7,878 research outputs found
The tertiary igneous geology of Strathaird, Skye
This study is concerned with the Tertiary igneous rocks found within an area some twenty square miles in extent on the south-east side of the Skye central intrusion complex. The Tertiary rocks include basic lavas, a small intrusion of granophyre, the margin of the Cuillin Gabbro, and numerous minor intrusions. Extrusive rocks occupy an area of some seven square miles, and have an aggregate thickness of about 1,000 feet. The greater part of the sequence consists of alkaline olivine basalts, but there is also one horizon of trachybasalt and thin group of picritic flows. Pyroclastic rocks are rare, being limited to one small agglomerate vent and an isolated lens of tuff. It has been found possible to divide the sequence into several mappable units based on groups of flows possessing common petrographical features. The laves which lie within half a mile of the Cuillin Gabbro have been metamorphosed by that intrusion, while an outer zone of lower temperature alteration includes the whole of the strathaird lava outcrop. Within the thermal aureole a narrow zone of pyroxene hornfels along the contact with the Gabbro is followed outwards by a broader zone charaterized by the presence of an actinolitic amphibole. Within this pyroxene hornfels zone the lavas have been thoroughly recrystalized to high temperature mineral assemblages, but within the amphibolezone equilibrium was only locally attained, and many of the lavas still posses much of their original texture and mineralogy. The transition from unmetamorphed lava to pyroxene hornfels was not accomplished by independently under its own particular pressure-temperature conditions. On the basis of both chemical and petrographical evidence it is considered probable that a small amount of silica was added to at least some of the lavas during metamorphism. The internal structure and composition of the Cuillin Gabbro do not come within the provenence of this thesis, but some attention has been given to the relationships between the Gabbro and its country rocks, especially in the neighbourhood of camasunary. In this latter area there is an extensive development of basic minor instructions pre-dating the Gabbo, and metamorphosed in a similar manner to the nearby lavas. Most of these small intrusions are emplaced into Torridonian sandstones, which locally extend up to several hundred feet from the contact, the Torridonian shows clear evidence of having been partially melted by the high temperatures induced by the intrusion of gabbro magma, and many of the early intrusions are veined and broken into fragments by the mobilized material. The vein material is chemically more basic in composition than the sediments from which it was derived, partly due to reaction with the basic minor intrusions. Parallel to the contact of the Cuillin Gabbro, in Strathaird, there is a series of irregularly shaped outer-ops of granphyre which are thought to be parts of a single intrusion exposed in the vicinity of its roof. The granophyre is fine-grained, is unusual in containing paramorphs after tridymite, and differs chemically from other Skye granitic rocks. Through there is sometimes a well-defined, chilled margin, many of the contacts against sedimentary rocks are complex and highly xenolithin. The granophyre post-dates the Cuillin Gabbro, but is earlier than the large granitic intrusions which lie to the north and north-east of the areas. One of the most impressive features of the local geology is the great profusion of north-west dykes, all but a few of which are basic in composition. Most of the dykes are later date than the Cuillin Gabbro, but their distribution shows that they are closely related to that centre. Other minor intrusions include a few acid and basic skills which are, in general, of earlier date then the dyke swarm, while basic cone-sheets occur in the vicinity of the Cuillin Gabbro and are later than most of the north-west dykes. In Strathaird, erosion to a relatively deep level allows the structural relationships between lavas, intrusions, and pre-Tertiary sediments to be more easily examined than elsewhere in Syke. Most of the sediments are of Jurassic age, and these rest uncon-formably on Torridonian sandstones. There were several phases of warping in Mesozic times, but the main period of deformation occurred after the outpouring of the lavas and gave rise to large arcuate folds. It is believed that these folds are one result of the stresses set up by the intrusion of the Cuillin Gabbro
Recommended from our members
The microstratigraphy of middens: capturing daily routine in rubbish at Neolithic Çatalhöyük, Turkey
Microstratigraphy — the sequencing of detailed biological signals on site — is an important new approach being developed in the Çatalhöyük project. Here the authors show how microscopic recording of the strata and content of widespread middens on the tell are revealing daily activities and the selective employment of plants in houses and as fuel. Here we continue to witness a major advance in the practice of archaeological investigation.</jats:p
Recommended from our members
Biomolecular and micromorphological analysis of suspected faecal deposits at Neolithic Çatalhöyük, Turkey
The problem of political science and practical politics
Copyright @ 2006 The AuthorsWe reflect on the reasons why there is not a greater and more fruitful relationship between those who seek to understand policy and the political process from academia and those with a similar task in ‘practical politics’. We attribute this lack of engagement to three core factors: (1) from without, instrumental government visions of political science perpetuate the view that the discipline exists to serve those with power; (2) from within, scientism and abstraction diminish the discipline's stock of ‘usable’ product for ‘practical politics’; and (3) where relevant research exists, its uptake is hampered by limited communication between these spheres
The challenges of renal replacement therapy and renal palliative care in the elderly
Much of the increase in take on rate for dialysis in recent years is accounted for by older patients in whom a treatment as demanding as dialysis was previously thought to be contraindicated. The decision to dialyse the elderly often remains difficult, as recent data suggest that those with significant comorbidities are unlikely to survive more than 4-6 months longer on dialysis than they would have done if treated conservatively. It is also important to recognise that conservative treatment is not simply defined by the decision not to dialyse. Good conservative care comprises active disease management eg treatment of anaemia with erythropoietin stimulating agents and intravenous iron, and supportive care which may become increasingly complex eg pain relief with fentanyl and alfentanyl, towards the end of life. Those older patients who do decide to dialyse must contend with all the usual end of life issues facing older people, in addition to the option, denied to the rest of us, of dialysis withdrawal which effectively allows them to die at a time of their choosing
Recommended from our members
Multi-scale analysis and validation of the Envisat MERIS Terrestrial Chlorophyll Index (MTCI) in woodland
Satellite remote sensing can be used to estimate and monitor the chlorophyll content of vegetation canopies which are a key and dynamic component of global terrestrial ecosystems. The red-edge algorithm can be used to estimate chlorophyll content from remotely sensed data but is unsuitable for use with most satellite sensor imagery. To overcome this problem, the new Envisat MERIS Terrestrial Chlorophyll index (MTCI) has been developed. It is the only operational satellite chlorophyll index and MTCI data are available as a Level 2 product from the European Space Agency. However, there is a need to ‘validate’ the MTCI over a wide range of environmental conditions. This paper reports on research that attempts to validate the MTCI using Compact Airborne Spectrographic Imager (CASI) imagery and ground data of chlorophyll content. The study site was predominantly woodland in the south of England (New Forest National Park) and had a wide range of chlorophyll contents. A transfer function derived from CASI data was used to produce a reference map of chlorophyll content, when aggregated it was compared to MERIS MTCI data and used to derive the MTCI – chlorophyll content relationship (R squared = 0.56)
- …