bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Note on Some Acid Breccias in the Kilchrist Vent, Skye
Authors: Ray P. S. 
Published: May 2009

AbstractThree acid breccia-bodies which are emplaced within the basaltic agglomerate of the Kilchrist vent of Tertiary age are described. They are considered to be of pyroclastic origin. Petrographic evidence which relates to the probable mechanism of emplacement of the breccias is discussed.
Stratigraphy and Origin of the Cork Red Marble
Authors: Nevill W. E. 
Published: May 2009

AbstractThe Cork Red Marble is a coarse, graded but poorly sorted, re-sedimented lime-conglomerate, of Caninian age. It occupies a central position within 4,000 feet of Waulsortian limestones. The pebble content of “porcellanous” calcite mudstone—not in reef facies—is set in a matrix of red clay. Mixed biofacies are represented, because of reworking: fragmented large molluscs, indicative of a nourishing reef habitat, contrast forcibly with a mollusc spat-ostracod assemblage as found in the pebbles. The conglomerate was probably formed when back-reef sediments, which included red clay, were elevated and then redeposited, possibly by turbidity currents
The Petrogenetic Model, an Extension of Bowen's Petrogenetic Grid
Authors: Wyllie Peter J. 
Published: May 2009

AbstractBowen's petrogenetic grid is a PT projection containing univariant curves for decarbonation, dehydration, and solid-solid reactions, with vapour pressure (Pf) equal to total pressure (Ps). Analysis of experimental data in the system MgO–CO2–H2O leads to an expansion of this grid. Three of the important variables in metamorphism when Pf = Ps are P, T, and variation of the pore fluid composition between H2O and CO2. These can be illustrated in a three-dimensional petrogenetic model; one face is a PT plane for reactions occurring with pure H2O, and the opposite face is a similar plane for reactions with pure CO2; these are separated by an axis for pore fluid composition varying between H2O and CO2. Superposition of the PT faces of the model provides the petrogenetic grid. The reactions within the model are represented by divariant surfaces, which may meet along univariant lines. For dissociation reactions, the surfaces curve towards lower temperatures as the proportion of non-reacting volatile increases, and solid-solid reaction surfaces are parallel to the vapour composition axis and perpendicular to the PT axes. The relative temperatures of reactions and the lines of intersections of the surfaces can be illustrated in isobaric sections. Isobaric sections are used to illustrate reactions proceeding at constant pressure with (1) pore fluid composition remaining constant during the reaction, with temperature increasing (2) pore fluid composition changing during the reaction, with temperature increasing, and (3) pore fluid changing composition at constant temperature. The petrogenetic model provides a convenient framework for a wide range of experimental data.
On the Supposed Evolution of Gryphaea in the Lias
Authors: Hallam A. 
Published: May 2009

AbstractA re-examination of Hettangian and Lower Sinemurian oysters has led to the rejection of Trueman's hypothesis on the evolution of Liostrea into Gryphaea. Gryphaea assemblages from two horizons in different parts of Britain have been subjected to bivariate and size frequency analysis. The only detectable difference is a slight size increase up the succession. No “gryphaeoid” trend is discernible in Liostrea up the Hettangian succession and the change to Gryphaea is in consequence abrupt. All the oysters of Trueman's series are referred to what are considered to be two different Linnaean species.
The Mechanics of Oblique Slip Faulting
Authors: Bott M. H. P. 
Published: May 2009

SummaryThe various mechanisms which could cause oblique slip faulting are briefly reviewed. It is thought that such faulting may frequently arise from the existence of preferred planes of fracture within the rocks. The dynamics of this mechanism is studied in some detail and an expression is obtained for the first direction of slip within the plane under the influence of a general stress system of given orientation it is found that the initial slip may occur in any possible direction within the plane, the direction depending on the relative values of the three principle pressures. The theory suggests that when a pre-existing fault is subjected to a reorientated stress system (typical or rotated) the movement after fracture will usually be oblique. In conclusion, the general implications of the theory are discussed.
Chess-Board Albite from New Brunswick, Canada
Authors: Starkey John 
Published: May 2009

AbstractChess-board albite is described and theories on its origin outlined. A new occurrence from New Brunswick, Canada, is noted and certain features of the chess-board albite, discussed which fit the theory that it results from two processes, namely metasomatism of potash feldspar to soda feldspar, and deformation. This hypothesis is applied to British localities.
Culm Stratigraphy and the Age of the Main Orogenic Phase in Devon and Cornwall
Authors: Simpson Scott 
Published: May 2009

AbstractThe major stratigraphic divisions of the Carboniferous rocks of Devon and Cornwall are characterized and new terms suggested to replace those of W. A. E. Ussher. It is shown that there is in South Devon and Cornwall a major unconformity separating an uncleaved group of post-orogenic Carboniferous strata (Ugbrooke Group) from underlying Devonian and Carboniferous with slaty cleavage. It is argued that the Ugbrooke Group is younger than any strata hitherto thought to be present in the Carboniferous of South-West England, and that the major orogeny is either Malvernian or Asturic in age.
Some supposed ‘raised beach’ deposits at Corran, Loch Linnhe, and Loch Etive
Authors: McCann S. B. 
Published: May 2009

AbstractTwo large gravel deposits, at Corran on Loch Linnhe, Inverness-shire, and at the entrance to Loch Etive, Argyll, are described, and it is considered that they are fluvio-glacial fans, marking a contemporaneous halt in the retreat of the valley glaciers which occupied the sites of these two lochs. Orientation analysis of the pebbles in the Corran deposit supports this conclusion. Similar analysis on gravels along the northern shore of Loch Etive indicates that they are not raised beaches, but were deposited in lakes held up by the glacier which deposited the Loch Etive fan.
The Age and Relationships of the Cornbrook Sandstone
Authors: Jones D. G. , Owen T. R. 
Published: May 2009

AbstractThe Cornbrook Sandstone of Titterstone Clee Hill has plants of Westphalian (Middle Coal Measures) age. It is thus probably a correlative of the lower Kinlet Group of the Forest of Wyre. The base is unconformable to the Old Red Sandstone and Carboniferous Limestone while the top is apparently conformable with Productive Coal Measures of the Sweet Coal Group, also of Middle Coal Measures age.
Rock Magnetism Applied to Some Geological Problems
Authors: Blundell D. J. 
Published: May 2009

AbstractRecent studies concerned with the application of rock magnetism to several geological problems serve to illustrate the scope of the methods at present available. Rock magnetism can usefully be applied to determine the age of a rock or to correlate it with some other. It may be used in studying the structural history of a formation or the thermal history of a rock. The examples cited deal with igneous rocks in Britain, but the methods also apply to some sediments, and possibly to metamorphic rocks.It is stressed that rock magnetism can be applied quite independently of any theory concerning the earth's field. It is necessary only to establish whether the magnetism measured in the laboratory is a true record of that acquired when the rock formed, or at some other known time in its history.
A Formation of Marekanite at El Fiscal, Guatemala
Authors: Ljunggren Pontus 
Published: May 2009

AbstractAn outcrop of obsidian pebbles in a grey volcanic rock was investigated in the field and subsequently examined in the laboratory by means of optical, X-ray, and D.T.A. methods. The results show that the grey rock arose from obsidian through a micro-cracking, causing a formation of marekanite balls (massive obsidian) surrounded by a very brittle grey rock (micro-cracked but completely unaltered volcanic glass).
Shear Failure of Anistropic Rocks
Authors: Jaeger J. C. 
Published: May 2009

AbstractThe two-dimensional theory of two simple generalizations of the Coulomb-Navier criterion for shear failure is developed. The first of these refers to a material with a single plane of weakness which has a different shear strength and coefficient of internal friction from the remainder of the material. In this case it is shown that failure may take place, according to circumstances, either in the plane of weakness or in planes cutting across it. The second criterion refers to a layered material whose shear strength varies continuously from a maximum in one direction to a minimum in the perpendicular direction. In this case it appears that, instead of the two directions of failure possible for an isotropic material, there is only one possible plane of failure which lies between the plane of minimum shear strength and the nearest to it of the two Coulomb-Navier planes. Numerical results are given for the case of uniaxial compression and experimental results are shown to be in reasonable agreement with them.
Inclined Granitic Pipes in the Diorites of Guernsey
Authors: Elwell R. W. D. , Skelhorn R. R. , Drysdall A. R. 
Published: May 2009

AbstractPipe-like bodies, of granitic composition, occur in certain meladiorities in Guernsey. Their average diameter is 3 inches, and they are all similarly inclined. Some connect downwards with an acid vein system; others with a discontinuous acid layer. It is considered that the pipes were formed before the meladiorite host rocks had solidified, and that their inclination was the result of relative movement between the rocks above and below.
A Fine Air-Heave Structure from the Old Red Sandstone of Lanarkshire, Scotland
Authors: Rolfe W. D. Ian 
Published: May 2009

AbstractAir-heave structures have previously been described from marine lagoonal deposits, both from present day and ancient sediments. This paper records the find of such structures in playa sediments from the Scottish Old Red—perhaps the first record of such structures from non-marine sediments in the geological column. It is suggested that the structures were formed on the beaches of “Lake Caledonia”, “during a storm, seich, or a heavy rainfall”.
A Garnet-Hornblende-Pyroxene Rock from Glenelg, Inverness-shire
Authors: ÓHara M. J. 
Published: May 2009

AbstractA garnet-hornblende-two pyroxene rock from Glenelg is described. It is assigned to the eclogite facies by virture of its density, mineral composition, and associations. Its chemical composition is that of a picrite-basalt. Comparison with other garnet-pyroxene assemblages suggests that there are no clear differences between the partition of major and minor elements in these minerals at the eclogite and granulite facies of metamorphism. A diagram to represent parageneses in basic and ultrabasic rocks of the eclogite facies is presented, and points of interest discussed.
Intra-Stratal Flow and Convolute Folding
Authors: Williams Emyr 
Published: May 2009

AbstractThe property of liquefaction of certain confined, water-logged, unconsolidated sedimentary layers is considered to play an important part in the development of much of convolute folding. Lateral intrastratal laminar flow of liquefied beds, according to flow patterns mainly determined by the distribution of parts of the layers that have remained solid, appears to account satisfactorily for internal folding. Although intra-stratal flow, which can result from a number of causes, may considerably deform the stratification planes of a liquefied layer, there is neither lateral shortening nor a notable change in the thickness of the bed.
A Note on the Disposition of Fold Axes in the Silurian Strata around the Newry Granodiorite
Authors: Anderson T. B. , Bates D. E. B. , Hamilton R. S. 
Published: May 2009

AbstractAn area of high, north-eastward plunge of b-axes has been mapped in Silurian greywackes around the mouth of Strangford Lough, N. Ireland. Reconnaisance over a wider area to the south-west is consistent with the hypothesis that this steep plunge is due to the upward push exerted during the emplacement of the Newry Granodiorite. A near surface extension of the intrusion towards the east-north-east is inferred.
The Laig Gorge Beds, Isle of Eigg
Authors: Hudson J. D. 
Published: May 2009

AbstractSome rocks exposed near Laig Farm, Isle of Eigg, have previously been referred to the Upper Oxfordian. In this paper their age is shown by foraminifera to be Upper Cretaceous, their petrology described and their stratigraphical significance discussed. Evidence is presented that the supposed unconformity below the Lower Corallian of North-West Scotland does not exist.
Origin of Convoluted Laminae
Authors: Sanders John E 
Published: May 2009

AbstractComparison of streaked-out “ripples” formed by the drag effects of a current passing over a watery, yet cohesive sediment bottom with convoluted laminae formed within beds of fine-grained sandstone suggests a common origin. Application of Bagnold's recent discoveries on the behaviour of cohesionless sediment in flowing fluids to the problem results in a modification of Kuenen's hypothesis of origin of the convolutions. According to the new interpretation, convolutions arise when formerly cohesionless sand grains become cohesive after deposition and respond to increased shearing due to higher current velocity by a décollementtype of adjustment with the plane or planes of adjustment located within, or in some cases at or below the base of the growing sandstone bed. Convolute “anticlines” in cohesive sand are thought to serve the same function as that played by current ripple-marks in cohesionless sand, i.e., they create additional bottom relief in order to increase the drag and restore equilibrium to the added shearing stress imposed by the current that cannot be counterbalanced by grain-to-grain encounters.
Metamorphism of the Jurassic Rocks of Glas Bheinn Bheag, near Dunan, Isle of Skye
Authors: Smith Shelagh M. 
Published: May 2009

AbstractA succession of Jurassic sediments is shown to have been metamorphosed in contact with a Tertiary microgranite. The meta-morphic features of the three main lithological groups of the sediments are described and the conclusion is reached that in addition to simple thermal metamorphism, which is apparent in most of the rocks, the rocks nearest the microgranite have been permeated by aqueous fluids containing K2O, Na2O, MgO, FeO and Fe2O3.
Corundum in Biotite-Sillimanite Gneiss From near Polgahawela, Ceylon
Authors: Cooray P. G. , Kumarapeli P. S. 
Published: May 2009

AbstractIdiomorphic, pale blue corundum crystals (S.G. =4·02, n0=1·770 ± 0·002) up to one inch long occur as porphyroblasts in a finegrained biotite-sillimanite gneiss cut by pegmatite veins at Gangoda, 5½ miles south of Polgahawela. The field relations and petrography of the corundum-bearing rocks are described briefly. The corundum is thought to have crystallized by metamorphic differentiation in alumina-rich silica-poor bands in a semipelitic gneiss.
The Distribution of some Elements across the Contacts of Four Xenoliths
Authors: Farrand M. G. 
Published: May 2009

AbstractTwo basic xenoliths were taken from the Shap adamellite and two from the Glen Fyne porphyritic granodiorite. Each specimen was divided into the three parts; margin and core of the xenolith and the surrounding host rock. Porphyritic alkali feldspar and sphene were separated from each part and the rocks and minerals were analysed for trace elements and for Na and K. Four specimens of the assumed parent rocks of the xenoliths were also analysed. The results indicate that the two host rocks are similar in trace element content, that equilibrium between minerals in host rock and xenoliths extends to their trace element content and that late stage magmatic fractions may have played a part in the alteration of the xenoliths.
Co-Existing Pyroxenes in Metamorphic Rocks
Authors: O'Hara M. J. 
Published: May 2009

AbstractChemical and optical data for eighteen granulite facies pyroxene pairs are compared. Compositions and tie-line trends derived from optical data are shown to be unreliable and it is recommended that no attempt be made to subdivide the granulite facies on the basis of optically derived tie-lines.
Post-Intrusion Deformation of a Dyke Swarm, Awatere Valley, New Zealand
Authors: Challis Gwyneth A. 
Published: May 2009

AbstractThe only known regional dyke swarm in New Zealand is described. Dykes are 1·5–2 feet thick and have been intruded vertically into unconsolidated Cretaceous sediments. The present attitude of dykes is found to be affected by compaction of these sediments and by regional folding and bedding-plane slip. A rough measure of total compaction is obtained.
On an Occurrence of Fayalite Quartz-Monzonite in the Basement Complex around Bauchi, Northern Nigeria
Authors: Oyawoye M. O. 
Published: May 2009

AbstractAn unusual fayalite-bearing quartz-monzonite occurs around Bauchi in Northern Nigeria and is distinguished from the high-level fayalite granites of the Newer Granites ring complexes by the presence of a linear structure conformable with those in the surrounding rocks, the gradational nature of its contacts, the extreme coarseness of its mineral constituents and the abundance of myrmekite. It is similar to them in its distinctive green colour and in the high FeO: Fe2O3 ratio. The rock is believed to be definitely older than the rocks of the ring-dyke complexes.
Stratigraphy of the Skiddaw Group between Buttermere and Mungrisdale, Cumberland
Authors: Jackson Dennis E. 
Published: May 2009

AbstractThe Skiddaw Group between Buttermere and Troutbeck is approximately 6,000 feet thick and can be subdivided into four formations which in ascending order are: Hope Beck Slates; Loweswater Flags; Mosser-Kirk Stile Slates; Latterbarrow Sandstone. The coarser elastics exhibit most of the characteristics of sediments deposited by turbidity currents. The source of these deposits is thought to lie to the south. The occurrence of contemporaneous vulcanism in the Loweswater Flags on Watch Hill has been confirmed. Tourmaline and andalusite are recorded for the first time from the metamorphic aureole east of Crummock Water.
Contrasted Styles of Folding in the Rocks of Ord Ban Mid-Strathspey
Authors: Weiss L. E. , McIntyre Donald B. , Kürsten Martin 
Published: May 2009

AbstractOn Ord Ban, quartzite in superposed recumbent folds trending north–south is separated by a slide from mica-schist, granulite, and marble folded in monoclines trending east–west. The reasons for distinguishing between these two styles of folding are given, and the characters of the two styles are contrasted. A fold in quartzite and a fold in marble are described in detail, and kinematic interpretations are attempted. It is concluded that evidence of an early deformation involving mylonitization has been preserved in the quartzite, and that the latest tectonic event distinguishable was the production of the monoclines with attendant twinning of calcite and dolomite.
The Geology of North-East Jan Mayen
Authors: Nicholls G. D. 
Published: May 2009

AbstractField observations collected on a short expedition to Jan Mayen indicate that ankaramite was extruded at three different periods at the north-eastern end of the island, either as lava flows or pyroclastic deposits. Cycles of volcanic activity, in which the earlier lavas are ankaramite and the later ones trachybasaltic, have been recognized.
Biotitite in the Basement Complex of Southern Nyasaland
Authors: Morel S. W. 
Published: May 2009

AbstractRecent work in the Middle Shire Valley has revealed a swarm of biotitite bodies emplaced in gneisses and granulites of the Basement Complex. The rocks of the Basement Complex are described briefly and referred to the Amphibolite and Granulite Facies of regional rnetarnorphism. The field relations, distribution, and petrology of biotitite bodies show that they are a series of metamorphosed ultrabasic intrusions. An occurrence is described in which hydrothermal agencies have altered biotitite to vermiculite rock.
On the Supposed Transformation of Tillite to Granite at Mount Fitton, South Australia
Authors: Chinner G. A. , Sando M. , White A. J. R. 
Published: May 2009

AbstractThe transformation of tillite to granite and gneiss by granitization has recently been postulated for rocks of the Mount Fitton area of South Australia. After examining the relationships in the field we have concluded that another interpretation is possible; the granites could be regarded as an older basement upon the eroded surface of which the tillites have been laid. The zone of feldspar rich rocks between the two could represent a basal arkose resting directly on the old granitic surface.
The Stratigraphy and Folding of some Metamorphosed Moine Sediments around the Carn Chuinneag and Inchbae granitic gneisses
Authors: Harker R. I. 
Published: May 2009

AbstractBy studying the current bedding in the hornfelsed rocks surrounding the ortho-gneisses of the Carn Chuinneag and Inchbae masses it has been possible to obtain some indication of the stratigraphic order and the nature of the folding of this part of the Moine series.
The Olivines of the Garbh Eilean Sill, Shiant Isles
Authors: Johnston R. 
Published: May 2009

AbstractOptical methods are employed in the re-determination of the composition of the olivines throughout the Garbh Eilean Sill. The olivines in the upper picrodolerite and the crinanite are zoned. The range of zoning and the iron content of the olivines increase progressively with height in the sill.
Magmatic and Amygdaloidal Plagioclases
Authors: Le Bas M. J. 
Published: May 2009

AbstractThermal metamorphism of zeolites in amygdales of basaltic rocks is shown to give glomero-porphyroblastic aggregates of plagioclase crystals. Plagioclase phenocrysts in basic rocks are shown to undergo but little change during similar degrees of metamorphism.
A Camptonitic Dyke Suite at Monar, Ross-shire and Inverness-shire
Authors: Ramsay John G. 
Published: May 2009

AbstractA swarm of basaltic and camptonitic dykes in the Northern Highlands of Scotland has been studied. The dykes include monchiquite, olivine basalt, olivine dolerite, and camptonite, and a study of the relations of the various types in individual dykes suggests that the camptonites have arisen by the crystallization of late fractions from a magma of fairly normal dolerite type.
Miocene Beds of the East African Coast
Authors: Eames F. E. , Kent P. E. 
Published: May 2009

AbstractNew discoveries of marine Lower Miocene beds on the Tanganyika and Kenya coasts and on the adjacent larger islands are briefly described, and the palaeontological evidence establishing their age outlined. Previous palaeontological evidence has had to be reassessed, a considerable number of supposed Pliocene index fossils having been found to occur in the Lower Miocene. The “ Chlamys werthi Beds ” are shown to include strata of both Lower Miocene and Pliocene ages.
The Ben Lui Recumbent Syncline (S.W. Highlands)
Authors: Cummins W. A. , Shackleton R. M. 
Published: May 2009

AbstractStructural evidence from the Ben Lui district supports Bailey's view that the hinge of a major recumbent fold can be demonstrated there. Way up evidence indicates that all the recumbent structures from the Ben Udlaidh fold upwards face towards the south-east and south-south-east. The Ben Udlaidh and Ben Lui folds are therefore synclines. The attitude and character of the folds suggest gravitational flow.