bluuebunny/crossref_metadata_2025_split huggingface dataset:
The age of the Watch Hill Grits (Ordovician), English Lake District: structural and palaeogeographical implications
Authors: Molyneux S. G. , Rushton A. W. A. 
Published: November 2011

ABSTRACTThe Watch Hill Grits, in the lower Ordovician Skiddaw Group of the Lake District, are dated as latest Tremadoc or earliest Arenig (older than theDidymograptus deflexusBiozone) by means of acritarchs and graptolites. This places them lower in the Skiddaw sequence than previous authors supposed, and they are thought to have been thrust southwards over younger Arenig rocks. The interval inferred for the Watch Hill Grits brackets theTetragraptus approximatusBiozone and its equivalents in Australasia, S China, N America and Scandinavia. The dating of the Watch Hill Grits suggests that equivalents of theTetragraptus approximatusBiozone are present in N England and that sedimentation continued in the Lake District during a period of global eustatic regression. Other beds in the Lake District and on the Isle of Man have yielded similar acritarch assemblages and are probably correlatives. Five new acritarch taxa are described:Caldariolagen. nov.,Acanthodiacrodium? dilatum, Stellechinatum sicaforme and Striatotheca prolixaspp. nov., andTetraniveum arenigum cumbriensesubsp. nov.; one new combination,Caldariola glabra(Martin) comb, nov., is proposed.
REE and trace element variations in accessory minerals and hornblende from the strongly zoned McMurry Meadows Pluton, California
Authors: Sawka Wayne N. 
Published: November 2011

ABSTRACTThe zoned McMurry Meadows Pluton has been examined for REE and trace element variations in hornblende, sphene, apatite, allanite and zircon. Mineral separates (17), were analysed by INAA from four granitoids spanning the compositional range of the pluton (60%–75% SiO2). All of the phases examined exhibit significant compositional variations, with sphene having the largest changes in chondrite normalised REE patterns. Compositional variations in these minerals are related to paragenetic sequence and, as the whole rocks become more evolved, increases in partition coefficients; not subsolidus re-equilibration. Hornblende is only a dominant site for REE in granites where sphene is a later crystallising phase, otherwise allanite (LREE only) and sphene are the dominant whole rock sites for REE. Zircon and apatite normally contribute less than 10% each to the whole rock abundance of REE. Three zircon samples contain only small compositional differences and are interpreted as having crystallised from the bulk magma prior to differentiation. Zr variation in the pluton is nonlinear, first increasing and then decreasing with whole rock fractionation. A simple process, analogous to “restite unmixing” applied to the Zr variation, defines a bulk magma composition of about 63% SiO2, before differentiation of the zoned pluton. The modelled bulk magma need only have evolved by about 2·5% silica and still have produced the entire compositional range (60–75% SiO2) observed in the pluton.
A global synthesis of the latest Ordovician Hirnantian brachiopod faunas
Authors: Jia-yu Rong , Harper David A. T. 
Published: November 2011

ABSTRACTA global review of new and existing data on the distribution of uppermost Ordovician (Hirnantian) brachiopods indicates the existence of at least three biogeographically distinct faunas. The typical Hirnantia fauna characterised subtropical and temperate latitudes and comprised a variety of ecological associations; the fauna reached its acme during the bohemicus and uniformis zones. Atypical Hirnantia faunas, developed marginal to Gondwana, are of low diversity and have few species in common with the typical Hirnantia fauna; their spatial distribution probably marked the margin of the polar ice sheets. The extinction of the Hirnantia fauna occurred in response to changes in sea level. Diverse and quite different faunas, including those from the Midcontinent of North America, Kolyma, the Oslo Region and probably Anticosti Island, occupied equatorial latitudes during the latest Ordovician. The Holorhynchus fauna, on evidence to date, predates the Hirnantia fauna.
Evolution of a machair landscape: pollen and related studies from Benbecula, Outer Hebrides, Scotland
Authors: Whittington Graeme , Edwards Kevin J. 
Published: November 2011

ABSTRACTLow altitude sandy plains (machair) are a common feature of the Atlantic coasts of the Outer Hebrides. They formed as a result of shoreward movement of material consequent upon a rise in Holocene sea levels. A number of earlier, partially inconclusive, investigations into machair evolution proposed that fuller understanding could arise from an examination of inter-tidal organic deposits, in so far as these could provide a fossil proxy record of the processes involved in machair formation. Study of a series of inter-tidal peats sites located on a beach platform at Borve, island of Benbecula, provided both spatial and chronological evidence for sand movement as well as furnishing new data on vegetational and environmental history. The pollen diagrams show a flora in whichCalluna vulgaris(heather) and Poaceae (grass) are frequent dominants, while such arbroeal taxa asBetula(birch) andCorylus avellana-type(cf. hazel) are notable. The existence of birch–hazel woodland for the periodc.8855–6190 BP might conceivably have had a retarding effect on sand movement. Later cycles of sand movement would not have met such obstruction with the consequence that sand mobility and machair plain evolution could have been faster. Sand arrival at the seaward site (Borve 3), is dated toc.6735 BP and it continued untilc.6045 BP, after which it slowed before increasing again from around 5990 BP. This sand incursion produced a machair plain over the Borve sites as part of a continuous, but variously paced, marine and aeolian process. The presence of charcoal from c. 6860 BP, with a major increase in charcoal to pollen ratios by 6190 BP, may suggest that natural or intentional burning of the vegetation cover of the machair occurred in Mesolithic times; if the burning was anthropogenic in origin, then it pushes the possible involvement of humans in machair destabilisation to a time long before the previously proposed Neolithic period. A wet slack deposit, dated to 3400 ± 70 BP, indicates a time when sand movement overwhelmed the area around the landward site (Borve 1) and when the rate of sand movement was likely to have been impeded. The data from Borve suggest that evolution of machair landforms occurs at a slow, variable rate and that there is considerable long-term stability.
Trilobites from the Ordovician Balclatchie and lower Ardwell groups of the Girvan district, Scotland
Authors: Tripp R. P. 
Published: November 2011

ABSTRACTAll trilobites known from the lower and upper Balclatchie and lower Ardwell groups of the Girvan district are listed and frequencies recorded. Eight new species are described, a number of generic assignments are new, and hitherto undescribed parts are illustrated. Of the 60 named species, 19 occur in the lower and upper Balclatchie and lower Ardwell groups; the upper Balclatchie Group yields the largest number of species. The assemblage is generally indicative of outer shelf conditions of deposition; a deeper water association at certain Balclatchie Group localities consists of 5 species identical with, or closely related to, species from the Liberty Hall facies of the lower Edinburg Formation of Virginia, U.S.A. This deeper water element constitutes a significantly larger proportion of the trilobite assemblages at certain localities than it does at others. A further 8 species from the Balclatchie Group are allied to lower Edinburg Formation forms, thus confirming the evidence of the brachiopods regarding the strong North American affinities of the fauna. The Balclatchie conglomerate is considered to be the result of a catastrophic event accompanied by slumping near the shelf edge causing the instantaneous entombment of the fauna.
Identification of toxic mineral dusts using mammalian cells
Authors: Davies R. , Chamberlain M. , Brown R. C. , Griffiths D. M. 
Published: November 2011

ABSTRACTCell culture systems have been developed to assess the potential pathogenicity of mineral dusts. The in vitro cytotoxicities of a variety of dusts towards mouse peritoneal macrophages, Chinese hamster lung cells (V79 cell line) and human alveolar type II cells (A549 cell line) were investigated.Non-pathogenic dusts were found to be inert in vitro. Fibrogenic non-fibrous dusts such as silica were only cytotoxic towards macrophages. Fibrous dusts which are both fibrogenic and carcinogenic in vivo are cytotoxic towards all three cell types, their cytotoxicity being dependent on fibre size. The size range important for the observed biological effect is longer than about 8 μm and thinner than about 1·5 μm.
Palaeoclimatic information from ice cores: the Vostok records
Authors: Jouzel J. , Petit J. R. , Raynaud D. 
Published: November 2011

ABSTRACTIce deposits from Greenland and Antarctic ice sheets have stored over long periods of time information about the climate and environment of our planet. Attention will be focused on the 2083 m Vostok Antarctic ice core which represents a unusually long record (160 000 ka) due to the low accumulation rate (∼2 g cm−2a−1) and the rather uniform conditions of ice flow. This ice core provides a unique opportunity to obtain several palaeo-data such as temperature, accumulation (precipitation), aerosol loading, CO2 and trace gases over a full glacial-interglacial climatic cycle.The Vostok temperature, deduced from the interpretation of the deuterium content, and the CO2 records show a large 100 ka signal with a change of the order of 10°C and 70 ppmv respectively. The two records are closely correlated and both display shorter periodicities characteristic of the earth orbital parameters. CH4 concentrations also show variations from about 0·35 to about 0·65 ppmv linked with the glacial-interglacial warming. These features suggest a fundamental link between the climatic system and the carbon cycle and stress the role of radiatively active gases in climatic changes.The accumulation (precipitation) record appears to be governed by temperature with values during the coldest stages reduced by a factor of 2 with respect to the present rate. Ice deposited during these coldest stage is also characterised by high concentration of marine and terrestrial aerosols; these peaks probably reflect strengthened sources and meridional transport during full glacial conditions, linked to higher wind speed, more extensive arid areas on surrounding continent and a greater exposure of continental shelves.
Physical interactions within a coupled climate model over the last glacial–interglacial cycle
Authors: Berger A. , Fichefet Th. , Gallée H. , Marsiat I. , Tricot C. , van Ypersele J. P. 
Published: November 2011

ABSTRACTA two-dimensional (2-D) seasonal model has been developed for simulating the transient response of the climate system to the astronomical forcing. The atmosphere is represented by a zonally averaged quasi-geostrophic model which includes accurate treatment of radiative transfer. The atmospheric model interacts with the other components of the climate system (ocean, sea-ice and land surface covered or not by snow and ice) through vertical fluxes of momentum, heat and humidity. The model explicitly incorporates surface energy balances and has snow and sea-ice mass budgets. The vertical profile of the upper-ocean temperature is computed by an interactive mixed-layer model which takes into account the meridional turbulent diffusion of heat. This model is asynchronously coupled to a model which simulates the dynamics of the Greenland, the northern American and the Eurasian ice sheets. Over the last glacial–interglacial cycle, the coupled model simulates climatic changes which are in general agreement with the low frequency part of deep-sea, ice and sea-level records. However, after 6000 yBP, the remaining ice volume of the Greenland and northern American ice sheets is overestimated in the simulation. The simulated climate is sensitive to the initial size of the Greenland ice sheet, to the ice-albedo positive feedback, to the precipitation-altitude negative feedback over the ice sheets, to the albedo of the aging snow and to the insolation increase, particularly at the southern edge of the ice sheets, which is important for their collapse or surge.
Regional and tectonic implications of parallel Caledonian and Permo-Carboniferous lamprophyre dyke swarms from Lismore, Ardgour
Authors: Morrison M. A. , Hendry G. L. , Leat P. T. 
Published: November 2011

ABSTRACTGeochemical data are presented for 166 minor intrusions collected across the axis of the Ardgour swarm in the Isle of Lismore. The intrusions can be divided into: an alkali basalt-camptonite-monchiquite group resembling other Scottish Permo-Carboniferous dykes; a group of calc-alkaline (shoshonitic) lamprophyres, diorites and porphyrites with affinities to the late Silurian-early Devonian appinite suite of Scotland; and Tertiary dolerites. The different groups cannot be unambiguously distinguished in the field and secondary alteration precludes petrographic division in many cases. The data indicate that Caledonian and Permo-Carboniferous lamprophyres have probably been confused in previous accounts of dyke distributions in the region. In Lismore the two groups have identical azimuths but the Caledonian intrusions appear to have a greater aggregate volume. The implications for tectonic and regional models of the area are discussed.
High-level emplacement of an olivine–dolerite sill into Namurian sediments near Cardenden, Fife
Authors: Walker Brent H. , Francis E. Howel 
Published: November 2011

ABSTRACTArchival and recent boreholes over an area of c. 3 km2 have revealed complex magma-host interaction at the termination of an olivine–dolerite sill in Fife. The sill interior has zones rich in plastically deformed, vesiculated heterogeneous sediment surrounded by amygdaloidal basalt. Sediments at the contacts have been reconstituted and enclose blebs of chilled vesicular basalt. Intrusion into low rank coal seams has produced multicomponent tuffisite. A vertically nested and laterally fingered sill front is envisaged as having propagated down dip under a thin cover (<500 m) of wet Namurian sediments. Non-explosive bulk interaction of fluidised sediment and devolatilising magma occurred at intrusive contacts. Steam explosivity was more vigorous where lobes of magma repeatedly intruded moist lignite, to produce compositionally banded tuffisite rich in basalt clasts and coal fragments. The hydrovolcanic explosions did not give rise to surface eruptions because the low volumes of porewater and the high permeability and low tensile strength of the lignite prevented a build-up of high pressure steam.
Emplacement of alkali-dolerite sills relative to extrusive volcanism and sedimentary basins in the Carboniferous of Fife, Scotland
Authors: Francis E. Howel , Walker Brent H. 
Published: November 2011

ABSTRACTNamurian alkali-dolerites in W and central Fife comprise up to nine component sills. These have three-dimensional shapes which are directly related to penecontemporaneous structures in the sedimentary host rocks. Two forms of control are identified. Basinal control is apparent where restored sill geometry shows thickening towards the bottoms of saucer-shapes which mimic sediment disposition at the time of emplacement. Fault control is evidenced by sills which change horizon along extensive E–W fractures once assumed to be entirely post-Carboniferous but now confirmed as growth-faults.There are no associated dykes representing likely feeders comparable with those of the later tholeiitic Midland Valley Sill, but evidence is presented to suggest that at least some of the alkali-dolerite magma reached sill intrusion levels through volcanic pipes.
Comparative physiology as a tool for investigating the evolutionary routes of animals on to land
Authors: Little Colin 
Published: November 2011

ABSTRACTAlthough many physiological characteristics are very labile, it is proposed that some are stable enough to provide evidence concerning the routes by which terrestrial animals moved on to land. Osmotic tolerance and osmoregulatory ability are investigated first. Marine littoral invertebrates tolerate wide osmotic changes but osmoregulate little. Freshwater invertebrates osmoregulate well, but over a narrow range. Terrestrial prosobranchs of the family Pomatiasidae, which have wide tolerance, may have originated directly from the sea. The Cyclophoridae, which are intolerant, may have moved to land from fresh water. Isopods and talitrid amphipods may all have had direct marine origins with no freshwater phase. Secondly, terrestrial animals of marine origin may have blood with higher osmotic pressures than those passing through fresh water. In prosobranchs, isopods and amphipods, the evidence agrees with the conclusions suggested from character one. Thirdly, the production of hypo-osmotic urine in terrestrial animals may be evidence of freshwater origin. The evidence again supports the initial suggestions about prosobranchs and amphipods. It is concluded that because there is little selection pressure acting on these characters on land, theycanbe used as evidence of ancestry. Possible use of further characters is discussed.
Physiological constraints upon marine organisms
Authors: Robertson J. D. 
Published: November 2011

ABSTRACTWhen compared with sea water, most marine invertebrates are isosmotic but show varying degrees of ionic regulation, from accumulation of potassium and calcium to reductions of magnesium and sulphate. A reduction of sulphate in pelagic animals such as jellyfish and salps, and an accumulation of ammonium ions in arrow-worms (Sagitta) contribute to their near-neutral buoyancy. Marked reductions in salinity exclude mahy marine invertebrates. In the Baltic, polychaetes, bivalve molluscs and decapod crustaceans are reduced from 193, ninety-two and sixty-four species in the Belt Sea (salinity S 10-30‰) to three, four and two in the Gulf of Finland (salinity S 5-9‰). The chelicerateLimuluscan stand a wide range in salinity, a few insect larvae can tolerate concentrations of 200% sea water, while the branchiopod shrimpArtemiacan stand crystallising brine (36-37% NaCl). Very few species can tolerate temperatures of 40°C. One such species is the polychaeteAlvinella pompejana,a hydrothermal vent animal at East Pacific Ridge (to the W of S America). The harpacticid copepodTigriopusliving in evaporating rockpools has a lethal temperature of 42°C at a salinity of S 90‰, but at S 8‰ that temperature is 34°C. Lack of oxygen and presence of hydrogen sulphide limit the distribution of animals in certain areas. Most active animals have respiratory pigments in their principal body fluid. Burrowing invertebrates such asArenicolaandLingulahave respectively haemoglobin in the blood and haemerythrin in the coelomic fluid, with mean oxygen capacities of 6 ml O2per 100 ml in each case, compared to 0·6 and 0·5 ml in sea water at 10° and 20°C.
Physiological adaptations of the living agnathans
Authors: Hardisty M. W. , Potter I. C. , Hilliard R. W. 
Published: November 2011

ABSTRACTThe modes of life and environments of the extant agnathans (cyclostomes) are discussed in relation to their adaptations to temperature, light, oxygen and salinity. As their antitropical distribution indicates, both hagfishes and lampreys are cold water groups. Since hagfishes live in deeper waters than lampreys, they are not exposed to the marked seasonal changes in temperature and light which influence major events in the lamprey life cycle. Both groups tend to be nocturnally active, either burrowing during daylight as in the case of larval lampreys (ammocoetes) and most hagfishes, or showing cryptic behaviour as in the case of adult lampreys. Olfaction plays a major part in the location of prey, presumably aided in adult lampreys by their eyes and sensitive electrosensory system. Rates of standard oxygen consumption, ventilatory frequency and heart rate of adult lampreys increase at night. Standard oxygen consumption is relatively low in ammocoetes (as it also is in hagfishes) but increases markedly during metamorphosis into the adult lamprey. Ammocoetes and hagfishes, and to a lesser extent adult lampreys, are resistant to reduced environmental oxygen tensions. Differences in the oxygen dissociation curves of ammocoetes, adult lampreys and hagfishes can be related to differences in the characteristics of their monomeric haemoglobins and their environments and modes of life. The extraordinary tolerance of the hagfish heart to hypoxia is a reflection of a robust capacity for glycolysis, an LDH isozyme geared towards anaerobic functioning and a low work output. The hagfishes, which are restricted to marine waters, are osmoconformers. The osmolality of their blood, which is almost wholly attributable to inorganic ions, is virtually identical to that of full strength sea water (c. 1000 mOsmkg−1). By contrast, the osmolality of the blood of larval and adult lampreys when in fresh water is only 205-260 mOsm kg−1, i.e. about one quarter to one fifth of those of hagfish, and these rise only to 240-270 mOsm kg−1in the adults of anadromous lampreys in sea water. The regulation of ions by adult lampreys is achieved by mechanisms similar to those adopted by teleosts. The implications of the contrasting ionic and osmotic physiology of the two living groups of agnathans are discussed in relation to their possible environmental history and against the background of their Carboniferous fossil representatives.
Physiology of Crustacea from difficult environments
Authors: Lockwood A. P. M. , Bolt S. R. L. 
Published: November 2011

ABSTRACTExamples of the mechanisms involved in body fluid regulation by present-day crustaceans inhabiting variable salinity habitats are described using amphipod gammarids and the isopodMesidotea (Saduria) entomonas models. Appropriately the species inhabiting the most demanding habitats have the greatest range and most sophisticated regulatory responses. Behaviour, micromorphology and physiology are all involved to a variable degree and, in the examples discussed, responses to salinity change seem finely tuned to countering the problems generated by particular environments. This applies both in the rapid responses to sudden alteration in salinity and to the longer term changes associated with acclimation to a new steady state condition. The isolation of populations and features of derived freshwater races are considered and the implications for the presumed physiological mechanisms of fossil forms discussed.
Palaeophysiology of terrestrialisation in the Chelicerata
Authors: Selden Paul A. , Jeram Andrew J. 
Published: November 2011

ABSTRACTThe wide range of organs of respiration (book-gills, book-lungs, sieve- and tube-tracheae), reproduction, sensory perception, etc., among the chelicerates indicates that the major groups made the transition to land life independently. The fossil record is patchy for most chelicerate groups, certain intervals (e.g. Westphalian) being particularly rich in chelicerate bearing Lagerstatten while in others (e.g. Mesozoic) they are sparse. Due, apparently, to their unusual hyaline exocuticle, scorpions are better preserved than other arthropods, and show a fairly continuous record from fully aquatic forms in the Silurian, to both aquatic and terrestrial faunas in the Carboniferous. In particular, new and well-preserved material of the earliest demonstrably terrestrial scorpions from the Lower Carboniferous of East Kirkton, West Lothian, suggests that book-lungs, at least in the scorpions, developed directly from book-gills by suturing of the covering plate (Blattfuss of the related eurypterids) to leave stigmata for diffusion of air. This evidence supports the ideas of early authors that the scorpion mesosomal ‘sternites’ are fused plates,contraKjellesvig-Waering (1986) who envisaged the plates being lost to reveal true sternites beneath. The fossil evidence also indicates that by the Triassic at least two scorpion lineages had evolved intra-‘sternite’ stigmata.