bluuebunny/crossref_metadata_2025_split huggingface dataset:
Basalt Textures from the Southeastern Lower Galilee, Israel
Authors: Oppenhein M. J. 
Published: May 2009

AbstractBasalt groundmass textural nomenclature is reviewed and revised. The intergranular and ophitic extures are seen as end members of a series with steadily increasing grain-size, the international representative of which is here termed the “isogranular” texture. Undere intrusive conditions the series may be extended to include the poikilitic texture. Ophitic texture is regarded as an intergrowth;the term “sub-ophitic”s not suitable for basalts but may be retained for texturally isotropic rocks. When basalts cool hurriedly they will tend to develop an intergranular texture whereas extension of the crystallization period permits the formation of an ophitic texture. Cooling conditions will be determined by a combination of the effects of the volatile concentration and the flow characteristics, the latter partly depending on topography.
Sedimentology of the Partry Series in the Partry Mountains, Co. Mayo, Eire
Authors: McManus John 
Published: May 2009

AbstractThe Lettereeneen fault, a newly recognized structure, brings the Mweelrea and Maumtrasna Groups of the Partry Series (Caradocian-Llandeilian age) into contact. The stratigraphy of the Mweelrea Group, of red bed facies, is followed from the presence of welded tuff horizons; no such markers exist in the Maumtrasna Group which lies unconformably upon the former.Sedimentary structures of shallow water origin occur in each group. Three types of conglomerate recognized in the area are examined. The immature feldspathic sandstones increase in arkosity upwards.A proluvial or proluvio-marine environment of deposition is suggested, with debris derived from an eastward extension of the metamorphosed Dalradian rocks of the Connemara Cordillera and foothills of sedimentary and volcanic rocks.
New Magmatic Features in Makhtesh Ramon, Southern Israel
Authors: Garfunkel Z. , Katz A. 
Published: May 2009

AbstractSix volcanic vents, trachybasaltic bosses, and new dykes replaced by kaolinite were discovered. The vents are built of trachybasaltictrachytic and basaltic plugs and of tuffisites and tuffs. In the trachybasalts, plagioclase and anorthoclase display complicated reaction phenomena, reflecting changes in crystallization conditions. The trachybasaltic and trachytic bodies were emplaced first and subsequently were altered to kaolinite (Upper Jurassic). Magmatic activity was resumed after an intense erosion period leading to the formation of the vents and of the Lower Cretaceous basaltic volcanic complex which was in part extruded through these vents.
Chemical and Mineralogical Changes Associated with the Laxfordian Metamorphism of Dolerite Dykes in the Scourie-Loch Laxford Area, Sutherland, Scotland
Authors: Burns D. J. 
Published: May 2009

AbstractChemical analyses of dolerites and metadolerites from the Scourie-Loch Laxford area have been made, together with analyses of amphiboles and a pyroxene from these rocks.Chemical variation within the dykes as originally emplaced has been investigated. Introduction of material during metamorphism is limited, only potassium showing a marked increase in concentration. In the least-altered dykes a relationship between degree of clouding in felspar and amount of H2O+ present is indicated.Chemical analyses and optical properties of amphiboles show no distinctive trends which could be associated with the progress of the metamorphism.
A Study of Density Variations in New Red Sandstones from the English Midlands
Authors: Brooks M. 
Published: May 2009

AbstractMethods are outlined by which density changes due to burial and compaction can be studied, and results are briefly discussed of an application of these methods to New Red Sandstone rocks from the English Midlands. From density measurements on surface rocks and compaction tests on a disaggregated sandstone it is concluded that there is no significant increase in density with depth down to 10,000 feet if the original, depositional, porosity of the sediment is low. Compaction tests suggest that sands with a high original porosity will, over a similar depth range, undergo permanent (i.e. non-elastic) deformation producing a 10 per cent increase in density.
The Flora of the Brora Coal
Authors: Harris T. M. , Rest Jane A. 
Published: May 2009

AbstractA flora of cuticle fragments obtained by maceration of the Bathonian coal of Brora is described together with some lycopod megaspores from the shale below the coal. All the species are known from the Bajocian or Bathonian of N. Yorkshire. Ptero-phyllum cycadites sp. nov. is described as new, the type being a Yorkshire specimen. The formation of the Brora coal is discussed.
A Geochronological and Strontium Isotope Study on the Garabal Hill-Glen Fyne Igneous Complex, Scotland
Authors: Summerhayes C. P. 
Published: May 2009

AbstractThe age of the Garabal Hill-Glen Fyne igneous complex has been determined as 392 ± 4 m.y., by the Rb-Sr method. The components of the complex had an average initial (87Sr/86Sr)0isotope ratio of 0·705 ± 0·003. Geological contamination of marginal components is reflected in the (87Sr/86Sr)0values of these rocks which were found to beca. 0·710, significantly higher than values from uncontaminated samples. The results are in accord with the view that the individual members of the complex had a common source, comparable with regard to the Rb/Sr ratio, to the source of basalts. It is inferred that complete melting of such source material followed by magmatic differentiation is an appropriate mechanism of origin for the complex.
Post-eruptive mechanical sorting of pyroclastic material — an example from Jamaica
Authors: Roobol M. J. 
Published: May 2009

SummaryThe unfossiliferous Maestrichtian Summerfield Formation of Central Jamaica is composed entirely of hornblende andesite. A measured section shows a 90 m-thick lower unit of greenish-grey, crystal-rich, pumice-poor sandstones and rare mudstones, which interdigitate with shallow-marine rudist limestone. The upper 370 m comprise pink-coloured, pumice-rich fluviatile sandstones and conglomerates with devitrified ignimbrites at two horizons. Although no lavas are exposed it is likely that the erupted magma is represented by the hornblende andesite boulders of the conglomerates. Whole rock chemical analyses show the lava boulders to have around 65% SiO2 the ignimbrites 62%, the shallow-marine crystal-rich sandstones 58% and the interstratified mudstones 69%. The marine sandstones are concentrations of phenocrysts and the mudstones represent the finest glassy ash — originally the liquid which coexisted with the phenocrysts before eruption. These variations illustrate that after leaving the vent the pyroclastic material lost much fine glassy ash during the pyroclastic flow stage to produce crystal-enriched ignimbrites. Where the pyroclastic material was deposited in a shallow- marine environment it underwent further mechanical separation with loss of pumice by flotation, lithics and separation into crystals (sandstones) and glassy ash (mudstones). Subtraction of glass (rnudstone) from the magma (conglomerate boulders) shows that the ignimbrite composition can be obtained by loss of around 40 wt. % of glassy ash. The crystal-rich marine sandstones – although no longer containing the phenocryst minerals in their original magmatic proportions – represent a loss of about 60 wt. % glassy ash.
Ignimbrite vents in the Sabaloka cauldron, Sudan
Authors: Almond D. C. 
Published: May 2009

SummaryLarge ignimbrite dykes continuous with an overlying sheet of rhyolitic ignimbrite have been found at two localities in the centrally-subsided block of the Sabaloka cauldron. There is good evidence that these dykes fed ash-flow eruptions. Other possible feeder vents occur along the marginal fracture zone of the cauldron but evidence for the origin of some of these structures is ambiguous. Ignimbrites within the dyke-shaped feeders contain a very strong eutaxitic foliation oriented parallel to the contacts and this feature is thought to result from inwardly-directed pressures exerted by the dyke walls during a collapse which followed eruption of the ash-flows. Vents of this type are believed to originate by permissive intrusion through the roof of a shallow-seated magma chamber, in contrast to forcefully injected diatreme vents. A broad genetic classification of these bodies is suggested, based on their mode of emplacement.
Inclusions in garnet: discussion and suggested mechanism of growth for syntectonic garnets
Authors: Cox F. C. 
Published: May 2009

SUMMARYInclusion textures within garnets are often used to demonstrate the relationship in time between garnet growth and deformation. The evidence for syntectonic growth is discussed, and it is shown that several thin sections are required before an accurate interpretation can be made. The patterns predicted by Powell & Treagus (1967) are matched with natural examples, and a mechanism for the aevelopment of these fabrics is suggested.
Folded overthrusts at Aljustrel (South Portugal)
Authors: Schermerhorn L. J. G. , Stanton W. I. 
Published: May 2009

SUMMARYThe Upper Palaeozoic rocks in the Aljustrel area of South Portugal suffered strong Hercynian deformation, including isoclinal overturned shearfolding of two important thrust planes bringing sub-Culm strata over Culm.
The breaking of magma
Authors: Walker G. P. L. 
Published: May 2009

SUMMARYBreadcrust blocks (bombs) on Vulcano, Sicily, show features which indicate that when they were of viscous lava they broke when stress was applied rapidly, and later flowed when it was applied slowly. If the magma of granitic intrusions behaves similarly, the perplexing “relict dykes” can be explained as due to the breaking of the magma and the injection of dykes into the fractures.
Some Permian foraminifera from north-western England
Authors: Pattison J. 
Published: May 2009

SUMMARYEight species of foraminifera from the Manchester Marl are described and foraminifera recently discovered in the Magnesian Limestone of both the West Cumberland and the Eden Valley areas are also mentioned. All the described forms are similar to, and some are possibly conspecific with, foraminifera previously recorded from the Lower Magnesian Limestone of north-eastern England or Zechstein 1 of north-western Germany.
The magmatic affinities of some volcanic rocks from the Tweed Shield Volcano, S.E. Queensland — N.E. New South Wales
Authors: Wilkinson J. F. G. 
Published: May 2009

SUMMARYSome basaltic and andesitic rocks from the Tweed Shield Volcano are tholeiitic in character as evidenced by their chemistry and the nature of their pyroxenes inferred from optical data. A common mineral assemblage in the more basic members is olivine-clinopyroxene-plagioclase-opaques-(glass). Petrographic criteria that characterize tholeiites are often lacking, and some of the more basic lavas appear to link the more typical tholeiites with transitional olivine basalts. Many of the Tweed volcanic rocks are more potassic than similar rocks in other tholeiitic sequences. The likelihood of differing lineages in the shield area is noted.
Stratigraphic classification in Pre-Cambrian rocks
Authors: Allen P. M. , Reedman A. J. 
Published: May 2009

SUMMARYThe system of stratigraphic classification used by field geologists working in Africa is briefly reviewed and a hierarchy of terms is suggested, taking into account the requirements of those interested in local field problems and those concerned with the tectonics and composition of the African continent as a whole. On the local scale, rock units are best named according to the lithostratigraphic classification. On a regional scale, the criteria for defining rock units are essentially tectonostratigraphic and two new terms for them, in ascending order of magnitude, Orogenic Assemblage and Orogenic Complex, are proposed. The two schemes are united through the Sequence, which can contain any number of lithostratigraphic units of any order of magnitude.
Gravitational sorting of phenocrysts in some Icelandic intrusive sheets
Authors: Blake D. H. 
Published: May 2009

SUMMARYSome thin basaltic intrusive sheets in south-eastern Iceland consist in cross-section of a porphyritic central zone sharply bounded by non-porphyritic margins. Within the porphyritic zone phenocrysts of plagioclase, augite and olivine are arranged in two main layers, an upper layer containing mostly plagioclase phenocrysts, and a lower layer containing concentrations of augite and olivine phenocrysts. The phenocrysts are considered to have been gravitationally sorted during the passage through the sheets of a highly fluid and strongly flowing porphyritic basalt magma.
The Petrology of the Guiana Dolerites
Authors: Hawkes D. D. 
Published: May 2009

AbstractTwo distinct suites of dolerite, the Roraima Intrusive Suite (Pre-cambrian) and the Minor Dyke Suite (?Mesozoic) intrude the Guiana shield. The dolerites of the Roraima Intrusive Suite, which occur as major dykes, inclined sheets and sills, are tholeiitic in character and have been strongly differentiated. The series orthopyroxene-dolerite → pigeonite-dolerite → ferrodolerite → leucogranophyre represents the main trend. Hornblende-granophyres represent heteromorphs of late pigeonite-dolerites and early ferrodolerites. Differentiation was accomplished mainly by crystal settling probably in the presence of convection currents; toward the close of crystallization a filter-press mechanism became operative. The Minor Dyke Suite comprises numerous small dykes of undifferentiated dolerite. The intrusion of these dykes may be related to orogenic movements in the adjacent Andean geosyncline.
Note onCampophyllum flexuosum(Goldfuss)
Authors: Hill D. , Jull R. K. 
Published: May 2009

AbstractThis note provides photographs of thin sections and cellulose peels prepared from the syntypes figured by Goldfuss (1826) ofCyathophyllum flexuosumGoldfuss, the type species by original designation ofCampophyllumEdwards and Haime, 1850.It is concluded thatC. flexuosumis not a disphyllid, and thatCampophyllummay be maintained as a genus distinct fromCaninia, Caninophyllum, andPalaeosmilia. For the present it is placed alone in the family Campophyllidae Wedekind, 1932.
The Petrography and Provenance of the Coniston Grits East of the Lune Valley, Westmorland
Authors: Furness R. R. 
Published: May 2009

AbstractThe petrography of the Coniston Grits is described. Volcanic and sedimentary rock fragments suggest that the sediments were derived from the Ballantrae Series of the Southern Uplands, and not the Borrowdale Volcanic Series.There is little palaeocurrent evidence for a border land mass, but it is suggested that coarse sedimentation during the Wenlockian was restricted to the Southern Uplands by a shallowing in the border area, which was finally overcome by Ludlovian times, to allow deposition of coarser material to the south.
A Llandovery Conglomeratic Limestone in Gullet Quarry, Malvern Hills, and its Conodont Fauna
Authors: Brooks M. , Druce E. C. 
Published: May 2009

AbstractA conglomerate band exposed in Gullet Quarry, at the southern end of the Malvern Hills, contains a layer of shelly limestone in which are embedded large, often angular, boulders of Malyernian rock. The character of the limestone and the form and distribution of included boulders suggest that a near-shore environment of carbonate deposition was continually supplied with clastic material from adjacent sea-stacks. The limestone has yielded a conodont fauna indicative of a Llandovery age earlier than that assigned to the conglomerate by Reading and Poole (1961) on the basis of brachiopod evidence.
Accretionary Lapilli in a Geosynclinal Environment
Authors: Bateson J. H. 
Published: May 2009

AbstractAccretionary lapilli have been described from rocks of all geological ages as well as from historical eruptions and in all cases they are associated with volcanic activity in which large amounts of steam accompany the eruption of dense clouds of ash material. Similar lapilli are described from deposits thought to have been deposited near to the flank of a well-established geosynclinal trough of the Precambrian Barama-Mazaruni Assemblage of British Guiana.
The Nature and Origin of the Groundmass Textures in Felsites and Granophyres from Rhum, Inverness-shire
Authors: Dunham A. C. 
Published: May 2009

AbstractChemical and mineralogical data are presented to demonstrate the overall similarity between granophyre and felsite from Rhum. However, although the compositions of the groundmasses of the two rock-types are very similar their characteristic textures are quite different. The felsitic texture is shown to be the result of devitrification of a glass, whilst the granophyric texture is attributed to the simultaneous crystallization of quartz and feldspar on the cotectic line in the system Ab–Or–SiO2–H2O. An explanation of the formation of the different textures is given in terms of the degree of super-cooling experienced by separate intrusions of the same magma in contrasted environments.
Quartz Microfracturing in the North Crop of the South Wales Coalfield
Authors: Roberts J. C. 
Published: May 2009

AbstractA microscopic study of sandstones of Old Red Sandstone and Carboniferous ages along a part of the North Crop of the South Wales Coalfield reveals that the rocks are extensively fractured. The fractures occur in the quartz grains and are often filled with bubble-like inclusions. These planes of inclusion were studied in specimens over a wide area, and are related to the directions of faulting and jointing. The consistency in trend between the macro and micro-structures suggests a homogeneity of the deforming stresses.
Dictyonema from the Tremadocian of Estonia and Norway
Authors: Bulman O. M. B. 
Published: May 2009

AbstractThe Dictyonema species currently named flabelliforme (Eichwald) (as distinct from D. norvegicum Kjerulf) from the Tremadocian of Estonia is described and compared with the lectotype of Kjerulf's D. graptolithinum from Norway, and their synonymy is confirmed.
The Geology of the North Cork (Kanturk) Coalfield
Authors: Nevill W. E. 
Published: May 2009

AbstractBasal and perhaps higher Coal Measures are overthrust by earlier rocks at the front of the Hercynian arc of southern Ireland. The marine bands, lacking cephalopod phases, are faunally poor and in respect are unlike the marine bands of the other Coal Measure outliers of the South. The coal seams are crushed and in part pulverized and appear to have developed a “pinch and swell” structure.
Origin of the White Allivalite, Western Cuillin, Isle of Skye
Authors: Hutchison Robert 
Published: May 2009

SUMMARYTholeiitic contact rocks and a wide zone (White Allivalite) rich in primary precipitate calcic plagioclase are marginal to a layered allivalite series in a funnel-shaped intrusion. The high structural level apparently precludes the possibility that the ultrabasic layered rocks are the basal part of an accumulate from a tholeiitic magma. It is suggested, therefore, that a suspension of calcic plagioclase in a liquid more basic than basalt gave rise to an approximately equal volume of layered ultrabasic rocks by fractional crystallization. Emplacement was probably initiated as a tholeiitic cone-sheet complex, followed by the injection of the ultrabasic suspension in a volume sufficiently large to form a funnel-shaped body within the cone-sheet complex.
Cambrian trilobites in central Newfoundland volcanic belt
Authors: Kay Marshall , Eldredge Niles 
Published: May 2009

SUMMARYThe discovery of species of Kootenia and Bailiella known from the Middle Cambrian of western Newfoundland (“Pacific Province”) and southeastern Newfoundland (“Atlantic Province”) in limestone within volcanic rocks near New World Island, eastern Notre Dame Bay, is the first demonstration of the presence of Cambrian in the volcanic belts in North America, and also shows the mixing of forms from the two provinces.
The origin of heteradcumulate and adcumulate textures in the Jimberlana Norite
Authors: Campbell I. H. 
Published: May 2009

SUMMARYIn the Jimberlana Norite the heteradcumulate and adcumulate rocks are found in adjacent layers. The heteradcumulate occur immediately before the heterad minerals appear as cumulus grains in an adcumulate rock. It is considered that both heteradcumulate and adcumulate textures result from supercooling in the magma. Heteradcumulates develop when seeds of the heterad mineral are not available in the magma and adcumulates after they have formed.
A new Lower Llandovery graptolite from Coal Pit Bay, County Down
Authors: Toghill P. 
Published: May 2009

SUMMARYMonograptus hipposideros sp. nov., a new Lower Llandovery monograptid, is described from Coal Pit Bay, Northern Ireland. With distinct “horseshoe” curvature and simple thecal shape it is similar to, and is compared with Monograptus cyphus s.l. Lapworth, M. gregarius Lapworth and M. leei Hsü.
The flow of basalt lava from air into water – its structural expression and stratigraphic significance
Authors: Jones J. G. , Nelson P. H. H. 
Published: May 2009

SummaryWhen basalt lava flows from air into water it leaves a distinctive record of the waterlevel of the time in the form of lava sheets overlying and passing down into vitric breccia and/or pillow lava. Relative movements of waterlevel and a volcanic pile or terrain over a period of time may be readily deciphered from such records.
Dolomitization and dedolomitization in the Senonian chalk of Northern Ireland
Authors: Wolfe M. J. 
Published: May 2009

SummaryA dolomite locality in the Senonian chalk at Mullaghcarton shows a sequence of fabric variations between the unconformity with the Trias and a discontinuity surface marking the top of the basal beds. The four main variations are (1) xenotopic dolomite at the base, (2) hypidiotopic dolomite with zoned crystals and a calcite sealed intercrystalline porosity, (3) zoned dolomite rhombs scattered in a microspar micrite matrix, and at the top (4) micrite with rhombohedral pores. The xenotopic fabric is interpreted as being due to distant source dolomitization and the hypidiotopic fabric with zoned crystals to local source dolomitization. The dedolomitization phenomena are related to the mechanisms of dolomitization; for distant source dolomitization the dedolomitization fabric mimics the dolomite fabric, whereas for local source dolomitization the dedolomite regenerates the pre-dolomitization fabric.
Retrograde contact meta-morphism in the granulite facies terrain of Mont Tremblant Park, Quebec, Canada
Authors: Katz Michael B. 
Published: May 2009

SUMMARYThe Pre-Cambrian rocks of the Grenville province of south-west Quebec in the Mont Tremblant Park area consists of granulites and associated gneisses formed under granulite facies conditions which are intruded by members of an anorthosite suite. At the contacts of these intrusives especially the late-stage members, the granulites and gneisses were found to be retrograded into rocks with mineral assemblages typical of the amphibolite facies. The transformation of the granulite facies rocks into rocks of lower amphibolite grade can be attributed to local introduction of water which was supplied during the emplacement and crystallization of this late-stage, volatile-enriched magma of the anorthosite suite.
Evidence for the Geological Dating of the Granitic Gneiss of Western Ardgour
Authors: Dalziel I. W. D. , Johnson M. R. W. 
Published: May 2009

AbstractEvidence is presented for the geological dating of the granitic gneiss of western Ardgour, the southernmost part of the discontinuous granitic gneiss outcrop which extends from Argyll to Inverness-shire along the Loch Quoich line between the “highly inclined” and “flat” belts of the Moines. The granitic gneiss is shown to have been formed before or early in the second of four main fold movements to which the surrounding metasediments have been subjected, and is thought to occupy the core of a complex anti-formal second major fold.