bluuebunny/crossref_metadata_2025_split huggingface dataset:
The ‘Precambrian’ in Cambria
Authors: Challinor J. 
Published: May 2009

SummaryThe history of investigation of the rocks at present classed as Precambrian in the type region of the Cambrian system in the north-west corner of wales (Cambria), where that system was first named and its lower limit locally defined, is reviewed. The Arvonian volcanic series was originally included in the Cambrian System, the Monian metamorphic group remaining as Precambrian.
Tectonic transpression in Caledonian Spitsbergen
Authors: Harland W. B. 
Published: May 2009

SummaryIn addition to the well-established extension, compression and transcurrent relative movements between plates of the lithosphere, this paper considers intermediate or oblique relative movements, namely, transtension and transpression. Transtension is already well established in oblique zones of ocean spreading which consist of stepped transform faults. Transpression is a more complex process. The tectonic consequences of a transpression model are outlined and it is suggested that the tectonic style in Caledonian Spitsbergen provides evidence for this transpression regime as an intermediate stage between compression and transcurrence. It is also suggested that transpression should occur generally and may relate the development of transcurrent faults in orogenic belts.
Palaeozoic glacial rocks recently discovered in northern Ethiopia
Authors: Dow D. B. , Beyth M. , Hailu Tsegaye 
Published: May 2009

SummaryTillite and other glacial rocks have been found at the base of a sedimentary sequence in the northern part of Tigre Province, Ethiopia. Their glacial origin cannot be doubted, for in addition to beds of tillite containing abundant striated boulders, glaciated bedrock has been found.
The rocks are correlatives either of the Upper Carboniferous glacial rocks of southern Africa or of Ordovician glacial rocks recently mapped in the Hoggar District of southern Algeria.
Alpine serpentinites, oceanic ridges, and continental drift
Authors: North F. K. 
Published: May 2009

SummaryIt is suggested that Alpine serpentinites are not a characteristic of eugeo-synclinal mountain development, but represent a special case in which the leading edge of a drifting continental mass overrode an oceanic ridge. Serpentinites younger than Caledonian are overwhelmingly of Mesozoic age, and essentially contemporaneous with the latest principal episode of continental drift. Furthermore, they occupy the leading edges of continental blocks which must have been moving during that episode.Older serpentinite belts of comparable proportions may reflect geosynclinal seaways originally wide enough to accommodate oceanic ridges. The Baltic-Breton and Siberian continents must in that case have drifted westward (with respect to their present alignments) in early Caledonian time, and Australia eastward in early Hercynian. The principal episode of Mesozoic drift is thought to have occurred during Triassic and Jurassic times, and not during Jurassic and Cretaceous.
An alternative to the ‘clastic trap’ interpretation of oolitic ironstone facies
Authors: Brookfield M. 
Published: May 2009

SummaryThe rarity or absence of clastic grains in oolitic ironstones is often explained by the hypothesis of a ‘clastic trap’ in which the clastic grains are deposited before reaching the zone of iron oolith formation. If the hydrodynamic behaviour of the iron ooliths and clastic grains is considered, this is unnecessary. The two components are spatially separated due to their different densities and different behaviour, depending on whether they are in suspension or saltating, or rolling. Iron ooliths can be rolled more easily than the equivalent clastic grain size, whereas clastic grains are more easily saltated or moved in suspension than the equivalent size of iron oolith. These differences cause spatial separation of the two facies.
Problematical Microfossils from the Gault Clay
Authors: Black Maurice 
Published: May 2009

SummaryFour species of calcareous microfossils whose systematic position is unknown occur in very small numbers in the English Gault (Middle and Upper Albian). They are associated with much more abundant coccoliths, and are believed to be the hard parts of planktonic organisms whose possible relationships are discussed, but cannot at present be determined.
The Pre-Cambrian rocks of the N.E. Ox Mountains, Eire
Authors: Lemon G. G. 
Published: May 2009

SummaryMoinian and Dalradian metamorphic rocks occur in the north-east extension of the Ox Mountains. The petrology and migmatization of the Moinian are discussed and Dalradian rocks are described for the first time from this area. Reference is made to the structure and brief comparisons are made with adjacent areas. The status of the so-called ‘eclogites’ in the Moinian is also discussed.
Coexisting chloritoid and staurolite and the staurolite–chlorite isograd from the Agnew Lake area, Ontario, Canada
Authors: Fox J. S. 
Published: May 2009

SummaryChloritoid and staurolite bearing rocks from the Agnew Lake area in northern Ontario were studied petrographically and with the electron microprobe. A staurolite–chlorite isograd is postulated, above which chloritoid and staurolite coexist in equilibrium, and a Schreinemakers-type petrogenetic grid is constructed to illustrate how the isograd might fit into a paragenetic sequence.The staurolites from the area are observed to be more ‘siderophile’ than the chloritoids and this suggests that the chlorite participating in the isograd reaction is prograde. This is confirmed in the ‘real’ isograd reaction:1.559ctd+5.000and+0.009rut+0.058ilm=0.881st+0.039chl+1.366qtz+1.040H2O the coefficients of which are calculated using the mineral analyses of the ideally univariant assemblage staurolite–chloritoid–chlorite–andalusite. Variations in the activity of the unsaturated component ZnO would affect the equilibrium temperature of the reaction and the reaction coefficients.
The petrography and chemistry of the Obudu type hornblende peridotite (cortlandtite), Ogoja Province, Eastern Nigeria.
Authors: Orajaka S. 
Published: May 2009

SummaryThe Obudu hornblende peridotite is described and briefly compared with similar rock types from other areas. Field evidence, petrographic studies, mineralogical and chemical composition have led to the conclusion that this rock is an independent magmatic intrusion into the hypersthene tonalite (enderbite) with which it is associated, and not a member of a differentiated series.
Zircon populations in Lewisian quartzite, gneiss and granite north of Loch Laxford, Sutherland
Authors: Chowdhary P. K. 
Published: May 2009

SummaryZircon populations in quartzo-feldspathic gneisses of the Rhiconich group of the Lewisian are indicative of a sedimentary derivation of the rocks. They are similar to the zircon population of an interbanded quartzite but differ markedly from that of an intrusive granite vein.
Geochronology of the Pre-Cambrian rocks of Singhbhum and adjacent regions, Eastern India
Authors: Sarkar S. N. , Saha A. K. , Miller J. A. 
Published: May 2009

SUMMARYTectonic implications of 32 new potassium-argon age determinations of minerals and rocks of Singhbhum and adjacent regions are discussed along with those of recent structural, stratigraphic and petrologic studies, and some pre-existing geochronologic data. Three distinct orogenic cycles with closing dates atc. 3200, 2700 and 850 m.y. respectively have been recognized. The earliest cycle is represented by the Older Metamorphic Group of metasediments with associated basic intrusives and biotite granodiorite gneiss; they occur mainly as relics within the huge Singhbhum granitic complex. Emplacement of the latter (c. 2700 m.y.) marks the culmination of the Iron Ore orogenic cycle which is characterized by the low-grade metamorphic Iron Ore Group sediments and volcanics and associated basic intrusives. Along the northern and eastern edges of the stabilized Iron Ore orogenic belt, thick sedimentation of the Singhbhum and Gangpur Groups (?2000–1700 m.y.) was followed by large scale basic volcanic activity (1700–1600 m.y.); these rocks were folded and regionally metamorphosed in several phases betweenc. 1550 andc. 850 m.y. (Singhbhum orogenic cycle); extensive thrusting and granitization occurred in the later part of the cycle.
The stratigraphical distribution of Bathonian ammonites in Central England
Authors: Torrens H. S. 
Published: May 2009

SUMMARYA correlation of the predominantly limestone deposits of the Bathonian (Middle Jurassic) stage in Central England is presented on the basis of the available ammonites. This is related to the standard sequence of Bathonian zones, which are briefly discussed in the introduction. All ammonites from the area of stratigraphic importance are listed. There is nothing to suggest that any of the zones are absent because of erosion or nondeposition, except in the East Midlands at the base of the Bathonian.
A redescription of the Llandoverian monograptid “Graptolithus” tenuis, Portlock, 1843
Authors: Hutt Jana 
Published: May 2009

SUMMARYThe type specimen, other figured specimens and supplementary material of Monograptus tenuis (Portlock, 1843) have revealed the presence of pronounced ventral apertural processes which place this species in a unique position in the Monograptina. The affinities of M. tenuis are discussed.
An aberrant species of Fibularia from Kenya and Madagascar
Authors: Stephenson D. G. 
Published: May 2009

SUMMARYEchinocyamus woodi Currie from the Miocene of Kenya is reexamined and considered to be conspecific with Fibulina gracilis Tornquist and Fibularia voeltzkowi Tornquist. This echinoid is a fibularid, not a laganid.
Pyrite Staining of Pellety Debris in Carbonate Sediments from the Middle East and Elsewhere
Authors: Sugden W. 
Published: May 2009

AbstractVarious limestones of Middle Jurassic and younger age in the Middle East and Britain, and certain Recent calcareous marine sediments contain pellety debris stained grey or black with finely divided pyrite. The staining appears to involve deposition on pellety debris of limonite, followed by its reaction with bacterially produced hydrogen sulphide to form first ferrous sulphide and subsequently pyrite.
On the occurrence of Parabrograptus and Sinograptus from the Middle Ordovician of Western Canada
Authors: Jackson D. E. 
Published: May 2009

AbstractSpecimens of Parabrograptus and Sinograptus from western Canada are described for the first time. An amended diagnosis of Parabrograptus is given. One pyritized fragment of a sinograptid stipe exhibits characters intermediate between Holmograptus and Sinograptus.
A New Occurrence of Sapphirine and Related Anthophyllite from Central Australia
Authors: Hudson D. R. , Wilson Allan F. 
Published: May 2009

AbstractPhlogopite-spinel-bronzite rocks, in which aggregates of bronzite and sapphirine appear to be pseudomorphs of aluminous anthophyllite, occur in a restricted low-granulite terrain in the Strangways Range, central Australia. The form of the postulated reaction is gedrite + ΔH = enstatite + sapphirine + silica + escaping “ water ”.
The Emplacement of the Main Glencoe Fault-Intrusion at Stob Mhic Mhartuin
Authors: Roberts John L. 
Published: May 2009

AbstractThe contact relationships of the Fault-Intrusion are described, in detail, from the type locality. Textural and mineralogical evidence indicates that the fine-grained marginal facies of the Fault-Intrusion is not a priori evidence for magmatic emplacement. The production of “ flinty crush-rock ” from brecciated quartzites downfaulted within the Glencoe cauldron is described from the south-western inner contact, and is shown to be a result of gas attrition. “ Flinty crush-rock ” is recorded for the first time from the north-eastern contact with the country rocks outwith the cauldron, separated from the latter by a sheared microbreccia not found at the inner contact. The contact relations of the Fault-Intrusion with these “ flinty crush-rocks ”, more properly termed pseudotachylites, indicates that the Fault-Intrusion was emplaced as an entrained fluidized system of gas, solid phenocrysts and, probably, liquid droplets. The production of the sheared microbreccia at the outer contact is thought to be due to shearing stresses exerted by the entrained system on the heated wall-rocks.
Minnivola sapolwanaensis, new species, from the Miocene of Zululand, South Africa
Authors: Carter A. N. 
Published: May 2009

AbstractA new species of Minnivola is described, from late Miocene lime-stone occurring in the valley of the Umfolosi River in Zululand, South Africa. The species extends the known range of the genus into the East African region and is distinguished by the presence on the adult right valve of about thirty-two ridges arranged in bundles of four, with prominent grooves between the bundles.
Amygdaloid Textures in the Lewisian Rocks of the Island of Tiree
Authors: Sinclair I. G. L. 
Published: May 2009

AbstractCertain amygdaloid textural features have been observed in a diopside-potash felspar rock within the Lewisian of the Island of Tiree; so far as the writer is aware, such features have not previously been noted in Lewisian rocks.Evidence as to the genesis of these textures is sparse but they appear to have attained their present nature after the principal metamorphic events which have affected the enclosing rocks.
A Miocene Gravity Slide Deposit from Eastern Timor
Authors: Audley-Charles M. G. 
Published: May 2009

AbstractA formation composed of unbedded scaly bentonitic clay containing abundant scattered exotic blocks, boulders, pebbles, and smaller fragments is described from eastern Timor. It is proposed to call this formation the Bobonaro Scaly Clay. This formation is compared closely with the Argille scagliosa of the northern Apennines. Its origin is ascribed to submarine sliding of an unstable clay mass from the area north of Timor under the influence of gravity, closely associated with the emplacement of large overthrust slices of strata that marked a climax of the mid-Tertiary orogeny in Timor. The discovery of this formation has helped to bring about a radical revision of the published views of the stratigraphy and structure of Timor.
Late Orogenic Events in the Northern Part of the Moine Nappe
Authors: Soper N. J. , Brown P. E. 
Published: May 2009

AbstractConjugate folds are recorded in Moine rocks some 15 miles east of the Moine thrust zone and their association with lamproschists and regional joint systems is described. This, and other evidence, is used to establish a sequence of late Orogenic events for the interior of the Moine nappe. A correlation with events in the thrust zone is suggested. It is concluded that the Moine thrust movements took place in Lower Old Red Sandstone times and that this coincided with a period of rapid isostatic uplift of the axial region of the Caledonian orogen.
The Torridonian Succession on the Islands of Fladday, Raasay, and Scalpay, Inverness-shire
Authors: Selley R. C. 
Published: May 2009

AbstractThe succession of the Torridonian rocks seen on the islands of Fladday, Raasay, and Scalpay is described. Three lithological fades indicative of three distinct sedimentary environments are recognized. Breccias and grits, believed to be sub-aerial in their lower part, are overlain, or pass laterally into, grey shales and sandstones of lacustrine or shallow water marine origin. These are succeeded by red fluviatile sandstones and shales, which, except near the base, are coarse grained and pebbly throughout much of the succession. Three cases of lateral facies variation are described and their significance discussed with regard to the Torridonian succession elsewhere in the Inner Hebrides and on the mainland.
Non-Metasomatic Chlorite in Igneous Rocks
Authors: Lehmann E. 
Published: May 2009

AbstractThe determination of the stability conditions of chlorite, especially the stability temperature between 500° and 700° C. by B. W. Nelson, D. M. Roy, R. Roy, and H. S. Yoder complements the conclusions arrived at from the microscopical study of the interstitial chlorite in the diabase-minverite series of south-west England. These disprove the assumption that the chlorite generally originates from metasomatic reaction or devitrification of a glassy residue. Considering the formation of chlorite at a late stage of solidification, an explanation of its genesis is attempted on that basis. Possible effects on the petrologic evolution are discussed.The chlorite taking part in the filling of amygdales and pseudoamygdales has formed preferentially by replacement of carbonates. Variation in form, degree, and associated products is exemplified. The appearance of a liquid carbonate phase, ascertained by P. J. Wyllie, O. F. Tuttle, and R. I. Harker in the system calcitewollastonite-water at temperatures between 640° and 680° C. seems to be realized likewise under natural conditions, and to provide a basis for the understanding of certain phenomena, especially in reaction zones.
On the Symmetry Principle and the Deformation Ellipsoid
Authors: Flinn Derek 
Published: May 2009

AbstractAccording to the symmetry principle the fabric of a tectonite reflects the symmetry of the deforming movements. Where the symmetry of the deformation varies from place to place this should be reflected in a similar variation in the fabric. The possible variation in homogeneous strain is best shown by the range of variation possible in the deformation ellipsoid. It is argued in the paper that rocks commonly occur which show a variation in fabric from place to place similar to the whole or part of the possible variation in shape of the deformation ellipsoid. It is concluded that such rocks have deformed by homogeneous strain. This conclusion is supported by the shapes and orientations of pebbles in deformed conglomerates.
Quartz Keratophyre Sills Intruded into Unconsolidated Sediments in North Queensland, Australia
Authors: Morgan W. R. 
Published: May 2009

AbstractQuartz keratophyre sills interbedded with folded Devonian sediments in the Annan River Tinfield area in North Queensland have probably been intruded when the sediments were unconsolidated or only partly consolidated. The sills are compared with similar occurrences in Wales, Alaska and Australia. Some of these may have been extruded prior to burrowing into sea-bottom muds but the North Queensland examples are probably true, though very high-level, sills.
The Niger Delta Region in the Light of the Theory of Continental Drift
Authors: Stoneley R. 
Published: May 2009

AbstractA recently computed fit of the African and South American continents is astonishingly close, apart from an overlap of some 120 miles in the vicinity of the Niger delta. This paper attempts to determine whether there is a genuine misfit at this point or whether the delta may have grown beyond the continental margin after the continents separated. The evidence suggests that final separation took place in Albian times, and that the bulge of the present continental edge into the Atlantic Ocean has resulted from post-Cretaceous development of the delta. The gross structure of the delta region and also the associated minor structures are considered to represent a passive response to the influx of sediment from the Niger River.
On the Magnetic Age of some Devonian Lavas from Devonshire
Authors: Cornwell J. D. 
Published: May 2009

AbstractThe directions of magnetization of samples from two sites in the Devonian Ashprington Volcanic Series, Devonshire, are similar in spite of the difference in the dip of the lavas. They are close to the mean direction for the Keuper Marls and it is concluded that they resulted from remagnetization of the lavas during the Triassic.
Fold Structures in the Mylor Beds, near Porthleven, Cornwall
Authors: Stone Maurice 
Published: May 2009

AbstractEarly folds (F1) in the Mylor Beds are upright or overturned to the north-west and trend north-easterly. They are cut by a flat-lying cleavage (S2) which is related to small-scale recumbent folds (F2) superimposed on the steep limbs of the early folds. The sequence of development of folds can be found elsewhere in the Mylor-Gram-scatho Beds and also in the Lizard Head mica schists. It is shown that F2 folds and S2 cleavage resulted from vertical shortening, which is believed to have been caused by the superimposition of slide sheets. It is suggested that the previously accepted age order of the Mylor and Gramscatho Beds should be reversed.
Kaolin Tonsteins in the Westphalian of North Staffordshire
Authors: Barnsley G. B. , Clowes J. M. , Fowler W. 
Published: May 2009

AbstractThe character, horizon, and extent of ten kaolin tonsteins occurring in the Westphalian strata of the North Staffordshire Coalfield are described, and four additional horizons considered worthy of further study, when this is possible, are noted. The value of these kaolin tonsteins in correlation, and the possibility that they may fall into two groups having different origins, is briefly discussed.
Geophysical Investigations on the Boundaries of the Mountsorrel Granite
Authors: Davies D. , Matthews D. H. 
Published: May 2009

AbstractAs a result of magnetic, seismic, and gravitational studies it has been possible to describe the nature of the boundaries of the Mountsorrel granite massif in more detail. Confirmation has been found of faulting postulated on other grounds; and also it is shown that there is no substantial underground extension of the granite beneath the surrounding Triassic countryside to the west of the outcrop.
A Columnar Growth of Dendritic Pyroxene
Authors: Preston J. 
Published: May 2009

AbstractOne of the internal contacts of a doleritic intrusion, Co. Donegal, is lined with large augite dendrites. The habit is revealed by parting on a median zone of chlorite which is regarded as an altered exsolution feature. It is suggested that an initial platy dendrite grew, in response to undercooling, as a metastable phase with the composition and structure of a high-calcic pigeonite. A later overgrowth of augite preserved the delicate crystal against destruction.
Cordierite and wollastonite-bearing rocks of south-western Ceylon
Authors: Hapuarachchi D. J. A. C. 
Published: May 2009

SUMMARYIn the region east of the south-western belt of Ceylon, garnet is stable in biotite-bearing pelitic rocks which belong to the hornblende-granulite subfacies. In the south-western belt, which includes Zone B of the eastern part of the Gampaha sheet, garnet is unstable in biotite-bearing pelitic rocks, garnet reacting with biotite to produce cordierite which has a widespread occurrence in the belt to which it is confined. To accommodate the stable cordierite-bearing pelitic assemblages the erection of a cordierite-granulite subfacies is necessary. Wollastonite-bearing rocks, which commonly occur in the belt and are confined to it, belong to the cordierite-granulite subfacies.
Cruziana: A stratigraphically useful trace fossil
Authors: Crimes T. P. 
Published: May 2009

SUMMARYCruziana semiplicata (Salter) is recorded, generally in abundance, from previously known and new localities within Upper Cambrian (Ffestiniog) sediments in Snowdonia, and the Portmadoc area, North Wales. C. furcifera (D'Orb) is recorded for the first time in the British Isles from four localities within Lower Ordovician (Arenig) sediments on St. Tudwal's Peninsula, North Wales.It is shown that each of these species is of limited but different range, and it is suggested that they could be useful in distinguishing between otherwise unfossiliferous Cambrian and Ordovician strata.
A note on some garnetiferous biotite schists from Gangpur, Eastern India, and their polyphase metamorphism
Authors: Choudhuri A. 
Published: May 2009

SummaryTextural features of two types of garnetiferous biotite-schists from the Iron-ore Series, Gangpur, developed at and near Potob, Ranchi District, indicate stages of development of the two rocks and their polyphase metamorphism.