bluuebunny/crossref_metadata_2025 huggingface dataset:
The age of the Whin Sill
Authors: Fitch F. J. , Miller J. A.
Published: July 2010

The Whin Sill and its related dykes are intruded into Carboniferous strata in the North of England. Together they form a distinct petrographical province in which basic magmatism appears to have been closely related to a single phase in the structural history of the area. The relevant stratigraphical, structural and isotopic evidence suggests to the authors that the Whin Sill suite was intruded during the Stephanian, around 295 ± 6 m.y. This conclusion is supported by twenty‐one new potassium‐argon age determinations accompanied by a petrographical study of the factors which cause discrepancy in isotopic results from Whin Sill rocks.
The metamorphic rocks of the southern part of the Mainland of Shetland
Authors: Flinn Derek
Published: July 2010

The paper presents a one mile to the inch geological map of the southern part of the Mainland of Shetland (excluding areas underlain by Old Red rocks) and an account of the metamorphic rocks occurring there.

The metasediments mostly belong to the East Mainland Succession which is about 14 km thick. They dip vertically and strike north‐south. The metasediments in the west were originally laminated sandstones devoid of current bedding and grading and composed of poorly weathered material. They include several limestones up to half a kilometer thick. In the east the metasediments were originally gritty quartzites and sandstones together with shales which are usually finer grained and composed of more weathered material than those to the west. On two occasions the deposition of these rocks was interrupted by outpourings of spilites.

The rocks show signs of four metamorphisms. The first metamorphism was accompanied by a penetrative deformation causing elongation of the rocks in a north‐south direction, shortening in an east‐west direction and elongation and shortening in different areas in a vertical direction. As a result of this metamorphism the pelitic rocks over the whole area became schists containing such minerals as biotite, chlorite, muscovite, quartz and feldspar, and possibly garnet. In a later metamorphism a belt of these rocks a kilometer or so wide became gneissified, probably due to the passage of high temperature fluids. In various parts of the area such minerals as biotite, chlorite, garnet, staurolite, chloritoid, and kyanite grew as porphyroblasts in a series of episodes referred to collectively as the porphyroblast metamorphism. After these metamorphisms the area was intruded, 400 m.y. ago, by a number of granites. In places these have produced extensive thermal aureoles containing such minerals as staurolite, chloritoid, andalusite, kyanite, sillimanite, garnet, muscovite, biotite and chlorite in pelitic rocks. The emplacement of one of the granites was accompanied by large and small scale folding.

Several major faults are described including the Nesting tear fault with a 16 km dextral displacement and a mélange zone beneath a nappe.
The source of ferroan and non‐ferroan calcite cements in the Halkin and Wenlock Limestones
Authors: Oldershaw A. E. , Scoffin T. P.
Published: July 2010

An early and a late calcite cernent are distinguished in limestones of Carboniferous age in N. Wales and Silurian age in Shropshire, England. Solution of aragonite, and preferential pressure solution of carbonate grains in day‐rich beds are considered to be the sources of the early and late cements, respectively. An association between the distribution of ferroan calcite and clay minerals indicates that clays may be an important contributor of iron during the precipitation of the late cernent.
Stratigraphy and geological history of the Malvern, Abberley and Ledbury Hills
Authors: Phipps C. B. , Reeve F. A. E.
Published: July 2010

A revised stratigraphy of the Malvern, Abberley and Ledbury Hills is given. The Silurian succession is considered in detail and shows a series of five major sedimentary rhythms or cycles between an initial Llandovery transgression and regression at the close of the Silurian period. The succession exhibits an alternation of shale with either limestones and/or terrigenous clastics, and the rhythmic nature of the sequence suggests a periodic change in base level. A number of different lithological facies can be distinguished in the limestone formations, particularly in the Wenlock limestone. A detailed faunal list is given for most of the Silurian sequence. From the evidence of the stratigraphic succession, an attempt has been made to decipher the complex geological history of the area.
Succession and structure in the Llwyd Mawr Syncline, Caernarvonshire north Wales
Authors: Roberts Brinley
Published: July 2010

A succession of strata ranging in age from Upper Cambrian to Valentian is described. They occupy ground in, and adjacent to, the Llwyd Mawr syncline. Most of the rocks are marine but during mid‐Caradocian (Soudleyan) times a rhyolitic ignimbrite sheet was emplaced and rests disconformably on Llanvirn slates. It has a remanant thickness of 2300 ft and is a single cooling unit. A second volcanic episode (Lower Longvillian) produced 600 ft of bedded pyroclastic rocks with only subordinate ignimbrites. Mid‐Caradocian minor intrusions of rhyolite occur as domes and sills in association with the volcanic rocks. Minor intrusions of dolerite and micro‐tonalite are probably of Caledonian age.

Three phases of movement are recognized within the main end‐Silurian Caledonian movements. The first movement phase, F1, produced the main fold architecture and the dominant associated axial‐planar cleavage, S1. The folds, which possess a Caledonoid trend, usually stand vertically, but rarely they verge slightly to the southeast. They are periclinal in style. The second movement phase, F2, was weak and produced a sporadically distributed set of open folds and associated axial‐planar crenulation cleavage, S2, of Caledonoid strike. The axial‐planes dip gently to the southeast quadrant. Folds of the third movement phase, F3, plunge northwest and the associated axial‐planar crenulation cleavage, S3, dips steeply to the northeast. The F3 folds produce a pronounced arcuation in the trace of the Fl structures from an azimuth of 60° in the northwest to 10° in the south of the area.
Sedentary kaolinitic soil on the carboniferous limestone series in anglesey
Authors: Ball D. F. , Mew G.
Published: July 2010

A soil overlying Carboniferous calcarenites in Anglesey has a clay fraction dominantly of kaolinite in contrast to the illite‐chlorite assemblages generally characteristic of North Wales soils. From the mineralogy and field evidence this soil is interpreted as resulting from Late Glacial in situ weathering of the underlying rocks.
A volcanic vent in the tremadocian rocks southeast of Blaenau ffestiniog, Merionethshire, North Wales
Authors: Bromley Alan V.
Published: July 2010

A tuff filled volcanic vent which outcrops among Tremadocian rocks about 2 miles southwest of Blaenau Ffestiniog is described. The vent is correlated with the lower Caradocian Moelwyn Volcanic Series. Comparisons are drawn between this vent and the fissures from which the dominantly ignimbritic rocks of the Snowdon Volcanic Series were erupted and these are extended to account for lithological differences between the Snowdon and Moelwyn volcanic rocks.
Conical folding and fracture patterns in the pre‐betic of Southeast Spain
Authors: Moseley F.
Published: July 2010

The Pre‐Betic Alpine ranges of southeast Spain consist of a series of ENE trending folds developed mostly in Mesozoic and Tertiary limestones. One of these folds, the Mongo Syncline is described here and is of interest because of firstly its anomalous ESE trend, secondly the clearly demonstrable conical form and thirdly the en‐echelon arrangement of the minor fold axes which comprise the axial zone of the main syncline. To facilitate interpretation of this structure a considerable number of bedding and fracture orientations were taken (the latter mostly joints) over an area of 3 sq. km. The fractures related to the structure of the syncline, reveal particularly important sets of ENE “sinistral” joints and northerly “dextral” joints. The origin of the fold is debatable but the interpretation favoured here is that of a second order drag fold to a major wrench fault in the pre‐Triassic basement. In both cases diapiric squeezing of the incompetent Trias, which outcrops as an elongated (NW‐SE) inlier adjacent to the Mongo structure is envisaged.
A fabric analysis of the ground moraine deposits of the lleyn Peninsula of Southwest Caernarvonshire
Authors: Saunders G. E.
Published: July 2010

An analysis of the preferred orientation of the long axes of erratics contained within the superficial deposits of the Lleyn Peninsula indicates that during the two recorded glacial advances the area was invaded by ice from two source regions—the Irish Sea ice‐sheet and local Welsh ice‐bodies. An attempt is made to re‐construct the pattern of ice movement during both glacial advances, to determine the extent to which ice from each source region penetrated Lleyn, and to interpret the environment under which the tills were deposited.
Carboniferous lithofacies, rhydymwyn to erryrys, North Wales
Authors: Banerjee A.
Published: July 2010

The Viséan sediments between Rhydymwyn and Erryrys have been mapped and divided into a number of lithologic units. A combined study of field relationships and petrography has been made and conclusions have been drawn about depositional environments.
The origin and development of kink‐bands in a foliated body
Authors: Dewey J. F.
Published: July 2010

Although the deformation of foliated rocks by kink and glide mechanisms has been studied in detail in recent years, fundamental differences of opinion have emerged, particularly as a result of experimental work. Most theories concerning the relationship of kink‐bands to stress‐fields are empirically based. Evidence on whether kink‐bands are the result of a shear couple and on limiting factors for external rotation is presented. It is concluded that kink‐bands are zones of externally rotated foliation bounded by kink‐planes which develop parallel to planes of high shearing stress at infinitesimal strain.
Facies change in upper devonian and lower carboniferous rocks of Southern Ireland
Authors: Naylor D.
Published: July 2010

In south‐west Ireland 8,000 ft (2,440 m) of marine sandstones and mudstones, the Cork Beds (?Upper Famennian to E Zone, Carboniferous, in age), overlie the Old Red Sandstone. Farther north the Old Red Sandstone is succeeded by thin Lower Limestone Shales overlain by thick Waulsortian bank limestones.

A critical section (North Ringabella) west of Cork Harbour, in which 6,500 ft (1,981 m) of Old Red Sandstone and Cork Beds is exposed, is described and divided into ten formations. By comparison with sections to the south the upper beds of the Old Red Sandstone are shown to pass southward into marine sandstones (Cork Beds) of ?Upper Famennian age. The successions in the Cloyne and Cork Synclines are described and reveal the progressive northward change in the Lower Carboniferous from the argillaceous Cork Facies through a zone of isolated bank limestones (Cloyne) to a thick, 4,000 ft (1,219 m), Waulsortian bank complex (Cork). Finally an attempt is made with use of isopachyte maps to reconstruct the palaeogeography of southern Ireland in Upper Devonian and Lower Carboniferous times.
Trace fossils from the cambro‐ordovician rocks of North Wales and their stratigraphic significance
Authors: Crimes T. P.
Published: July 2010

In North Wales, Cruziana semplicata (Salter) is recorded from three otherwise unfossiliferous localities and Teichichnus sp. (Seilacher) and Phycodes circinatum (Richter) are shown to be widely distributed within the lower Arenig (Didymograptus extensus zone) sediments. P. circinatum is also recorded from the otherwise unfossiliferous Upper Pennant Quartzite. From a discussion of the stratigraphic ranges of these trace fossils it is suggested that the rocks of the C. semplicata bearing localites are Upper Cambrian (Ffestiniog) in age while the Upper Pennant Quartzite is Ordovician, probably Arenig.
Hornblende, gabbros and picrites at Rhiw, Caernarvonshire
Authors: Hawkins T. R. W.
Published: July 2010

Three hornblende‐bearing intrusive masses consisting mainly of cumulate rocks derived from a water‐rich, alkali‐basalt magma are described. They probably all belong to one Lower Palaeozoic 'sill‐like' intrusion with an original sloping floor. The sequence is divided into nine zones, and three major, and numerous minor units are recognized. Deuteric activity produced important alteration sequences, while Caledonian regional metamorphism only caused substantial alteration to the mineralogy in the marginal zones of the intrusion.
Hydrocarbon‐bearing nodules from Heysham, Lancashire
Authors: Harrison R. K.
Published: July 2010

Nodules enriched in hydrocarbon occur sparingly in a subarkose bed of Namurian (?Kinders‐coutian) age near Heysham, Lancashire. The nodules are commonly spheroidal to ellipsoidal (1‐9 cm across) and are composed of alternating shells of hydrocarbon‐rich and hydrocarbon‐poor sandstone. Irregular impregnations and pellets are also formed from hydrocarbon. The hydrocarbon is infusible, insoluble in CCl4, CS2 and petroleum naphtha, and is classified as a pyrobitumen. Ash content averages 22.1% and the ash contains major V; subordinate Fe, U, Ca; minor Pb, Ti; traces of Ba, Mn, Zr, Ga, Y, Sr, Ni and Th. Sulphide inclusions in the hydrocarbon are comprised of chalcopyrite and pyrite. Hydrocarbon, commonly with illite, replaces primary sandstone matrix and clastic grains. The nodules may have formed as periodic structures (cf. Liesegang rings) with precipitation from thixotropic hydrocarbon compounds. The available evidence is insufficient, however, to postulate with any certainty the origin of the hydrocarbon. It may have formed syngenetic accretions with clastic detritus or alternatively it may have been introduced after deposition of the sandstone, although no feeders have been observed.
Structures of the Skiddaw Slates in the Caldew Valley, Cumberland
Authors: Roberts D. E.
Published: July 2010

The hornfelsed Skiddaw Slates in the River Caldew, Cumberland, exhibit one of the best displayed sets of folds in the country. Patterns resulting from an analysis of these folds and the structures on the valley sides, indicate that the rocks have suffered several phases of deformation. Evidence is produced to suggest that folding was initiated during the pre‐Bala movements, and re‐folding occurred during the main end‐Silurian orogeny. During the end‐Silurian movements, folding due to collapse under gravity also occurred.
The exposures of Ludlow rocks and associated beds at Tites Point and near Newnham, Gloucestershire
Authors: Cave R. , White D. E.
Published: July 2010

The Leintwardine and Whitcliffe Beds of the Ludlow Series outcropping at Tites Point and near Newnham, Gloucestershire, are described and compared with similar beds exposed at May Hill. Data from the Brookend Borehole, 1 ½ miles (2.41 km) south of Tites Point, reveal that southward thickening affects all subdivisions of the Ludlow Series. The occurrence of the Ludlow Bone Bed in the Tites Point outcrop is also recorded.
The Carboniferous Limestone of Chipping Sodbury and Wick, Gloucestershire
Authors: Murray J. W. , Wright C. A.
Published: July 2010

The rock types and successions encountered at two localities have been described and interpretated with reference to modern analogues. In the Clifton Down Limestone a cycle of sedimentation is recognised passing from intertidal algal mats, through lagoons, barrier and open shelf deposits and back through the same sequence to intertidal algal mats.
The structures of the Ardsheal Peninsula, Argyll, their age and regional significance
Authors: Treagus J. E. , Treagus S. H.
Published: July 2010

The lithologies and structures of the Dalradian rocks of the Ardsheal Peninsula, Argyllshire are described. The structures associated with the main synformal fold (part of the Appin Syncline) are shown to be F1 in age. F2 structures cross the Syncline and show progressive development towards the east. The Syncline is correlated and compared with other major F1 folds in the region. This interpretation is contrasted with other interpretations of the Syncline as a third‐phase structure which can be correlated with late‐phase folds in the Dalradian.
Remains of pingos in Wales and the Isle of Man
Authors: Watson E.
Published: July 2010

Remains of pingos have already been reported from east central Wales. This paper records a further group from west central Wales and a probable group from the Isle of Man. When they are compared with contemporary pingos it is clear that they belong to the open system type, which, in contrast with the solitary pingo of the closed system type, tends to occur in clusters of mutually interfering forms and on melting to result in a complex pattern of ramparts.

Much of the recently discovered group in central Wales shows this complexity and suggests later pingos developing on the sites of earlier ones as the injection centres migrated upslope. On more open sites simpler solitary pingos occur, including some elongated forms. The Isle of Man group consists of depressions without ramparts but their location and orientation suggest they represent pingo basins. It is argued that although the most convincing evidence for pingos consists of arcuate to annular ramparts enclosing basins, the ramparts may disappear through cultivation.
A record of palynomorphs from the Waterstones (Triassic) of Liverpool
Authors: Fisher M. J.
Published: July 2010

A rich microflora from the Waterstones of St. James' Cemetery, Liverpool, is noted. The age of this assemblage and of others recorded from the Waterstones Formation and associated strata is discussed.
Melting relations of some ultra alkali volcanics
Authors: Tilley C. E. , Thompson R. N.
Published: July 2010

The melting relations of a group of ultra alkali lavas are determined. They include a range of types rich in melilite and nepheline (melilite nephelinites) from the Nyiragongo volcano of the Congo and a group rich in olivine (olivine nephelinites).

The liquidi of these assemblages range from 1100°C (the melilite nephelinite of the lava lake of Nyiragongo) through the Cameroons etindite (clinopyroxene nephelinite, 1118°C to 1300°C for the olivine nephelinites.

For the most part the liquidi follow a course dependent on iron‐enrichmcnt. Notable departures are examples rich in leucite.
A British meta‐anthracitic coal of Devonian age
Authors: Cook A. C. , Murchison D. G. , Scott E.
Published: July 2010

Vitrinite from the Devonian Gramscatho Beds at Pendower in southwestern Cornwall displays optical properties which indicate an extremely high rank (meta‐anthracite). Despite this high rank, wood structures are clearly evident in polished sections between crossed polars. Some coke is present and this feature, together with the optical properties of the main vitrinite mass, suggests that relatively high temperatures (probably in excess of 350°C), were associated with the metamorphism of the host rocks. Reflectivity measurements on oriented blocks show that the vitrinite is optically biaxial, which conflicts with the widely accepted view that vitrinites are negative uniaxial materials.
Tectonically dewatered slates in the Ludlovian of the Lake District, England
Authors: Mca. Powell C.
Published: July 2010

Multiple siltstone dykes intruded parallel to cleavage in the Ludlovian argillites and graywackes of the Lake District throw new light on the origin of slaty cleavage. Pore pressures equalling lithostatic pressure developed during the Caledonian orogeny and caused tectonic dewatering of the partially lithified sediments. Slaty cleavage was initiated as an essentially planar structure by the intrusion of thin pelitic folia during the escape of the pore water. Cleavage folia and fold axial planes may have a common geometric relationship to the deforming stresses, but are independent of each other in origin. Continued deformation after tectonic dewatering refracted the cleavage by rotation of competent layers. Critical examination of evidence supporting traditional theories of slaty‐cleavage formation shows that all observed relationships are compatible with the tectonic‐dewatering theory.
Downward‐facing structures in the Birnam Slates, Dunkeld, Perthshire
Authors: Treagus J. E. , Talbot C. J. , Stringer P.
Published: July 2010

New and accessible exposures are described in which the downward‐facing of folds in the axial‐zone of the Tay Nappe can be convincingly demonstrated.
On the age of the Hoxnian interglacial
Authors: Page N. R.
Published: July 2010

Fifteen new radiocarbon datings from British Pleistocene deposits are described. The datings are related to the classic Pleistocene succession and shown to be consistent with the stratigraphic sequence of East Anglia. On the basis of these datings, an absolute chronology is developed. According to this chronology, the glacial drifts of East Anglia ought to postdate 40,000 B.P. and hence belong to the Last Glaciation of the British Isles. The Hoxnian interglacial of this chronology is dated between about 25,500‐21,000 B.P. The conventional age for the Hoxnian interglacial is 175,000–120,000 B.P. The validity of the radiocarbon datings is considered and some of the implications and problems of a revised age for the Hoxnian interglacial are reviewed.
A preliminary study of the structure, stratigraphy and metamorphism of some contact rocks of the western Andes, near the Quebrada Venado Muerto, Peru
Authors: Atherton M. P. , Brenchley P. J.
Published: July 2010

The sequence and structure of the volcanic rocks of a small area lying within the main belt of plutons of the Peruvian Andes were mapped and are here described. Metamorphic zoning of the calcareous aureole minerals was shown to be similar to that described elsewhere, e.g. wollastonite, diopside, hornblende with increasing distance from the contact. The mineral assemblages and their spatial and textural character indicate rapid heating of the aureole, with only a short time at maximum temperatures. The complex mineralogy in individual rocks is interpreted in terms of changing physical conditions during the thermal event. The sequential assemblages are the result of changes in activity of CO2, H2O and Fe3+ in particular.
Facies and faunal changes in the Ludlovian rocks of Aymestrey, Herefordshire
Authors: Lawson J. D.
Published: July 2010

The Aymestrey area displays changes in facies, faunas and thicknesses which can be related to its position on the shelf edge during later Silurian times. The Wenlock Limestone becomes an alternation of limestones and mudstones. The Lower and Middle Elton Beds, however, are substantially similar to their development at Ludlow. The Upper Elton Beds and the Bringewood Beds thin westwards within the area, probably due to non‐deposition or erosion on a ridge at the hinge between shelf and basin. The most striking change is the rapid westward passage of the Aymestry Limestone facies of the Upper Bringewood Beds into siltstones, which are considered to be shallow‐water deposits and not basinal. The Leintwardine Beds exhibit a westward thickening, and slumping is developed in the Lower Leintwardine Beds; the faunas relate more to the basin facies than to the shelf. The Whitcliffe Beds thicken markedly westwards but retain their shallow‐water characteristics.
New exposures on forestry roads near Ludlow
Authors: Lawson J. D.
Published: July 2010

Seventy‐three new exposures of Upper Silurian rocks along forestry roads in the Ludlow area are recorded and an indication is given of their stratigraphical significance and of their potential research value.
Sorting of bivalve populations in a beach environment
Authors: Trewin N. H.
Published: July 2010

Size sorting of shells and valves of transported death assemblages of Mytilus edulis is shown to have taken place, and greatly affected size‐frequency distributions of shell accumulations deposited in a beach environment. Selective transport and deposition of different size grades gives histograms which may be strongly skewed or multimodal, and include numerous small shells. The usually predicted bell‐shaped distributions for sorted assemblages are not always produced. Little evidence of growth and mortality rates can be deduced with confidence from the transported assemblages.
Early phases of Caledonian deformation in the Dalradian of the Ballachulish district, Argyll
Authors: Bowes D. R. , Wright A. E.
Published: July 2010

Two 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

Lewisian 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

The 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

The 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

A 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

Carbonate 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

The 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

The 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

Two 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

The 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

The 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

The 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

The 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

A 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

A 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

Marginal 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

The 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

Previously 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

The 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

Joints 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

A 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

A 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.