bluuebunny/crossref_metadata_2025 huggingface dataset:
The envjronment of deposition of the Caradoc Alternata Limestone and contiguous deposits of Salop
Authors: Hurst J. M.
Published: July 2010

The middle Caradoc rocks of Salop are a mosaic of sedimentary facies deposited in nearshore environments. The uppermost Horderley Sandstone in the Onny Valley is interpreted as formed by migrating marine bars and proximal and distal stonn deposits. The time equivalent Chatwall Sandstone of the Chatwall district is interpreted as a beach sequence. The overlying Alternata Limestone is a product of both proximal and distal storm deposits, associated with marine bars, in which different faunal assemblages are mized. Correlation of local sections is difficult due to facies and faunal changes and non‐deposition events. Based on a sedimentary model and palaeoecological information it is suggested that the Alternata Limestone in the Chatwall area is older than elsewhere, and that the base of the Cheney Longville Flags youngs southwards. Four faunal events are defined based on transect collecting, discriminant function and cluster analysis. These are theHowellites antiquior, Dalmanella leptaandBancroftina robusteAssociations and theHeterorthis alternatainterregnum.
The age, stratigraphy and genesis of the Coniston Limestone Group in the southern Lake District
Authors: McNamara K. J.
Published: July 2010

The Coniston Limestone Group (Ashgill Series) in the southern Lake District shows greater lithological variation and lateral facies variation than hitherto suspected. The oldest part, the Longsleddale and Stile End Formations, is shown to correlate with the Cautleyan Stage, Zone 2, at Cautley; consequently the entire Coniston Limestone Group in the southern Lake District is considered to belong within the Ashgill Series. In the early Cautleyan, sedimentation was largely influenced by a central ridge which extended northward into a southerly transgressive sea. Later Cautleyan and Rawtheyan sedimentation was affected by an area of positive tectonic activity in the east of the region.
A cyclicity in the early Brigantian (D2) limestones east of the Clwydian Range, North Wales and its use in correlation
Authors: Somerville I. D.
Published: July 2010

For the first time, minor cyclicity is described from some limestones in the lower part of the Brigantian (D2) succession of the Mold district North Wales which can be traced throughout the area enabling a detailed correlation to be established. The minor cyclicity may have been caused by eustatic sea‐level fluctuations. Periods of emergence associated with each regressive phase are demonstrated by the presence of subaerial features and terrestrial deposits. The lateral persistence of the cycles is confirmed by comparison with established faunal and lithological horizons. Correlation with other cyclic Brigantian strata in Yorkshire, Derbyshire and Bristol is briefly discussed. The Asbian/Brigantian (D1/D2) boundary in North Wales is described and distinctive faunal and lithological changes similar to those in the area of the stratotype in north England have been recorded.
An Upper Llandoverian turbidite sequence of the Bwlch‐glas area, near Aberystwyth, Dyfed
Authors: Strong G. E.
Published: July 2010

Petrographical investigation of an Upper Llandoverian turbidite sequence has been undertaken in conjunction with the primary 1:50,000 geological survey of the Aberystwyth District (Sheet 163) by R. Cave and B. A. Hains of the Institute of Geological Sciences. The sequence represents distal thin‐bedded turbidite deposition in a NW‐SE channel, with material derived from the southeast.
Late Pleistocene rock‐basin lakes in South Wales
Authors: Culver S. J. , Bull P. A.
Published: July 2010

Laminated silts and clays recovered by coring and drilling in Swansea Bay are shown to be of lacustrine origin. Similar deposits penetrated by boreholes onshore in the Swansea area have also been ascribed to a lacustrine origin by several authors; a map showing the shape and distribution of five lakes in this area has been produced. Stratigraphic relationships and palynological evidence indicate that the lacustrine conditions probably lasted from about 16,000 to 10,000 years B.P.
Geomagnetic polarity measurements from Pleistocene deposits in Southwest France and their chronological implications
Authors: Oldfield F. , Thompson R.
Published: July 2010

Measurements of palaeomagnetic inclination in sediments from the French Pays Basque, representing three of the major Pleistocene biostratigraphic subdivisions previously identified, confirm normal polarity in all cases. Taken together with the palaeobotanical, stratigraphic and geomorphological evidence they suggest that the Moulignan, Senixian and Ilbarritzian stages lie within the early part of the present Brunhes normal polarity epoch and probably correlate with some unknown part of the “Cromerian Complex”. The Bidartian is thought to lie within a normal polarity event during the Matuyama epoch and to correlate with part of the Tiglian ‘A’ sub‐stage of the Netherlands.
The Longdendale landslides
Authors: Johnson R. H. , Walthall S.
Published: July 2010

Throughout its geomorphological history the South Pennine valley of Longdendale has been especially prone to landsliding and some ten landslide areas have been identified. These prove on analysis to be bedding plane slides with a strong degree of translation but often exhibiting non‐circular rotational elements as well. Instability in the lower slopes has often led to cambering and valley bulging so that the slopes become deformed and slump earth flows developed at some sites. Several different types of landslide are examined in detail and by means of pollen analysis the slides are dated from the early postglacial to at least as recently as two thousand years B.P. although it has not yet been possible to decide when these slides started. The causes of sliding are identified, and comments are made upon.

The location of slip surfaces–which are frequently at the base of the Grindslow Shales above a sandstone aquifer.

The geomorphic processes which built up high pore‐water pressures and steep pressure gradients in the past.

The effects of sliding on the development of hillslopes in the post‐glacial period.
Authigenic iron and titanium oxides in Triassic red beds: (St. Bees Sandstone), Cumbria, Northern England
Authors: Ixer R. A. , Turner P. , Waugh B.
Published: July 2010

Authigenic iron and titanium oxides occur in three main textural varieties in the St. Bees Sandstone, a Triassic red bed succession in Cumbria. These are: (a) overgrowths of haematite, titaniferous haematite, anatase, and rutile which generally occur on detrital host grains of similar compositions. The overgrowths may occur as syntaxial rim cements or rhombohedral and prismatic projections and are always in optical continuity, (b) discrete crystals of anatase (including octahedrite) and haematite 10‐40 μm in size occur in pore spaces, and (c) fine grained ( < 1 μm) pigmentary haematite occurs as grain coatings around detrital grains and in the interstitial matrix.

The euhedral nature and pore‐filling habit clearly indicate the authigenic origin of these iron‐ and titanium oxides. All three textural varieties are believed to have been precipitated from ground waters containing dissolved ferrous and titanium ions. These ions were derived from the intrastratal solution of detrital iron and titanium bearing grains including ferromagnesian silicates and iron‐titanium oxides. The precipitation of iron oxides from migrating ground waters in the manner described here goes some way to explaining how thick, uniformly red successions can be formed.
The age, stratigraphy and genesis of the coniston limestone group in the southern lake district
Authors: McNamara K. J.
Published: July 2010

The Coniston Limestone Group (Ashgill Series) in the southern Lake District shows greater lithological variation and lateral facies variation than hitherto suspected. The oldest part, the Longsleddale and Stile End Formations, is shown to correlate with the Cautleyan Stage, Zone 2, at Cautley; consequently the entire Coniston Limestone Group in the southern Lake District is considered to belong within the Ashgill Series. In the early Cautleyan, sedimentation was largely influenced by a central ridge which extended northward into a southerly transgressive sea. Later Cautleyan and Rawtheyan sedimentation was affected by an area of positive tectonic activity in the east of the region.
A cyclicity in the early brigantian (D2) limestones east of the clwydian range, north wales and its use in correlation
Authors: Somerville I. D.
Published: July 2010

For the first time, minor cyclicity is described from some limestones in the lower part of the Brigantian (D2) succession of the Mold district North Wales which can be traced throughout the area enabling a detailed correlation to be established. The minor cyclicity may have been caused by eustatic sea‐level fluctuations. Periods of emergence associated with each regressive phase are demonstrated by the presence of subaerial features and terrestrial deposits. The lateral persistence of the cycles is confirmed by comparison with established faunal and lithological horizons. Correlation with other cyclic Brigantian strata in Yorkshire, Derbyshire and Bristol is briefly discussed. The Asbian/Brigantian (D1/D2) boundary in North Wales is described and distinctive faunal and lithological changes similar to those in the area of the stratotype in north England have been recorded.
An upper llandoverian turbidite sequence of the bwlch‐glas area, near aberystwyth, dyfed
Authors: Strong G. E.
Published: July 2010

Petrographical investigation of an Upper Llandoverian turbidite sequence has been undertaken in conjunction with the primary 1:50,000 geological survey of the Aberystwyth District (Sheet 163) by R. Cave and B. A. Hains of the Institute of Geological Sciences. The sequence represents distal thin‐bedded turbidite deposition in a NW‐SE channel, with material derived from the southeast.
Geomagnetic polarity measurements from pleistocene deposits in southwest France and their chronological implications
Authors: Oldfield F. , Thompson R.
Published: July 2010

Measurements of palaeomagnetic inclination in sediments from the French Pays Basque, representing three of the major Pleistocene biostratigraphic subdivisions previously identified, confirm normal polarity in all cases. Taken together with the palaeobotanical, stratigraphic and geomorphological evidence they suggest that the Moulignan, Senixian and Ilbarritzian stages lie within the early part of the present Brunhes normal polarity epoch and probably correlate with some unknown part of the “Cromerian Complex”. The Bidartian is thought to lie within a normal polarity event during the Matuyama epoch and to correlate with part of the Tiglian ‘A’ sub‐stage of the Netherlands.
The longdendale landslides
Authors: Johnson R. H. , Walthall S.
Published: July 2010

Throughout its geomorphological history the South Pennine valley of Longdendale has been especially prone to landsliding and some ten landslide areas have been identified. These prove on analysis to be bedding plane slides with a strong degree of translation but often exhibiting non‐circular rotational elements as well. Instability in the lower slopes has often led to cambering and valley bulging so that the slopes become deformed and slump earth flows developed at some sites. Several different types of landslide are examined in detail and by means of pollen analysis the slides are dated from the early postglacial to at least as recently as two thousand years B.P. although it has not yet been possible to decide when these slides started. The causes of sliding are identified, and comments are made upon.

the location of slip surfaces–which are frequently at the base of the Grindslow Shales above a sandstone aquifer;

the geomorphic processes which built up high pore‐water pressures and steep pressure gradients in the past; and

the effects of sliding on the development of hillslopes in the post‐glacial period.
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.
Authigenic iron and titanium oxides in triassic red beds: (St. Bees Sandstone), Cumbria, Northern England
Authors: Ixer R. A. , Turner P. , Waugh B.
Published: July 2010

Authigenic iron and titanium oxides occur in three main textural varieties in the St. Bees Sandstone, a Triassic red bed succession in Cumbria. These are: (a) overgrowths of haematite, titaniferous haematite, anatase, and rutile which generally occur on detrital host grains of similar compositions. The overgrowths may occur as syntaxial rim cements or rhombohedral and prismatic projections and are always in optical continuity, (b) discrete crystals of anatase (including octahedrite) and haematite 10‐40 μm in size occur in pore spaces, and (c) fine grained ( < 1 μm) pigmentary haematite occurs as grain coatings around detrital grains and in the interstitial matrix.

The euhedral nature and pore‐filling habit clearly indicate the authigenic origin of these iron‐ and titanium oxides. All three textural varieties are believed to have been precipitated from ground waters containing dissolved ferrous and titanium ions. These ions were derived from the intrastratal solution of detrital iron and titanium bearing grains including ferromagnesian silicates and iron‐titanium oxides. The precipitation of iron oxides from migrating ground waters in the manner described here goes some way to explaining how thick, uniformly red successions can be formed.
Some last glaciation drift deposits near Pontypridd, South Wales
Authors: Harris C. , Wright M. D.
Published: July 2010

Drift deposits exposed in a large open cut are described. The basal member of the sequence consists of bedded sandy gravels, and these are overlain by a grey silty sand containing abundant striated pebbles and boulders. The uppermost deposit consists of a brown poorly sorted drift containing silty and sandy lenses. Analysis of the texture, index properties and densities of the sediments, together with the shape, lithology and fabric of the contained pebbles suggests that the basal gravels were deposited by subglacial meltwater, the grey drift is a lodgement till, and the uppermost brown rubbly drift was formed by solifluction of the till, with the addition of frost shattered sandstone from the hilltop above. It is suggested that the glacigenic sediments are of Devensian age, and the solifluction layer Late Devensian.
Rhythmic sedimentary sequences in the triassic Keuper Marl (mercia mudstone group) of cheshire, northwest England
Authors: Arthurton Russell S.
Published: July 2010

Cored boreholes in the central part of the Cheshire‐Shropshire basin form the basis of a sedimentological description of three separate parts of the Keuper Marl succession. The uppermost sequence examined is the lower part of the Middle Keuper Marl within which blocky silty mudstones and well laminated mudstones and siltstones form a rhythmically alternating pattern. Similar alternating patterns are described from the Lower Keuper Saliferous Beds and the top of the Lower Keuper Marl although, in these, the alternations are interrupted to various degrees by halite rock. The blocky and laminated facies are considered to have accumulated in emergent and flooded conditions respectively, the alternations reflecting eustatic variation.
Silurian metabentonites in County Down, Northern Ireland
Authors: Cameron T. D. J. , Anderson T. B.
Published: July 2010

Thin beds of pale green and grey ‘claystone’ in the Birkhill Shales (Lower Silurian) of County Down are positively identified as bentonite. In the overlying turbidites, previously regarded as entirely of sedimentary origin, numerous metabentonites demonstrate continuing Silurian vulcanicity.

The metabentonites contrast with the enclosing sediments in mineralogy and geochemistry. Illite, with subsidiary chlorite, is the chief alteration product of the primary volcanic glass, and comprises two co‐existing polymorphs. Clay‐grade 1Md mica is derived from montmorillonite, and a coarser 2M variety may be an anchimetamorphic alteration of the former. Some beds additionally contain accessory phenocrysts of orthoclase, oligoclase, biotite or chlorite, and small amounts of apatite and ilmenite. Statistical analysis of the geochemical data indicates that primary alteration of volcanic glass to bentonite was accompanied by relative enrichment of Al, K, Rb, Zr, Nb, and Y, and depletion of Na; additional enrichment of K and Rb occurred with collapse of mixed‐layer clay to illite during Caledonian anchimetamorphism.
Sedimentary facies, production rates and facies models for recent coralline algal gravels, Co. Galway, Ireland
Authors: Bosence Daniel W. J.
Published: July 2010

Five sedimentary facies are described from SCUBA diving examination and sampling of Mannin Bay, Ireland. A Bank facies is built up by the unattached coralline algae Lithothamnium corallioides and Phymatolithon calcareum. This autochthonous facies occurs in shallow sheltered environments. In exposed areas a rippled Clean Algal Gravel facies is found composed of coralline and molluscan debris. In intermediate energy areas a Muddy Algal Gravel facies is found with small amounts of live corallines. Sheltered creeks have a Mud facies which is partly carbonate and partly terrigenous. The shallow water coralline algal sediments are overlapped by a Fine Sand facies of mixed biogenic composition. Each facies is characterized by particular phenotypic growth forms of the unattached corallines. Rates of organic calcium carbonate production are obtained which are found to be similar to rates from shallow tropical non‐reef environments. The carbonate sediments of Mannin Bay are compared with similar sediments from Kilkerrin Bay. Ireland, from Brittany and from Falmouth Harbour. From these comparisons, facies models are proposed for these carbonate sediments. The major factor controlling facies distribution is coastal morphology. The present day shelf is considered to be too exposed to preserve complete sequences of the shallow water sediments.
A suggested re‐interpretation of the Lower Palaeozoic stratigraphy around Llanafan Fawr, Central Wales
Authors: Davies J. H.
Published: July 2010

A recent paper by Lockley (1978) described the stratigraphy of the Towy Anticline around Llanafan Fawr, Brecknock, based on the proposition that there exists a syncline which crosses the Chwefru Valley at Lan Fach. Way up evidence from the area indicates the absence of this fold and a rearrangement of the local stratigraphical sequence is therefore necessary. The revised stratigraphy resembles much more closely that of other sections across the Towy Anticline in south Central Wales.
Lepidostrobus haslingdenensis: A new species from the Lancashire Millstone Grit
Authors: Thomas B. A. , Dytko Alicja
Published: July 2010

A collection of microsporangiate cones is described from the topmost Namurian of Rossendale, Lancashire. The microspores are closely comparable with the dispersed spore species Lycospora noctuina, being of a type that has not been previously recorded from a fructification.
The ordovician‐silurian boundary in the garth area of southwest powys, wales
Authors: Williams Alwyn , Wright Anthony D.
Published: July 2010

The Ordovician‐Silurian rocks at Garth, 30 km northeast of Llandovery, have been remapped. Within the siltstone‐dominated succession, the coarser Cwm Clŷd Formation is regarded as stratigraphically equivalent to the A1 sandstone of Llandovery and has yielded a single specimen of Eostropheodonta hirnantensis from near the base in the northernmost exposures. The Formation rests with a stratigraphical break on fossiliferous Rawtheyan siltstones in the south but is underlain by later Rawtheyan and abundantly fossiliferous Hirnantian sediments (Wenallt Formation) further north where the succession appears continuous. Sedimentary and faunal evidence demonstrates the shallowing of the Ashgill sea before a transgression and deepening started in late Hirnantian times. The implications of the sequence in determining the systemic boundary are discussed.
Peralkaline rhyolites from the ordovician tweeddale lavas, peeblesshire, scotland
Authors: Thirlwall M. F.
Published: July 2010

The riebeckite‐bearing rhyolite of Winkston Hill, Peebles, is shown to be peralkaline and may be named a pantellerite. Trace element comparison with other more altered members of the Tweeddale lavas from Wrae Hill suggests that the whole suite is peralkaline. It is thought most unlikely that the suite was developed in association with an Upper Ordovician subduction zone, and it was perhaps erupted on an oceanic island.
A tunnel section through a prograding Namurian (Arnsbergian, E2a) delta, in the western Bowland fells, north Lancashire
Authors: Johnson Eric W.
Published: July 2010

The Wyresdale Tunnel was driven through Roeburndale Grit Group sediments in the western Bowland Fells. An Arnsbergian age for the strata is confirmed in a palynological study. The tunnel provided a section through a prograding delta front sequence, and proved the Roeburndale Grit Group to be much thicker than previously recorded. Syndepositional instability within the deltaic sediments is illustrated by slumps and debris slides. A comparison is made with modern deltas. It is suggested that the regional variation in sediment thickness is tectonically controlled.
Faunas from the upper silurian (upper ludlovian) in the ludlow‐much wenlock district, England
Authors: Antia David D. J.
Published: July 2010

Faunal lists for 17 sections in the Overton Formation are presented. Faunal diversity appears to increase towards the formations base while faunal dominance appears to increase towards its top.
Glyptograptus? persculptus (Salter), its tectonic deformation, and its stratigraphic significance for the Carys Mills Formation of N.E. Maine, U.S.A.
Authors: Rickards R. B. , Riva John
Published: July 2010

The Carys Mills Formation of NE Maine represents the SW extension of the Matapedia Group and the White Head Formation of southern Gaspé, Quebec. This formation has yielded two main collections, one hitherto considered of Middle Ordovician age (zone 13 of Berry's 1960 Marathon, Texas, zonation) with 7 species referred to 4 genera, and one of the Early Silurian age. A revision of the supposed Middle Ordovician collections reveals that the graptolites are basal Silurian and consist of only one species, Glyptograptus? persculptus. Several hundred specimens, preserved both flattened and in three dimensions, the latter in iron pyrites, allow an analysis of both the rhabdosome changes wrought by diagenetic flattening and those caused by severe tectonic deformation. It is shown that those specimens lying parallel to the bedding plane lineation caused by a high‐angle main cleavage have a silhouette appearance close to Glyptograptus tamariscus (Nicholson), whilst those at right angles to this direction superficially resemble robust Amplexograptus spp., or Diplograptus s.s., or Diplograptus s.l. spp., thus explaining the stratigraphic assignment of earlier workers. An analogue video reshaper confirms the above conclusions.

This determination assigns the whole Carys Mills Formation to the Lower Silurian, but the possibility that part of the formation is of Late Ordovician age cannot be excluded. This much is suggested by the Matapedia Group and the White Head Formation which are of Late Ordovician to Early Silurian age, and the Honorat Group, which has yielded graptolites of late Middle Ordovician age.
A note on the stratigraphic relationship of the leven schist and monadhliath schist in the central highlands of Scotland
Authors: Haselock P. J. , Winchester J. A.
Published: July 2010

The Monadhliath and Leven Schists are separated north of Glen Roy by some 500m of psammitic rock. Junctions are gradational and conformable, and evidence from sedimentary structures indicates that all three face upwards. The two schists should not be equated, nor should the Monadhliath Schist be included in the Dalradian Supergroup unless the entire Grampian Division is also included.
Carbon isotopic change at the base of the upper permian zechstein sequence
Authors: Magaritz Mordeckai , And Peter Turner , Käding Karl‐Christian
Published: July 2010

Fluctuation of the carbon isotope composition of marine carbonates has recently been developed as a powerful tool for the identification of ocean‐wide anoxic conditions and changes in the world budget of carbon and oxygen. A change in δ13 from the normal marine values (0 to + 2%) to values highly enriched in 13C (+3·5 to 4·5%) is recorded at the base of the Zechstein sequence both in central Germany and northeastern England. The change occurred over a relatively short period of time indicating a rapid and pronounced change in the organic carbon/carbonate budget. Evidence from other Permian basins show similar highly enriched δ13C values. This change may correspond to that in carbon balance distinguished by the Garrels and Perry (1975) model and based on the change in sulphur isotopic composition during the Permian.
Palynofloras from tournaisian lacustrine and tidal sequences in slieve bloom, counties laois and offaly, Ireland
Authors: Keegan James B. , Feehan John
Published: July 2010

Tournaisian miospore assemblages are used to determine the age of some plant‐bearing horizons in the Old Red Sandstone succession of the Slieve Bloom Mountains, Counties Laois and Offaly, Ireland, and the sedimentology and conditions of deposition of the productive lithologies are described. The age of the marine transgression which terminated continental sedimentation is indicated, and the associated depositional environment is discussed. Comparisons are made with other micro‐ and macrofloras from Ireland, Britain, Canada, the U.S.S.R. and Bear Island.
Sandy gravel accumulation in a fluvial environment
Authors: Blacknell Clive
Published: July 2010

Particle size, pebble shape, pebble fabric, discharge and flow velocity data are used to introduce a model of sandy gravel formation in Welsh gravel‐bed rivers. The development of contact‐imbrication of the typically very bladed and very platy cobbles and larger pebbles subsequently acts to significantly affect the depositional modes and patterns of small pebbles and sand particles. An important distinction is drawn between sand deposition, which can occur at or below the bed surface, and pebble and cobble deposition, which is merely a surface phenomenon.
Petrology and geochemistry of the Fishguard Volcanic Complex, Wales
Authors: Bevins R. E.
Published: July 2010

The Fishguard Volcanic Complex represents an important volcanic episode which occurred within the Welsh sector of the British Caledonide region during early Ordovkian times. A variety of extrusive and contemporaneous intrusive rocks are present, ranging in composition from basic, through intermediate to acidic. Mineral and whole‐rock chemical analyses have been determined on a representative suite of rocks from the complex and, despite secondary alteration effects, the original tholeiitic characteristics of the suite can be discerned. The variation observed is considered to result largely from low‐pressure crystal fractionation, although the origin of the acidic magma remains speculative in view of subsequent extensive recrystallization. The rocks of the Fishguard Volcanic Complex formed in the Welsh Basin, which has been likened by earlier workers to a marginal basin. Comparison of the geochemical characteristics of the Fishguard Volcanic Complex with that of documented marginal basin rocks appears to favour this contention.
The palynology and provenance of the coal fragments contained in the late‐Pleistocene Lleiniog gravels of Anglesey, North Wales
Authors: Walsh P. T. , Butterworth M. A. , Wright K.
Published: July 2010

The numerous coal clasts in the late‐Pleistocene fluvioglacial Lleiniog Gravels of eastern Anglesey contain a varied assemblage of Westphalian A (and possibly also early Westphalian B) spores. Directional sedimentary structures indicate that the meltwater currents which deposited the gravels came mainly from the north and east, while glacial striae and erratic trains indicate that the parent (? Devensian) glacier flowed from the northeast. Consideration is given to the possibility that the coal clasts were derived from the breaking‐up, fairly locally, of far‐travelled rafts of Coal Measures. It is concluded, however, that the most probable explanation is still Greenly's (1919) postulate that the source is a yet‐to‐be‐identified submarine outcrop situated only a few kilometres northeast of Lleiniog.
Late pleistocene (Devensian) glaciofluvial outwash at Banc‐y‐Warren, near Cardigan (west Wales)
Authors: Allen J. R. L.
Published: July 2010

On the southwest‐facing slopes of a bedrock ridge lying between Cardigan Bay to the north and the Afon Teifi to the south stands a group of hills in which 30‐35 m of cross‐laminated and parallel‐laminated sands with lenticular upward‐fining gravel sequences are overlain by 10‐12 m of gravel in a single foreset bed. The sediments mantle a surface of till sloping gently toward the southwest, were transported toward the southwest (across one margin of the Afon Teifi valley), and were cut by a system of densely arranged conjugate normal faults striking northwest‐southeast.

The lenticular gravels and fault system suggest that the deposits accumulated as a glaciofluvial outwash spread, and on top of an ice‐lobe that became isolated in the Teifi valley during the downwasting of a glacier which had occupied Cardigan Bay and much of the country to the south. The large gravel foresets capping the succession are the only indication at Banc‐y‐Warren of the former existence of a lake, but neither a large nor deep body of water need be envisaged.
A new isogon‐cleavage classification and its application to natural and model fold studies
Authors: Treagus Susan H.
Published: July 2010

Traditional methods of studying natural folds are reviewed. A new method of describing cleavage attitude in folds is presented; the β plot. The combined graph of dip isogon angle ϕ (Hudleston 1973) and cleavage angle β is proposed as a linked classification of fold and cleavage geometry. Plots of β and βϕ are given for three natural fold examples. The classification is extended to the geometry and strain attitude (βϕ5) of two finite‐element models and the classical folding models. Results are compared and some tentative conclusions drawn on the relationship of cleavage, the XY plane of strain and dip isogons.
A palaeomagnetic investigation of the Malvernian and Old Radnor Precambrian, Welsh Borderlands
Authors: Piper J. D. A.
Published: July 2010

Alternating field and thermal demagnetization of igneous rocks of the Malvern Hills identifies a number of magnetite‐held components which are characterized by a high blocking temperature (M2) componentD= 283°,I= 47°, and lower blocking temperature (M3) componentD= 269°,I= −43° which is of complex origin or more than one age. Two subordinate components are (M1)D= 7°,I= 56° and (M4)D= 174°,I= 51° in later dolerites. A pervasive hematite‐held remanence with a meanD= 186°,I= −5° is linked to Hercynian palaeofield directions and the uplift/folding of the Malvernian axis. The similarity of the magnetization directions in the Stanner–Hanter (702 Ma) and Malvernian (681 Ma) rocks suggests that folding of the Palaeozoic rocks in the Malvern Hills was achieved by upthrust of the basement and involved little folding of the latter. The Old Radnor sediments possess a post‐folding remanenceD= 117°,I= −13° of probable Cambrian age and a subordinate remanence which may be Hercynian in age.

The late Precambrian–Cambrian palaeomagnetic record (ca.700–500 Ma) of England and Wales is compared with data from the Armorican Massif. Although the apparent polar wander (a.p.w.) paths are widely dissimilar prior to 550 Ma, the two regions had similar latitudes and went through similar palaeolatitudinal movements throughout this interval. The palaeomagnetic data support models involving tectonic rotations but little closure across this part of the Hercynian Belt.
Major element composition of the pelites of the Scottish Dalradian
Authors: Atherton M. P. , Brotherton M. S.
Published: July 2010

Major element composition of the available analysed pelitic rocks of the Dalradian of Scotland is examined in relation to geographical position, mineralogy, metamorphic grade and stratigraphy. Some of the large variations found are due to geographical position, possibly reflecting different provenance. A major compositional difference exists between the two lower Barrovian metamorphic zones and the four higher zones. This is considered to be a reflection of the original sedimentary composition and large scale metasomatism is not considered likely.
The stratigraphy of the Drummuck Group (Ashgill), Girvan
Authors: Harper D. A. T.
Published: July 2010

The Drummuck Group of the Girvan district (S. W. Scotland) comprises a varied sequence of marine siliciclastic sedimentary rocks some 350 m thick and ranging in age from early Cautleyan to late Rawtheyan (Ashgill Series). Deposition in an unstable slope environment is envisaged. These upper Ordovician rocks crop out in the centre of the Craighead inlier, north of the Girvan valley and are sporadically exposed and locally very fossiliferous. A detailed revision of the Drummuck rocks has permitted, for the first time, the formal lithostratigraphical division of the group. Four main units, in ascending order, the Auldthorns, Quarrel Hill, Lady Burn and South Threave formations are recognized and, within these, a number of smaller, useful divisions are defined. Detailed geological maps of the Drummuck outcrop are presented. Brachiopods numerically dominate the shelly faunas and all the divisions named are characterized by distinctive brachiopod assemblages. Preliminary correlations are discussed with selected upper Ordovician successions elsewhere but the emphasis of this study is placed upon the establishment of a stratigraphical framework within which future detailed research on the Drummuck faunas may be carried out.
Rb‐Sr isochron study of the Thorr and Main Donegal Granites, Ireland
Authors: O'Connor P. J. , Long C. B. , Kennan P. S. , Halliday A. N. , Max M. D. , Roddick J. C.
Published: July 2010

A Rb‐Sr whole‐rock isochron study indicates that the entire Donegal granite suite was emplaced into orthotectonic Caledonian (Dalradian) rocks over a short interval during mid‐Silurian to earliest‐Devonian times. The Thorr pluton, probably the earliest member of the suite, yields an age of 418 ± 26 Myr and initial87Sr/86Sr ratio of 0·7055 ± 4, while the latest member, the Main Donegal pluton has an age of 407 ± 23 Myr and initial87Sr/86Sr ratio of 0·7063 ± 5 (Λ87Rb = 1·42 ± 10−11yr−1). Errors on both the age and initial Sr isotope ratios incorporate botha prioriand geological scatter components and are quoted at the 2‐sigma level. The low and restricted range of initial Sr isotope ratios suggests small but significant differences in the composition of the parental granitic magmas which were derived from a low Rb/Sr, low87Sr/86Sr source.
The Late‐Quaternary deposits of the middle Dyfi Valley, Wales
Authors: Thomas G. S. P. , Summers A. J. , Dackombe R. V.
Published: July 2010

The surficial deposits and landforms of the middle Dyfi Valley, Wales, are examined and a sequence of glacial, glacio‐fluvial and glacio‐lacustrine sediments is identified. This is considered to relate to a late stage in the wastage of the Late‐Devensian Merioneth ice‐cap. A sequence of terrace gravels overlying the giacigenic succession represents dissection during early Flandrian times.
Geophysical and radiometric studies of the Northern Units of the Leinster Intrusion
Authors: Cassidy J. , Locke C. A.
Published: July 2010

The Leinster intrusion, S.E. Ireland, is one of a group of Caledonian granites, sensu lato, of Siluro‐Devonian age, which typically exhibit strong geophysical and geochemical contrasts with their host rocks. New gravity data supplement previous road‐based data and define, over the Northern Units of the intrusion, a closed residual anomaly (‐160 g.u.) with steep gradients. The Northern Units are shown to comprise a large volume of low‐density material extending to a depth of 8 km, and hence to constitute a significant contribution to Caledonian crustal growth. The sub‐surface form of the intrusion is essentially vertical‐sided having no broad root, in contrast with other Siluro‐Devonian granites (s.l.).

Radioelement concentrations in the Northern Units were mapped quantitatively by in situ gamma‐ray spectrometry. The mean concentrations of 4·2 per cent K2O, 3·0 ppm U and 8·1 ppm Th measured are lower than those typical of the Siluro‐Devonian granites (s.l.), suggesting depletion associated with high‐level fractionation, and in addition a possible Th‐depleted source region. Complex areal radioelement distributions reflect both the multiple intrusive event, and later secondary remobilization, particularly of U. This is demonstrated using fission‐track radiography which shows that U, at least, is located in both primary and secondary minerals.
Interpretation of field relationships of Diorites and associated rocks with particular reference to northwest Guernsey, Channel Islands
Authors: Topley C. G. , Brown M. , Power G. M.
Published: July 2010

In northwest Guernsey, excellently exposed sections of coast reveal a wide variety of diorites and associated rocks which are particulariy instructive in understanding field relationships in diorite complexes generally. In this area, three groups of rocks may be distinguished. A Diorite Group consists of even grained diorite, acicular diorite and appinite, believed to be related to each other by fractionation. This group was intruded by a Granodiorite Group which contains diorite xenoliths. In turn, both of these were intruded by an Inhomogeneous Suite of rocks varying from meladiorite through to tonalite. Field evidence and geochemistry show that this last, highly variable suite of rocks was formed by the unusual process of fractional crystallization coupled with disruption and partial redigestion of early solid fractionates by derivative liquids, leading to the marked inhomogeneity. Such a mechanism may be more generally applicable but clear evidence for it seems to be restricted to rocks of dioritic composition. The margins of the Inhomogeneous Suite usually consist of tonalite which has piped into the surrounding diorites of the Diorite Group, and the two rock groups are thought to have been at least partially liquid at the same time. The exact shape of pipes may prove to be a useful indicator of physicai conditions at the time of magma emplacement in this and other intimate associations of magmas of contrasted composition. Although the Diorite Group was emplaced first, dark (apparently chilled) margins sometimes occur in diorites of this Group where they are in contact with the later Inhomogeneous Suite. In such intimate associations as this, dark margins must be interpreted with extreme caution.
Middle carboniferous marine transgression, Bjørnøya, Svalbard: facies sequences from an interplay of sea level changes and tectonics
Authors: Gjelberg J. , Steel R.
Published: July 2010

The Svalbard Platform, in middle Carboniferous time, was dominated by a series of NNW‐SSE oriented, asymmetric rift basins. The Landnørdingsvika Formation represents the infill of one such basin in the Bjørnøya (Bear Island) area and consists of red beds deposited during a regional rise of sea level. The basin was filled mainly from the west and southwest across a Carboniferous fault zone, the West Bjørnøya. Fault, which bounded the deep edge of the basin.

The basin succession is dominated by floodplain and coastal plain deposits in its lower part and fanglomerates interbedded with shallow marine clastics and carbonates in its upper part. The marine facies gradually increase in volume upwards and culminate in the overlying, carbonate‐dominated Kapp Kåre Formation (Moscovian). This continental‐marine transition, which has also been identified in the other Svalbard basins, thus reflects an important middie‐late Palaeozoic transgression. Analysis of the facies sequences shows that there are repeated submergence‐emergence events which are superimposed on the longer term transition. These are interpreted in terms of repeated basin floor tilting and sinking against the upland block.
The Monian ‘Penmynydd Zone of Metamorphism’ in Llŷn, North Wales
Authors: Gibbons W.
Published: July 2010

In the Mona Complex of Llŷn, a narrow, steep belt of fine grained schists known as the Penmynydd Zone of Metamorphism lies between a deformed melange (Gwna Group) and a unit of gneisses and plutonic rocks (Sarn Complex). Rocks within and adjacent to this Zone are characterized by mylonitic textures. The highest grade Penmynydd rocks on Llŷn reached greenschist and, locally, glaucophanitic greenschist fades conditions. The schist belt is interpreted as a major shear zone formed as the Sarn Complex moved up against the lower grade Gwna Group. A previous interpretation of the schists (Shackleton 1956) as being the result of a prograde metamorphism from sub‐greenschist facies Gwna Group to anatectic granitic and gneissic rocks of the Sarn Complex is rejected.
Metasomatism and the formation of greisen in Grainsgill, Cumbria, England
Authors: Roberts D. E.
Published: July 2010

A section of hornfelsed Skiddaw Slate adjacent to the margin of the Grainsgill Greisen is described and chemical analyses of the various rock types presented. The results confirm that hydrothermal fluids liberated K and Na from the granite to produce the greisen. This gave rise to K metasomatism of the adjacent hornfels and to retrogressive metamorphism over a radius of 200m from the intrusion. Na leached from the hornfels near the intrusion and that liberated during the formation of the greisen are probably the sources of the Na in the brines recorded in fluid inclusions within the nearby quartz‐tungsten veins.
The skipton rock fault–‐an Hercynian wrench fault associated with the Skipton Anticline, northwest England
Authors: Arthurton Russell S.
Published: July 2010

A zone of deformation characterized by en échelon faults and folds extends along the Skipton Anticline. The zone is well exposed on its northern margin at Haw Park, where it involves early Dinantian strata. Here a high‐angle reverse fault–‐the Skipton Rock Fault–‐is broadly coincident with the axial surface of the Skipton Anticline. This fault and its associated subsidiary faults and folds form a structural pattern consistent with an origin in dextral convergent wrenching or transpression.
On the occurrence of an unusual form of monazite in panned stream sediments in Wales
Authors: Cooper D. C. , Basham I. R. , Smith T. K.
Published: July 2010

An unusual nodular form of monazite has been found to account for abnormally high levels of cerium in panned heavy mineral concentrates from stream sediments in several areas in Wales and pan of Exmoor. Textural features indicate a pre‐metamorphic, diagenetic origin within Lower Palaeozoic shale or siltstone host‐rocks but REE patterns show only minor variation, including relative enrichment in europium, from ‘average’ granitic monazite. The similarities between these occurrences, described for the first time from the British Isles, and those previously described from Brittany and elsewhere are discussed.
The distribution of hydrocarbon minerals in the Welsh borderlands and adjacent areas
Authors: Parnell J.
Published: July 2010

Solid hydrocarbon minerals occur in small quantities in the Lower Palaeozoic Welsh Basin, where Ordovician igneous intrusions mobilized them from local organic‐rich source rocks. Hydrocarbon minerals are widespread in the Wenlockian and Carboniferous Limestones, and at least in the Carboniferous Limestone they show a close and probably genetic relationship with lead‐zinc mineralization. The association of hydrocarbon minerals with lead‐zinc‐copper ores in Ordovician and Longmydian rocks' in the West Shropshire mining region is however largely coincidental. The hydrocarbon minerals in that region are residual from Carboniferous reservoir hydrocarbons. Reservoir hydrocarbon minerals in a breccia at Row Brook include crystallites of iron sulphides and manganese oxides. Hydrocarbon minerals in siderite nodules in the Coal Measures are spatially related to metal sulphides.
Low‐grade metamorphism within the Welsh sector of the paratectonic Caledonides
Authors: Bevins R. E. , Rowbotham G.
Published: July 2010

Mineral assemblages within metabasites from the paratectonic Caledonides of Wales show that the grade of metamorphism was predominantly within the prehnite‐pumpellyite facies, although green‐schist fades assemblages occur in the more central parts of the region. General agreement with this pattern of metamorphism is seen in recent studies of illite crystallinity and conodont colour. Comparison with other regions suggests that all of the paratectonic Caledonides of the British Isles has suffered a low‐grade of regional metamorphism during late Caledonian times.
The Avalon Zone: A Pan‐African terrane in the Appalachian Orogen of Canada
Authors: O'Brien S. J. , Wardle R. J. , King A. F.
Published: July 2010

The Precambrian sequences of the Avalon Zone in Canada (southeastern margin of the Appalachian Orogen) are interpreted as a Pan‐African orogenic belt incorporated into the Appalachian Orogen during Palaeozoic times as its southeastern margin. The Precambrian evolution of the Avalon Zone was genetically unrelated to subsequent Palaeozoic evolution. The Avalon Zone shows marked similarities in age, tectonic history, and facies development to the Pan‐African belts adjacent to the West African Craton.

Precambrian evolution of the zone began with circa 800 Ma rifting of a sialic gneissic basement and deposition of a Middle Proterozoic(?) carbonate‐clastic cover sequence. Early crustal rifting was associated with localized partial melting and metamorphism. Limited crustal separation led to the restricted development of circa 760 Ma oceanic volcanics. Continued rifting and subsequent closure of these narrow ocean basins led to the eruption of widespread subaerial volcanic suites, block faulting, granite plutonism, and local, late Proterozoic sedimentary basin formation. Precambrian evolution of the zone terminated with the Avalonian Orogeny (circa 650‐600 Ma), a deformational event, the affects of which are most evident locally along the northwestern margin of the zone.

The controlling features of the Proterozoic evolution of the Avalon Zone are a series of linear intracratonic troughs and small ocean basins that formed during thinning and separation of the crust by ductile spreading, rupture, and delamination (cf. Martin and Porada 1977). The variation in degree of crustal separation led to subsequent variation in orogenesis during late Proterozoic compression.

The zone marks the original westward limit of Pan‐African activity and displays no apparent genetic link with the Appalachian Orogen in Canada until Devonian times.