Fair Head Research Articles

A Lower Devonian age for the Corvock Granite and its significance for the structural history of South Mayo and the Laurentian margin of western Ireland

The Silurian Croagh Patrick succession, which crops out just south of a fundamental Caledonian structural zone near Clew Bay, western Ireland, is a series of psammites and pelites with a strong penetrative cleavage. These rocks are intruded by the Corvock granite. A suite of minor intrusions associated with the granite contains the regional cleavage whereas the Corvock granite is undeformed. New U–Pb dates are 413 +7 / –4 Ma for a strongly cleaved sill and 410 ± 4 Ma for the main granite, and closely constrain the age of crystallization of the granite and coeval cleavage formation as Lower Devonian (Lochkovian or Pragian), implying syn- to late-kinematic granite emplacement. These data are consistent with evidence for strong sinistral shear shown by the Ox Mountains granodiorite just to the northeast dated at 412.3 ± 0.8 Ma. This Devonian cleavage is superimposed on Ordovician rocks of the South Mayo Trough. The localisation of the strong deformation is interpreted as being due to its position at a restraining bend during regional sinistral motion on a segment of the Fair Head – Clew Bay Line to the north. Contemporaneous deformation in the syn-kinematic Donegal batholith suggests a transfer of sinistral motion to this intra-Grampian structure rather than simple along-strike linkage to the Highland Boundary Fault in Scotland. Our new data indicate diachronous deformation during the late Silurian and early Devonian history of the Irish and Scottish Caledonides and also support previous interpretations of diachronous deformation between these areas and the Appalachian orogens.

Abbâsȋler Döneminin İlk Mehdisi Muhammed b. Abdullah ve Onun Mehdiliği ile İlgili Rivayetlerin Değerlendirilmesi

Tarih ve hadis kaynaklarımızda adaleti yeryüzüne hâkim kılacak kurtarıcı kişiyi ifade eden mehdinin farklı özelliklerini belirten rivayetler mevcuttur. “İsmi ismime, babasının ismi babamın ismine uygun” şeklinde tarif edilen mehdi hadisinin tarihte ilişkilendirildiği ilk kişi, Hz. Hasan’ın torunlarından “Nefsü’z-Zekiyye” lakaplı Muhammed b. Abdullah’tır. Böylece o, Abbâsî Devleti’ndeki ilk mehdi olarak kaynaklara yansımıştır. İlk defa Mugîre b. Saîd tarafından ona mehdi denildiği ve onun ilgili rivayeti delil olarak getirdiği görülmektedir. Dolayısıyla rivayetin Şiî eğilimli kaynaklara girişinin kaynağı burası olmalıdır. Öte taraftan aynı rivayetler, Üçüncü Abbâsî Halifesi Muhammed b. Abdullah için de kullanılmıştır. Hatta onun Mehdi lakabı kaynaklarımızda adının önüne geçmiştir. Böylece rivayetimiz Sünnî kaynaklarda da görülmeye başlamış ve hadis kaynaklarında ilgili mehdi rivayetleri yerini almıştır. Sünnî kaynaklarda konumuzla ilgili olan mehdi rivayetleri, Ebû Dâvud ve Tirmizî’nin sünenlerinde ve başka hadis kaynaklarında geçmektedir. Dört farklı şekilde gördüğümüz hadis rivayetlerinin senetleri genel itibariyle zayıftır. Hasen olduğu kabul edilen bir rivayetin senedindeki Ebü’n-Nücûd Âsım b. Behdele’nin iyi bir kıraat âlimi olmakla birlikte hadisçiliğinde ihtilaf vardır. Konumuzla ilgili mehdi rivayeti birçok tarih kaynağımızda nakledilmiştir. Ancak bunun, bazı tarihçiler tarafından Muhammed Nefsü’z-Zekiyye, bazıları tarafından ise Üçüncü Abbâsî Halifesi Muhammed b. Abdullah ile ilişkilendirilmesi dikkat çekmektedir. Hatta söz konusu rivayetin Abbâsî Halifesi Müstekfî’nin oğlu Ebü’l-Hasan Muhammed b. Abdullah için de kullanıldığı ifade edilmiştir. Bu durum da hadis ilmi açısından zayıf olan rivayetin, tarihin farklı dönemlerinde siyasete malzeme olarak kullanıldığını açıkça ortaya koymaktadır.

Cumulative impact assessment of tidal stream energy extraction in the Irish Sea

A cumulative impact assessment of tidal stream developments in the Irish Sea has been conducted on a high-resolution depth-averaged hydrodynamic model, using Telemac2D. Eight sites were investigated, representing the proposed developments at the time of study. These included: Ramsey Sound, Anglesey, Strangford Loch, Mull of Kintyre, Torr Head, Fair Head, Sound of Islay and West of Islay. Only three projects showed array-array interaction: Fair Head, Torr Head and Mull of Kintyre. A smaller model domain was created for further analysis. Results showed Mull of Kintyre had little impact. Fair Head reduced the energy production at Torr Head by 17%, whereas, Fair Head only reduced by 2%. This was caused by the tidal asymmetry whereby the flood was stronger. When operated concurrently, the maximum power-output at Torr Head is 64.5MW, representing 31% reduction. If Torr Head can still operate commercially in the presence of Fair Head, then the additional environmental impact of Torr Head, such as the change in bed shear stress, is small. Within the Irish Sea, very few of the tidal projects investigated are geographically close to each other. As the industry develops, the risk of interaction to these sites will grow when more intermediary sites are developed.

Secure and fair cluster head selection protocol for enhancing security in mobile ad hoc networks.

Mobile ad hoc networks (MANETs) are wireless networks consisting of number of autonomous mobile devices temporarily interconnected into a network by wireless media. MANETs become one of the most prevalent areas of research in the recent years. Resource limitations, energy efficiency, scalability, and security are the great challenging issues in MANETs. Due to its deployment nature, MANETs are more vulnerable to malicious attack. The secure routing protocols perform very basic security related functions which are not sufficient to protect the network. In this paper, a secure and fair cluster head selection protocol (SFCP) is proposed which integrates security factors into the clustering approach for achieving attacker identification and classification. Byzantine agreement based cooperative technique is used for attacker identification and classification to make the network more attack resistant. SFCP used to solve this issue by making the nodes that are totally surrounded by malicious neighbors adjust dynamically their belief and disbelief thresholds. The proposed protocol selects the secure and energy efficient cluster head which acts as a local detector without imposing overhead to the clustering performance. SFCP is simulated in network simulator 2 and compared with two protocols including AODV and CBRP.

The tectonothermal evolution and provenance of the Tyrone Central Inlier, Ireland: Grampian imbrication of an outboard Laurentian microcontinent?

The Tyrone Central Inlier is a metamorphic terrane of uncertain affinity situated outboard of the main Dalradian outcrop (south of the Fair Head–Clew Bay Line) and could represent sub-arc basement to part of the enigmatic Midland Valley Terrane. Using a combination of isotopic, structural and petrographic evidence, the tectonothermal evolution of the Tyrone Central Inlier was investigated. Sillimanite-bearing metamorphic assemblages ( c . 670 °C, 6.8 kbar) and leucosomes in paragneisses are cut by granite pegmatites, which post-date two deformation fabrics. The leucosomes yield a weighted average 207 Pb/ 206 Pb zircon age of 467 ± 12 Ma whereas the main fabric yields a 40 Ar– 39 Ar biotite cooling age of 468 ± 1.4 Ma. The pegmatites yield 457 ± 7 Ma and 458 ± 7 Ma Rb–Sr muscovite–feldspar ages and 40 Ar– 39 Ar step-heating plateaux of 466 ± 1 Ma and 468 ± 1 Ma, respectively. The metasedimentary rocks yield Palaeoproterozoic Sm–Nd model ages and laser ablation inductively coupled plasma mass spectrometry detrital zircon U–Pb analyses from a psammitic gneiss yield age populations at 1.05–1.2, 1.5, 1.8, 2.7 and 3.1 Ga. Combined, these data permit correlation of the Tyrone Central Inlier with either the Argyll or the Southern Highland Group of the Dalradian Supergroup. The inlier was thus part of Laurentia onto which the Tyrone ophiolite was obducted.

Constraining Sinistral Shearing in NW Ireland: A Precise U–Pb Zircon Crystallisation Age for the Ox Mountains Granodiorite

The age of the Ox Mountains Granodiorite has proved controversial in the past. Two published Rb‐Sr whole rock isochrons suggest ages of 487 ± 6 Ma and 500 ± 18 Ma, respectively (� 87 Rb = 0.0139 Ga ‐1 ), whereas Rb‐Sr muscovite‐feldspar isochrons from undeformed pegmatites associated with the intrusion have yielded c. 400Ma ages. The syn-kinematic nature of the Ox Mountains Granodiorite has been clearly demonstrated by several workers, with the pluton being emplaced as a series of sheets in a major transpressive sinistral shear zone. Knowledge of the age of crystallisation of the Ox Mountains Granodiorite would thus constrain the timing of strike-slip movement along this shear zone, which forms part of a major Caledonide structure known as the Fair Head ‐ Clew Bay Line. A U‐Pb zircon age (conventional isotope dilution TIMS) of 412.3 ± 0.8 Ma from a tonalitic facies of the pluton is presented here. The age confirms that emplacement was broadly contemporaneous with the majority of other volumetrically important Irish granite

1:2,500 Geological Map of South Achill Island and Achill Beg, Western Ireland

Please click here to download the map associated with this article. In Ireland, a major NE-SW trending fault zone (the Fair Head—Clew Bay line) separates high-grade metamorphic rocks (the Dalradian Supergroup) that were originally deposited on an ancient continental margin from lower-grade rocks of oceanic affinity (the Clew Bay Complex). This fault zone continues towards the NE into Scotland, where it is known as the Highland Boundary Fault, and to the west into Newfoundland and the Appalachians, where it is termed the Baie Verte—Brompton line. As such, it is one of the longest fault zones in the Caledonian/Appalachian mountain belt. It has been active several times during this mountain-building episode, and has thus played an important role during the evolution of this orogenic belt. In Scotland and most of Ireland, this fault zone is generally very poorly exposed, and the relationships between the rock units on either side of this discontinuity have therefore proved controversial in the past. However, it is superbly exposed on the coastline sections of Achill Island and Achill Beg in western Ireland. This enables detailed geological field mapping of the fault zone and the adjacent rock units, and thus a fuller understanding of the tectonic significance of this major lineament. A 1:2,500 geological map has been completed of the region surrounding the fault zone, which is locally termed the Achill Beg Fault. This has demonstrated that the two rock units (the Dalradian Supergroup and the Clew Bay Complex) have a very similar history of deformation, and were likely to have been deformed contemporaneously during an early phase of the Caledonian Orogeny.

Controls on reactivation of a major fault zone: the Fair Head–Clew Bay line in Ireland

The Fair Head–Clew bay line, a major Caledonian fault zone in Ireland was reactivated throughout the Palaeozoic. At a regional scale, basement configuration controlled fault zone segmentation and the response to plate vector variations during and after plate collision. In the Ox Mountains inlier, mid-crustal deformation partitioning in both metasedimentary and igneous rocks influenced the formation of a sinistral Early to Mid-Devonian pull-apart basin. Subsequent reactivation by Late Devonian dextral strike-slip and Early Carboniferous normal faulting was focused on the margins of a structural high formed by the then exhumed Ox Mountains metamorphic block.

Caledonian transpressional terrane accretion along the Laurentian margin in Co. Mayo, Ireland

The Highland Border–Fair Head–Clew Bay–Baie Verte–Brompton Suture (Clew Bay Suture) on Achill Island, western Ireland is an E–W-trending zone of vertical, ductile dextral transpression bounding the southern edge of the Dalradian terrane. The Achill Dalradian, a sequence of coarse-grained psammite overlain by conglomerate, quartzite, schist and limestone, disposed in recumbent curvilinear folds, represents Laurentian continental margin deposits which were translated westward during deformation, parallel to the suture trace. Studies of fabric development and albite porphyroblast growth indicate that E–W dextral transpression and west-directed recumbent folding were synchronous, and are interpreted as separate expressions of the same NW-directed terrane impingement event. This process of terrane-docking was marked by a c .4kbar phase of decompression Within the suture, four separate terrane-slivers are recognized. The presence of pyrope-garnet and crossite-amphibole within two imply the Clew Bay Zone experienced sufficient displacement to exhume rocks from deep lithospheric-levels. In addition, the extensive retrogression and destruction suffered by these remnant high pressure mineral assemblages during the albite-generating transpressional phase, implies that ductile deformation was enhanced by the introduction of fluid into and along the suture zone during impingement.

Laser desorption/ionisation mass spectrometry in the study of natural and synthetic melanins. III. Human hair melanins

Four samples of natural melanin extracted from red, fair, black and brown human head hair were studied by both laser desorption/ionisation (LDI) and matrix-assisted laser desorption/ionisation (MALDI) methods. Clear differences were found among the LDI and MALDI mass spectra of the four melanins. In red hair melanin, there was a major peak at m/z 842 attributed to an oligomeric cluster, together with lower-intensity peaks in the range 4000‐5000 Da. In fair hair melanin, only species with molecular masses from 300 to 600 Da were evidenced. In black hair melanin, clusters up to 25,000 Da were detectable, and in brown hair melanin, there were two main oligomeric clusters in the ranges 600‐900 Da and 3000‐5000 Da, respectively, and a large oligomer distribution from 11,000 to 16,000 Da. It is concluded that there is an increase in relative molecular masses of melanins on passing from fair to black hair, suggesting that in “dark” hair the colour is related to melanins with a higher degree of polymerisation.

Magmatic and solid state deformation partitioning in the Ox Mountains granodiorite

AbstractThe Ox Mountains granodiorite (western Ireland) is situated along the Fair Head—Clew Bay line, a major Caledonian structure. The pluton was emplaced synchronously with respect to deformation on a major strike-slip shear zone system and experienced a pervasive episode of sinistral shear. Remnants of magmatic state deformation such as phenocryst alignments and tiling fabrics are present. An early phase of strain partitioning produced sinistral offsets on internal contacts. These structures were overprinted by a solid state fabric characterized by crystal plastic deformation in feldspar and the operation of recovery processes during quartz deformation indicating temperatures in the range 450–500 °C. A sinistral shear band fabric is ubiquitous and its formation was enhanced by myrmekite production leading to the formation of fine-grained feldspar and quartz. Late deformation partitioning during further pluton cooling produced a conjugate shear zone system containing mylonites. Deformation within the Ox Mountains granodiorite provides important constraints on the nature of late Caledonian age mid-crustal deformation along the Highland Boundary fault. The pluton also provides exceptional examples of the range of structures that may form in a syntectonic pluton.

The Caledonian evolution of the Laurentian margin in western Ireland

The Highland Border–Clew Bay–Fair Head–Baie Verte–Brompton Line, which probably marks the Laurentian margin, passes through Achill Island in western Ireland as a zone of ductile transpression within which the Clew Bay Complex and Dalradian Supergroup are juxtaposed. Dextral greenschist facies transpression fabrics in the Clew Bay Complex record the northwest directed emplacement of terranes, bearing high P –low T mineral assemblages, against Laurentia, causing the Dalradian continental margin sediments to be thrust westward. There are significant differences in timing, structural geometry and regional facing between W Ireland and the Scottish Highland Border Zone.

DESEMO seats for young children with cerebral palsy.

Twelve children with cerebral palsy ages 18 months to eight years received custom-molded DESEMO seats. All had markedly abnormal motor function manifested in spastic, athetoid, or mixed patterns of movement. None sat independently or were expected to gain such function. Three had minimal head control, and the remaining nine had fair head control. All were inadequately positioned in commercially available seats. The custom-molded DESEMO seat was clinically evaluated with regard to its ability to produce overall relaxation, assist head control, enhance feeding, improve upper extremity function, and prevent deformities. Also assessed were parents' acceptance of the device, cost, cosmesis, convenience, and its capacity to accommodate growth. Seven children utilized the seat as an insert for a motorized wheelchair. The secure positioning provided by this device permitted operation of a standard hand operated joystick control. Two seats were used as floor sitters, allowing the children to participate in peer group activities. Feeding improved dramatically with two children, as evidenced by weight gain and decreased feeding time. Three children with kyphotic spinal deformities showed no improvement or progression of their curves despite the seating device. The positioning device assisted head control for 10 children but failed to enhance head control in the remaining two. The overall cost of the device, including orthotist and physical therapist time, is $640.00 (1985). The average growth potential of the seat is six to nine months.

Ophiolitic mélange separates ortho- and para-tectonic Caledonides in western Ireland

The nature of the contact between the orthotectonic (late Pre-cambrian to Cambrian) and the paratectonic (Ordovician and Silurian) Caledonides has long been a source of discussion. In western Ireland this junction occurs in a complex zone which crops out along the southern shores of Clew Bay, County Mayo, where Dalradian (Middle Cambrian) and Ordovician (Arenig) rocks are separated by a pre-Silurian rock unit termed the Deer Park Complex1 (Fig. 1). The complex contains both meta-sedimentary and meta-igneous rocks and has been variously interpreted as representing a pre-Caledonian basement ridge1, an imbricate thrust zone2 related to the development of a major fault system, the Fair Head–Clew Bay line3 or an Arenig ophiolite4. We report here geological, geochemical and geophy-sical studies on the Deer Park Complex which indicate that it is a northerly dipping melange unit containing the components of a dismembered ophiolite. These findings imply a source of ophiolitic rocks to the north possibly within the orthotectonic Caledonides.

Supine stander for severely handicapped child.

Positioning handicapped children to normalize tone and enhance educational programming is a major responsibility of therapists in educational settings. The standing position is valuable for proprioceptive and visual stimulation, as well as for skeletal development. Yet, although prone standers and standing boxes are useful for clients with fair head control, we have found no standers designed for cerebral palsied children with poor head control. We developed a supine stander for a severely involved cerebral palsied child who is a noisy breather, is dominated by extensor reflexes, and has very poor head control. He is positioned in the stander at school for classroom activities. His teacher and his therapists have been pleased to observe more normal breathing, muscle tone, and arm control when he is standing.

The Mesozoic Rocks of the North-east coast of Ireland. (Plate ii.)

The grandeur, so distinctive of the scenery of this coast, is due to the nature of the materials of which it is composed. There are many who have heard about the columnar rocks of the Giants’ Causeway, but few know that it is not so much on the ground of possessing such objects of interest as the Causeway or Fair Head, that this coast lays claim to be one of peculiar geological interest. Here, in one narrow strip, we find the only representatives in Ireland of those Mesozoic deposits, which occupy such a broad expanse of country in England. Whether they were at one time deposited, and have been afterwards removed by denudation, or whether the geological history closed for Ireland in the carboniferous period, to be taken up again in the tertiary, must ever remain a matter of doubt. “While the north coast rejoices in the presence of these peculiar deposits, it is also characterised by the absence of the carboniferous limestone, the deposit par excellence, of which the rock surface of Ireland is composed. The deposits before mentioned, are invaluable in proving the western extension of their English equivalents, and indicating by their texture and contents, that we are approaching the limits of the area of deposit. Within the confines of the limited area under consideration, there is one of those coal-fields, which are all too few for the manufacturing prosperity of Ireland, for, though the carboniferous limestone occurs in Ireland in such great force, the deposits which ...

XIV.—On the Syenite Veins which traverse Mica Slate and Chalk at Goodland Cliff and Torr Eskert, to the south of Fair Head, in the County of Antrim.

The geology of the northern portion of the county of Antrim, has been often treated of; but there are several interesting facts, which have apparently escaped the attention of preceding observers. One of the most important was described by me in the Geological Section at the late meeting of the British Association in Dublin; and I have since revisited the place, accompanied by my friends Professor Sedgwick and Mr. Murchison, at whose request I have prepared the following memoir for the Geological Society*. The part of Antrim to which this paper refers, is situated between Fair Head, on the north, and Cushleake Mountain, on the south. The geological structure of the country is exhibited in the accompanying section, No. 1. It will be seen, that mica slate forms the substratum or base of the country; that secondary rocks, belonging to the coal formation, the new red sandstone, and chalk rest upon it unconformably; and that these secondary rocks are surmounted by an overlying mass of rudely columnar trap, which at its northern extremity, forms the magnificent promontory, called Fair Head. The mica slate is distinctly bedded, and passes from a fine-grained, shining, slaty rock, into a coarsely granular gneiss. Its subordinate strata are hornblende slate and schistose limestone; the latter occurring in several places, particularly on the sea shore, close to the south side of Torr Point, and on the shore at West Torr. At Goodland Cliff, near the northern extremity, the dip is north-west, at an angle of 15°