Northwestern Scotland Research Articles

Challenging Classifications? Interpreting a “Difficult” Enclosure at Inchnadamph in Northwestern Scotland

ABSTRACT This paper explores some challenges of archaeological interpretation and classification through an enclosure at Inchnadamph in Sutherland, northwestern Scotland, a site that has proven difficult to interpret. Despite a small number of archaeological interventions, including topographic and geophysical survey and excavation, the site remains enigmatic. We discuss the different interpretations suggested for the site in turn, concluding that the enclosure does not fit readily into existing classification schemes. This raises issues surrounding the use of classification systems, prior assumptions, and the need for critical thinking in interpretation. These are universal issues, applicable beyond the Scottish example chosen, and this paper highlights concerns and difficulties encountered by all who deal with the classification of sites and monuments. Ultimately, this challenges some of our preconceptions and sheds light on the limits of our knowledge, as well as the limits of our classification systems.

Image dataset of benthic foraminifera in multicorer and gravity corer sediments from north-western Scotland shelf (North Atlantic Ocean).

Geological studies in the seas and oceans often give preference to the study of benthic foraminifera, which are a widespread and taxonomically diverse group of shell protozoa. In this paper, we present an extensive image dataset produced during the detailed micropaleontological analysis of 146 samples of bottom sediments collected by multicorer and gravity corer AMK-5656 from the Westray Basin on the north-western Scotland shelf (North Atlantic Ocean). In total, 106 taxa (at species and genera level) of benthic foraminifera were identified and photographed using the high-resolution microscope camera. This dataset can aid as a guide for identification of the benthic foraminiferal taxa at the paleoecological studies, stratigraphic works and interregional paleoceanographic correlation in the North Atlantic Ocean.

Structural, petrological, and tectonic constraints on the Loch Borralan and Loch Ailsh alkaline intrusions, Moine thrust zone, northwestern Scotland

During the Caledonian orogeny, the Moine thrust zone in northwestern Scotland (UK) emplaced Neoproterozoic Moine Supergroup rocks, metamorphosed during the Ordovician (Grampian) and Silurian (Scandian) orogenic periods, westward over the Laurentian passive margin in the northern highlands of Scotland. The Laurentian margin comprises Archean–Paleoproterozoic granulite and amphibolite facies basement (Scourian and Laxfordian complexes, Lewisian gneiss), Proterozoic sedimentary rocks (Stoer and Torridon Groups), and Cambrian–Ordovician passive-margin sediments. Four major thrusts, the Moine, Ben More, Glencoul, and Sole thrusts, are well exposed in the Assynt window. Two highly alkaline syenite intrusions crop out within the Moine thrust zone in the southern Assynt window. The Loch Ailsh and Loch Borralan intrusions range from ultramafic melanite-biotite pyroxenite and pseudoleucite-bearing biotite nepheline syenite (borolanite) to alkali-feldspar–bearing and quartz-bearing syenites. Within the thrust zone, syenites intrude up to the Ordovician Durness Group limestones and dolomites, forming a high-temperature contact metamorphic aureole with diopside-forsterite-phlogopite-brucite marbles exposed at Ledbeg quarry. Controversy remains as to whether the Loch Ailsh and Loch Borralan syenites were intruded prior to thrusting or intruded syn- or post-thrusting. Borolanites contain large white leucite crystals pseudomorphed by alkali feldspar, muscovite, and nepheline (pseudoleucite) that have been flattened and elongated during ductile shearing. The minerals pseudomorphing leucites show signs of ductile deformation indicating that high-temperature (~500 °C) deformation acted upon pseudomorphed leucite crystals that had previously undergone subsolidus breakdown. New detailed field mapping and structural and petrological observations are used to constrain the geological evolution of both the Loch Ailsh and the Loch Borralan intrusions and the chronology of the Moine thrust zone. The data supports the interpretation that both syenite bodies were intruded immediately prior to thrusting along the Moine, Ben More, and Borralan thrusts.

Variation of lead isotopic composition and atomic weight in terrestrial materials (IUPAC Technical Report)

Abstract The isotopic composition and atomic weight of lead are variable in terrestrial materials because its three heaviest stable isotopes are stable end-products of the radioactive decay of uranium (238U to 206Pb; 235U to 207Pb) and thorium (232Th to 208Pb). The lightest stable isotope, 204Pb, is primordial. These variations in isotope ratios and atomic weights provide useful information in many areas of science, including geochronology, archaeology, environmental studies, and forensic science. While elemental lead can serve as an abundant and homogeneous isotopic reference, deviations from the isotope ratios in other lead occurrences limit the accuracy with which a standard atomic weight can be given for lead. In a comprehensive review of several hundred publications and analyses of more than 8000 samples, published isotope data indicate that the lowest reported lead atomic weight of a normal terrestrial materials is 206.1462 ± 0.0028 (k = 2), determined for a growth of the phosphate mineral monazite around a garnet relic from an Archean high-grade metamorphic terrain in north-western Scotland, which contains mostly 206Pb and almost no 204Pb. The highest published lead atomic weight is 207.9351 ± 0.0005 (k = 2) for monazite from a micro-inclusion in a garnet relic, also from a high-grade metamorphic terrain in north-western Scotland, which contains almost pure radiogenic 208Pb. When expressed as an interval, the lead atomic weight is [206.14, 207.94]. It is proposed that a value of 207.2 be adopted for the single lead atomic-weight value for education, commerce, and industry, corresponding to previously published conventional atomic-weight values.

Distribution and prevalence of ticks and tick-borne disease on sheep and cattle farms in Great Britain

IntroductionThe most abundant and widespread tick species in Great Britain, Ixodes ricinus, is responsible for the transmission of a range of pathogens that cause disease in livestock. Empirical data on tick distribution and prevalence are required to inform farm management strategies. However, such data are largely unavailable; previous surveys have been rare and are usually relatively localised.MethodsA retrospective questionnaire survey of farmers was used to assess the reported prevalence of ticks on livestock across Great Britain. Spatial scan statistics and kernel density maps were used to assess spatial clustering and identify areas of significantly elevated risk, independent of the underlying distribution of respondents. Logistic regression models were used to identify risk factors for tick presence.ResultsTick infection risk to livestock is shown to be spatially aggregated, with areas of significantly elevated risk in north Wales, northwest England and western Scotland. Overall, the prevalence of farms reporting tick presence was 13% for sheep farms and 6% for cattle farms, but in “hot spot” clusters prevalence ranged between 48–100%. The prevalence of farms reporting tick-borne disease overall was 6% for sheep and 2% for cattle, but on farms reporting ticks, prevalence was 44% and 33% for sheep and cattle farms, respectively. Upland farming, larger flock sizes, region and the presence of sheep on cattle farms were all significant risk factors for tick presence.ConclusionsThese data have important implications for assessing both the risk of tick-borne disease in livestock and optimising approaches to disease management. In particular, the study highlights the need for effective livestock tick control in upland regions and the southwest, and provides evidence for the importance of sheep as tick maintenance hosts.

Sequence stratigraphy, chemostratigraphy and facies analysis of Cambrian Series 2 – Series 3 boundary strata in northwestern Scotland

AbstractGlobally, the Series 2 – Series 3 boundary of the Cambrian System coincides with a major carbon isotope excursion, sea-level changes and trilobite extinctions. Here we examine the sedimentology, sequence stratigraphy and carbon isotope record of this interval in the Cambrian strata (Durness Group) of NW Scotland. Carbonate carbon isotope data from the lower part of the Durness Group (Ghrudaidh Formation) show that the shallow-marine, Laurentian margin carbonates record two linked sea-level and carbon isotopic events. Whilst the carbon isotope excursions are not as pronounced as those expressed elsewhere, correlation with global records (Sauk I – Sauk II boundary andOlenellusbiostratigraphic constraint) identifies them as representing the local expression of the ROECE and DICE. The upper part of the ROECE is recorded in the basal Ghrudaidh Formation whilst the DICE is seen around 30m above the base of this unit. Both carbon isotope excursions co-occur with surfaces interpreted to record regressive–transgressive events that produced amalgamated sequence boundaries and ravinement/flooding surfaces overlain by conglomerates of reworked intraclasts. The ROECE has been linked with redlichiid and olenellid trilobite extinctions, but in NW Scotland,Olenellusis found after the negative peak of the carbon isotope excursion but before sequence boundary formation.

Precambrian reidite discovered in shocked zircon from the Stac Fada impactite, Scotland

Terrestrial impact events have had a profound influence on Earth’s geological, geochemical, and biological evolution. However, the record of Precambrian impacts is poorly constrained due to the dynamic nature of plate tectonics, erosion, and deposition of younger rocks that may destroy or cover the evidence. Here we report the first Precambrian occurrence of the rare mineral reidite (ZrSiO4) within grains of shocked zircon in the ca. 1.18 Ga Stac Fada Member (Stoer Group), northwestern Scotland. The reidite, preserved as <2-µm-wide lamellae, is unambiguous evidence of shock pressures in excess of ∼30 GPa and confirms the impact origin for the Stac Fada deposit. The reidite lamellae are locally deformed, and sites of deformation record its decomposition to baddeleyite (ZrO2) and amorphous silica, the first natural example of this transformation. The findings demonstrate that reidite and baddeleyite may form and be transported in high-energy ejecta without physical or chemical breakdown and are stable during sedimentary diagenesis and low-grade metamorphism. Thus, reidite may be preserved over time scales exceeding 1 b.y., establishing the use of reidite within detrital shocked zircon from Precambrian strata as a viable and valuable means of recognizing and characterizing ancient terrestrial impact events.

Bax and the ‘Celtic North’

Scholars of Arnold Bax have long acknowledged the influence of the Irish Literary Revival on the composer’s compositional output up to about 1920, of Sibelius from the late 1920s onwards, and of the continuity of styles between these two periods. In this article I argue that this continuity relies on what Bax draws from early Yeats, which is less Celtic mythology or folklore than a particular way of imagining nature; that Bax’s use as a compositional stimulus of what he called the ‘Celtic North’ (essentially the landscapes of western Ireland and north-western Scotland) had parallels in the literature and art of 1920s Ireland; and that the ‘Celtic North’ offers a means of critiquing inter-war English pastoralism, which has traditionally been associated with what Alun Howkins, after Hilaire Belloc, has called the ‘South Country’. Bax thus offers a musical engagement with nature that is essentially dystopian, sublime and (within the discourse of British pastoralism) non-Anglo Saxon.

An overview of the consequences of paraglacial landsliding on deglaciated mountain slopes: typology, timing and contribution to cascading fluxes

Three decades after the early definition of the concept, a general model of paraglaciation was established, integrating the typical sediment paraglacial cascading system and the responses of associated sediment storages. The residuals of this model should now be examined and explained through controlling factors that may act at both regional (e.g. tectonics) and local (topography, lithology, etc.) scales. We compare here the patterns identified in a few mountain ranges of the northern hemisphere, located in various seismotectonic settings (especially western Alps, northwestern Scotland, central Norway, Svalbard and Iceland). By combining our field observations with a literature review, the effectiveness of the paraglacial response on mountain-slope erosion and the contribution of paraglaciation to the sedimentary cascading system are discussed. In most cases, paraglaciation generates sediment storage and aggradation in headwaters and glacial trough, as the evacuation rate into sinks remains low. Finally, paraglaciation appears to be a period of hillslope denudation, preparing reservoirs of sediments, which can only be effectively evacuated during further glaciation periods.

Timing of the East Antrim Coastal Readvance: phase relationships between lowland Irish and upland Scottish ice sheets during the Last Glacial Termination

A submillennial ice readvance from upland centres of ice dispersal in west central Scotland into northeastern Ireland post-dates the retreat of lowland Irish ice immediately after the Killard Point Stadial (max. 16.5 cal ka BP). The dimensions of this southerly and westerly ice sheet readvance on the margins of the North Channel are reconstructed from subglacial bedform patterns, subglacial tectonic deformation of Tertiary lignite and glacigenic sediment, limiting moraines/outwash and glacial stratigraphy. Morainic ridges at Rams Island and Sandy Bay on the eastern margin of the Lough Neagh basin which mark this ice limit are perpendicular to a well-defined field of subglacial bedforms across east County Antrim. At the ice readvance limits glacial lakes impounded in the Lagan Valley were partially infilled with subaqueous outwash known as the Malone Sands. This water body drained south along the Dundonald/Comber Gap spillway providing sediment which formed extensive, late-glacial marine terraces at the northern end of Strangford Lough around 15–15.5 cal ka BP. The East Antrim Coastal Readvance is part of a much more extensive readvance southwards along the North Channel and adjacent lowlands associated with ice sheet reorganisation and ice sheet growth in west central Scotland. It is now termed the North Channel Readvance and may be similar in age to the Wester Ross Readvance moraines in northwestern Scotland.

Evaluation of data sources for mapping glacial meltwater features

The meltwater system of disintegrating ice sheets provides an important source of information for the reconstruction of ice-retreat patterns during deglaciation. Recent method development in glacial geomorphology, using satellite imagery and digital elevation models (DEMs) for glacial landform mapping, has predominantly been focused on the identification of lineation and other large-scale accumulation features. Landforms created by meltwater have often been neglected in these efforts. Meltwater features such as channels, deltas and fossil shorelines were traditionally mapped using stereo interpretation of aerial photographs. However, during the transition into the digital era, driven by a wish to cover large areas more economically, meltwater features were lost in most mapping surveys. We have evaluated different sets of satellite images and DEMs for their suitability to map glacial meltwater features (lateral meltwater channels, eskers, deltas, ice-dammed lake drainage channels and fossil shorelines) in comparison with the traditional mapping from aerial photographs. Several sets of satellite images and DEMs were employed to map the landform record of three reference areas, located in northwestern Scotland, northeastern Finland and western Sweden. The employed satellite imagery consisted of Landsat 7 Enhanced Thematic Mapper Plus (ETM+), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Satellite Pour l'Observation de la Terre (SPOT) 5 and Indian Remote Sensing (IRS) 1C, and the DEMs used were from NEXTMap Britain, Panorama, National elevation data set of Sweden and National Land Survey of Finland. ASTER images yielded better results than the panchromatic band of Landsat 7 ETM+ in all three regions, despite the same spatial resolution of the data. In agreement with previous studies, this study shows that DEMs display accumulation features such as eskers suitably well. Satellite images are shown to be insufficiently detailed for the interpretation of smaller features such as meltwater channels. Hence, satellite imagery and DEMs of intermediate resolution contain meltwater system information only at a general level that allows for the identification of landforms of medium to large sizes. It is therefore pertinent that data with an appropriate spatial and spectral resolution are accessed to fulfil the need of a particular mapping effort. Stereo interpretation of aerial photographs continues to be an advisable method for local meltwater system reconstructions; alternatively, it can be replaced by mapping from high-resolution DEMs such as NEXTMap Britain. For regional to sub-continental reconstructions, the use of ASTER satellite imagery is recommended, because it provides both spectral and spatial resolutions suitable for the identification of meltwater features on a medium to large scale.

Reconstruction of a Lateglacial (Younger Dryas) mountain ice field in Sutherland, northwestern Scotland, and its palaeoclimatic implications

AbstractQuaternary geomorphological and geological mapping of a large area (∼1800 km2) in the northwestern Scottish Highlands has led to the reconstruction of a coherent mountain ice field approximately 45 km long and 30 km wide at its maximum extent. This West Sutherland ice field covered an area of ∼350 km2 and had a mean equilibrium‐line altitude of 334 m, assuming that the outlet glaciers all reached their maxima simultaneously. Numerical dating strongly suggests a Younger Dryas (12.9–11.7 ka) age of the mapped limits of this mountain ice field. This study also shows that the area of northwestern Scotland covered by Younger Dryas glaciers was five times larger than previously thought. Palaeo‐temperature estimates, obtained from chironomid and beetle assemblages elsewhere, have been used to reconstruct palaeo‐precipitation during the Younger Dryas for west Sutherland. Using a previously published global empirical dataset, annual precipitation of 2344 ± 248 mm a−1 at sea level is inferred from our new palaeo‐glacier reconstruction, suggesting slightly wetter conditions compared to the present day. These figures are in good agreement with those reconstructed for other parts of the Scottish Highlands and Islands, and this may indicate a marked W–E palaeo‐precipitation gradient during the Younger Dryas. This paper goes on to discuss the wider validity of palaeo‐climatic reconstructions from inferred palaeo‐glacier geometries and presents a number of possible Scottish Lateglacial climate scenarios which warrant further testing. Copyright © 2010 John Wiley &amp; Sons, Ltd.

The Laxford Shear Zone: an end-Archaean terrane boundary?

Abstract The Lewisian Gneiss Complex of northwestern Scotland consists of Archaean gneisses, variably reworked during the Proterozoic. It can be divided into three districts – a central granulite-facies district between districts of amphibolite-facies gneiss to the north and south. Recent work has interpreted these districts in terms of separate terranes, initiating a controversy that has implications for how Precambrian rocks are understood worldwide. The northern district of the Lewisian Gneiss Complex (the Rhiconich terrane) is separated from the central district (the Assynt terrane) by a broad ductile shear zone known as the Laxford Shear Zone. This paper reviews the geology of the Laxford Shear Zone, clarifying field relationships and discussing other evidence, to consider whether or not it does indeed represent a terrane boundary. A detailed review of field, geochemical and geochronological evidence supports the recognition of the separate Assynt and Rhiconich terranes. Mafic dykes (the Scourie Dyke Swarm) and granitoids, of Palaeoproterozoic age, occur on both sides of the Laxford Shear Zone and thus the terranes were most probably juxtaposed during the late Archaean to early Palaeoproterozoic Inverian event. Subsequently, the less-competent, more-hydrous amphibolite-facies gneisses of the Rhiconich terrane were affected by later Palaeoproterozoic (Laxfordian) deformation and partial melting, to a greater extent than the more-competent granulite-facies gneisses of the Assynt terrane.

British Ice Sheet dynamics inferred from North Atlantic ice‐rafted debris records spanning the last 175 000 years

AbstractSediment core MD04‐2822 from the Rockall Trough, northeast Atlantic, provides lithological evidence for the expansion of the British Ice Sheet (BIS) onto the Hebridean margin during both the penultimate (Marine Isotope Stage (MIS) 6/Wolstonian/Saalian) and last glaciation (Devensian/Weichselian). A composite chronology is constructed using: (i) the benthic foraminiferal oxygen isotope record, matched to an orbitally tuned stacked record of global ice volume (SPECMAP); (ii) the synchronisation of the planktonic foraminiferal (Neogloboquadrina pachyderma (sinistral)) and ITRAX XRF Ca records to the Greenland ice core (NGRIP) back to ca. 123 ka; and (iii) the synchronisation of the same N. pachyderma (sinistral)) and ITRAX XRF Ca records to the atmospheric methane record of the Antarctic ice core (EPICA Dome C) beyond 123 ka. The first offshore evidence for the expansion of the last BIS within MIS 4 is presented, suggesting extensive glaciation of northwestern Britain during the Devensian/Weichselian as early as 70 ka. The proximity of this long sediment core to the glaciated margin of northwestern Scotland makes it ideal to capture the ice‐rafted debris (IRD) signal of the BIS for the last 175 ka, via a continuous flux record of IRD. British Geological Survey © NERC 2009. All rights reserved.

Lgwave attenuation in Britain

SUMMARY The Lg wave quality factor (QLg) in Britain has been modelled using data from the UK Seismic Network, operated by the British Geological Survey. The data set consists of 631 vertical, mostly short-period recordings of Lg waves from 64 earthquakes (2.7–4.7 ML) and 93 stations. We have inverted for both regional average QLg and tomographic images of QLg, and simultaneously a source term for each event and a site term for each station for 22 frequencies in the band 0.9–10.0 Hz. The regional average model is 266 f 0.53 between 1.0 and 10.0 Hz and indicates that attenuation in Britain is slightly higher than in France, and significantly higher than in eastern North America and Scandinavia. Tomographic inversions at each frequency indicate that QLg varies spatially. Broadly speaking, southeastern England, the Lake District and parts of the East Irish Sea Basin, and a small region between the Highland Boundary Fault and the Southern Uplands Fault are characterized by higher than average attenuation. Southwestern England, eastern central England and northwestern Scotland are regions of relatively low attenuation. To some extent, these regions correlate with what is known about the tectonics and structure of the crust in the UK.

Extent and deglacial chronology of the last British–Irish Ice Sheet: implications of exposure dating using cosmogenic isotopes

AbstractOver 160 10Be and 36Cl exposure ages pertaining to the extent and chronology of the last British–Irish Ice Sheet (BIIS) are critically reviewed. Despite uncertainties inherent in the use of exposure ages, this approach has demonstrated that at the Last Glacial Maximum (LGM; ca. 26–21 ka) the BIIS extended over all low ground in Scotland and all (or almost all) of Ireland, consistent with recent models depicting extension of the last BIIS to the Atlantic shelf edge. All exposure ages obtained for high‐level sites above trimlines on the mountains of northwestern Scotland and Ireland pre‐date the LGM. This finding confirms that high plateaux in these areas escaped significant glacial erosion, probably under a protective cover of cold‐based glacier ice that remained frozen to the underlying substrate. In terms of deglaciation chronology, the southern Irish Sea basin was probably deglaciated by 19–18 ka, with extensive deglaciation of low ground in Ireland and northeastern Scotland prior to ca. 14.5 ka. Ice cover on low ground in northwestern Scotland apparently persisted after 14.0 ka, suggesting survival of ice in favourable locations during the Lateglacial Interstade (ca. 14.5–12.9 ka). Attempts to date readvances have had mixed success. The Wester Ross Readvance in northwestern Scotland was initially dated to ca. 16.3 ka, but more recent research implies a much younger age (ca. 14.0–13.5 ka). Exposure ages indicating a prolonged stillstand during ice sheet retreat in the Cairngorms at ca. 14.5–14.0 ka conflict with ages obtained on postglacial rockslides and basal radiocarbon dates, which indicate deglaciation before ca. 15.5–15.0 ka. Exposure dating has been successfully employed to confirm a Loch Lomond Stadial (ca. 12.9–11.5 ka) age for moraines in several mountain areas, and to constrain the minimum altitude of the ice cap that extended over the Western Grampians at that time. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Two high resolution terrestrial records of atmospheric Pb deposition from New Brunswick, Canada, and Loch Laxford, Scotland

Environmental archives like peat deposits allow for the reconstruction of both naturally and anthropogenically forced changes in the biogeochemical cycle of Pb as well as the quantification of past and present atmospheric Pb pollution. However, records of atmospheric Pb deposition from pre-industrial times are lacking. In a publication by Weiss et al. [Weiss, D., Shotyk, W., Boyle, E.A., Kramers, J.D., Appleby, P.G., Cheburkin, A.K., Comparative study of the temporal evolution of atmospheric lead deposition in Scotland and eastern Canada using blanket peat bogs. Sci Total Environ 2002;292:7–18]. Pb isotopes data measured by Q-ICP-MS and TIMS, concentration and enrichment data was presented for sites in eastern Canada (PeW1) and northwestern Scotland (LL7c), dating to 1586 A.D and 715 A.D., respectively. Here these same cores are re-analysed for Pb isotopes by MC-ICP-MS thereby acquiring 204Pb data and improving on the original data in terms of resolution and temporal coverage. Significant differences were found between the Q-ICP-MS/TIMS and MC-ICP-MS measurements, particularly at PeW1. These discrepancies are attributed to the problematic presence of organic matter during sample preparation and analysis complicated by the heterogeneity of the organic compounds that survived sample preparation steps. The precision and accuracy of Pb isotopes in complex matrices like peat is not always well estimated by industrial standards like NIST-SRM 981 Pb. Lead pollution histories at each site were constructed using the MC-ICP-MS data. The entire LL7c record is likely subject to anthropogenic additions. Contributions from local mining were detected in Medieval times. Later, coal use and mining in Scotland, Wales and England became important. After industrialization (ca. 1885 A.D.) contributions from Broken Hill type ores and hence, leaded petrol, dominate atmospheric Pb signatures right up to modern times. At PeW1 anthropogenic impacts are first distinguishable in the late 17th century with the mining and use of local coal. After industrialization (ca. 1810 A.D.), coal and petrol are the main Pb sources. A comprehensive estimate of the natural atmospheric background 206Pb/ 207Pb signature in eastern Canadian aerosols is made with a value of ~ 1.19.

Digeneans from deep-sea marine teleosts off the Outer Hebrides, Scotland, including the description of Brachyenteron helicoleni sp. nov. (Zoogonidae)

AbstractFifteen species of digeneans are reported from the waters off the islands of the Outer Hebrides, off north-western Scotland. Trifoliovarium allocytti comb. nov. from Neocyttus helgae is described, figured, and reported for the first time in the northern hemisphere. Brachyenteron helicoleni sp. nov. from Helicolenus dactylopterus is described and considered distinct from other species in the genital pore being at the level of the pharynx, the relatively narrow caeca, the vitellarium being mainly at the level of the ventral sucker and the anterior hindbody, the posteriorly situated, oblique testes, the small amount of post-testicular uterus, the small, delicate cirrus-sac and the large eggs. Derogenes varicus and Lepidapedon arlenae are reported from Caelorhinchus labiatus and Paralepidapedon williamsi is reported from Cottunculus thomsoni for the first time. Steringovermes notacanthi and Prodistomum priedei are reported from off Scotland for the first time. The reports of Derogenes varicus at 1,800 m depth and Zoogonoides viviparus at 1,000 m are deeper records than have previously been published.

The Effects of Livestock Grazing and Recreation on Irish Machair Grassland Vegetation

Machair grassland uniquely occurs over sandy, calcareous soils of coastal sand-plains in dune systems of north-western Scotland and Ireland. This study assesses the plant species composition of Irish machair grassland at a landscape-scale. Machair sites were sampled with quadrats and multivariate analysis was used to assess relationships between species abundance, soil physical variables, livestock grazing and recreation activity. Grazing by cattle and sheep was recorded at most sites, with recreation activities at nearly half the sites. Detrended and Canonical Correspondence Analysis ordinations showed that the main gradients of community composition were related to the key variables of soil calcium carbonate content, soil organic matter content, livestock grazing intensity and recreation pressure. Partial Canonical Correspondence Analysis showed that livestock grazing intensity and recreation pressure explained about twice as much variation as the key soil variables and that rabbit grazing had a much smaller but significant effect. Livestock grazing and recreation activities were shown to be ecologically damaging in terms of having a larger area of bare sand and a lower species diversity. Bare sand can increase the risk of storm damage and reduce habitat heterogeneity by sand-plain deflation. Controls on livestock density, the length of the grazing season and recreation activities are proposed, which we suggest would facilitate vegetation recovery. We highlight the need for local planning authorities, who control coastal development in Ireland, to include agricultural management prescriptions in their machair site management plans.

Velocity structure of the UK continental shelf from a compilation of wide-angle and refraction data

Maps showing depth to the Moho, the 6 km/s and 7 km/s isovelocity surfaces and the thickness of the crust with a velocity greater than 7.0 km/s for the UK and surrounding continental crust have been generated from a compilation of wide-angle/refraction data. The data show that the crust beneath northwestern Scotland is thinner and of higher velocity than that beneath southern Britain. The lower crust beneath the East Irish Sea and parts of the southern North Sea is formed from thick layers of high velocity rock. The lateral extent of these layers cross-cuts the downward projection of major structures mapped at the surface. This suggests that the major structures do not bound regions of lower crust with contrasting properties at depth. Instead these structures may be overprinted by modification of the lower crust, for example, by magmatic underplating, which is not observed directly at the surface. Mapped variations in crustal thickness do not mirror the variations in surface topography, which appears to contradict the view that the crust is in Airy isostatic equilibrium.