Age of the Lough Talt and Easky adamellites in the central Ox Mountains,N.W. Ireland,and their structural significance     

C. B. Long  M. D. Max  P. J. O'Connor 《Geological Journal》1984,19(4):389-397

The Lough Talt and Easky adamellites in the north-central Ox Mountains inlier were originally regarded as being nearly synchronous in age of emplacement with the more strongly deformed c. 480 Ma Ox Mountains granodiorite. They are now shown by Rb-Sr whole-rock dating to be significantly younger at c. 400 Ma. This recognition of the emplacement of late Silurian/early Devonian Newer Caledonian granites in the central Ox Mountains inlier indicates that the thermal overprinting by the adamellites of the regionally metamorphosed Ox Mountains succession is not an early Ordovician event. Earlier interpretations, using deformationai events and igneous intrusions, advanced by others to suggest that the Ox Mountains succession is pre-Caledonian are now greatly weakened since the deformationai sequence in the Ox Mountains succession is now known to span a longer period of time, ranging from Grampian (late Cambrian to early Ordovician) to Caledonian sensu stricto, and therefore leaves fewer events to have occurred prior to the early Ordovician emplacement of the Ox Mountains granodiorite.  相似文献   

Periglacial trimlines and nunataks of the Last Glacial Maximum: the Gap of Dunloe,southwest Ireland     

Alaric C. Rae  Stephan Harrison  Timothy Mighall  Alastair G. Dawson 《第四纪科学杂志》2004,19(1):87-97

During the last main phase of glaciation (26–13 ka) an ice‐cap developed in southwest Ireland and ice, from a dispersal centre in the vicinity of Kenmare, flowed north through the Gap of Dunloe in the Macgillycuddy's Reeks. On surrounding hillsides a weathering limit separates ice‐moulded bedrock, on low ground, from frost‐weathered terrain above. Assessment of bedrock dilation joint characteristics, Schmidt hammer R‐value data and clay‐sized mineral contents of basal soil samples, demonstrate significant contrasts in the degree of weathering above and below this limit. The weathering limit declines in altitude along former ice flow‐lines and is confluent with morainic deposits on the eastern side of the Gap. This supports the assertion that the high‐level weathering limit is a periglacial trimline that marks the former maximum upper limit of the body of ice which occupied the Gap of Dunloe during the Last Glacial Maximum (LGM). Reconstruction of the former ice‐surface profile from periglacial trimline limits on the eastern side of the Gap yields a mean estimate for basal shear stress of 106.5 kPa. This value suggests that the ice mass which occupied the Gap of Dunloe at the LGM was warm based and flowed on a bedrock substrate. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Late-Pleistocene tidewater glaciers and glaciomarine sequences from north County Mayo,Republic of Ireland     

A. Marshall McCabe  John R. Haynes  Nora F. Macmillan 《第四纪科学杂志》1986,1(1):73-84

Late-Pleistocene deposits in north County Mayo were deposited in three main glacigenic environments. 1. Drumlins and basal tills were formed when ice moved from the Irish lowlands and local mountain catchments into Donegal Bay. 2. Gilbert-type deltas accumulated up to 80m I.O.D. on the lowlands and subaqueous moraines formed across minor valleys when marine-based ice grounded inland. 3. A thick drape of fossiliferous glaciomarine mud along the coastal fringe was deposited from meltwater plumes and by ice-rafting immediately outside of these ice limits. The muds contain an Elphidium clavatum-dominated, low-diversity microfauna which is characteristic of cold-water conditions adjacent to glacier termini. Valves of Macoma calcarea from the mud have been ¹⁴C dated at 16940 ± 120 and 17300 ± 100 BP. The high-level delta complex was deposited from tidewater glaciers in a peripheral depression adjacent to the drumlin ice limits of north County Mayo. Although the field evidence cannot be used to determine former sea level history with any accuracy, it poses general problems for sea level history and isostatic effects of the last major ice sheet in the west of Ireland. Raised glaciomarine sequences commonly occur in close association with drumlin ice limits elsewhere in Ireland and represent marine transgressions prior to glacial unloading. It is suggested that the magnitudes and patterns of crustal depression are greater and geometrically more complex at the margins of ice sheets in Ireland than hitherto realised.  相似文献   

The role of ternary projections in colour displays for geochemical maps and in economic mineralogy and petrology     

P. A. Sabine  R. J. Howarth   《Journal of Geochemical Exploration》1998,63(2)

Ternary (triangular) diagrams show the compositional variation of three end-members, recalculated to 100%, and represent the projection into two dimensions of three or more components (since an end-member may represent the sum of more than one original component), and hence multiple space. During the present century they have been of particular importance in chemistry, the earth sciences, colour-mixing and the studies of colour that underlie the development of geochemical colour maps. Such concepts can be traced back to Newton's Opticks although he did not use an explicit ternary theory of colour mixing. Development of the trichromatic theory of colour deficiency began with Mariotte in the 17th century and was definitively established by Maxwell in the 1850s. These colour theorems underlie the development in recent years of the colour maps now in widespread use in geochemistry. The progress of regional geochemical mapping in the British Isles has gone hand-in-hand with the development of computer software and hardware. The use of multi-element colour-combined geochemical maps can be traced from early work at Imperial College by Webb and his co-workers (1964–79) to its later application in the British Geological Survey's Geochemical Atlas series (from 1983 onwards). Between 1955 and 1975 the use of ternary diagrams came to be commonly used in studies of mineralogical composition, including economic minerals, petrology, classification, and phase relationships. In igneous petrology, the quartz–alkali-feldspar–plagioclase-feldspathoid double-triangle has achieved increasing international acceptance. We illustrate these applications with examples pertinent to the Northern Highland Caledonides, with particular emphasis on the lamprophyres and associated rocks. Two distinct multivariate trends of variation are shown to be present which may warrant further investigation to elucidate their bearing on Caledonian mineralisation.  相似文献   

The role of ternary projections in colour displays for geochemical maps and in economic mineralogy and petrology     

P.A. Sabine  R.J. Howarth 《Journal of Geochemical Exploration》1998,63(2):123-144

Ternary (triangular) diagrams show the compositional variation of three end-members, recalculated to 100%, and represent the projection into two dimensions of three or more components (since an end-member may represent the sum of more than one original component), and hence multiple space. During the present century they have been of particular importance in chemistry, the earth sciences, colour-mixing and the studies of colour that underlie the development of geochemical colour maps. Such concepts can be traced back to Newton's Opticks although he did not use an explicit ternary theory of colour mixing. Development of the trichromatic theory of colour deficiency began with Mariotte in the 17th century and was definitively established by Maxwell in the 1850s. These colour theorems underlie the development in recent years of the colour maps now in widespread use in geochemistry. The progress of regional geochemical mapping in the British Isles has gone hand-in-hand with the development of computer software and hardware. The use of multi-element colour-combined geochemical maps can be traced from early work at Imperial College by Webb and his co-workers (1964–79) to its later application in the British Geological Survey's Geochemical Atlas series (from 1983 onwards). Between 1955 and 1975 the use of ternary diagrams came to be commonly used in studies of mineralogical composition, including economic minerals, petrology, classification, and phase relationships. In igneous petrology, the quartz–alkali-feldspar–plagioclase-feldspathoid double-triangle has achieved increasing international acceptance. We illustrate these applications with examples pertinent to the Northern Highland Caledonides, with particular emphasis on the lamprophyres and associated rocks. Two distinct multivariate trends of variation are shown to be present which may warrant further investigation to elucidate their bearing on Caledonian mineralisation.  相似文献   

The 1980/1981 phytoplankton cycle in the coastal waters off Connemara,Ireland     

C.M. Roden 《Estuarine, Coastal and Shelf Science》1984,18(5):485-497

The results of a phytoplankton survey conducted in coastal waters off western Ireland in 1980/1981 are reported. Surface values of temperature, salinity, NO₃N, PO₄P, Si, total N, total P and chlorophyll a (Chla) collected at 6 stations during 14 cruises are presented along with the species composition of the net phytoplankton.The spring bloom occurred in late April and was dominated by diatoms. Between April and July further diatom blooms occurred. In July and August dinoflagellates were dominant. This change was associated with the stratification of offshore water and low concentrations of Chla and nutrients. In Autumn large blooms of Ceratium tripos were found; it is suggested that the cause was heavy freshwater runoff. In autumn and winter some warm water oceanic species (e.g. Oxytoxum scolopax) occurred.  相似文献   

Coastline configuration disrupts the effects of large-scale climatic forcing, leading to divergent temporal trends in wave exposure     

Andrew J. Davies  Mark P. Johnson   《Estuarine, Coastal and Shelf Science》2006,69(3-4):643-648

Both climate change and the North Atlantic Oscillation (NAO) may influence coastal systems by altering wave exposure. The effects of such climatic forcing are often coherent over relatively large geographic areas. Temporal trends in wave exposure at any particular shore are, however, the result of an interaction between site-specific fetch characteristics and changes in wind climate. This leads to contrasting trends in wave exposure at locations separated by no more than a few kilometres. Wave exposures were estimated at locations around a sea lough over 32 years to characterise these scales of variability. Locations separated by approximately 5 km had independent dynamics with respect to the temporal trend (correlation range −0.35 to 0.44) and to associations with the NAO (correlation range −0.18 to 0.40). Wave exposure can therefore be increasing for a section of shore while nearby areas have the opposite trend. Mean exposure at a location was not a good predictor of the temporal trend. More exposed sites were, however, sensitive to variations in the strength of the NAO. The reduction of large scale forcing to small-scale variability has implications for the detection and mitigation of potential climate change impacts.  相似文献   

Birds, seals and the suspension culture of mussels in Bantry Bay, a non-seaduck area in Southwest Ireland   总被引：1，自引：0，他引：1  

D. Roycroft  T.C. Kelly  L.J. Lewis 《Estuarine, Coastal and Shelf Science》2004,61(4):703-712

Concerns about the environmental impacts of mariculture have grown in recent years in response to the rapid expansion of the industry. The blue mussel (Mytilus edulis) is the main product of shellfish mariculture in the Northeast Atlantic and Baltic Sea, with approximately one third of the harvest cultured using suspended longlines within sheltered marine areas. The main aim of this study was to examine the interactions, and assess the impacts (if any) of mussel suspension culture on the seabird and seal community, employing a simultaneous study of culture and control sites. The study spanned a 20-month period (from November 2001 to August 2003) and encompassed six sites in Bantry Bay (Southwest Ireland).There was no significant difference in species richness between mussel and control sites. Similarly, species diversity did not significantly differ between the mussel and control sites although control sites were generally more diverse than mussel sites, the latter particularly dominated by large numbers of Laridae.Significantly higher numbers of Phalacrocoracidae, Laridae and Alcidae were recorded in mussel sites than in control sites. However, no significant difference was found between Gaviidae or common seal (Phoca vitulina) numbers in mussel and control sites. Seasonal patterns of abundance were similar in mussel and control sites, with peak numbers of most species groups occurring in spring.Mussel suspension culture does not appear to have an adverse effect on the abundance of seabirds or common seals in this area. The safe perching platforms provided by suspension culture floats, combined with a number of other factors, contribute to an increased abundance of a number of seabird species, particularly Laridae. The possible interactions between vertebrate predators and mussel suspension aquaculture are discussed and possible explanations for the increased seabird abundance observed in these areas are offered.  相似文献   

Gender Differences in the Association between Common Mental Disorders and Regional Deprivation in Ireland     

Karyn Morrissey 《The Professional geographer》2016,68(1):129-137

This article aims to add a gender and place perspective to our understanding of depression and anxiety (common mental disorders [CMDs]) through the use of multilevel models. To date, regional variations in the prevalence of CMDs in Ireland have not been explained adequately. Using data from the 2007 Quarterly National Household Survey special module on health and health service utilization, this article examines whether regional differences in CMDs persist after accounting for both individual and regional characteristics. The null model indicated that 2 percent of the variance in CMDs occurred at the regional level. Including contextual interaction variables, the level of variance at the regional level increased to 3.3 percent. Of specific interest to this article was the association between place-based deprivation and gender on CMDs at the regional level. This article found that although regional deprivation alone did not have a significant impact on CMDs, the interaction between female and regional relative deprivation was significant. Specifically, this means that women living in more deprived regions tend to have a greater number of CMDs.  相似文献   

Australian Immigration Policy in Practice: a case study of skill recognition and qualification transferability amongst Irish 457 visa holders     

Fidelma Breen 《The Australian geographer》2016,47(4):491-509

ABSTRACT

Immigration quotas in Australia are guided primarily by economic policy—the needs of the nation are quite rightly the principal concern of policymakers. Using data from a mixed-methods study, this article engages in a dialogue between labour geography and population and migration studies through an examination of the lived experiences of migrating workers and their families. The paper examines a number of cases where policy and practice have detrimentally affected the migration experience of Irish migrants who came to Australia under the Temporary Work (Skilled) (subclass 457) visa. The case study focuses on interviews with secondary 457 visa applicants, namely the wives of former 457 workers. These interviews highlight the problems faced by newcomers to Australia who arrive under this visa. The experiences relayed by these women demonstrate how ill-considered policy relating to qualification transferability makes entering the workplace and, therefore, transition to life in Australia more difficult than it needs to be. While the cases that underpin this paper ended in migration failure (the families involved returned to Ireland), the core issues of qualification transferability and skill comparison were replicated in the wider study dataset (of 1022 survey responses and 80 qualitative interviews). While acknowledging that citizens generally have more freedom and more civil rights than non-citizens, the findings of this study indicate that further review of Australia’s 457 visa is needed, particularly with respect to the limitations placed on the agency of migrant workers. Greater awareness amongst prospective migrants as to the purpose and limits of the 457 visa is also necessary, in order to avoid misinterpretation and the extreme personal repercussions outlined in this paper.  相似文献