bluuebunny/crossref_metadata_2025_split huggingface dataset:
The stratigraphy of Wilhelmøya and Hellwaldfjellet, Svalbard
Authors: Smith David G. 
Published: May 2009

SummaryStratigraphic sections measured at Wilhelmøya and Hellwaldfjellet in eastern Svalbard are described in their entirety in terms of formal lithostratigraphic units for the first time. They include rocks of mid-Triassic to late Jurassic age. The Uleneset Member is newly described and palynological evidence is used to show that it is largely Norian (late Triassic) in age.
Phlogopitization of pyroxenite; its bearing on the composition of carbonatite magmas
Authors: Gittins J. , Allen C. R. , Cooper A. F. 
Published: May 2009

SummaryPhlogopitization of pyroxenite is common in contact zones between clinopyroxenites and carbonatite dikes of the Cargill ultramafic rock—carbonatite complex near Kapuskasing, Ontario. The most typical development is a mica zone 1–10 cm wide but phlogopite is also developed in a more pervasive manner throughout the groundmass of several types of ultramafic rock. Fenitization is most commonly thought of as a process whereby aegirine and riebeckitic amphiboles are formed in the host rock while feldspar is recrystallized and silica progressively removed. Phlogopitization of pyroxenite can properly be referred to, however, as a type of fenitization. It is clearly related to the intrusion of carbonatite into pyroxenite and is further testimony to the fact that many carbonatite magmas are initially alkalic but lose alkalies to the surrounding rocks and crystallize as calcitic and dolomitic carbonatite with alkali contents restricted to the amounts that could be fixed as micas, pyroxenes or amphiboles. This in turn is controlled by the silica and alumina activity of the carbonatite magma. Abundant evidence for considerable amounts of fluorine in carbonatite magmas suggests that alkalies may be transported into the country rocks as fluorides. It is further suggested that late-stage feldspathization in carbonatite complexes is explained by the abstraction of potassic halide solutions from the crystallizing carbonatite magma. The conclusion seems inescapable that alkali carbonatite magmas, far from being the curiosity thought by many petrologists, are in fact very common during the evolutionary history of carbonatites. The common calcitic and dolomitic carbonatites have not generally crystallized from a magma of the same composition but are the residue remaining after the abstraction of an alkali-rich aqueous fluid. Consequently, there is a need to redesign the experimental phase equilibrium approach to problems of carbonatite genesis in order to take account of the presence of alkalies in most carbonatite magmas.
Ages of Pre-Mesozoic formations of the Lesser Himalaya, Hazara District, Northern Pakistan
Authors: Crawford A. R. , Davies R. G. 
Published: May 2009

SummaryThree samples of low-grade metamorphic rocks from the Hazara Group, northern Pakistan, analysed as total-rock samples by the Rb—Sr method, give model ages of 765±20 and 950±20 Ma. The results are discussed in terms of the stratigraphy of Hazara, northwestern Iran, and certain other areas.
Tidal flat and shallow marine sediments from the Craignish Phyllites, Middle Dalradian, Argyll, Scotland
Authors: Anderton Roger 
Published: May 2009

SummarySediments from 6 localities showing negligible deformation are described from a generally strongly deformed formation of metasediments. The tidal flat facies include decimetre-thick tabular sands, interpreted as the flood tide storm deposits of subtidal to intertidal channels, as well as centimetre to millimetre thick, rippled and laminated sands and silts with gypsum pseudomorphs. The gypsum crystals grew at interfaces where more permeable, overlaid less permeable, sediment and then underwent partial solution before being replaced by ferroan calcite and quartz. The shallow marine facies are centimetre-thick rippled sands interbedded with muds, interpreted as storm sediments.
Gravity tectonics or plate tectonics: example of the Numidian flysch, Tunisia
Authors: De Jong K. A. 
Published: May 2009

SummaryThe Numidian flysch unit is the largest tectonic unit in the western Mediterranean, extending from Gibraltar to southern Italy. Displacement of the unit is supposedly to the S, a result of either gravity tectonics or plate tectonics. Both interpretations have their adherents, and to solve this dilemma the Numidian flysch in Tunisia was studied. Field data indicate surprisingly that the Numidian flysch in northeastern Tunisia (Mogods–Hedil area) did not move at all, which renders the question of the emplacement mechanism irrelevant. In northwestern Tunisia (Kroumiria) the flysch moved presumably only a few km to the S, not 50 km as was thought previously. Analysing this small displacement it appears unlikely that gravity tectonics was of importance because move ment over the fault was probably upward; moreover, sedimentological data do not indicate a high area from which sliding could have occurred. A plate tectonic interpretation cannot explain, however, why flysch movement was spasmodic instead of continuous and contemporaneous with plate movement, or why plate deformation was restricted to the thin flysch unit.
Age limits for the Ubendian metamorphic episode in Northern Malawi
Authors: Dodson M. H. , Cavanagh B. J. , Thatcher E. C. , Aftalion M. 
Published: May 2009

SummaryThe Nyika granite gives a U-Pb zircon age of 1970±30 Ma, which is a minimum age for the high-grade Ubendian metamorphism in Northern Malawi. Cordierite gneisses from the same region yield an Rb-Sr whole-rock isochron age of 1815±260 Ma. Because this age is believed to reflect the high-grade Ubendian metamorphism, the latter cannot be significantly older than about 2100 Ma.
Regional distribution and thickness of post-Palaeozoic sediments on the continental margin of southern Africa
Authors: Dingle R. V. 
Published: May 2009

SummaryThe asymmetry of the continental margin around southern Africa can be related to Mesozoic sediment thicknesses, which were in turn controlled by the local structural setting. On the west coast, the Orange Basin sediments were built out as a thick wedge over the margin of the continent by discharge from the Orange River, whereas on the Agulhas Bank, sedimentation was confined to continental areas. Off the east coast the extremely narrow margin of the continent did not form an effective trap for sediments, which were readily carried beyond it. Cainozoic sediments are thin, and modify the Mesozoic sediment pile only locally on the outer shelf and slope.
Uralites and uralitization in the ultramafic belt of southern New Caledonia
Authors: Rodgers K. A. 
Published: May 2009

SummaryChemical examination of uralites and their parent pyroxenes from associated eucrites and bronzitites indicate that the alteration can proceed by diverse paths and yield differing actinolites. Alteration in eucrites can be interpreted as occurring in a near closed system but in the bronzitites an external source of Ca and Al is required.
The origin of kink bands near Tintagel, North Cornwall
Authors: Hobson D. M. 
Published: May 2009

SummaryNear Tintagel, southerly verging kink bands cut flat-lying Upper Palaeozoic Plates and schists. The bands are about 2 cm wide and most of them terminate by a Decrease of amplitude but not wavelength. The length of the kinked limb and the frequency of the bands were probably determined by lithology when the deformation began, The bands may have formed under a N-S directed maximum principal stress which was Slightly oblique to the layering.
Sedimentary facies of the Forest Marble (Bathonian), Shipton-on-Cherwell Quarry, Oxfordshire
Authors: Allen J. R. L. , Kaye P. 
Published: May 2009

SummaryThe unrivalled exposures of the quarry show the Forest Marble to comprise a complex association of vertically and laterally changing facies. These are interpreted to represent environments ranging from subtidal-intertidal fully marine sand shoals and hard substrates colonized by corals, to mud flats and tidal channels associated with coastal swamps. An earlier interpretation of calcarenites in the Forest Marble is inapplicable at Shipton-on-Cherwell.
The form of the Beinn an Dubhaich granite, Skye, Scotland
Authors: Raybould J. G. 
Published: May 2009

SummaryThe Beinn an Dubhaich granite has previously been interpreted as a boss, and as a sheet intrusion. The present paper suggests that the structure of the granite is more complex than either of these interpretations implies, and the form is probably that of a shallow funnel intrusion.
The Lewisian Geology of the Little Sand Dioritic Mass, Gairloch
Authors: Bhattacharjee C. C. 
Published: May 2009

AbstractA study of the geological history of a small dioritic mass near Gairloch has revealed the presence of rock types and structural elements not represented in most of the Lewisian of the district. Coarse grained diorite, showing intrusive relations to granulitic rocks of possible sedimentary derivation, has been foliated and subsequently intruded by microdiorite during pre-Laxfordian episodes. The Little Sand mass has subsequently been involved, probably as a thrust slice of basement, in the sequence of Laxfordian (about 1,500 m.y.) structural and metamorphic episodes which affected the more common Lewisian metasediments and metabasites.
Notes on some Ferruginous Strata in Buckinghamshire and Wiltshire
Authors: Casey R. , Bristow C. R. 
Published: May 2009

AbstractThe name Whitchurch Sands is proposed for patches of ferruginous strata scattered for 75 miles along the western edge of the Cretaceous from Stewkley, Buckinghamshire, to the Vale of Pewsey, in Wiltshire. They are interpreted as the vestiges of a marine-brackish formation of Middle Purbeck age indicating the transgressive front of an advancing sea thought to have come from the north and which left its mark farther south in the Cinder Bed of Dorset. In the past they have been regarded as Lower Greensand, Wealden, or Portland Sand. In places, e.g. Quainton, Buckinghamshire, they are overlain by undoubted Lower Greensand (Seend Ironsand) of Upper Aptian date. Both in faunal characters and in stratigraphical relations the Whitchurch Sands have much in common with the Serpulite of Hanover and the basal “Wealden” of the Bas Boulonnais.
Age Relations of Lewisian Basic Rocks, South of Gairloch, Ross-shire
Authors: Bowes D. R. , Ghaly Tharwat S. 
Published: May 2009

AbstractDuring the Laxfordian orogenic period dolerite intrusions crosscut and were chilled against vertical bands of hornblende schist that trend N.W.–S.E. Subsequent metamorphism affected both the regional hornblende schists and the dolerites, and narrow bands of hornblende schist were formed in places at the expense of doleritic chilled margins. Previous interpretations of Lewisian geochronology, tectonics and metamorphic history made on the basis of a unique pre-Laxfordian basic dyke phase, cannot be applied to the rocks south of Gairloch.
Joint Patterns at Dalrymple Hill, North-east Tasmania
Authors: Williams Emyr 
Published: May 2009

AbstractPatterns of joints in flat-lying Permian rocks have been compared with those of folded Mathinna beds, of Siluro-Devonian age, across an exposed unconformity, and with those of a nearby Late Devonian granite. The patterns of the Permian rocks and the granite are similar, and each joint set appears to be related to parallel-trending post-Permian faults in the region. However, there is no representation of the joint sets of the Permian rocks in the Mathinna beds, considered to be due to shear failure either along bedding up to 18 degrees from the expected position, or along pre-existing open joints up to 65 degrees away. Lack of apparent order in the deflection and termination of joints against one another in the Mathinna beds indicates contemporaneity of formation of the open continuous fractures of differing attitudes, suggesting that the initial form of joints is as minor discontinuous cracks, which later develop into the open joints examined in surface outcrops.
The Trilobite Anacheirurus frederici (Salter) from the Tremadoc Series of North Wales
Authors: Whittard W. F. , Dean W. T. 
Published: May 2009

AbstractCheirurus (Eccoptochile) Frederici Salter, 1864, the type species of Anacheirurus is redescribed. It is considered to be synonymous with Lehua, thus extending the stratigraphical range of Anacheirurus upwards to the Llanvirn, or perhaps Llandeilo, Series.
The Lower Carboniferous Limestone Knolls of Clitheroe, Lancashire
Authors: Parkinson Donald 
Published: May 2009

AbstractThe problem of the genesis of these biohermal structures is re-examined to test the hypothesis that they are bank sediments and not knoll-reefs. The study is based largely on the field work of the Geological Survey (Earp et al., 1961). It is argued that depositional dips have not been increased by differential compaction and it is demonstrated, by elimination of the tectonic component of the existing divergent dips, that original dips locally exceeded 60 degrees. It follows that the knolls possessed some rigidity of frame and the term “reef” seems appropriate. It is argued that the Worsaw and Twiston knolls rose upwards of 600 feet above the surrounding muds.The conclusions of the Clitheroe Memoir that certain beds of the Worston Shale Group formerly thought to post-date the knoll limestone are in fact of the same age is accepted, but it is argued that these sediments, which are not differentiated from other deposits by the Survey officers, follow a non-sequence.
A Note on Costellae in Orthid and Strophomenid Brachiopods
Authors: Kemežys K. J. 
Published: May 2009

ABSTRACTThe costellae of a population of brachiopods can be quantitatively described by plotting the total number of costellae on a valve against the length of its margin. The resultant curve describes the continuous change of the average distance between adjacent costellae during growth. When costellae first appear, this distance has the value of about 0·06 mm and it increases during growth to various degrees in different brachiopod species.If it is assumed that costellae mark the sites of setae, then the magnitude of the distance between adjacent costellae can be discussed in terms of the function of setae.The magnitude of the parameters of the distribution of setae and punctae are compared to the silt/sand dividing line.
Osculocystis, a New British Silurian Cystoid
Authors: Paul C. R. C. 
Published: May 2009

ABSTRACTOsculocystis, a new scoliocystine cystoid, is characterized by reduced oral plates which form a tubercle; three pectinirhombs, B2: IL2, L2: R1, and L4: R4; and apparently only one brachiole. Osculocystis is based on a single specimen of the type species, O. monobrachiolata, from the Lower Silurian of Buildwas, Shropshire. It is the first recorded Lower Silurian cystoid from Britain and is most closely related to Glansicystis Paul.
The Alkaline Centre of Yelele and its Bearing on the Petrogenesis of other Eastern Uganda Volcanoes
Authors: Nixon P. H. , Clark L. 
Published: May 2009

ABSTRACTAn account is given of Yelele, a Miocene volcano, situated on the Turkana escarpment, north-east Uganda. It is composed of lavas and dykes of nephelinite, phonolite, tephrite, and trachyte together with olivine-bearing varieties, and has a central plug of ijolite and nepheline syenite.The lavas are described and compared with those of other eastern Uganda centres and the petrogenesis discussed in the light of experimental data from the Geophysical Laboratory of the Carnegie Institution of Washington.A northern (Yelele) plagioclase-bearing suite of lavas and a southern (Elgon) melilite-bearing suite are derived by different fractionation trends from an olivine melanephelinite parent which itself is the dense portion of a nephelinitic parent magma.
Ordovician Conulariids from the Bosphorus Area, Turkey
Authors: Sayar C. 
Published: May 2009

AbstractFour species of Exoconularia, including E. istanbulensis, sp. nov., and one Archaeoconularia, are recorded from beds hitherto regarded as Silurian, but which are now shown to be of Middle Ordovician age. A revised stratigraphical succession is proposed.
The Luxembourg Colloquium and the Revision of the Stages of the Jurassic System
Authors: Lloyd A. J. 
Published: May 2009

AbstractA report is given of the origin, aims, proceedings, and conclusions of the “Colloquium on the Jurassic” held in Luxembourg, August, 1962. The English version of its recommendations to the International Geological Congress are quoted in full; the effects of their adoption on current English usage are discussed and some critical opinions on the report of the International Sub-Commission on Stratigraphical Terminology are expressed.
The Petrogenesis of Hornblende-mica-lamprophyre Dykes at South Hill, Jersey, C. I.
Authors: Bishop A. C. 
Published: May 2009

AbstractAt South Hill, 1/2 mile south-east of St. Helier, two hornblende-mica-lamprophyre dykes cut the Fort Regent granophyre. They are themselves displaced by two gently dipping shear zones and a dolerite dyke belonging to the main Jersey dyke swarm cuts the granophyre, lamprophyres, and shears, Petrographically the lamprophyres are of the spessartite-kersantite type, but the presence of euhedral brown amphibole invites comparison with the camptonites. The genesis of the lamprophyres is discussed and a significant role is assigned to volatile constituents.
The Early Development of Gryphaea
Authors: Swinnerton H. H. 
Published: May 2009

AbstractThe material for this work came from an extensive temporary exposure in the Vale of Belvoir (South Notts) which cut across the outcrops of some 70 feet of Lower Liassic Beds. Approximately one–third of the Gryphaea shells carried developmental stages. The youngest of these consisted of larval shells closely resembling those of the modern Ostrea. During the breeding season larvae settled at least twice. The growth of spat is described. The great majority of these died in early life and relatively few grew to later stages. About 5 per cent broke loose. Many of the host shells started life attached to small shells or fragments. A study of life conditions throws light on the course of deposition in Liassic waters.
Some Structures in the Dalradian Pillow Lavas of the Tayvallich Peninsula, Argyll
Authors: Wood Dennis S. 
Published: May 2009

AbstractPillows are described in various stages of production from small parent lava flows. The lavas flowed into water–laden sediments down to depths at which the latter were capable of supporting the weight of lava. Because of their lack of systematic relationship to tectonic axes, certain structures observed in these sediments are interpreted as pushing folds induced by the “intrusion” of lava flows. The direction of flow of the lavas was towards the north.
A Re-Interpretation of the Ben Lui Fold
Authors: Roberts John L. , Treagus J. E. 
Published: May 2009

AbstractA re-interpretation of the Ben Lui Fold (and its equivalents) is suggested on the basis of correlating the structures in the South-West Highlands (Roberts, 1963) with those in Upper Glen Lyon (Treagus, in preparation) and the Tummel (Sturt, 1961) and Blair Atholl (Harris, 1963) districts. In all these districts the Cowal-Loch Tay flat belt and the steep belt to its north-west define a structure previously interpreted as the hinge of the primary and recumbent Ben Lui Syncline. As primary structures are themselves folded round this hinge, and as minor secondary structures are congruent with it, the authors interpret the Ben Lui Fold as a secondary structure.
Cross-bedding in the Millstone Grit of the central Pennines and its Significance
Authors: Wright M. D. 
Published: May 2009

AbstractMost of the cross-bedding in the Central Pennine Millstone Grit occurs in the coarse sandstones and indicates that they are probably fluvial in origin. The cross-bedding often occurs within sheets of sandstone, and it is suggested that each sheet was deposited during one episode of flooding. Medium-grained arenaceous rocks show other varieties of cross-bedding that could have been formed on tidal flats, but this evidence is inconclusive.
Observations on the Nepheline Syenites of Koraput, Orissa
Authors: Bose M. K. 
Published: May 2009

AbstractThe nepheline syenites of Koraput, Orissa, in eastern India, are described for the first time with mineralogical details. The major rock type is a hypersolvus nepheline syenite. The mafic minerals are iron-rich biotite and subordinate alkali ferrohastingsite, the latter coexisting with titanomagnetite. The crystallization history of the magma has been interpreted in the light of chemical data on the rock and coexisting nepheline and alkali feldspar.
The Association of Amphibolite and Albitite, Kragerø, South Norway
Authors: Elliott R. B. 
Published: May 2009

AbstractIn the Kongsberg-Bamble series of South Norway leucocratic albitites are associated with amphibolites. The plagioclase of the albitites is An2-An13, that of the amphibolites is commonly An28-An40. The metamorphic facies is upper almandine amphibolite and the inferred P. T. conditions are about 700° C. and 7,000 to 8,000 bars. Recent experimental work indicates that at these temperatures and pressures amphibolites will begin to melt and the first liquid will be of albitic composition. It is suggested that the albitites owe their origin to the partial fusion of their enclosing amphibolites.
An Association of Rhyolite and Ignimbrite in the Kilchrist Vent, Skye
Authors: Ray Prem S. 
Published: May 2009

AbstractA small mass consisting of three intrusions of fine-textured acid rocks occurs within the basaltic agglomerates of the Kilchrist Vent of Tertiary age. One of the intrusions comprises flow-layered rhyolite and ignimbrite. It is thought that the rock-types represent two distinctive eruptive waves. A form of ovoidal structure not seen elsewhere in the Kilchrist area occurs in another rhyolite intrusion.
An Analysis of the Deformation in a Fold in North-east Tasmania
Authors: Williams Emyr 
Published: May 2009

AbstractMicroscope studies of a flattened fold are consistent with conclusions from macroscopic observations that whereas mudstone cleavage development may have resulted from a laminar-type flow governed by competent confining sandstone beds, the sandstone cleavage appears to be related to the dilation of texture during the early stages of deformation. Continued deformation results in a textural disruption of the initially competent sandstone, which is considered to allow flattening.
Crystal Size Frequency Distribution of Garnets in Some Analysed Metamorphic Rocks from Mallaig, Inverness, Scotland
Authors: Galwey A. K. , Jones K. A. 
Published: May 2009

AbstractIn an attempt to obtain information about garnet nucleation a series of eleven apparently homogeneous metamorphic rocks, from a small area near Mallaig, Inverness, Scotland, have been analysed to determine bulk chemical and modal compositions, garnet grain size and number of garnet crystals occurring in unit volume of rock (N). No correlation of N with any function of chemical and modal compositions could be found, and it is therefore concluded that, if the influence of trace components can be neglected, externally imposed factors (for example, time-temperature variation) or internal physical factors (for example, the surface area of the rock just prior to garnet formation) must exert a controlling influence on garnet nucleation. It was found, however, that in each specimen, there was a preferred crystal radius and the relative frequency of occurrence about this preferred value was constant for all samples studied. Preliminary comparison with other systems, investigated by the authors, suggested that the nature of this relationship may provide evidence of the conditions under which these rocks recrystallized.
Combined Palaeomagnetic and Petrological Delineation of Faults in Miocene Basalts of Oregon
Authors: Watkins N. D. , Larson E. E. 
Published: May 2009

AbstractDistinct variations of the natural remanent magnetism in a section of volcanic rocks in Greaser Canyon, Lake County, Oregon, correlate with faulting inferred independently. The palaeomagnetic data is also consistent with the occurrence of a suspected diastem in the local volcanic sequence.