bluuebunny/crossref_metadata_2025_split huggingface dataset:
Early phases of Caledonian deformation in the Dalradian of the Ballachulish district, Argyll
Authors: Bowes D. R. , Wright A. E. 
Published: July 2010

AbstractTwo early phases of deformation preceded the development of the major NE‐SW‐trending folds, including the Appin Fold. The earliest recognized structures include small folds, lineations and inclusion trails in garnet porphyroblasts. The dominant schistosity and mineral lineation was developed during the second phase of deformation, associated with the formation of similar folds and tectonic banding, under garnet grade conditions over much of the area. The later‐formed major folds are associated with low grade retrogressive metamorphism and crenulation and fracture cleavage formation. These folds are concentric folds and have associated tectonic slides producing low grade cataclastic schists. On the basis of fold style and sequence and metamorphic grade there is a great similarity between the structures in the Dalradian rocks of the Ballappel Foundation and those of the Iltay Nappe.
Caledonian metamorphism in part of northwest County Mayo, Ireland
Authors: Max M. D. 
Published: July 2010

AbstractLewisian gneisses, Moinian and Dalradian sediments, and dolerites have been deformed and metamorphosed under Amphibolite Fades conditions. The metamorphic climax, with the growth of kyanite and staurolite, occurred after the cessation of the second deformational episode and before the onset of the third. Plagioclase growth ceased at or about the time of kyanite and staurolite nucleation.Metamorphic effects become less to the south and southeast while the most advanced stages occur around Inver. A single heat pulse appears to be not directly related to any structure.
Studies in fluviatile sedimentation: Lateral variation in some fining‐upwards cyclothems from the Red Marls, Pembrokeshire
Authors: Allen J. R. L. 
Published: July 2010

AbstractThe lateral lithological variability of 18 stratigraphically close fluviatile cyclothems is analysed in three ways: (1) qualitatively, (2) by means of the upwards facies transition probability matrix, and (3) using the non‐parametric Mann‐Whitney U statistic. Some cyclothems are relatively very uniform over lateral distances comparable with 100 cyclothem thicknesses, whereas others have a lateral variability similar to the variability characteristic of the set of cyclothems. Hence some amongst stratigraphically close cyclothems are considered to show real differences, which may be attributed to allocyclic environmental factors operating on a relatively large time scale. The variation within cyclothems can be explained by shorter term autocyclic factors.
Aspects of magmatism and plate tectonics in the Precambrian of England and Wales
Authors: Thorpe R. S. 
Published: July 2010

AbstractThe geological features of igneous, metamorphic and sedimentary rocks comprising the Precambrian of England and Wales suggest formation in one or more Precambrian orogenic cycles. They are now interpreted in terms of plate tectonics. Evidence for Late Proterozoic plate subduction in the Mona Complex of Anglesey is suggested by the association of pillow lavas, cherts, high P/T metamorphic rocks and by the occurrence of gabbros and serpentinites with similar features to rocks believed to comprise the oceanic crust. Precambrian rocks in England and South Wales include calc‐alkaline plutonic complexes (Malvern and Johnston Complexes), calc‐alkaline lavas (Uriconian and Charnian) and basic and intermediate intrusions of tholeiitic affinity (dykes in the plutonic complexes and granophyric diorites in Charnwood Forest). The features of these rocks indicate formation in a continental margin setting and this is consistent with features of the Rushton Schist and Primrose Hill “gneiss” which suggest that they predate the Late Proterozoic orogenic activity. This evidence is consistent with plate tectonic models involving oceanic plate subduction below the Mona Complex from an ocean to the northwest, or from a small ocean basin southeast of the complex. The Warren House lavas show some affinities to ocean floor basalts and are problematic with regard to the Precambrian history of the area.
An interpretation of some magnetic data off the west coast of Ireland
Authors: Young D. G. G. , Bailey R. J. 
Published: July 2010

AbstractA total field magnetic anomaly contour map of the continental margin west of Ireland is described by reference to geological structure previously established by seismic reflection profiling. The western Irish Mainland Shelf, Porcupine Seabight Trough and Porcupine Ridge were previously defined as major north‐south elements in the structure of the margin. Each is readily distinguished on the magnetic anomaly contour map. To the north these features terminate against, or merge with, the east‐west Slyne Ridge. A pronounced change in the magnetic anomaly pattern at about 53°N suggests that the southern limit of this Ridge coincides with a major geological discontinuity extending from near the coast of Ireland to the continental slope, some 320 km to the west.The magnetic anomaly contour map gives general support to the idea that the Slyne Ridge and Porcupine Ridge represent submerged blocks of marginal continental crust, and that the Porcupine Seabight Trough is founded upon crust significantly different in character.
Studies in fluviatile sedimentation: Implications of pedogenic carbonate units. Lower Old Red Sandstone, Anglo‐Welsh outcrop
Authors: Allen J. R. L. 
Published: July 2010

AbstractCarbonate units occur in varying numbers in the fine‐grade members of the alluvial fining‐upwards cyclothems present in the Lower Old Red Sandstone of the Anglo‐Welsh outcrop. They closely resemble contemporary soil‐carbonates (calcretes) and hence show that the local Siluro‐Devonian climate was relatively hot with a comparatively low seasonal rainfall. Compared with contemporary calcretes, the units suggest that sites on the alluvial plains were denied river‐borne sediments for periods each in the general order of 104 years. The pedogenic interpretation of the carbonate units, developed in the light of the behaviour of rivers today, leads to alternative models for the geomorphology of the Siluro‐Devonian alluvial plains and for their gross subsurface structure. Geomorphologically, the plains at any instant presented depositionally active and inactive areas in juxtaposition. Under some circumstances the relief was provided only by alluvial ridges. Under others, relief was afforded by valley sides and perhaps river terraces, in addition to ridges. Knowledge of the character of the Lower Old Red Sandstone in vertical sequence leaves as plausible three alternative gross structures for the alluvial pile beneath the plains. They differ chiefly in the lateral variability and connectedness of the palaeosols and place hitherto unavailable limits on the three‐dimensional character of the cyclothems.
Late Pleistocene terrace deposits at Beckford, Worcestershire, England
Authors: Briggs D. J. , Coope G. R. , Gilbertson D. D. 
Published: July 2010

AbstractThe Pleistocene deposits in the area of the village of Beckford, in the Carrant Valley, Worcestershire are described. A radio‐carbon date of 27,650±250 years B.P. has been obtained from plant material in the terrace deposits in the valley. Detailed studies have been made of the terrace sediments and of the remains of Mollusca and Coleoptera in fossiliferous layers. Frost structures are described and their stratigraphy considered. The nature of the local environment and regional climate in the final stages of the Upton Warren Interstadial period is reconstructed in detail. The terrace appears to have aggraded in a periglacial environment, dominated initially by solifluction processes. Extensive solifluction may have led to local diversions of drainage. In time, the climate deteriorated, becoming cooler and somewhat less continental with the onset of the main Devensian glaciation. This latter stage was characterised by extensive ice‐wedge growth, aeolian activity and, subsequently, by river incision.
The age of the Lower Carboniferous conglomerate at Lligwy Bay, Anglesey
Authors: Cope F. Wolverson 
Published: July 2010

AbstractThe Lower Carboniferous conglomerate at Lligwy Bay, Anglesey, is shown to be underlain as well as overlain by limestones of D1 age so that the conglomerate is of intra‐D1 age. It is considered to have been deposited very close to a coastline.
The structure of the Moine and Dalradian Rocks in the Dalmally District of Argyllshire, Scotland
Authors: Roberts J. L. , Treagus J. E. 
Published: July 2010

AbstractTwo phases of deformation are described from the area. D1 is related to the first phase movements widely recognised in the Dalradian; D2 is related to more localised modifications of the D1 fold pattern.Four major D2 folds are recognised from the evidence of minor structures. Three of these, the Beinn Chuirn, the Ben Lui and the Ra Chreag Folds, had previously been considered as D1 structures, whilst the fourth, the Dalmally Fold, was unrecognised. These folds provide continuity between the southeast facing of the D1 folds of the Moine and Ballachulish Succession of Glen Orchy (Thomas and Treagus 1968) and the southeast facing of the D1 Jay Nappe (Shacketon 1958) in the Iltay Succession above. The D2 deformation reaches a climax at the junction between the two Successions, the Iltay Boundary Slide, which is now regarded as a D2 structure. The regional implications of these results are briefly considered.
The structure of the Swansea Valley Disturbance between Clydach and Hay‐on‐Wye, South Wales
Authors: Weaver J. D. 
Published: July 2010

AbstractThe Swansea Valley Disturbance is one of four NE‐SW belts of faulting and folding which cross the northern limb of the South Wales Coalfield syncline at variance with the normal E‐W Variscan structures. The Disturbance extends from Hay‐on‐Wye (Herefordshire) southwestwards to Clydach (near Swansea) and may extend northeastwards to Titterstone Clee Hill (near Ludlow) and southwestwards along the Tircanol Fault to Swansea Bay.The main structural elements of the Disturbance are: impersistent NE‐SW folds; NE‐SW normal faults; and NE‐SW and NNW‐SSE wrench faults. The NE‐SW structures are confined to a narrow zone which seldom exceeds two kilometres in width.It is suggested that this narrow belt of faulting and folding has been controlled mainly by sub‐Devonian basement structures, which involve faulting and/or folding. The effect of the Variscan compression was to reactivate the basement structure, which had the effect of resolving this compression along the disturbed zone to produce sinistral wrench movements. The structure of the Disturbance has been complicated by folding, produced by the Variscan force driving the Upper Palaeozoic rocks against the Lower Palaeozoic block.It is concluded that the main movements are of Variscan age and that vertical movements may have taken place in post‐Carboniferous and post‐Neogene times.
A re‐interpretation of the origin of sands and gravels around Banc‐y‐warren, near Cardigan, west Wales
Authors: Helm D. G. , Roberts B. 
Published: July 2010

AbstractThe sands and gravels form part of a once more continuous succession comprising parts of three delta lobes which advanced into a deepening pro‐glacial lake. Normal delta construction was accompanied by sporadic rapid mass movement of coarse sediment. This generated turbidity currents which gouged and filled remarkable channels. The deposits are cut by a very large number of normal faults which bear a strike relationship to the bedding showing they were produced by down‐dip extension of the beds as a result of slope instability. The consistently southwesterly current directions, deduced from various sedimentary structures, and the constant strike orientation of faults together show that the mounds cannot be ice‐contact features as was previously widely believed. The external form of the deposits is related more to subsequent erosion than to their original mode of formation.
Palaeogeographic significance of pedogenic carbonates in the topmost Upper Old Red Sandstone of the Scottish border basin
Authors: Leeder M. R. 
Published: July 2010

AbstractThe alluvial depositional surface of the Scottish Border Basin in youngest Upper Old Red Sandstone times is thought to have been dissected and subsequently disrupted and buried as an effect of magma formation and lava eruption. Lengthy periods of surface stability occurred during these events, as implied by the occurrence of up to two thick carbonate palaeosols over much of the Old Red outcrop.
Metamorphic textures and deformation: A new mechanism for the development of syntectonic porphyroblasts and its implications for interpreting timing relationships in metamorphic rocks
Authors: De Wit M. J. 
Published: July 2010

AbstractThe formation and growth of porphyroblasts is treated in detail, with particular reference to garnet. Previous explanations for included fabrics in porphyroblasts, and mechanisms of syntectonic growth leading to sigmoidal inclusion patterns, are shown to be based on invalid assumptions and are unacceptable. The following new mechanism for garnet porphyroblast growth is proposed. During deformation, fluid filled veins open, particularly where micaceous foliae open in folds associated with crenulation cleavages and kink bands. Garnet nucleates in these veins as they develop. The geometry of the veins depends on variability of strain rates, fluid diffusivity and the sequence of progressive deformation. In areas of low strain rate and high diffusivity, long and widely spaced macroscopic garnet veins form. These may be buckled during the continuous deformation process. Conversely, where strain rates are high, and diffusivity is low, short and closely spaced microscopic garnet veins form. Buckling and shear may alter the vein shapes during their formation and sigmoidal veins can result. Veins join and coalesce to form single porphyroblasts, leaving a selvage of quartz and other minerals as an included fabric. The finite geometry of the included fabric ranges from helicitic to sigmoidal, which is interpreted to reflect the local deformation history during vein propagation. The fabric geometry is finalized when the veins fail to respond individually to the deformation due to their coalescence and formation into a single porphyroblast. Continuous vein propagation without significant deformation of the veins could lead to augen textures, whilst a process of continuous vein formation and rotation is shown to explain apparent syntectonic rotations of more than 180°. This new hypothesis has the merit of being very simple, but it does require a new approach. This approach necessarily questions a number of previously well established “facts”, such as pre‐, syn‐, and post‐tectonic textures. It is argued that extreme care must be taken, when relating deformation episodes and metamorphic growth periods.
Flandrian sea‐level changes in west Lancashire and their implications for the ‘Hillhouse Coastline’
Authors: Tooley M. J. 
Published: July 2010

AbstractA relative sea‐level curve for the Flandrian Stage has been drawn, based on twenty‐three index points from west Lancashire and three from north Cheshire. Twenty‐two of the points derive from a restricted area flanking the River Ribble, and one from Morecambe Bay. Evidence for sea‐level changes comes from detailed stratigraphic and pollen analyses on material selected for radiocarbon assays. Eleven periods of marine transgression are recognised in northwest England, and these are compared with periods of marine transgression elsewhere in northwest Europe. The evidence for the ‘Hillhouse Coastline’ is considered in relation to the periods of marine transgression established in northwest England.
The Marsdenian (Namurian R2) succession west of Blackburn: Implications for the evolution of Pennine Delta Systems
Authors: Collinson J. D. , Jones C. M. , Wilson A. A. 
Published: July 2010

AbstractA recently driven sewer tunnel west of Blackburn has shown the presence of a thick turbidite sequence between the R. gracile and R. bilingue Goniatite Bands. Above the R. bilingue Band, turbidites pass up through delta slope deposits into delta top fluviatile sandstones, derived from the northeast. The section provides evidence for the westward limit of advance of the pre‐R. gracile Kinderscoutian delta slope and also enables a more accurate R2 isopachyte map to bc drawn.
The Marginal Triassic deposits of South Wales: Continental facies and palaeogeography
Authors: Tucker M. E. 
Published: July 2010

AbstractMarginal Triassic deposits in Glamorgan, South Wales, occur beneath and laterally equivalent to the Keuper Marl. They consist of coarse elastics, locally interbedded with finer sediments, limestones and replaced evaporites. Fluviatile sediments are chiefly sorted conglomerates and cross‐bedded sandstones of stream‐flood origin. Other conglomerates and sandstones, associated with siltstone and calcrete, are interpreted as the deposits of semi‐permanent streams with well‐developed floodplains. Ill‐sorted breccias accumulated as screes against former cliffs. Matrix‐supported conglomerates of mudflow origin are a minor facies. Thin graded beds were deposited from sheet floods and other finer clastic sediments formed on floodplains and playas. Lacustrine shore‐zone elastics, limestones and evaporites are also present.The distribution of the various facies is related to the Trassic geomorphology, which was controlled by the structure of the underlying Palaeozoic. The South Wales Coalfield formed an upland area bounded to the south by an escarpment. Stream‐flood conglomerates of the Radyr‐Llandaff area were part of an alluvial fan which formed at the foot of this escarpment, perhaps at the mouth of a canyon on the site of the present‐day Taff gorge. South of the escarpment semi‐permanent streams with well‐developed floodplains occupied a broad valley, draining eastwards and cut into the axial region of the plunging Cowbridge anticline. South of the anticline, stream‐flood and sheet‐flood deposits interdigitated with wave‐rippled and desiccated siltstones deposited on playas. The latter, together with the shore‐zone sediments, were marginal to the lake in which the Keuper Marl accumulated. With rising base‐level during the Norian, the Keuper Marl facies spread north and west into the Vale of Glamorgan, covering the Marginal Triassic and inliers of Carboniferous Limestone.
The computation of deformations
Authors: Flinn Derek 
Published: July 2010

AbstractThe mathematics of irrotational deformation are simplified by presentation in matrix form. Matrix equations are easily programmed and are easily interpreted in geometrical terms. Graphical operations commonly carried out on orientation nets such as rotation of data can be translated into simple matrix equations for use with a computer. If the shape and orientation of the deformation ellipsoid for a pure shear are known, a matrix can be constructed for use as a deformation matrix. This can be used to deform other deformation ellipsoids to obtain a resultant ellipsoid. It can also be used to deform geological structures such as lineations and planes. The matrix equations for these operations are very simple, but their numerical solution often requires a computer.
Meltwater phenomena in the area between Bala and Corwen, North Wales
Authors: Rowlands B. M. 
Published: July 2010

AbstractPreviously unrecorded glacio‐fluvial phenomena are identified and mapped. These are shown to conform in part with the known southwest to northeast movement of meltwater from the wasting ‘Merioneth’ icecap in late Devensian time. A further series of meltwater channels and associated kames is also revealed, connecting southwards with the Dee Valley. Orientation of bedding within these latter kame deposits at Sarnau (971394) is also shown to accord with deposition by meltwater from an ice front to the southwest. Petrological analysis of igneous erratics within the Sarnau deposits suggests an origin entirely within the Arenig Mountains. It is thus postulated that the features relate to a late stage in the wasting of the ‘Merioneth’ ice cap, when a series of meltwater escape routes to the Dee Valley became progressively ice‐free, and that the newly‐discovered meltwater channel system is thus complementary to previously recorded phenomena.
Metadolerite age relationships in the Dalradian of northwest Donegal, Ireland and their orogenic significance
Authors: Hutton D. H. W. 
Published: July 2010

AbstractThe structural relationships of several intrusive sheets belonging to the extensive metadolerite suite of the Appin (lower) Dalradian rocks of the Creeslough area, northwest Donegal, Ireland have been examined. It is concluded that, relative to the regional chronology of deformation of the enclosing metasediments, sheet emplacement has occurred: pre‐D2; syn‐D2; between D2 and D3; and syn‐D3. The height of activity came in the post‐D2, pre‐D3 interval and coincided with the peak of regional metamorphism in the area. These relationships in Donegal are compared with those of the pretectonic basic rocks of the southwest Highlands and models are discussed.
Jointing and minor tectonics of the south gower Peninsula between mumbles head and Rhossilli Bay, South Wales
Authors: Roberts J. C. 
Published: July 2010

AbstractJoints and other minor structural elements were recorded at 429 stations on the S. Gower coast. A systematic pattern exists comprised of up to 6 sets of joints which strike at 360°, 340°, 290°, 270°, 240° and 200°. Joint set maxima are frequently parallel to the strike of major and minor faults, but no simple geometric relationship exists between joint orientation and fold axis trend. Axial‐trace‐fracturing has been recognized, whilst en echelon gash arrays, mineralized joint sets and their cross‐cutting relationships enable a tectonic sequence of events to be determined. The systematic joints are thought to have developed during the folding under the influence of a N–S compression, but variation in the strike of minor structures suggests a swing in orientation of o through time. Subsequent stress relaxation facilitated dilation and the production of mineralized vein suites.
The structural setting of the Main Donegal Granite; comments on a recent interpretation
Authors: Berger A. R. 
Published: July 2010

AbstractA recent interpretation of the structural geology and chronology of the northwestern envelope of the Main Donegal Granite by Hutton (1977) is critically examined.Although many aspects of this analysis are sound, there remains serious doubt concerning Hutton's main conclusion that the intense deformation near the granite resulted from its forceful intrusion.
The geology of the Llanuwchllyn to Llanymawddwy area, south gwynedd, north wales
Authors: Lockley M. G. 
Published: July 2010

AbstractA geological map of the Caradoc rocks of the Llanuwchllyn to Llanymawddwy area is presented and the geology of the area described in detail. Hitherto unrecorded outcrops provide important stratigraphical evidence which is used to redraw the Caradoc‐Ashgill Series boundary and many of the formational boundaries within the Caradoc Series.The stratigraphy of the area is revised to conform with the standard classification of the Caradoc Series in the Bala region. The only modifications are as follows: the Llaethnant Siltstone is proposed as a formational name for a group of beds which are broadly equivalent to the Glyn Gower Formation but which represent a distinct facies. The greater part of the Nod Glas Formation north of Dinas Mawddwy is shown to be laterally equivalent to the upper part of the Gelli‐grin Formation; it is also subdivided into two members, the Dyfi Mudstone and the Corris Shale, differentiated on lithological and faunal grounds. The stratigraphy of the Dinas Mawddwy area is also amended.Faunal elements (genera) new to the Caradoc Series of this area, and to Wales, are noted.