogressive smectite appears to be localized to the vicinity of the Bala Fault and is probably of Variscan age.

It is proposed that north–south crustal extension and related sedimentary basin formation commenced in the early Miocene. This extension is believed to be related to a spreading of a thickened crust as a result of Palaeogene compression. That such spreading commenced virtually immediately after the cessation of this compression is considered to be due to the high thermal profile of the crust in that area at the end of the Palaeogene.

Pre-Caledonian basement is juxtaposed with an inverted Upper Dalradian cover sequence along the Lough Derg Slide, in south Donegal, northwest Ireland. Shear-sense criteria indicate that the Dalradian Succession is translated via oblique dextral thrusting over high pressure granulite facies basement in the footwall. Crustal thickening induced by large scale folding associated with this ductile thrusting resulted in mid-amphibolite facies metamorphism adjacent to the sole of the Dalradian nappe. Subsequent to peak metamorphism, the overthickened Dalradian cover sequence suffered heterogenous deformation associated with ductile extension concentrated in the strain-softened mylonites of the hangingwall. The oblique ductile thrusts initiated during crystal thickening were reactivated in a normal sense. Pre-existing fold axes rotated towards the extensional transport direction, which is marked by a secondary stretching lineation with associated S–C fabrics. Ductile extension and hangingwall collapse are considered to be related to gravitational instability induced by the earlier crustal thickening episode.

Detailed sampling of the Little Minch Sill Complex reveals that it is composed of both single and multiple sills. These are formed of three main, genetically related units: picrite, picrodolerite and crinanite, which are the result of differentiation of an alkali-olivine basalt magma (approximately 10% MgO) in an upper-crustal magma chamber. Variations in igneous stratigraphy and the presence of internal chills in the Trotternish sills suggest that they were emplaced by multiple intrusion and subsequently differentiated in situ. Changes in petrography adjacent to pegmatite veins and textures within picrite units indicate compaction and filter-pressing were important processes after emplacement. Rhythmic layering (1 cm to 1 m thick) is conspicuous in the sills near contacts but does not involve cryptic mineral variation. Such modal layering may be more common than realised in relatively small-scale intrusions and maybe modelled in terms of in situ differentiation under conditions of significant undercooling in a changing thermal gradient at the synthetic for-sterite-diopside-anorthite eutectic.

Two boreholes in the Vale of Glamorgan have provided new data on the nature of the early Dinantian (Courceyan) transgression in South Wales. This transgression is manifested by the transition from the largely fluviatile, late Devonian, Upper Old Red Sandstone (Quartz Conglomerate Group) to the predominantly marine, early Dinantian, Lower Limestone Shale Group. The marine sequence comprises five shoaling upwards cycles, constructed from a suite of sedimentary lithofacies which record deposition in environments ranging from coastal plain, peritidal, lagoon, barrier and embayment to subtidal, open marine shelf. Each cycle represents a pulse of the transgression, and each successive pulse appears to have been larger than the preceding one, introducing progressively less restricted and more distal marine environments.

Thirty-seven samples were processed for palynological analysis. Miospore biozonation supports the cycle correlations between the two boreholes, suggested by the sedimentary event stratigraphy. Detrital kerogens from the samples comprise both terrestrially derived and marine types in varying proportions. Each kerogen type is described as well as the size, sorting and preservation of each assemblage. A palynofacies profile is presented for eachof the depositional environments recognized.

An upper Santonian fauna dominated by the curved baculitid Boehmoceras Riedel, 1931, occurs as phosphatic moulds in the Tombigbee Sand Member of the Eutaw Formation in Mississippi and Alabama, and also is reworked into the base of the Mooreville Chalk; a similar assemblage is present in the middle part of the Pen Formation of the Big Bend area, Texas. The assemblage is: Pseudoschloenbachia (Pseudoschloenbachia) mexicana (Renz, 1936), Placenticeras syrtale (Morton, 1834), Reginaites leei (Reeside, 1927a), Reginaites exilis sp. nov., Texanites (Texanites) sp. juv. cf. gallicus Collignon, 1948, Texanites (Plesiotexanites) shiloensis Young, 1963, Texanitinae incertae sedis, Hyphantoceras (?) amapondense (van Hoepen, 1921).Glyptoxoceras spp., Boehmoceras arculus (Morton, 1834) and Scaphites (Scaphites) leei Reeside, 1927a, form I. The assemblage is referred to the uppermost Santonian Texanites (Plesiotexanites) shiloensis zone of the Gulf Coast sequence. Common occurrence of Scaphites (S.) leei I and Reginaites leei suggest correlation with the Upper Santonian Desmoscaphites erdmanni zone of the U.S. Western Interior; common occurrence of Boehmoceras arculus (= B. loescheri of European authors) suggests correlation with the Marsupites–granulata zone at the top of the North German Santonian. These data strengthen intercontinental correlation of the Santonian–Campanian boundary sequence. They also provide a biostratigraphic link to a numerical age of 84.2±0.9 Ma from a bentonite at a slightly lower level in the Tombigbee Sand Member of the Eutaw Formation in Mississippi.

A ‘reg’-type palaeosol occurs at the top of the Lower Triassic Budleigh Salterton Pebble Beds at Budleigh Salterton, south Devon. Its morphology supports the idea that such soils form by the introduction of wind blown fines below a surface stone layer by a process of wetting–drying and crack formation. The degree of profile development indicates a prolonged period of pedogenesis, corresponding to a major stratigraphic break. The palaeosol formed under arid conditions, and represents a change in climate during Scythian times from a semi-arid to arid regime.

The sedimentology, micropalaepntology and palynology of Lower Pleistocene sediments recovered from a borehole at Ormesby St Margaret, near Great Yarmouth, Norfolk, have been investigated. The sediments, consisting of a lower clay facies overlain by an upper predominantly sandy facies, were deposited in inner neritic environments. Micropalaeontological and palynologicalevidence allows comparisons with the nearby Ludham sequence but an unequivocal correlation cannot be made. The Ormesby Borehole sequence includes representatives of the Pre-Ludhamian to Early Pastonian stage interval and the presence of a late Pre-Ludhamian to late Baventian/Pre-Pastonian a hiatus. Foraminiferal faunas matched to grain size analysis are indicative of transportation and considerable post-mortem sorting.

Using geophysical borehole log signatures and basic lithological information from sidewall cores and well-cuttings, division and correlation of the mid-Cretaceous sediments of the Wessex Basin can be achieved. A sub-Gault (early Albian) unconformity surface is mapped with some accuracy across the Hampshire–Dorset area, and the deposits of a previous, Aptian transgression are observed. The distinctive log signatures aid in facies reconstructions and sequence stratigraphical analysis: especially the onlap of basal Gault horizons onto and across basement ‘highs’. The highly variable thickness and lithological distributions characteristic of the Wealden pass upward into laterally extensive facies distributions in the Lower Greensand and Gault. Sequence boundaries are identified at the base of the Wealden; Lower Greensand; Gault; within the Gault (cristatum subzone); and base Chalk.

Chlorite–mica stacks in the Llandovery sedimentary rocks of central Wales have been studied, both within cleaved turbidite mudrocks, and within early diagenetic apatite, carbonate and monazite concretions. Stacks show a graded distribution within turbidite units, indicating an origin as detrital particles. Concretions provided an arrested diagenetic environment which restricted subsequent deformation and so revealed the nature of the stack precursor minerals. These included detrital mica, and also probable pyroxenes, amphiboles and volcanic rock particles, relic textures of which can be seen preserved within the concretions. Diagenetic alteration to chlorite, probably with some white mica intergrowth, occurred, most probably via smectite and then mixed-layer or swelling chlorite intermediates. Subsequent modification, during the Caledonian cleavage-forming episode, determined the present shape and mineralogy of the stacks. Outside concretions, chlorite pseudomorphs were rotated by tectonic compression, crushed at their margins and pulled apart along (001) cleavage and slip planes. Growth of at least two generations of secondary mica infillings has been recognized, and this was probably accompanied by the growth of secondary chlorite. This resulted in barrel-shaped stacks, elongated parallel with cleavage, and with the (001) plane rotated from the bedding towards the perpendicular to the cleavage. Within early diagenetic concretions it is evident that some stacks had formed prior to lithification. However, these have a relatively simple morphology and the original bedding-parallel grain shapes are largely preserved.

Sm–Nd and K–Ar isotopic determinations on an amphibolite from the Highland Border Complex yield Cambrian ages. Collisional events which might have generated the amphibolite appear incompatible with the passive margin character of Laurentia at that time. A possible explanation is that the part of the Highland Border Complex containing the amphibolite and associated rock units was generated outside Laurentia.

Measurements of fuselli and cortical bandages on thecae which show both of these enable a hypothesis about the dimensions of graptolite zooids to be put forward. This leads to a method for estimating zooid size when fusellus height alone can be measured. Results are shown for some species and the implications for theca formation and reproduction are discussed.

The Tien Shan is a Cenozoic orogenic belt in central Asia caused by the post-collisional convergence of India with Asia that reactivated Palaeozoic faults. The Korla Basin is a complex foreland basin within the Chinese Tien Shan; elongate sub-basins within it have received sediment from both the hangingwall and footwall blocks above and below reverse faults on their northern margins. The footwall blocks are themselves uplifted by the next fault to the south: the greater part of the sediment supply measured by area comes from the footwall block. This sediment supply pattern is analogous to that of extensional half-graben.