New, well-preserved material of the Ordovician proetacean trilobite Rorringtonia, hitherto of uncertain taxonomic position, indicates that it belongs to the aulacopleurid subfamily Scharyiinae. It also elucidates the position of another problematic proetacean, Analocaspis, which is now considered to be congeneric with Rorringtonia.

Biostratigraphical ranges and palaeogeographical distribution of mid-Givetian to end-Frasnian odontopleurids are investigated. The discovery of Leonaspis rhenohercynica sp. nov. in mid-Givetian strata extends this genus unexpectedly up to the late Middle Devonian. New material of Radiaspis radiata (Goldfuss, 1843) and the first koneprusiine in Britain, Koneprusia? sp., are described from the famous Lummaton shell-bed, Torquay, Devon. New taxa of Koneprusia, K. serrensis, K. aboussalamae, K. brevispina, and K. sp. A and K. sp. B are defined. Ceratocephala (Leonaspis) harborti Richter & Richter, 1926, is revised and reassigned to Gondwanaspis Feist, 2002. Two new species of Gondwanaspis, G. dracula and G. spinosa, plus three others left in open nomenclature, are described from the late Frasnian of Western Australia. A further species of Gondwanaspis, G. prisca, is described from the early Frasnian of Montagne Noire. Species of Gondwanaspis are shown to possess a number of paedomorphic features. A functional analysis suggests that, unlike other odontopleurids, Gondwanaspis actively fed and rested with the same cephalic orientation. The sole odontopleurid survivors of the severe terminal mid-Givetian biocrisis (‘Taghanic Event’) belong to the koneprusiine Koneprusia in the late Givetian and Frasnian, and, of cryptogenic origin, the acidaspidine Gondwanaspis in the Frasnian. Whereas the former became extinct in the late Frasnian at the Lower Kellwasser Event, the latter disappeared, and with it the entire Odontopleuroidea, at the terminal Frasnian Upper Kellwasser global biocrisis.

The results of a gravity survey of Islay indicate that, with respect to a local Bouguer anomaly datum of 260 g.u., a positive anomaly of 100 g.u. occurs over the Lewisian gneiss of the Rhinns of Islay, and, immediately to the E, a negative anomaly of —120 g.u. occurs S of Bowmore. Both anomalies trend N—E to S—W. The negative anomaly is interpreted as due to the presence of a structural basin occupied by a maximum 4600 m of Bowmore Sandstones and Dalradian meta-sediments. The boundary between the Lewisian gneiss and this basin is the Loch Indaal fault. At the head of Loch Indaal this fault bifurcates, one branch continuing north-eastwards as the Bonahaven fault, the other trending northwards as the Loch Gruinart fault, All the faults are considered to possess transcurrent components. The stratigraphic position of the Bowmore Sandstones is similar to that of the supposed Torridonian sediments of western Islay.

Upper water column dynamics in the eastern Arabian Sea were reconstructed in order to investigate changes in the activity of the South Asian / Indian monsoon during the early Pleistocene (c. 1.5–2.7 Ma). We used planktic foraminiferal assemblage records combined with isotopic (δ18O and δ13C) data, Mg/Ca-based sea surface temperatures and seawater δ18O records to estimate changes in surface water conditions at International Ocean Discovery Program (IODP) Site U1457. Our records indicate two distinct regimes of monsoon-induced changes in upper water structure during the periods c. 1.55–1.65 Ma and c. 1.85–2.7 Ma. We infer that a more stratified upper water column and oligotrophic mixed layer conditions prevailed during the period 1.85–2.7 Ma, which may be due to overall weaker South Asian / Indian winter (NE) and summer (SW) monsoon circulations. The period 1.55–1.65 Ma was characterized by enhanced eutrophication of the mixed layer, which was probably triggered by intensified winter (NE) monsoonal winds. The long-term trend in hydrographic changes during 1.55–1.65 Ma appears to be superimposed by short-term variations, probably reflecting glacial/interglacial changes. We suggest that an intensification of the South Asian / Indian winter monsoon circulation occurred between ∼1.65 Ma and 1.85 Ma, which is most likely due to the development of strong meridional and zonal atmospheric circulations (i.e. Walker Circulation and Hadley Circulation) because of strong equatorial East–West Pacific temperature gradients.

The diamictites of the Neoproterozoic Kapp Lyell Sequence in northern Wedel Jarlsberg Land, southwest Spitsbergen, have long been recognized as ancient glacial deposits, but their place within the global stratigraphic framework of ‘snowball Earth’ has remained unclear, owing to the complexity of superimposed Caledonian deformation and to the relatively inaccessible terrain in which they occur. Recently deglaciated exposures of the rocks now provide a more complete picture of the changing environment in which the diamictites were deposited, and new understanding of regional correlations help constrain their place in the global chronostratigraphy of the Cryogenian Period. The 2500 m thick Kapp Lyell Sequence consists of three distinct types of glaciomarine diamictite. The succession begins with about 1000 m of finely laminated diamictite containing abundant lonestones. The millimetre- to centimetre-scale laminae, apparent suspension deposits, consist of sand- to silt-sized particles of quartz and dolomite alternating with thin films of graphitic phyllite. The laminated unit gives way abruptly to 500–1000 m of unsorted, unlayered diamictite that alternates and interfingers with graded beds of conglomerate to sandstone. These apparent turbidite deposits become increasingly prevalent toward the top of the exposed section. Regional lithostratigraphic relationships suggest that the Kapp Lyell sequence corresponds to the second major stage of Neoproterozoic glaciation at c. 635 Ma. The graphitic material in the laminated unit yields δ13C values in the range of −20 to −22 ‰, pointing to a biogenic origin and an active marine biosphere at the time of deposition. The preservation of organic carbon and unusually large ratios of highly reactive Fe to total Fe suggest that low oxygen conditions prevailed in the deep basin that received these sediments. The transition from laminated, to unsorted, to graded diamictites may represent change from (1) a stable ice margin that released rare icebergs into a deep, quiet basin to (2) a collapsing ice sheet that unleashed flotillas of icebergs and large volumes of sediment to (3) submarine landslides that triggered turbidity flows from the rapidly deposited, gravitationally unstable sediments. The Kapp Lyell diamictite sequence appears to chronicle the demise of a large ice mass in this part of the Neoproterozoic world.

Theory based on the sphere as the ideal particle, fails to account satisfactorily for the concentration of solids observed in unconsolidated natural sands, which at the same time display a substantial degree of dimensional ordering of the particles. However, when the prolate spheroid of moderate axial ratio is substituted for the sphere, a theory which is satisfied by observation becomes possible, for the reason that equal spheroids can be regularly packed in both close and open ways. A spheroid assemblage of mixed open and close packings can retain a high degree of dimensional ordering of the constituent solids, yet have a relatively low particle concentration. Observations made on sandstones carefully selected for evidence of rapid cementation seem to bear out the theory as applied to natural sands. Clusters of grains resembling the open packings of equal spheroids are found in these sandstones to be uncommon but not rare, in accordance with the theory as thus far developed.

Gabbro and leucogabbro are volumetrically important rocks in the Nordingrå rapakivi complex, East Central Sweden. Plagioclase, ortho- and clinopyroxenes, and olivine dominate the gabbro. Perthitic orthoclase and quartz are interstitial in relation to the major minerals. The present work is based on 232 major-element and a large number of trace element analyses together with 15 whole rock Sm–Nd isotope analyses of the Nordingrå gabbroic rocks. εNd(T) values are negative, −1.1 to −3.2; the most negative values come from the gabbro. Most rocks are enriched in iron, some extremely enriched; none represent primitive mantle melts. The range of Mg-numbers is the same in the gabbro and the leucogabbro. Plots of the Ni-content vs. the Mg-number are scattered, but there is a positive correlation between these two parameters. The primary mantle-normalized ratios between similar trace elements are normally strongly different from one. Values larger as well as smaller than one are found for the same ratio in different rocks. The rare earth elements are only weakly fractionated with small Eu anomalies, negative for the gabbros and positive for the leucogabbros. The primary magma of the Nordingrå gabbro-anorthosite is thought to have been derived from a mildly depleted mantle source. Variations in the degree of partial melting of a reasonably homogeneous enriched mantle do not explain the observed chemical evolution. Crystal differentiation can account for some geochemical features, especially the Fe-enrichment. Crustal contamination is required by other characteristics as, for example, the negative εNd(T) values and the irregular and sometimes high primary-mantle normalized incompatible trace-element ratios. Al-rich relic material from the formation of the rapakivi granite melt is another source of assimilation. Most probably contaminants are heterogeneous, including undepleted crust (represented, for example, by early Svecofennian and Archaean granitoids), depleted crust (restitic after rapakivi magma extraction), and to some degree the associated rapakivi magma itself. Significant parts of this crust should be Archaean in age.

Nine species (eight new) of holothurian spicules are recorded from the Oxford Clay (cordatum zone) of Redcliff, near Weymouth on the Dorset coast. The new species are described and named and the significance of a close association of Rhabdotites and Theelia is discussed. Previous records of holothurian spicules from British strata are reviewed.

Modern detailed stratigraphical studies have demonstrated very clearly the long and involved tectonic history of the majority of the main structural units of England. It has been proved that, in certain areas, the thickness and the lithology of the sediments were partly determined by repeated pene-contemporaneous folding along definite axes, and thus it has been possible to trace the gradual growth of some of the main fold lines of the country. The Weald is typical of these areas, whose structure, at first sight simple enough, reveals on closer study much complexity of the minor folding and faulting and also gives evidence of long continued movement along certain lines; movement contemporaneous with the deposition of beds which were involved in the final crescendo of tectonic activity.

Southwestern Europe is one of the best regions for characterizing the dinosaur assemblages that prevailed just before the end-Cretaceous extinction. Aiming to better document this scenario, we provide the first evidence of dinosaur skin impressions in the red-beds of the Tremp Formation (southern Pyrenees). The impressions are assigned to sauropods (probably titanosaurians) on the basis of their scale morphology, arrangement and size. They represent a valuable tool for analysing the last occurrences of the sauropod clade before the K–Pg extinction, as they fall within chron C29r (latest Maastrichtian), thus representing some of the last in situ remains of this clade worldwide.

Various ways in which Lower Carboniferous reef limestones have accumulated are described, and terms defining them are introduced. Regional sedimentation, lithology, structure, fauna, and erosion history are kept separate in the discussion. The reef limestones of Northern England are briefly reviewed in the light of this classification.

The Castores and probably the Santa Rosa plutons of north-west Isla Navarino, southern Chile, have been emplaced by in situ diapirism into metasedimentary rocks of the Upper Jurassic (?)–Lower Cretaceous Yaghan Formation. For the former, this model is consistent with the concentric foliation paralleling the margin of the pluton and the foliation and stratification planes in the metamorphic aureole. Only the southern part of the Santa Rosa Pluton is preserved, and it has some structures similar to those of the Castores Pluton, which can also be interpreted as produced by an inflating diapir. The main intrusive rocks of these plutons are quartz-monzodiorites and quartz-diorites with synmagmatic foliation. They were preceded by minor bodies of hornblende gabbros, and followed by dykes and small bodies of non-foliated granodiorites. Non-foliated to weakly foliated granodiorites, forming the centre of the Castores Pluton, probably represent a younger intrusive pulse.

Twelve K–Ar mineral dates from 10 specimens of plutonic rocks, interpreted as near crystallization ages, span the period 80–90 Ma. These dates do not show the sequence of intrusion of the different rock-types, which may suggest that all of them were intruded and cooled in a short period of time. The timing of emplacement of these plutons in relation to tectonism is difficult to determine; however, a post-tectonic emplacement for at least the Castores Pluton, is proposed.

Utahcaris orion Conway Morris & Robison, 1988, from the lower middle Cambrian (Series 3, Stage 5) Spence Shale Member situated in Utah, USA, is redescribed based on a restudy of the original material. Newly recognized features, including ventral lateral eyes, trunk appendages, and a bulbous cephalic shield with subtriangular extension, reinforce similarities with Sanctacaris uncata from the middle Cambrian Burgess Shale. Both are assigned to the new family, Sanctacarididae. Sanctacaridids represent the oldest chelicerates. Their ecology and that of their nearest non-chelicerate relatives indicate that Chelicerata were plesiomorphically predatory.

THE origin of chert has of late been discussed with renewed activity, especially in American scientific journals. Difference of opinion centres mainly round the question of the source of the silica; whether it is of direct inorganic origin, or the result of the solution and redeposition of organic silica. Further points at issue relate to the age and formation of the chert; whether it is an original deposit contemporaneous with the country rock, or a metasomatic replacement of the latter and therefore of later age.

The previous literature on the pre-Cambrian rocks of Ireland is considerable in amount. The views of the early workers are briefly referred to in the Handbook of the Geology of Ireland, by G. A. Cole and T. Hallissy, published in 1924. This work doubtless expresses the opinion of Irish geologists of the present day.

Several enigmatic sedimentary structures are present in Upper Silurian and Lower Devonian terrestrial rocks of south Wales. These are millimetre ripples, wrinkle structures, ‘cauliflower’ and ‘molehill’ structures, calcretized matgrounds, ‘pepper-pots’ and ‘fairy rings’. Most of the structures occur on fine-grained sandstone bedding surfaces in both inclined and non-inclined red heterolithic deposits that form a large part of the Lower Old Red Sandstone in south Wales. These deposits consist of conspicuous units up to 3 m thick, comprising millimetre- to centimetre-scale laminasets of alternating mudstone and fine-grained sandstone, interpreted as muddy point bars on ephemeral channel margins, crevasse-splay lobes or distal flood-out deposits from ephemeral flow. They are rich in trace fossils reflecting animal locomotion, burrowing, foraging, ploughing and resting. Millimetre ripples and wrinkle structures are related to rapid growth of cyanobacterial mats on wet sediment surfaces, especially in films of standing water, that may have been a critical constituent of the food chain for terrestrial communities. Pustular ‘cauliflower’ and ‘molehill’ structures are preserved on tuffs and have been linked to algal blooms formed following an increase in nutrients due to ashfall into floodplain ponds. The tuffs are associated with a diverse ichnofauna indicating that opportunist colonizers took advantage of an abundant food source.

This study is concentrated on Ludlow (to Pridoli?) miospores from the Los Espejos Formation at the Quebrada Ancha locality, Central Precordillera, San Juan Province, Argentina. The Ludlow age is in agreement with the age based on acritarchs. The assemblage of continental palynomorphs is composed of 43 miospore species (29 trilete spores and 14 cryptospores). A new synonymy is proposed: Chelinospora poecilomorpha is here considered a junior synonym of Clivosispora verrucata. In addition, specimens belonging to C. verrucata var. verrucata and C. verrucata var. convoluta are included in a new morphon. This study represents the second Late Silurian miospore assemblage described from South America; the first was from the Urubu River, Amazon Basin, northern Brazil. The Quebrada Ancha assemblages allow a reasonably good correlation with biozones established for the Upper Silurian from the Cantabrian Mountains, northern Spain. The dendrogram analysis between coeval miospore assemblages from different localities shows a strong palaeogeographic affinity with the miospores recovered from northern Brazil and North Africa. Miospore assemblages from Spain show influences from Baltica and North Africa, demonstrating their intermediate position between these two continental plates. Conversely, dissimilarities recognized between Libya and Tunisia are most probably owing to local ecology and/or environmental conditions.

The Neihart Quartzite is the basal quartz arenite unit (≍270m thick) of the Mid-Proterozoic Belt Supergroup of western North America. Petrographic studies indicate a source area with plutonic granitic, metamorphic and felsic volcanic rocks. Extreme textural maturity and bimodality indicate an episode of aeolian transport for the detrital quartz grains. The lower 80% of the Neihart Quartzite were probably deposited by braided streams, whereas the upper 20% were deposited in shoreline environments. Residual material that was ‘stored up’ on the pre-Beltian cratonic surface and underwent aeolian reworking was the likely source material for most of the Neihart Quartzite. Less mature sediments in the top portion of the Neihart Quartzite indicate uplift and erosion of new source material during Neihart deposition. Other known cratonic quartz arenites, such as the St. Peter Sandstone (Ordovician), Lamotte Sandstone (Cambrian) and Flathead Quartzite (Cambrian), are thin (tens of metres thickness) and exhibit sheet-like geometry. In contrast, the Neihart Quartzite and its probable lateral equivalents are considerably thicker and increase in thickness towards the central portions of the basin. It thus appears that Belt sedimentation began with accumulation of a basal quartz arenite unit, and that sand for that unit was transported by braided streams from the surrounding craton to a gradually subsiding Belt basin.

A preliminary examination of Moine rocks containing rolled garnets from three widely spaced localities in the North-West Highlands indicates that the lineation in all cases is parallel to b. This is in accord with Phillips' theory that the metamorphism of the Moine schists was due to movement in a north-easterly or south-westerly direction. A Caledonian age for the metamorphism of the Moines therefore appears to be unlikely.