bluuebunny/crossref_metadata_2025_split huggingface dataset:
The origin of a Pre-Cambrian diorite-granite plutonic series from Pembrokeshire (Wales)
Authors: Thorpe R. S. 
Published: May 2009

SummaryA series of dioritic, granodioritic and granitic igneous rocks, of Pre-Cambrian age, is exposed near Johnston in south Pembrokeshire. Chemical analyses of representative rocks show the suite to be of calcalkaline type. An origin is suggested involving magmatic differentiation of a diorite parent magma, and the granitic rocks are compared with a granophyre of similar composition in north Pembrokeshire.
Whole-rock Rb-Sr Isotopic Investigation of some East African Granulites
Authors: Spooner C. M. , Hepworth J. V. , Fairbairn H. W. 
Published: May 2009

SummaryPreliminary Rb-Sr whole-rock isotopic analyses of some East African granulites give the following ages and initial ratios:The initial ratios, at the 0.705–0.706 level, conform with a world-wide pattern found for granulites and other deep crustal rocks. The whole-rock ages are the first such study on East African granulites. They confirm in West Nile the suspected early Pre-Cambrian age of the Uganda basement, and in Tanzania raise source rock problems which involve the Mozambique Front.
Methods and applications of fracture trace analysis in the quantification of structural geology
Authors: Huntington J. F. 
Published: May 2009

SUMMARYNaturally occurring linear features recognisable on aerial photographs may be related to bedrock tectonics. The identification and analysis of such linear elements, “megajoints”, reveals much information about the style and dimensions of subsurface geologic structures. Various terminologies, as applicable to air photo linears, are brought together and analysis is carried out in four test applications of Permyakov's original methods, the calculation of three-dimensional parameters from two-dimensional data. Some comparison is made with other techniques. Much of this linear vector analysis is carried out manually but possibilities exist for mechanical analysis and synthesis using certain up-to-date techniques. The methods described are applicable to many fields of academic and practical geology at or above the reconnaissance level.
Algal Limestones and Associated Sediments in the Basal Purbeck of Dorset
Authors: Brown Philip R. 
Published: May 2009

AbstractThe basal Purbeck of Dorset includes interesting “dirt-beds” or fossil soils. The limestones, previously considered freshwater, are here shown to be largely of marine algal origin containing species of Ortonella, Girvanella, and Solenopora and presumed algal stromatolites. Petrographic evidence of anhydrite, gypsum, and celestine suggests evaporitic conditions during their formation. This is supported by the presence of ostracods belonging to marine or super-saline species, and by the scarcity of other fauna.
The Growth and Form of Brachiopod Shells
Authors: Rudwick M. J. S. 
Published: May 2009

AbstractThe form of a brachiopod shell is the product of the rates of growth operating at all points on the valve edges during successive stages of growth. Shell form is analysed here in terms of these rates of growth, the rate at each point being resolved into component rates. If the antero-posterior growth gradients are linear, the shell is rectimarginate; if non-linear, the lateral commissure is “flexed” throughout ontogeny. Localized anomalies in the growth rate may modify either of these basic growth patterns at any stage in ontogeny. They produce deflections in the commissure, and these generally produce deformations in the valve surfaces (e.g. folds, sulci, costae). Two major varieties of external hinge structure are defined: strophic shells have a true hinge line and may also have interareas; non-strophic shells have no true hinge line but may have palintropes. The implications of this formal analysis are examined in relation to the systematic description of the shell form.
The Pre-Cambrian Rocks of Southern Co. Wicklow (Ireland)
Authors: Tremlett W. E. 
Published: May 2009

AbstractA sedimentary formation beneath the Bray Series is found to have an extensive outcrop in southern Co. Wicklow. Evidence is given of the Pre-Cambrian age of both series. They are exposed in a Caledonian anticlinorium, which has been cut by thrusts and high-angle faults, but they had suffered strong orogenic deformation and prolonged erosion before the unconformable deposition of Lower Palaeozoic strata.
Welded tuffs and the Maelifell caldera, Alftafjordur volcano, south-eastern Iceland
Authors: Blake D. H. 
Published: May 2009

SUMMARYThe ‘Maelifell caldera’ is the name given to a separate collapse area situated on the southern margin of the main caldera of the Tertiary Alftafjordur volcano. It is 2 km in diameter and is made up of inward dipping welded tuffs, agglomerate (including patches of welded agglomerate), tuffaceous sediments and rhyolite and andesite lavas. The welded tuffs occur as thin pitchstone sheets and as much thicker felsitic masses: the former contain inclusions of basalt glass and are good examples of the simultaneous eruption of acid and basic magmas. It is suggested that the caldera represents the core of a parasitic volcano, beneath which there was a high level acid magma chamber, the immediate source of the local acid rocks. The magma chamber was intersected by numerous intrusions of basic magma, and these caused explosive eruptions and the emission of acid and basic magma to form thin pitchstone sheets. Decreased pressure in the magma chamber after eruptions caused repeated collapse within the cal
The Silurian volcanic rocks of the Mendip Hills, Somerset; and the Tortworth area, Gloucestershire, England
Authors: van De Kamp P. C. 
Published: May 2009

SUMMARYField, petrographic and chemical studies on the Silurian volcanic rocks of the Mendip Hills show that there are probably 15 or more rock units in the series including andesite and rhyodacite lavas, rhyodacite tuffs, agglomerates, and a dolerite dyke. The predominant rock type is rhyodacite which may be as much as 80 percent of the volcanics. Volcanics of Silurian age from the Tortworth area, Gloucestershire, are of latite-andesite composition.The Mendip rocks have been deuterically altered. Calcite-quartz-laumontite veins are common in fractures in these rocks. The agglomerates are particularly susceptible to weathering and some bombs are extensively altered to clays. Twelve rocks were chemically analysed for 36 elements each. No anomalous base metal concentrations were found in the volcanics although Pb, Zn, and Cu mineralisation is known in the area. K/Rb varies from 202 to 909 in these calc-alkaline rocks.
Microscopic and megascopic fabrics in the Skiddaw Group, Black Combe inlier, English Lake District
Authors: Helm Douglas G. 
Published: May 2009

SUMMARYThe rocks of the Skiddaw Group of the Black Combe inlier were subjected to low grade regional metamorphism during the D1 movementphase of an intra-Lower Ordovician orogenic episode. Mimetic recrystallisation of clay minerals parallel to the bedding was ubiquitous. Later, axial-plane cleavages were superimposed on this fabric. The nature of the cleavages and possible mechanism of their formation is discussed.Silica has been mobilised on at least three occasions during the tectonic history of the inlier. In no case was this due to metasomatism but simply to metamorphic differentiation. The D1 veins are of either quartz, or quartz and chlorite whereas veins of later generations are of quartz alone.
Pseudo-pleochroic Calcite in Recrystallized Shell-Limestones
Authors: Hudson J. D. 
Published: May 2009

AbstractLimestones consisting of recrystallized shells of lamellibranchs, originally composed of aragonite, contain a brown-coloured calcite which is strongly pleochroic. Maximum “absorption’ corresponds to the extraordinary ray. The effect is shown to be a pseudo-pleochroism, caused by scattering of the extraordinary ray by inclusions, which follow the shell structure, in the calcite. Aragonite shells, which have not recrystallized, show a pseudo-pleochroism of similar colour but reversed sign. The inclusions originate in the conchiolin of the lamellibranch shell; their present nature is not known. Their progressive destruction by thermal metamorphism is described.
The Petrology of the Mt. Alford Ring-Complex, S.E. Queensland
Authors: Stevens N. C. 
Published: May 2009

AbstractThe Mt. Alford ring-complex consists of a central boss of porphyritic microdiorite, granophyre and andesite, with a semicircular zone of rhyolitic and trachytic ring-dykes intrusive into upturned sandstones, and cross-cutting non-arcuate dykes of rhyolite, comendite, trachyte, andesite, phonolite and basalt. The petrology and geochemistry of these rocks are discussed and it is concluded that the various rocks have been produced by differentiation of a basic magma.
An Interpretation of Moine-Lewisian Relations in Central Ross-shire
Authors: Sutton John , Watson Janet 
Published: May 2009

AbstractThe paper describes those features of the Scardroy Lewisian mass, a sheet-like body of basement rocks thrust into the younger Moine Series, which suggest that this mass was driven up through a thickness of several kilometres of Moinian rocks and inserted as a narrow wedge within the Moine succession, never penetrating the highest members of that succession. The relations of the Scardroy mass, to which most of the Lewisian outcrops of central Ross-shire belong, differ from those of the more westerly outcrops of Lewisian in the region of Glenelg where the basement rocks have been shown by the work of Clough and others to represent wedges lying between tightly-compressed synclines of Moinian rocks which form a more or less autochthonous cover. The connection between the two types of structure is discussed.
The Tectonics of the Aberystwyth Grits
Authors: Price Neville J. 
Published: May 2009

AbstractA brief description is given of the sedimentary features of the Aberystwyth Grits. The form and distribution of the major folds are demonstrated and their relationship to the sedimentary pattern is indicated. Thrust, wrench, and normal fault systems are discussed in relation to the stress field which initiated them. Cleavage and joint patterns are also considered. Finally the major structures of the Aberystwyth Grits are compared and contrasted with those which have developed in adjacent areas.
Gravity Anomalies in the Channel Islands
Authors: Day A. A. 
Published: May 2009

AbstractBouguer gravity anomalies have been determined at seventy-nine stations on Alderney, Guernsey, and Jersey. On Alderney the anomalies are clearly dependent on the nature of the outcropping rock-types, and permit approximate values for the thickness of two outcropping rock masses to be obtained. On Guernsey the anomalies are not closely related to the surface geology, and suggest that the north-eastern coastal area is underlain by a body of dense rock, possibly of ultrabasic composition. The anomalies on Jersey indicate that the sedimentary rocks of western Jersey are underlain at no great depth by rock of density comparable to that of granite. In eastern Jersey the dominating feature of the anomalies is a pronounced “high” centred near Grande Charriére. It is shown that this feature is most reasonably considered to be the effect of a large buried gabbro intrusion.
Mechanics of Jointing in Rocks
Authors: Price Neville J. 
Published: May 2009

AbstractThe current theories dealing with the mechanics of joint development are discussed critically. An analysis of the stress conditions which can exist in competent rocks in the crust is presented. The conclusion is reached that “Master” and “Regional” Joints can be, generically, either “tensional” or “shear” structures. They are, however, post-tectonic phenomena which develop as a result of uplift. Joints form a part of “movement pictures” because their orientation is determined by residual stresses. Reasons are given which indicate that the mechanism described is generally applicable to joint development in folded sediments, igneous rocks, and also to incompetent material.
The Upper Devonian and Lower Carboniferous Stratigraphy of Boscastle and Tintagel, Cornwall
Authors: Selwood E. B. 
Published: May 2009

AbstractThe discovery of trilobites characteristic of the Gattendorfia Zone is described from the California Quarry, Boscastle. The possible stratigraphical implications are discussed and a comparison is made with beds of similar age at Launceston. It is suggested that there is no important stratigraphical break at the top of the Devonian and that there is a conformable passage from the Tintagel Volcanic Series into the Carboniferous. The Tredorn Phyllites are tentatively equated with the Woolgarden Phyllites. There is no evidence to support the contention that the Lower Culm contains an important greywacke sequence; these beds are probably of Upper Culm age.
The Torridonian Succession of the Isle of Rhum
Authors: Black G. P. , Welsh W. 
Published: May 2009

AbstractThe Torridonian rocks of Rhum are divided into five sub-divisions on lithological grounds and the succession is found to be closely comparable with that of Skye. On the basis of the comparison, four sub-divisions, totalling 8,500 feet in thickness, are allocated to the Diabaig Group while the 6,000 feet of strata belonging to the fifth and highest sub-division are allocated to the Applecross Group. The sediments of the Diabaig Group are now seen to form a great wedge thickening and coarsening consistently from Gairloch south-south-westwards to Rhum; a phenomenon obscured by the previously held correlation of the Rhum Torridonian with that of Skye and the Mainland.
The Deformation of Confined, Incompetent Layers in Folding
Authors: Williams Emyr 
Published: May 2009

AbstractShearing stresses acting on an incompetent layer confined between competent beds during its deformation in the development of folds, differ from those commonly accepted as the cause of a number of minor structures associated with the deformation. It is suggested that the effect of bedding drag is negligible, and that the structures described as slaty cleavage, fracture cleavage, and drag folds can be explained by the laminar flow of the incompetent material whilst accommodating itself to the interspaces determined by the more competent layers.
Scapolite-Bearing Marbles and Calc-Silicate Rocks from Tungkillo and Milendella, South Australia
Authors: White A. J. R. 
Published: May 2009

AbstractOn the eastern side of the Mount Lofty Ranges of South Australia, impure marbles and calc-silicate rocks characterized by assemblages rich in scapolite and pyroxene have been formed on a regional scale by high grade metamorphism of limestones and calcareous shales. It is suggested that this metamorphism is essentially iso-chemical and that even chlorine in the scapolite (Me 55[60) could have been derived from the original sediments.A secondary paragenesis consisting of epidote, actinolite, and calcite at Tungkillo and epidote, actinolite, calcite, and garnet at Milendella, is the result of late metasomatism and reaction associated with the formation of granites, migmatites, and veined gneisses. At Tungkillo, outside the sphere of granite activity, the secondary, retrograde assemblage is due to limited metasomatism chiefly involving the introduction of water, whereas at Milendella where marbles and calc-silicate rocks are intimately associated with granitic rocks, reaction and metasomatism giving rise to the secondary minerals has been more intense. Here garnet of the andradite-grossularite series has developed.
Concerning Mr. A. Hallams' Article on Gryphaea
Authors: Swinnerton H.H. 
Published: May 2009

AbstractThe basis for Mr. Hallam' rejection of the hypothesis on the evolution of Liostrea into Gryphaea is briefly examined and is shown to be inadequate. For Liostrea real evidence is lacking. For Gryphaea the evidence, though copious, is unsound for it is based upon an improper treatement of his collections. Moreover, the features he measures are not sufficiently significant and the reader is left in considerable doubt as to the actual range of his measurements. His aspersion upon previous workers in this field is entirely unjustified.
The Ordovician and Associated Pre-Cambrian Rocks of the Pontesford District, Shropshire
Authors: Dean W. T. , Dineley D. L. 
Published: May 2009

AbstractFollowing a recent re-mapping of the district east of Pontesford Hill, Shropshire, it now seems likely that the Uriconian and Longmyndian rocks at The Lyd Hole are faulted against one another, and that the Pontesford Shales form two outcrops, separated by faulting, and not a single outcrop as previously suggested. Doubt is cast on the validity of the so-called “rhyolite” of Habberley Brook, and the faunas and correlation of the Pontesford Shales are reviewed in the light of new evidence.
The Central and Eastern Parts of the Lammermuir-Stranraer Moraine
Authors: Sissons J. B. 
Published: May 2009

AbstractThe Lammermuir-Stranraer moraine was first described by Charlesworth and interpreted by him as marking an important readvance. The central and eastern parts of this feature are discussed. It is concluded that it is not a true moraine in these areas and that the readvance supposed to have formed it did not occur.
A Note Concerning the Age of the Metamorphism of the Dalradian Rocks of Western Ireland
Authors: Dewey J. F. 
Published: May 2009

AbstractEvidence is adduced to relate the published minimum absolute date of — 475 m.y., for the metamorphism of the Connemara Schists, to its correct position in the Lower Palaeozoic stratigraphy of Western Ireland. The metamorphism pre-dates the Didymograptus extensus zone of the Arenig in Connemara and South Mayo and an Upper Cambrian or Tremadocian age is considered likely.
The Non-marine Mollusca of the Cainscross Terrace near Stroud, Gloucestershire
Authors: Large N. F. , Sparks B. W. 
Published: May 2009

AbstractRecent collecting has revealed a typical cold mollusc fauna in the Cainscross Terrace of the Frome valley near Stroud. Cold conditions are also indicated by lithology and vertebrates. The most likely date seems to be the Irish Sea Glaciation, i.e. the main phase of the Last Glaciation.
Notes on the distribution of English Bathonian Foraminifera
Authors: Cifelli Richard 
Published: May 2009

AbstractThe English Bathonian contains a rich foraminiferal fauna composed largely of Lagenidae. The succession of foraminifera is as yet only partially revealed, but some faunal changes between the Lias and Bathonian are apparent, and four faunules have been distinguished in the Bathonian. In Dorset and the vicinity of Bath the faunules occur in the same order of superposition. In comparing the English Bathonian foraminifera with those in the German section the present data suggest that a number of species range higher in England than in Germany.
Cornstone
Authors: Allen J. R. L. 
Published: May 2009

AbstractTwo dissimilar rocks have been confused under the title “cornstone”: one is a concretionary limestone, the other a calcareous conglomerate. A return to the names “concretionary cornstone” and “conglomeratic cornstone” is advocated since the rocks differ in their significance. Conglomeratic cornstones, intra-formational in character, point to sudden increases in current activity. Concretionary cornstones suggest declines in the supplies of clastic detritus.
Mudstone Inclusions in Salopian Conglomerates from County Clare
Authors: Weir J. A. 
Published: May 2009

AbstractMudstone inclusions in graded greywacke-conglomerates of Salopian age from the Slieve Bernagh Mountains, Co. Clare, are considered to have been formed by fracture of the conglomerates in the course of slumping shortly after deposition and the infilling of the resulting cavities by mud derived from the underlying beds. The attitudes of the inclusions and of associated pebble imbrication suggests that slumping took place on a slope with a northerly inclination of 10°.
Eocene Limestones to the West of Jersey
Authors: Curry Dennis 
Published: May 2009

AbstractThis note records the presence of Eocene limestones in situ on the bed of the English Channel along an east-west line to the west of the island of Jersey. The microfauna of samples of these limestones is compared with those of some other beds of similar age. There are comments on the relevance of the above discoveries to the structural history of the area.
A New Species of Tretaspis from South Wales
Authors: Cave R. 
Published: May 2009

AbstractTretaspis moeldenensis sp. nov. from “Bala Limestone” of Carmarthenshire is described. Almost identical forms previously referred to T. kiaeri Størmer and T. aff. kiaeri occur in the Calymene Beds of Northern England. The trilobite previously described as T. cf. kiaeri from the Phillipsinella parabola Zone of the Ashgill Series of North Wales is discussed and thought to be another new species.
On the Tectonic Environment Of Basic Magma
Authors: Joplin Germaine A. 
Published: May 2009

AbstractAn attempt has been made to show that basic magma is associated with vertical and not with folding movement, that basic intrusions take the form of those characteristic of unfolded regions and of relatively high levels and that differentiation in situ is common.It is argued that basic magma is emplaced in the orogenic belts as flows and typically non-orogenic intrusions during the geosynclinal or sinking phase of the orogenic cycle, that rocks of the appinitic suite, which commonly occur as stocks associated with granodiorites, are formed from these non-orogenic basic rocks by a process of hybridization during a subsequent folding phase, but that no further basic magma is introduced during this phase.It is suggested that the terms Non-orogenic Association and Orogenic Association might replace Volcanic Association and Plutonic Association to indicate the relation of basic and acid magmas to their tectonic environment.
Cyclic Sedimentation: A Review
Authors: Wells Alan J. 
Published: May 2009

AbstractThe well-known Carboniferous cyclothems of North America and Europe are discussed as examples to illustrate the great extent and lateral variation of sedimentary cycles. Very many other instances of cyclic sedimentation, in rocks of most ages, in many parts of the world, are also characterized by a more or less regular lateral migration of simultaneously existing depositional environments, caused by repeated transgressions and regressions of the sea over an epicontinental platform. Theories of varying complexity which have sought to explain cyclic sedimentation are briefly summarized, and it is suggested that the two basic requirements are a slowly subsiding sedimentary basin and more or less regular eustatic changes of sea level. The former will decide the geographical location. The latter could be a natural, periodic and world-wide consequence of the combination of the continuous effects of sedimentation and sostatic or orogenic movements of the sea floor.
Large Scale Patterned Ground in the Valley of the Worcestershire Avon
Authors: Shotton F. W. 
Published: May 2009

AbstractCrop markings reveal a polygonal network resembling that of “patterned ground” in arctic Alaska. From this the former presence of perennially frozen ground is inferred, with the implication that the mean annual isotherm of this part of Worcestershire was at least 13½° C. lower than it is at present. It is argued that this condition obtained at the period of the Irish Sea Glaciation maximum.
The Oslobreen Series, Upper Hecla Hoek of Ny Friesland, Spitsbergen
Authors: Gobbett D. J. , Wilson C. B. 
Published: May 2009

AbstractSix formations, totalling 1,210 metres and grouped as the Oslobreen Series, are dominantly of dolomite and limestone often with evidence of discontinuous deposition. They contain a Lower Cambrian and a Canadian fauna. The succession is similar to those of this age in N.W. Scotland, where a revised thickness is given, and in E. Greenland. A new species of Canadian trilobite (Hystricurus) is described in the Appendix.