bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies of andean uplift part I‐post‐cretaceous evolution of the San Bartolo Area, North Chile
Authors: Hollingworth S. E. , Rutland R. W. R.
Published: July 2010

On the eastern side of the Atacama Desert an early Tertiary planation surface may be recognised across the major structures. Subsequent tectonic activity has taken place along particular lineaments and each episode has induced a period of dissection. The tectonic activity and associated dissection can be correlated with a period of ignimbrite deposition, and by inference with the period of Andean uplift. Isotopic ages on the ignimbrites can therefore be used to date Andean uplift. They suggest that uplift began in late Miocene times. Important later phases can be dated as mid‐Pliocene and Late Pliocene or Pleistocene.
The faunal‐stratigraphy of the ludlovian rocks between Craven Arms and Bourton, near Much Wenlock, Shropshire
Authors: Shergold J. H. , Shirley J.
Published: July 2010

The Ludlovian Series has been mapped between the River Onny at Craven Arms and the village of Bourton which lies 2½ miles SW of Much Wenlock. Ten subdivisions are recognised on biostratigraphical and lithostratigraphical criteria. For these divisions the stratigraphical terminology established by Holland, Lawson and Walmsley (1959, 1963) in the Ludlow area has been utilised. Two breaks occur in the otherwise continuous succession of variable calcareous sediments: there is lithological and faunal discontinuity at the base of the Leintwardine Beds and within the Upper Leintwardine Beds. The latter can be recognised over a wide area of the Ludlovian shelf. Accordingly alternative correlations, to those presently accepted, are proposed for the Leintwardine Beds.
folding and slumping in a layered gabbro
Authors: Thompson R. N. , Patrick D. J.
Published: July 2010

The layered gabbroic intrusion of Sarqata qaqa, Ubekendt Ejland, West Greenland contains numerous xenoliths of thermally metamorphosed picrite‐basalt. Folding and slumping of the layering occurs adjacent to some of these blocks. It is postulated that the structures were formed by sloped lava xenoliths hitting the unconsolidated layers of crystals forming the floor of the magma chamber during the cooling history of the intrusion. The settling velocities of the xenoliths, and thickness and viscosity of the crystal mush are estimated and discussed.
Geophysical investigations of buried river valleys around Cardigan Bay
Authors: Blundell D. J. , Griffiths D. H. , King R. F.
Published: July 2010

Gravity and seismic surveys over the estuaries of the rivers Dovey, Dysynni, Glaslyn and Mawddach have indicated that the rock floor lies at depths of from 100 to 1,250 ft (30 m to 380 m) below the present surface. The methods of survey and difficulties of interpretation are discussed, and the significance of the results is assessed in conjunction with those already published for the Teifi estuary and with preliminary results obtained by seismic reflection profiling in. Cardigan Bay. It is concluded that all the valleys with the exception of the Glaslyn could have been carved during Pleistocene times, but that the much deeper buried valley of the Glaslyn, extending south of Portmadoc across Morfa Harlech, is probably of earlier origin.
Carboniferous lithofacies, Halkyn Mountain, North Wales
Authors: Oldershaw Alan E.
Published: July 2010

A brief description of the carboniferous succession on Halkyn Mountain, North Wales, together with a map illustrating the areal distribution of upper Viséan carbonate and Namurian non‐carbonate lithologies, is presented. The upper Vistan carbonates have been divided into four major units termed in ascending order: A1 (pelsparites and biopelsparites); A2 (alternating biopelmicsparites, non‐argillaceous biomicrites and micrites); B1 (argillaceous calcite siltstones); B2 (alternating non‐argillaceous and argillaceous biomicrites and micrites). Analysis of the distribution of microfacies within each unit indicates that during upper V i s h times, deposition of shallow water, off‐shore, carbonate sand banks alternated with, and finally gave way to, the deposition of in‐shore, lagoonal carbonate muds. The presence of an erosional surface at the top of Unit B2 suggests that a period of emergence took place prior to the deposition of the succeeding Namurian bedded cherts. The cherts can be differentiated into three major lithologies which exhibit characteristics that are consistent with cyclic deposition in a marginal, restricted basin.
PHYSIOGRAPHY, FORAMINIFERA AND SEDIMENTATION IN THE Dovey Estuary (Wales)
Authors: Haynes John , Dobson Max
Published: July 2010

A study of the chemistry, circulation and sedimentation is followed by an outline account of the living and dead communities (particularly foraminifera) characteristic of the main physiographic subenvironments. On the basis of the relationships established these results are used in an interpretation of the vertical sequence.
The namurian succession between Tenby and Waterwynch, Pembrokeshire
Authors: Jones D. G. , Eagar R. M. C.
Published: July 2010

Namurian cliff sections are described in detail. A minimum thickness of about 76 m is ascribed to Namurian A and 198 m and 104 m respectively to Namurian B and C. Faunal marker bands enable the Chokierian, Marsdenian and Yeadonian Stages to be recognised and the detailed structure to be worked out and this confirms the structural interpretation of Dixon. The succession is correlated and compared with adjacent areas in Pembrokeshire and South Wales. The Marsdenian includes a fauna of highly variable Sanguinolites. S. ovalis Hind is redescribed and a lectotype chosen.
The upper cretaceous ophiolite complex of Masirah Island, Oman
Authors: Moseley F.
Published: July 2010

Masirah Island is almost entirely composed of a highly faulted and unmetamorphosed folded ophiolite complex which is unconformably overlain by unfolded Eocene limestone and is correlated with the Upper Cretaceous Semail Complex of the Oman Mainland. The ophiolites include serpentine, basalt, pyroclastics and some radiolarite, and intrusive complexes largely composed of serpentine, peridotite, picrite, anorthosite, gabbro and granite, with transitional varieties. Emplacement structures within the intrusions are extremely complicated, with the gabbros full of blocks mostly of serpentine up to 1 km or more in diameter. There are also late stage veins, lenses and irregular bodies of granite. Ophiolites, probably derived from the mantle, are ultrabasic differentiates with soda metasomatism. Tectonic structures are largely pre‐Eocene. They include fractures, some of which are parallel to the late Tertiary submarine Masirah fault which is related to continental drift.
Sedimentology and petrography of three tuff horizons in the Caradocian sequence of the Bala area (North Wales)
Authors: Schiener E. J.
Published: July 2010

Three interstratified pyroclastic deposits in the Caradocian marine sequence around Bala (N. Wales) are investigated. Their petrology is used for identification and correlation.

The Cefn Gwyn Ash is a vitric tuff, locally indicating subaerial deposition. The Frondderw Ash is the product of subaqueous pyroclastic flows, giying evidence of very short‐lived volcanic activity. The Pont‐y‐Ceunant Ash is a waterlaid vitric crystal tuff. Lateral changes in lithology allow a north‐easterly source‐area to be inferred for the former two members. Sedimentary structures show partial emergence of the area during Soudleyan times.

The highest member, the Pont‐y‐Ceunant Ash, is restricted to the south‐west of the area.
The imprint of structural grain on the micro‐relief of the Welsh uplands
Authors: Thomas T. M.
Published: July 2010

Structural lineations of varying orders have been mapped for the full extent of the Welsh uplands where in some areas their clear impress in the micro‐relief has revealed minor structures not previously described in geological literature. Although significant variations in the strike of these structurally induced breaks of slope may be noted they display the more typical Caledonoid alignments (NE—SW or NNE—SSW) in nearly 60 per cent of the total area of the country. The dominance of these trends has been somewhat accentuated by the fact that even along the northern edge of “Armorican” South Wales, where low dips are a feature, a NE–SW grain is also evident in extensive tracts of the prevalent scarplands.
A quantitative model of grain size and sedimentary structures in lateral deposits
Authors: Allen J. R. L.
Published: July 2010

The secondary flow and transverse changes of water depth in curved stream channels are exploited to develop a quantitative, partly empirical model of the way lithology varies vertically in deposits accumulated through processes of lateral deposition. According to the model, grain size decreases upward in a lateral deposit and the sedimentary structures change from those denoting large stream powers upward to kinds indicative of small powers. The model also shows that the proportion of flat‐bedded sand‐grade material in a lateral deposit is essentially independent of stream power but controlled by channel curvature and hence general sinuosity. The predictions of the model compare satisfactorily with the characteristics of selected coarse members in fining‐upwards cycles of fluviatile origin from Devonian strata in Britain and North America. The model is thought to have value as a tool for environmental interpretations.
The structural relationships of the Loch Borrolan Complex, Scotland
Authors: Woolley A. R.
Published: July 2010

The Borrolan Complex comprises earlier and later rock suites which are separated by an intrusive junction. The earlier suite forms a conformable sheeted complex which has been punched through by a later plug‐like body and includes several distinct magma types; while the later suite differentiated gravitationally in place. Field and microscopic evidence suggests that some of the earlier rocks were emplaced prior to the principal movements on the Assynt Thrust Plane, while the later suite post‐dates the development of the Assynt Thrust, although it is affected by a deformation. It is suggested that the emplacement of the greater bulk of the Borrolan rocks after movement on the Assynt Thrust Plane had ceased excludes the possibility of the Borrolan, and nearby Loch Ailsh, intrusions being the trigger mechanism which set off the great duplication of strata in the Assynt Culmination.
Sedimentation of the Triassic (Scythian) Red Pebbly Sandstones in the Cheshire Basin and its margins
Authors: Thompson D. B.
Published: July 2010

This magnalithofacies, which forms the bulk of two formations, the Bunter Pebble Beds and the Lower Keuper Sandstone, is described and interpreted as the deposits of former low‐sinuosity, largely braided, streams which flowed across a regional palaeoslope inclined to the north‐west. Arid blocks of the Welsh and Pennine Massifs lay to the west and east. Lithofacies A, conglomerate breccia and gravel, is interpreted as a deposit of former channel floors and sometimes bars. Lithofacies B crossbedded pebbly coarse sandstone, formed from large‐scale ripples developed on channel (? braid) bars of flood courses, whilst lithofacies C, argillaceous finer sandstone, represents the large‐scale ripples of quieter channels at lower stage and discharge. Lithofacies D, interbedded fine sandstone and shale, formed a riverplain topstratum deposit and, rarely, a levee. Lithofacies E is similar to D except that the sandstone is coarser and injects the mudstones repeatedly. Lithofacies F, red shales and mudstones (largely the ‘marl’ bands of former authors), may be laterally restricted or extensive. The former bands represent deposits of bar swales and abandoned cut‐off channels of varying stage: the latter suggest the development of a riverplain topstratum. Lithofacies X, soft fine sandstone, is aeolian. These lithofacies are arranged in vertical repetitions of varying thicknesses which are often asymmetric. Allocyclic climatic influence, reflected in varying discharge and sediment load under conditions of net accretion and steady subsidence, is regarded as a dominant factor in the origin of miocycles, megacycles and magna‐cycles, though in smaller repetitions the possibility of channel wandering, and in magnacycles the influence of tectonics, is possible.
Succession and sedimentation of glacigenic deposits at Hendre, Anglesey
Authors: Helm D. G.
Published: July 2010

The application of sedimentological and other techniques in a detailed small‐scale study of Quaternary meltwater deposits around Pentraeth in Anglesey, North Wales has shown that interpretations based solely on surficial form are incorrect. Previous views held that the sediments were deposited sub‐glacially as eskers by meltwater flowing south‐west from decaying ice in Red Wharf Bay.

The present work shows that in general the deposits form a coarsening upwards sequence with distinctive divisions corresponding to the lacustrine, deltaic and fluviatile phases of basin filling. The glacigenic sediments were transported by rivers flowing predominantly south‐eastward and deposited in a shallow lake or lakes.
Solution subsidence outliers containing probable Tertiary sediment in north‐east Wales
Authors: Walsh P. T. , Brown E. H.
Published: July 2010

The pale‐coloured clays and lignites of presumed Tertiary age from the upper parts of the Mochras borehole (Wood and Woodland 1968) are not the first such materials to be recovered from the existing Welsh landscape. Similar clays and sands, and, occasionally, pebble beds and lignites have been recorded from over twenty localities, preserved beneath Glacial deposits in solution subsidence cavities in the Carboniferous Limestone. The best known such occurrence is the isolated mass at Flimston, Pembrokeshire, which has long been thought to be of Tertiary age (Dixon 1921).

The others are scattered along the Carboniferous Limestone outcrop of north Wales between Llandudno in the north‐west and Mold in the south‐east. Their proximity to each other, and records of fossil remains in some of them suggested that it might be possible to effect a regional stratigraphical correlation. Certainly, whatever their age, they form a critical stratigraphical reference in hypotheses concerning the geomorphological evolution of the Welsh landscape.

The Flintshire and Denbighshire occurrences are reviewed in the light of information recorded by Maw (1865 and 1867), Strahan (1890) and others, and information forthcoming from recent excavations and augering is presented.

It is concluded that, like the pocket deposits of Derbyshire (with which there are numerous analogous relationships) the north Wales pockets are probably solution subsidence outliers of a sheet of fluvio‐lacustrine Tertiary sediments, in part at least 70 m thick, the product of Palaeogene deep weathering, that formerly spread over much of the area of north Wales now occupied by the Alun, Clwyd and Conway catchments.
The Ballybofey Anticline: A solution of the general structure of parts of Donegal and Tyrone
Authors: Pitcher W. S. , Shackleto R. M. , Wood R. S. R.
Published: July 2010

A tight early fold, the Ballybofey anticline, trends south‐eastwards across central Donegal. South‐west of its axial trace the Dalradian strata are inverted so that the rocks high in the Series occur at the lowest structural level, next to, and facing downwards, the supposedly Moinian psammites in the core of the Lough Derg antiform. Rapid facies changes occur in the Dalradian rocks across the Caledonian strike.
A continuous seismic profile survey of Windermere
Authors: Howell Frank T.
Published: July 2010

Continuous seismic profile devices, modified for use in freshwater have been used on Windermere to determine the total thickness of lakebed sediments and the morphology of the underlying bedrock. The survey detected two overdeepened irregularly shaped rock basins. The northerly one approaches 110 feet (34 m) below sea level and contains 70 feet (21 m) of sediment. The corresponding dimensions of the Southern basin are 120 feet (37 m) and 130 feet (40 m) respectively. Glacial scouring is postulated as the origin of the rock basins. Some profiles show two types of sediment; the higher parts of which are known to be Post Glacial.
The origin of banding in the Main Donegal Granite, N.W. Ireland
Authors: Berger A. R.
Published: July 2010

This Caledonian pluton exhibits a regular, sub‐vertical banding in which layers of dark, relatively fine grained trondhjemite alternate with layers of light, coarse grained granite. The textures and the presence of cross‐cutting bands of granite indicate that the light bands were derived by potash feldspathization of the trondhjemite. The geometry of the banding indicates that it formed during the “synplutonic” deformation of the pluton, largely in situ. The bands formed by segregation of alkalies into dilatant zones of movement produced during the deformation of partly consolidated magma.
The faunal stratigraphy of the Kirkby Moor Flags of the type area near Kendal, Westmorland
Authors: Shaw R. W. L.
Published: July 2010

The rocks generally referred to the Kirkby Moor Flags have been mapped in the Kendal area, roughly bounded by Underbarrow, Sedbergh and Kirkby Lonsdale. The succession is divided into four units: the Lower Underbarrow Flags, the Upper Underbarrow Flags, the Kirkby Moor Flags and the Scout Hill Flags. These represent a redefined succession derived from what had been lumped together as ‘Kirkby Moor Flags’. These units correlate with the Upper Leintwardinian, the Whitcliffian and the Downtonian of the Welsh Borderland. Proof that rocks of Downtonian age occur is demonstrated in an unbroken succession of uniform lithology. Ostracodes form an invaluable part of the fauna in both subdivision and correlation of the succession.

The fauna of the Kirkby Moor Flags and the Scout Hill Flags can be classified into assemblage groups which possibly represent communities of species.
A geoelectrical investigation of the drift deposits in Northwest Lancashire
Authors: Worthington P. F.
Published: July 2010

A surface resistivity survey around and to the south of Garstang has indicated a predominance of boulder clay, with some sands and gravels, in an overburden of markedly variable thickness and lithology. The survey techniques, data processing and interpretation are discussed. The data suggest that the Lower Boulder Clay may be represented northeast of Garstang, with the Middle Sands present over a much wider area. The major subdivision, the Upper Boulder Clay, seems to be overlain by patches of presumed Upper Sands. Possible isopachytes of these four suggested subdivisions are presented, and certain hydrogeological implications briefly mentioned.
Minor thrust faults in the Avonian of the North Crop of the South Wales Coalfield
Authors: Roberts J. C.
Published: July 2010

Small‐scale thrust faults are described from the North Crop of the South Wales Coalfield in strata of Avonian age. Two main sets occur which strike at east‐west and north‐south respectively, and show apparent stratigraphic zonation. It is suggested that the sets were initiated during the early stage of deformation of the area in response to primary and secondary resolved compressional forces.
The Stratigraphy of the Ordovician rocks of Anglesey
Authors: Bates D. E. B.
Published: July 2010

Arenig sandstones, grits and conglomerates rest unconformably on pre‐Cambrian rocks (the Mona Complex) and are of variable thickness and facies. Higher Arenig and Llanvirn shales, grits, conglomerates, shaly breccias and ironstones are related to contemporaneous fault movements, with abundant slump structures and rare turbidites. A pre‐Caradoc break in sedimentation was followed by deposition of shales, cherty shales, sandstones, breccias and conglomerates on Llanvirn, Arenig and pre‐Cambrian rocks. The Carmel Head Thrust acted as a major line controlling sedimentation, with upthrow to the north. Lower Silurian graptolitic shales at Parys Mountain rest on an acid volcanic group of Caradoc (?) age.
Melting relations of some oceanic basalts
Authors: Tilley C. E. , Thompson R. N. , Lovenbury P. A.
Published: July 2010

The melting relations of a group of oceanic basalts—olivine basalts, tholeiitic to midly alkaline, and high‐alumina tholeiites are determined. The liquidi of these rocks follow closely the course of the temperature—iron enrichment relationship of Kilauean thoeliitic basalts, ranging from 1430°C for an olivine enriched tholeiite, to a tholeiite of liquidus temperature of 1190°C, the liquidus phase of the assemblages being either olivine or plagioclase.
Comparative petrology of the leucocratic syenites of the Northwest Highlands of Scotland
Authors: Parsons I.
Published: July 2010

The normative mineralogy of the Loch Borralan, Loch Ailsh and Loch Loyal leucosyenites is compared to the System Ab – Or – An ‐ Qz. At Borralan, the upper quartz‐syenites of Cnoc‐na‐Sroine plot within the plagioclase volume, the lower perthosites within the alkali feldspar volume. This mineralogy cannot have been attained by in situ crystal fractionation. The Ailsh rocks plot within the plagioclase volume, the Loyal syenites within the alkali feldspar volume. The three complexes cannot have been derived from a single magma body at depth, and are not precisely coeval.
Pre‐Cambrian landscapes in Northwest Scotland
Authors: Stewart A. D.
Published: July 2010

An old land surface carved out of basement gneisses is extensively preserved beneath Torridon Group sandstones (deposited ca. 750 m.y. B.P.). Contoured reconstructions show that relief declines westward from 2000 ft (600 m) to almost nothing over a distance of 25 km. North‐northeast trending zones of similar dissection can be traced for 160 km. Weathering up to 2 m deep is locally present in the flat zone. The essentially unweathered land surface forming the mountains probably originated by dissection of a palaeoplain. The flat zone is probably, but not certainly, a relatively young pediplain. All land forms are thought to have developed before, not during, deposition of the overlying sediments.
The mineralogy and origin of interbedded clay wayboards in the Lower Carboniferous of the Derbyshire Dome
Authors: Walkden G. M.
Published: July 2010

Interbedded clays, or clay wayboards, from the Lower Carboniferous Limestones of Derbyshire and Staffordshire, are discussed in terms of their geological relationships, textural features and mineralogy, and comparison is made between these clays and other interbedded argillaceous materials from the area. It is concluded that the clay wayboards are the argillation products of contemporaneous volcanic ashfalls, and lie within the definition of K‐bentonites.

Stratigraphical and palaeogeographical aspects of clay wayboard distribution are briefly discussed, and it is shown that despite the probable widespread extent of individual clay horizons they are only of limited value for the purposes of correlation.
The geological significance of a negative gravity anomaly in the South Wales Coalfield
Authors: Thomas M. D. , Brooks M.
Published: July 2010

Three gravity traverses across the eastern half of the South Wales Coalfield indicate a local, elongate, negative Bouguer anomaly of a few milligals amplitude bordering the southern rim. The anomaly has a maximum amplitude of 4 mgal near Maesteg and attenuates eastward, dying out in the vicinity of the East Crop. Two possible geological causes of the anomaly are examined, namely a local thick sequence of normal Upper Carboniferous strata and a discrete, low‐density body of Carboniferous age with no apparent surface expression. The former, uncontroversial explanation requires rock densities at variance with measured values. In the case of the hypothetical low density body which can explain the anomaly, a variety of possible ages and configurations are discussed.
The Pleistocene history of Wales and the borderland
Authors: Bowen D. Q.
Published: July 2010

The Pleistocene rock‐stratigraphic record is accorded more or less traditional time‐stratigraphic interpretation which was held widely before application of an Irish developmental model in 1960. The following sequence of events are recognised: (1) Complete glaciation, of indeterminate age, which antedated the raised beach interglacial. (2) The raised beach episode which is shown to be the last (Ipswichian) interglacial. (3) The last (Devensian/Weichselian) glaciation, followed by possible readvance in northwest and northeast Wales; prior and subsequent to glaciation periglacial conditions obtained. It is shown that the Irish model, relying heavily as it does on the equation of rock and time stratigraphy, is inapplicable in Wales.
The age and stratigraphy of the Sholeshook Limestone of Southwest Wales
Authors: Price D.
Published: July 2010

Local developments of the Upper Ordovician Sholeshook Limestone are briefly described and inter‐correlated on the basis of their trilobite faunas. The base of the formation is diachronous and overlies the Mydrim Shales unconformably. The base of the normally succeeding Slade and Redhill Mudstones is also diachronous and to the north and west of Haverfordwest this formation contains strata laterally equivalent to the main part of the Sholeshook Limestone.

It is suggested that the Sholeshook Limestone falls within the Cautleyan Stage of the Ashgill Series. This extends the range of several trilobite species normally regarded as Middle Ashgill (Rawtheyan) indices.
The sub‐drift surface of the Mersey and Weaver catchment and adjacent areas
Authors: Howell F. T.
Published: July 2010

Evidence from 1,450 boreholes and coastal seismic profiles adds further precision to the form of the sub‐drift channels of South Lancashire and North Cheshire. These channels resemble sub‐aerial valleys, but commonly have ungraded profiles locally reaching at least 289 ft (87 m) below O.D. In some places they are still below present sea level, 40 miles (64 km) inland. It is suggested that previous views of origin can be reconciled by considering them to be river valley Systems, partly rejuvenated by low Pleistocene sea levels, and locally modified by sub‐glacial meltwater.
Vesicles and related structures in lavas
Authors: Whitford‐Stark J. L.
Published: July 2010

A review of certain late‐stage textures in subaerial, submarine and lunar extrusive rocks is presented, together with a genetic classification of vesicles. The term paravesicle is introduced for hollows in lavas caused by the introduction of a gaseous phase into the lava after extrusion. Examples taken from the andesitic lavas of the Borrowdale Volcanic Series are used to illustrate the usefulness of studying such features.
The structure of the Taff Gorge area, Glamorgan, and the stratigraphy of the Old Red Sandstone—Carboniferous Limestone transition
Authors: Gayer R. A. , Allen K. C. , Bassett M. G. , Edwards D.
Published: July 2010

Lithostratigraphical and structural mapping of the Taff Gorge area, Glamorgan, has revealed a number of E‐W trending folds and thrusts. These were developed during the early stages of the Hercynian deformation as a result of an approximately N‐S principal compressive strain. Coeval with the folding, a conjugate set of sub‐vertical wrench faults, symmetrical about the principal compressive strain, divided the area into tectonic blocks and to some extent controlled the progressive development of folds and thrusts within the individual blocks. Later Hercynian deformation gave rise firstly to oblique‐slip and finally to dip‐slip movement on the faults.

The lithological transition between the Old Red Sandstone and Carboniferous Limestone is described in detail, including the diagenetic history of the limestones. Marine horizons are shown to be present within the dominantly fluviatile Old Red Sandstone, and the base of the Carboniferous Limestone is defined at the base of the lowest limestone of the continuous marine sequence. Studies of spores, macroplants, conodonts and brachiopods indicate that the whole of the Upper Old Red Sandstone and Lower Limestone Shale in the Taff Gorge are of Tournaisian age.
The structure of the Lower Palaeozoic rocks of Anglesey, with special reference to faulting
Authors: Bates D. E. B.
Published: July 2010

The principal structures of the Lower Palaeozoic rocks of Angelsey are described. Tight folding, with variably developed slaty cleavage and a first phase of reverse faulting, took place probably in late Silurian times, along axes which are parallel to pre‐Cambrian foliation trends. A second phase of reverse faulting followed basic dyke intrusion and was succeeded by normal faulting and mineralization. Joint production was a comparatively late feature. A technique for analysing fault data, in terms of stress axes, is outlined and applied to faulting within the Lower Palaeozoic rocks.
The structure of the Moine‐like rocks near Lough Derg, County Donegal, Eire
Authors: Borradaile G. J.
Published: July 2010

The Moine‐like rocks are shown to have major, southward‐leaning, isoclinal F2 folds which may be synchronous with the nappe‐like Ballybofey Antiform of the overlying Dalradian rocks. The deformation of the immediately adjacent Dalradian rocks is consistent with a previous suggestion that they are in contact with the Moine‐like rocks along a major tectonic slide.
A geophysical interpretation of the structure of the Vale of Clwyd, North Wales
Authors: Collar F. A.
Published: July 2010

Detailed gravity and resistivity surveys have been made in the Vale south of Denbigh, and from the combined interpretations a Trias isopachyte map has been produced. The gravity interpretation indicates that the en echelon faults of the western side extend across to the Vale of Clwyd fault, and separate a complementary set of en echelon synclines. These structures are systematically arranged in a pattern that may be attributed to dextral wrenching, and are discussed against a range of literature on that subject. The wrenching may have been a prolonged activity that commenced during Carboniferous times.
Structure and stratigraphy of the Borrowdale Volcanic rocks of the Kentmere area, English Lake District
Authors: Soper N. J. , Numan N. M. S.
Published: July 2010

The Borrowdale Volcanic rocks of Kentmere have been reinvestigated. A previous structural interpretation (Mitchell 1929) involving Caledonian isoclines superimposed upon pre‐Caradocian NNE trending folds is shown to be incorrect; neither set of structures exist. The geometry of the major structural elements in the area, the Nan Bield Anticline and the Caledonoid cleavage, is described. Evidence is adduced which suggests that the anticline was formed in pre‐Caradocian time as a large open fold trending approximately E‐W. Its present geometry and that of the Wren Gill Monocline result from the superimposition of the regional end‐Silurian cleavage obliquely and inhomogeneously across this pre‐existing fold.

The volcanic succession is divided into four compositionally and petrographically defined formations. In upward sequence these are the Nan Bield and Wren Gill formations (andesitic lavas and tuffs), Kentmere Formation (mainly dacitic pryoclastic rocks) and the Garbourn Formation (andesites and dacites), totalling over 2800 m. It is thought that much of this succession was deposited subaqueously.
A resistivity section of Holy Island (Anglesey)
Authors: Habberjam G. M. , Jackson A. A.
Published: July 2010

An account is given of the use of square array resistivity techniques to derive an apparent resistivity section down the length of Holy Island (Anglesey). Possible interpretations of this section in terms of the distribution of true resistivity with depth are given and discussed briefly in relation to proposed geological structure.
On the thermodynamics of open systems in geology
Authors: Ostrovsky I. A.
Published: July 2010

Semipermeable membranes are necessary conditions for the realisation of equilibrium open systems in the Earth's crust. Membraneless cases, as at the boundary Earth‐Atmosphere, are rather exceptional. The application of the D. S. Korzhinskii's thermodynamics of open systems to mineral equilibria in rocks may be justified only if the perfect mobility of components is proved independently viz: by means other than the analysis of mineral paragenesis alone.
Some late Pleistocene involutions at Dalton‐in‐Furness, northern England
Authors: Johnson R. H.
Published: July 2010

Involutions are reported for the first time from northwest England. They occur in ‘head’ deposits of reworked mudstone, shale, sandstone and breccia soliflucted over glacio‐fluvial sands and gravels in the Poaka Beck valley. The involutions were developed in the late Devensian period and most present a strongly festooned cross‐section. Excavation of these features showed that the regular form was a result of chance sectioning and that the cryoturbate structures were a cellular or pocket type of feature. Frost heave, ice segregation and a reversed density stratification all probably contributed to the development of the involutions, but an important factor was the ground water hydrology which gave especially favourable conditions for strong cryergic activity at this site.
The geology of Howth and Ireland's Eye, Co. Dublin
Authors: Van Lunsen H. A. , Max M. D.
Published: July 2010

The Cambrian sediments in Howth and Ireland's Eye to the northeast of Dublin have been mapped and the submarine deltaic Censure Group and the overlying Nose of Howth Group, which consists of interbedded turbidites and olistostromes, have been distinguished. Large scale sedimentary disruption has accompanied detachment of quartzitic sandstone beds in the Censure Group, where the bases of detached blocks have slump features while their tops generally do not. This contrasts with the chaotic sedimentary breccias in the olistostromes of the Nose of Howth Group. Blocks in the Censure and Nose of Howth Groups are up to 450 m and 700 m across respectively. The turbidies have come from the southeast and east whereas the slumping appears to have been generated from the southwest.

Slumping during sedimentation was followed closely by large‐scale folding and sliding of sedimentary or tectono‐sedimentary origin, and the bulk appearance of the sediments is due to these sedimentary and tectono‐sedimentary mechanisms. The main structure is an easterly facing, steep plunging syncline which locally is associated with a poorly preserved cleavage. This structure predated the main penetrative cleavage which is not axial planar to it.
The stratigraphy of Ordovician volcanic rocks on the southern and eastern flanks of the Harlech Dome in Merionethshire
Authors: Ridgway J.
Published: July 2010

The stratigraphy of nine areas of Ordovician volcanic rocks flanking the Harlech Dome is dcscribed and a correlation of the Ordoyician volcanic succession from Arenig to Cader Idris proposed. Nine formations are distinguished which together form a distinct lithostratigraphic unit termed the Aran Volcanic Group. At least six disconformities can bc recognised within the Group.
Gravity stratification in the Freetown Basic Igneous Layered Complex, Sierra Leone, West Africa
Authors: Umeji A. C.
Published: July 2010

An area of 78 sq. km in the vicinity of Freetown is mapped for the first time. By systematic mapping and study of about 1,500 thin sections, nine macro layered units have been recognized in this lowest exposed part of the intrusion. Each unit grades upward from magnetite or olivine‐rich layers, through pyroxene‐rich to plagioclase‐rich rock. Field data of fine‐scale layering, ‘false‐bedded’ layers and slumping are given. These and other sedimentary structures and features indicate that the Freetown magma was convective. It is suggested that rhythmic layering in the Freetown basic intrusion originated from slow accumulation of density‐sorted crystals which precipitated simultaneously from the magna‐pulses.
Jointing and minor tectonics of the S. Crop of the South Wales Coalfield between Machen and Bridgend
Authors: Roberts J. C.
Published: July 2010

Observations on joints, minor faults and mineral veins at 47 localities along the south and south east crop of the S. Wales Coalfield indicate the presence of a joint system comprised of up to 6 sets of fractures striking at 350°, 330°, 290°, 270°, 250° and 210°. The joint sets are parallel to minor faults of strike and dip‐slip types, whilst minor thrust faults indicate an early phase of sub‐horizontal compression. The joint system is thought to be of tectonic origin and developed early in the deformational history of the area in response to a N‐S compression. Later, dilational episodes facilitated the infilling of mineral veins, with the W.N.W. trending set probably indicating the latest phase of dilation in the area. All structures are considered to be of Armorican age, whilst the marked similarity in the orientation of the joint system to that of the North Crop of the Coalfield suggests that the brittle deformation was relatively homogeneous on both flanks of the Coalfield.
The succession of the Lower Old Red Sandstone (Siluro‐Devonian) along the Ross‐Tewkesbury Spur Motorway (M.50), Hereford and Worcester
Authors: Allen J. R. L. , Dineley D. L.
Published: July 2010

The motorway cuts approximately 1900 m of strata, of which about 56 per cent are continuously exposed in numerous long sections, a new standard being afforded for the Lower Old Red Sandstone in the southern Welsh Borders. The succession recognized is:

LOWER OLD RED SANDSTONE

Brownstones (L. Dev.) at least 795 m

St. Maughan's Group (L. Dev.) 630 m

Raglan Marl Group (Siluro‐Dev.) 385 m

Clifford's Mesne Sandstone (Sil.) at least 9 m

LUDLOW SERIES (Silurian) at least 5 m

The uppermost Ludlow Series and the Clifford's Mesne Sandstone are exposed in the core of the May Hill‐Woolhope upfold. They are overlain in the complimentary syncline to the west by the Raglan Marl Group, St. Maughan's Group and Brownstones, in ascending order. Above the Clifford's Mesne Sandstone, there is a progressive upward increase in the number and thickness of sandstone relative to mudstone beds. Pedogenic limestones are largely concentrated in two short stratigraphic intervals. The lowest, mainly in the uppermost Raglan Marl Group but reaching into the St. Maughan's Group, includes the “Psammosteus” Limestone recognised elsewhere in the area. The second concentration occurs in the uppermost St. Maughan's Group. Vertebrates in the Raglan Marl Group and the St. Maughan's Group allow the Downtonian and Dittonian “stages” to be recognized.
A rediscovered 114‐foot Lepidodendron from Bolton, Lancashire
Authors: Thomas B. A. , Watson Joan
Published: July 2010

Sixteen specimens of known heights from a Lepidodendron trunk, about 34·5 m long, are described in detail. The surface features show upward change from fissured bark to well defined leaf cushions. These features are discussed in relation to growth patterns in arborescent lycopods.
Erosion surfaces and ignimbrite eruption, measures of Andean uplift in northern Peru
Authors: Myers J. S.
Published: July 2010

Remnants of five mature erosion surfaces occur on the rugged western flank of the Andes, and each is deeply incised. They indicate alternation of arid with more humid conditions, and that the western Andes were raised in five major pulses from a subdued early Tertiary landscape of volcanic flows. Each pulse of uplift was accompanied by south‐westward tilting of the older erosion surfaces. The surfaces developed before an ignimbrite was erupted down the ancestoral Rio Fortaleza valley 6 m.y. ago. Since then, renewed uplift has led to further incision of the main valleys and the formation of canyons.
The crystallisation and differentiation of a layered intrusion of hydrated alkali olivine‐basalt parentage at Rhiw, North Wales
Authors: Cattermole P. J.
Published: July 2010

Three outcrops of hornblende‐bearing basic intrusives at Rhiw, S.W. Lleyn, are considered to represent faulted remnants of a single larger intrusion. The layered rock series evolved by fractional crystallisation of hydrated alkali olivine‐basalt magma which was emplaced as a number of distinct pulses. The trend of differentiation is similar to that for the Hawaiian series: alkali olivine basalt‐ hawaiite‐trachyte. Consideration is given to the respective roles of pO2 and pH2O in controlling the course of differentiation.
Upper Llandoverian Grogal Sandstones and Aberystwyth Grits in the New Quay area, Central Wales: A possible upwards transition from contourites to turbidites
Authors: Anketell J. M. , Lovell J. P. B.
Published: July 2010

The lower boundaries of the Aberystwyth Grits Formation and the underlying Grogal Sandstones Formation (new name) in the New Quay area are defined. The Grogal Sandstones Formation is described, and interpreted as a contourite deposit on a continental rise; we believe these are the first rocks in the British Isles to be identified as contourites. The transition within a few tens of metres from Grogal Sandstones Formation contourite facies, displaying bimodal current directions, to Aberystwyth Grits Formation turbidite facies, with unimodal current directions, can be seen well in two places on the coast southwest of New Quay. Regionally, an upward transition from finegrained contourites to turbidites of varying facies can be recognised. Our results are compatible with Ziegler's interpretation of early Upper Llandoverian palaeogeography.
A geological framework for the continental margin to the west of Ireland
Authors: Riddihough R. P. , Max M. D.
Published: July 2010

On the basis of newly released magnetic data, a major fault feature is traced southwest across the Irish continental shelf; along the northwestern margin of the Slyne‐Erris Trough, the northern termination of the Porcupine Seabight, and across the Porcupine Ridge toward the vicinity of the eastern termination of the Gibbs Fracture Zone. This major fault passes into, and is identified with, the Great Glen Fault system. Apparent sinistral movement of the order of 50–70 km along the fault displaces a feature tentatively identified as the Highland Boundary Fault. A weak magnetic feature is also identified that might represent the course of the Moine Thrust. The Slyne‐Erris Trough has been referred to as part of a ‘failed’ rift associated with the Seabight opening, but might instead be related to the wrench faulting similar to that seen elsewhere along the Great Glen Fault line. An apparent transform movement along the portion of the fault at the head of the Porcupine Seabight may relate to rifting and the generation of oceanic crust in the central part of the Seabight.

Two possible courses for the westward continuation of the Hercynian Front are recognized, and a major Tertiary intrusive centre is identified and related to a zone of dyke swarms.
Ordovician palaeogeography of the southern and eastern flanks of the Harlech Dome, Merionethshire, North Wales
Authors: Ridgway J.
Published: July 2010

The Arenig to Caradoc palaeogeographic evolution of the Harlech Dome region is interpreted from a study of the volcanic and sedimentary successions on the eastern and southern flanks of the Dome. Acid ignimbrite volcanism is shown to have been associated with periods of uplift and intermediate to basic volcanism with periods of subsidence. The evolution of the region can be compared to that of an island arc.
The sequence of Silurian graptolite zones in the British Isles
Authors: Rickards R. B.
Published: July 2010

Much modern work on graptolite sequences in the British Isles has provided considerably greater detail regarding species occurrence and range than was available to Elles and Wood (1901‐18) and requires that the more refined zonal schemes of, for example, Rickards (1967, 1969, 1970) and Toghill (1968a) should be more fully discussed than was possible in Strachan (1971), Cocks et al. (1971), or Ziegler et al. (1974). The zonal scheme favoured by the writer is discussed zone by zone, and reference is made to the various difficulties which may obtain, to other zonal schemes in use, and to the questions of local, national and international usage. A summary range chart of British Silurian graptoloids is included as Table I.
Trace fossils from the Upper Ordovician (Caradoc) of the Berwyn Hills, Central Wales
Authors: Pickerill R. K.
Published: July 2010

A suite of Caradocian trace fossils from the Berwyn Hills, Central Wales, are examined. They include forms produced by trilobites (Cruziana, Rusophycus, Trichophycus, Monomorphichnus), pelecypods (Lockeia), ?gastropods (?Imponoglyphus) and traces of debatable affinity probably produced by oligochaete and polychaete annelids, amphipods and crustaceans (Skolithos, Planotites, Teichichnus, Diplocraterion, Arenicolites, ?Gyrochorte, ?Palaeophycus, Vermiforichnus). Representatives of the Skolithos and Cruziana communities coexist in this assemblage and no subdivision into discrete ichnofacies is therefore possible. The trace fossils are examined in terms of their relationship to the structure and composition of Upper Ordovician communities and it is concluded that substrate and ecological controls were more important limiting environmental parameters than depth.
Llanvirn stratigraphy of the Galway‐Mayo border area, western Ireland
Authors: Archer J. B.
Published: July 2010

The Rosroe Formation is established as the lowest part of the Llanvirn succession exposed on the southern limb of the Mweelrea‐Partry Syncline. Lithological description is followed by interpretation in terms of two structurally controlled submarine fans, developed at the southern margin of the South Mayo Trough. A review of stratigraphic relations between succeeding parts of the Llanvirn succession leads to reinterpretation of the closing marine phases of the South Mayo Trough: northward slope progradation is inferred to have resulted in graduai northward spread of shallow water and emergent conditions.
Serpentinites and related rocks of Anglesey
Authors: Maltman A. J.
Published: July 2010

A series of ultramafic igneous bodies occurs in the Pre‐Cambrian (Monian) metasedimentary rocks of Anglesey. The latter are finely‐banded semi‐pelites of greenschist facies and have undergone two main phases of deformation. Most of the structures are weakly developed near the intrusions where an irregular zone of epidote hornfels was produced. The ultramafic bodies were emplaced as peridotite magmas immediately prior to D. Thorough serpentinization followed and the resulting serpentinites have a variety of appearances. A later carbonatization was intense in places. The structures and textures of the intrusive rocks can be correlated with regional events. Various melagabbroic rocks, now highly altered, may be comagmatic with the peridotite although intruded rather later.
Lower Cambrian palynomorphs from Howth, Co. Dublin
Authors: Smith D. G.
Published: July 2010

Evidence for the age of the Bray Group in southeastern Ireland is very limited. In this paper, a sample from the Gaskin's Leap Formation of the Bray Group succession in the Howth peninsula is shown to contain acritarchs of probable Lower Cambrian age.
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.